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Testing Methods for Fertilizers(2021)

Incorporated Administrative Agency
Food and Agricultural Materials Inspection Center

Testing Methods for Fertilizers（2021）
Contents (2021)
1. General Rule

･････

1

1.1 Common Items

･････

1

1.2 Validity check of testing methods

･････

6

1.3 Adoption of testing methods

･････

7

1.3.1 Competence evaluation of laboratory

･････

7

1.3.2 Evaluation of test result

･････

7

2. Handling of samples

･････

8

2.1 Sampling

･････

8

2.2 Storage of samples

･････

9

2.3 Preparation of test samples･････ 102.3.1 Pre-drying･････ 112.3.2 Reduction (Separation)･････ 132.3.3 Grinding･････ 14

3. General tests･････ 16

3.1･････ 16

Moisture or moisture content

3.1.a Loss on drying method with drying apparatus･････ 16

3.1.b Loss on drying method by moisture analyzers･････ 19

3.2 Ash content･････ 22

3.2.a Ignition residue method･････ 223.3 pH･････ 23

3.3.a Glass electrode method･････ 23

3.4･････ 25

Electrical conductivity

3.4.a Measurement method with an electrical conductivity meter･････ 25

3.5 Granularity･････ 27

3.5.a Dry-type sieving testing method･････ 27

3.6 Oil content･････ 29

3.6.a Diethyl ether extraction method･････ 29

4. Main components, guaranteed components, etc.

･････ 31

4.1

Nitrogen･････ 314.1.1 Total nitrogen･････ 314.1.1.a Kjeldahl method･････ 314.1.1.b Combustion method･････ 37

4.1.1.c Devarda’s alloy – Kjeldahl method･････ 424.1.1.d Reduced iron– Kjeldahl method･････ 47

4.1.1.e Calculation with ammoniacal nitrogen and nitrate nitrogen･････ 53-i-

Testing Methods for Fertilizers（2021）
4.1.2 Ammoniacal nitrogen･････ 544.1.2.a Distillation method･････ 544.1.2.b Formaldehyde method･････ 63

4.1.3 Nitrate nitrogen･････ 68

4.1.3.a Devarda’s alloy - distillation method･････ 68

4.1.3.b Reduced iron- distillation method･････ 73

4.1.3.c Phenol sulfuric acid method･････ 78

4.2 Phosphoric acid（P2O5）･････ 84

4.2.1 Phosphoric acid･････ 84

4.2.1.a Ammonium vanadomolybdate absorptiometric analysis･････ 84

4.2.1.b Quinoline gravimetric analysis･････ 91

4.2.2 Citrate-soluble phosphoric acid･････ 94

4.2.2.a Ammonium vanadomolybdate absorptiometric analysis･････ 94

4.2.2.b Quinoline gravimetric analysis･････ 100

4.2.3 Citric acid-soluble phosphoric acid･････ 1044.2.3.a Ammonium vanadomolybdate absorptiometric analysis･････ 1044.2.3.b Ammonium vanadomolybdate absorptiometric analysis (Fertilizers containing
phosphorous acid or phosphite)･････ 1104.2.3.c Quinoline gravimetric analysis･････ 116

4.2.3.d ICP Optical Emission Spectrometry･････ 1194.2.4 Water-soluble phosphoric acid･････ 124

4.2.4.a Ammonium vanadomolybdate absorptiometric analysis･････ 124

4.2.4.b Ammonium vanadomolybdate absorptiometric analysis (Fertilizers containing
phosphorous acid or phosphite)･････ 1314.2.4.c Quinoline gravimetric analysis･････ 138

4.2.4.d ICP Optical Emission Spectrometry･････ 142

4.3 Potassium（K2O）･････ 147

4.3.1 Total potassium･････ 147

4.3.1.a Flame atomic absorption spectrometry or flame photometry･････ 147

4.3.1.b Sodium tetraphenylborate gravimetric analysis･････ 153

4.3.2 Citric acid-soluble potassium･････ 157

4.3.2.a Flame atomic absorption spectrometry or flame photometry･････ 157

4.3.2.b Sodium tetraphenylborate gravimetric analysis･････ 162

4.3.2.c Sodium tetraphenylborate volumetric analysis･････ 165

4.3.2.d ICP Optical Emission Spectrometry･････ 168

4.3.3 Water-soluble potassium･････ 173

4.3.3.a Flame atomic absorption spectrometry or flame photometry･････ 173

4.3.3.b Sodium tetraphenylborate gravimetric analysis･････ 181

4.3.3.c Sodium tetraphenylborate volumetric analysis･････ 185

4.3.3.d ICP Optical Emission Spectrometry･････ 189
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Testing Methods for Fertilizers（2021）
4.4 Silicic acid（SiO2）･････ 196

4.4.1･････ 196

Acid and base-soluble silicic acid

4.4.1.a Potassium fluoride method･････ 1964.4.1.b Potassium fluoride method (Silica gel fertilizers, etc.)･････ 2024.4.1.c Potassium fluoride method (Fertilizers containing silica gel fertilizers)･････ 2064.4.1.d Perchloric acid method･････ 2124.4.2 Water-soluble silicic acid･････ 215

4.4.2.a Potassium fluoride method･････ 215

4.5 Lime（CaO）, calcium（Ca） and alkalinity･････ 2204.5.1 Total lime･････ 2204.5.1.a Flame atomic absorption spectrometry･････ 2204.5.2 Acid-soluble lime･････ 226

4.5.2.a Flame atomic absorption spectrometry･････ 226

4.5.3 Citric acid-soluble lime･････ 230

4.5.3.a Flame atomic absorption spectrometry･････ 230

4.5.3.b ICP Optical Emission Spectrometry･････ 235

4.5.4 Water-soluble calcium･････ 240

4.5.4.a Flame atomic absorption spectrometry･････ 240

4.5.4.b ICP Optical Emission Spectrometry･････ 2434.5.5 Alkalinity･････ 247

4.5.5.a Ethylenediamine tetraacetate method･････ 247

4.5.5.b Calculation with acid-soluble lime and acid-soluble magnesia･････ 253

4.6 Magnesia（MgO）･････ 254

4.6.1 Total magnesia･････ 254

4.6.1.a Flame atomic absorption spectrometry･････ 254

4.6.2 Acid-soluble magnesia･････ 260

4.6.2.a Flame atomic absorption spectrometry･････ 260

4.6.3 Citric acid-soluble magnesia･････ 264

4.6.3.a Flame atomic absorption spectrometry･････ 264

4.6.3.b ICP Optical Emission Spectrometry･････ 269

4.6.4 Water-soluble magnesia･････ 274

4.6.4.a Flame atomic absorption spectrometry･････ 274

4.6.4.b ICP Optical Emission Spectrometry･････ 278

4.7 Manganese（MnO）･････ 283

4.7.1 Acid-soluble manganese･････ 283

4.7.1.a Flame atomic absorption spectrometry･････ 283

4.7.2 Citric acid-soluble manganese･････ 286

4.7.2.a Flame atomic absorption spectrometry･････ 286

4.7.2.b ICP Optical Emission Spectrometry･････ 291

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Testing Methods for Fertilizers（2021）
4.7.3 Water-soluble manganese･････ 295

4.7.3.a Flame atomic absorption spectrometry･････ 295

4.7.3.b ICP Optical Emission Spectrometry･････ 301

4.8 Boron（B2O3）･････ 308

4.8.1 Citric acid-soluble boron･････ 308

4.8.1.a Azomethine-H method･････ 308

4.8.1.b ICP Optical Emission Spectrometry･････ 318

4.8.2 Water-soluble boron･････ 323

4.8.2.a Azomethine-H method･････ 323

4.8.2.b ICP Optical Emission Spectrometry･････ 333

4.9 Zinc･････ 339

4.9.1 Total zinc･････ 339

4.9.1.a Flame atomic absorption spectrometry･････ 339

4.9.1.b ICP Optical Emission Spectrometry･････ 344

4.9.2 Water-soluble zinc･････ 348

4.9.2.a Flame atomic absorption spectrometry･････ 348

4.9.2.b ICP Optical Emission Spectrometry･････ 352

4.10 Copper･････ 356

4.10.1 Total copper･････ 356

4.10.1.a Flame atomic absorption spectrometry･････ 356

4.10.1.b ICP Optical Emission Spectrometry･････ 361

4.10.2 Water-soluble copper･････ 365

4.10.2.a Flame atomic absorption spectrometry･････ 365

4.10.2.b ICP Optical Emission Spectrometry･････ 369

4.11 Organic carbon and carbon-nitrogen ratio･････ 373

4.11.1 Organic carbon･････ 373

4.11.1.a Dichromate oxidation･････ 373

4.11.1.b Combustion method･････ 377

4.11.2 Carbon-nitrogen ratio･････ 381

4.11.2.a Calculation with organic carbon and total nitrogen･････ 381

4.12 Sulfur･････ 382

4.12.1 Total sulfur content（SO3）･････ 382

4.12.1.a Potassium permanganate analysis･････ 382

4.12.1.b Barium chloride gravimetric analysis･････ 384

4.12.1.c Transmitted light analysis･････ 389

4.12.2 Acid-soluble sulfur (S)･････ 394

4.12.2.a Ion Chromatography･････ 394

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Testing Methods for Fertilizers（2021）
4.13 Iron･････ 398

4.13.1 Water-soluble iron･････ 398

4.13.1.a Flame atomic absorption spectrometry･････ 398

4.13.1.b ICP Optical Emission Spectrometry･････ 402

4.14 Molybdenum･････ 406

4.14.1･････ 406

Water-soluble molybdenum

4.14.1.a Sodium thiocyanate absorptiometric analysis･････ 406

4.14.1.b ICP Optical Emission Spectrometry･････ 410

4.15 Cobalt･････ 414

4.15.1 Water-soluble cobalt･････ 414

4.15.1.a Flame atomic absorption spectrometry･････ 414

4.15.1.b ICP Optical Emission Spectrometry･････ 416

5. Harmful components･････ 420

5.1 Mercury･････ 420

5.1.a Cold vapor atomic absorption spectrometry･････ 420

5.1.b Cold vapor atomic absorption spectrometry (Fluid sludge fertilizers)･････ 424

5.2 Arsenic･････ 428

5.2.a Hydride generation atomic absorption spectrometry･････ 428

5.2.b Silver diethyl dithiocarbamate absorptiometric analysis･････ 434

5.2.c ICP Mass Spectrometry･････ 439

5.3 Cadmium･････ 445

5.3.a Flame atomic absorption spectrometry･････ 445

5.3.b ICP Optical Emission Spectrometry･････ 449

5.3.c ICP Mass Spectrometry･････ 453

5.3.d･････ 459

5.4 Nickel･････ 460

5.4.a Flame atomic absorption spectrometry･････ 460

5.4.b ICP Optical Emission Spectrometry･････ 464

5.4.c ICP Mass Spectrometry･････ 468

5.4.d･････ 474

5.5 Chromium･････ 475

5.5.a Flame atomic absorption spectrometry (Fertilizers containing organic matters)･････ 475

5.5.b Flame atomic absorption spectrometry (Fertilizers mainly containing molten matters,slag, etc.)･････ 479

5.5.c Flame atomic absorption spectrometry (Fertilizers not containing organic matters)･････ 484

5.5.d ICP Optical Emission Spectrometry･････ 490

5.5.e ICP Mass Spectrometry (Fertilizers containing organic matters)･････ 494

5.5.f･････ 500-v-

Testing Methods for Fertilizers（2021）

5.6 Lead･････ 501

5.6.a Flame atomic absorption spectrometry･････ 501

5.6.b ICP Optical Emission Spectrometry･････ 505

5.6.c ICP Mass Spectrometry･････ 509

5.6.d･････ 515

5.7 Sulfamic acid (amidosulfuric acid)･････ 516

5.7.a Ion Chromatography･････ 516

5.7.b･････ 520

High-Performance Liquid Chromatograph Mass Spectrometry

5.8 Ammonium thiocyanate (Sulfurized cyanide)･････ 526

5.8.a Ion Chromatography･････ 526

5.8.b High-Performance Liquid Chromatography･････ 530

5.9 Nitrous acid･････ 536

5.9.a High-Performance Liquid Chromatography･････ 536

5.10 Biuret nitrogen･････ 542

5.10.a High-Performance Liquid Chromatography･････ 542

5.11･････ 548

Titanium

5.11.a ICP Optical Emission Spectrometry (1)･････ 548

5.11.b ICP Optical Emission Spectrometry (2)･････ 552

5.12

Sulfurous Acid･････ 555

5.12.a Iodine method･････ 555

6. Testing relating to the other limitations･････ 556

6.1 Dicyandiamide nitrogen･････ 556

6.1.a High-Performance Liquid Chromatography (1)･････ 556

6.1.b High-Performance Liquid Chromatography (2)･････ 560

6.2 Chlorine･････ 566

6.2.a Ion Chromatography･････ 566

6.2.b Silver nitrate method･････ 571

6.3 Urea nitrogen･････ 574

6.3.a Urease method･････ 574

6.3.b High-Performance Liquid Chromatography･････ 582

6.3.c p-dimethylaminobenzaldehide absorptiometry･････ 588

6.4 Guanidine nitrogen･････ 591

6.4.a High-Performance Liquid Chromatography･････ 591

6.5 Cold buffer solution soluble nitrogen (water-soluble nitrogen)･････ 596

6.5.a Cold buffer solution method･････ 596

6.6 Heat buffer solution soluble nitrogen (hot-water soluble nitrogen)･････ 602

6.6.a Heat buffer solution method･････ 602

6.7 Activity coefficient of nitrogen･････ 609
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Testing Methods for Fertilizers（2021）
6.7.a Buffer solution method･････ 609

6.8 Initial elution rate･････ 616

6.8.a Standing-in-water method･････ 616

6.9 Humic acid (Acid insoluble - alkali soluble component)･････ 619

6.9.a Gravimetric analysis･････ 619

6.10 Sulfuric acid･････ 623

6.10.1･････ 623

6.10.2 Sulfate･････ 624

6.10.2.a Barium chloride method･････ 624

6.11 Carbon dioxide･････ 625

6.11.a Barium chloride method･････ 625

7. Nitrification inhibitor･････ 626

7.1 2-amino-4-chloro-6-methylpyrimidine (AM)･････ 626

7.1.a High-Performance Liquid Chromatography･････ 626

7.2 1-amidino-2-thiourea (ASU)･････ 630

7.2.a High Performance Liquid Chromatography･････ 630

7.3 4-amino-1,2,4-triazole hydrochloride (ATC)･････ 634

7.3.a High-Performance Liquid Chromatography･････ 634

7.4 N-2,5-dichlorophenyl succinamic acid (DCS)･････ 637

7.4.a High-Performance Liquid Chromatography･････ 637

7.5 Dicyandiamide (Dd)･････ 641

7.5.a High-Performance Liquid Chromatography･････ 641

7.6 2-sulfanilamide thiazole (ST)･････ 647

7.6.a High-Performance Liquid Chromatography･････ 647

7.7 3,4-Dimethylpyrazole phosphate (DMPP)･････ 651

7.7.a High-Performance Liquid Chromatography･････ 651

8. Others･････ 655

8.1 Melamine and its degradation products･････ 655

8.1.a Gas Chromatography/ Mass Spectrometry･････ 655

8.1.b･････ 662

8.1.c High-Performance Liquid Chromatography (Fertilizers not containing organic matters) ･････ 663
8.1.d High-Performance Liquid Chromatography (Fertilizers containing organic matters)･････ 669

8.2 Clopyralid and its degradation products･････ 673

8.2.a High-Performance Liquid Chromatography/ Tandem Mass Spectrometry･････ 673

(Simultaneous analysis of three components for clopyralid, etc.)
8.2.b High-Performance Liquid Chromatography/ Tandem Mass Spectrometry･････ 682

(Microanalysis for clopyralid (1))
8.2.cHigh-Performance Liquid Chromatography/ Tandem Mass Spectrometry- vii -･････ 692

Testing Methods for Fertilizers（2021）(Microanalysis for clopyralid (2))
8.3 Residue agrichemicals (multicomponent)･････ 701

8.3.1 Residue agrichemicals multicomponent analysis (1)･････ 701

8.3.1.a High-Performance Liquid Chromatography/ Tandem Mass Spectrometry･････ 701

8.3.2 Residue agrichemicals multicomponent analysis (2)･････ 710

8.3.2.a Gas Chromatography･････ 710

8.4 Sodium･････ 717

8.4.a Flame atomic absorption spectrometry･････ 717

8.5 Guanylurea nitrogen･････ 721

8.5.a High-Performance Liquid Chromatography･････ 721

8.6 Uric acid･････ 727

8.6.a High-Performance Liquid Chromatography･････ 727

8.7 Organofluorine compounds･････ 732

8.7.a High-Performance Liquid Chromatography/Tandem Mass Spectrometry･････ 732

Explanation of Testing Methods for Fertilizers (2021)- viii -Explanation - 1

Testing Methods for Fertilizers(2021)
1.

General Rule
1.1 Common Items(1) Applicable range
The Testing Methods for Fertilizers stipulate the official method of analysis of fertilizers and fertilizer
materials. The type of samples in the tests is shown in the summary of respective test items.
Reference: The Ministry of Agriculture, Forestry and Fisheries (Hereinafter referred to as MAFF)
Public Notices which adopt the “Testing Methods for Fertilizers” are shown below.
1) MAFF Public Notice: Prescribing for the quality labeling standards of special fertilizers, MAFF
Public Notice No. 1163 of August 31, 2000, MAFF Public Notice No. 2087 (2020) of October 27,
2020, as amended.
2) MAFF Public Notice: Prescribing for the particulars detailed in the assurance label regarding thetype of raw material as well as material, name and an amount of usage of normal fertilizers,
pursuant to Article 11-2 Paragraph 1 and Paragraph 2 of Regulation for Enforcement of Fertilizer
Regulation Act, MAFF Public Notice No. 700 of March 16, 1984, MAFF Public Notice No. 2085
(2020) of October 27, 2020, as amended.
3) MAFF Public Notice: Prescribing for the official specification of normal fertilizers pursuant to
Fertilizer Regulation Act, MAFF Public Notice No. 284 of February 22, 1986, MAFF Public
Notice No. 2126 (2020) of October 30, 2020, as amended.
4) MAFF Public Notice: Prescribing for the major components whose contents are detailed in theassurance label of normal fertilizers listed in Fertilizer Regulation Act Article 4 Paragraph 1
Clause 3, pursuant to Fertilizer Regulation Act Article 17 Paragraph 1 Clause 3, MAFF Public
Notice No. 96 of January 27, 2000, MAFF Public Notice No. 2086 (2020) of October 27, 2020,
as amended.
(2) General matters in common, procedures and terms(2.1) Terms related to laws and ordinancesa) Main components or major components: The main components or major components infertilizers in Table 1 are stipulated as components to be calculated by a public notice of the
Ministry of Agriculture, Forestry and Fisheries.

(2.2) General matters and terms that cite Japanese Industrial Standards (JIS)1Testing Methods for Fertilizers(2021)a) General notices: General matters common to analysis are according to JIS K 0050.
b) Definition: The definitions of major terms used in the Testing Methods for Fertilizers areaccording to JIS K 0211, JIS K 0214, JIS K 0215, JIS Z 8101-1, JIS Z 8101-2 or JIS Z 8101-3.
c) Laboratory sample: A sample transferred to a laboratory. Laboratory sample as specified in
JIS K 0211.
d) Test sample: A sample obtained from a laboratory sample after pretreatment such as grinding.
Test sample as specified in JIS K 0211.
e) Analytical sample: A sample measured from a laboratory sample or a test sample and to be
used in one test. Test sample or analytical sample as specified in JIS K 0211.
f) Sample: A sample in the testing methods indicates c) a laboratory sample, d) a test sample ore) an analytical sample.
g) Rounding numbers: Methods of rounding the numbers are according to JIS Z 8401.
h) Absorptiometric analysis: General rules for absorptiometric analysis are according to JIS K
0115.
i) Atomic absorption spectrometry: Atomic absorption spectrometry includes flame atomic
absorption spectrometry, electrically heated atomic absorption spectrometry (hereinafterreferred to as “electrically heated atomic absorption spectrometry”) and other atomic absorption
spectrometry. General matters common to these are according to JIS K 0121.
j) Gas chromatography: General matters common to gas chromatography are according to JIS
K 0114.
k) Gas Chromatography/Mass Spectrometry: General matters common to Gas
Chromatography/Mass Spectrometry are according to JIS K 0123.
l) Electrical conductivity measuring method: General matters common to electricalconductivity measuring methods are according to JIS K 0130.
m) Test sieving: General matters common to test sieving are according to JIS Z 8815.
n) High-Performance Liquid Chromatography: General matters common to High-Performance
Liquid Chromatography are according to JIS K 0124.
o) High-Performance Liquid Chromatography/ Mass Spectrometry: General matterscommon to High-Performance Liquid Chromatography/ Mass spectrometry are according to
JIS K 0136.
p) ICP Optical Emission Spectrometry: General matters common to ICP Optical Emission
Spectrometry are according to JIS K 0116.
q) ICP Mass Spectrometry: General matters common to ICP Mass Spectrometry are according
to JIS K 0133.
r) Ion Chromatography: General matters common to Ion Chromatography are according to JIS
K 0127.
(2.3) Description methods, procedures and terms in testing methods for fertilizers.
a) Reagent name: Unless otherwise specified, conform to the names by the chemical
nomenclature established by the Chemical Society of Japan [in accordance with theInternational Union of Pure and Applicable Chemistry (IUPAC) nomenclature of inorganic
chemistry and nomenclature of organic chemistry] and the names of JIS reagents.
b) Organic matters: Fertilizers such as Organic fertilizers, sludge fertilizers and compost andfertilizer materials. However, organic compounds such as urea and urea compounds are
excluded.
c) Actual article: A laboratory sample in original state.
d) Drying matter: The matter which remains after drying the actual article.
e) Notes, comments, figures, tables and formulae: Serial numbers for each test item should berecorded in notes, comments, figures, tables and formulae.
2Testing Methods for Fertilizers(2021)f)

Dilution of solution: “Transfer accurately a predetermined amount (to a vessel)” means theprocedure to measure any volume of solution with a measuring instrument specified in JIS K
0050 (into a vessel).
Also, “dilute accurately a predetermined amount (with solvent or solution)” means theprocedure to measure any volume of solution with a measuring instrument specified in JIS K
0050 into a volumetric flask of arbitrary volume and fill up to the marked line (with solvent or
solution) (1).
g) Description of mixture solution: Mixture solutions are described as shown in 1) - 4).
1) Reagent + reagent: Describe as reagent name 1−reagent name 2 (V1 + V2). In this case, V1
volume of reagent name 1 is mixed with V2 volume of reagent name 2.
Example: acetonitrile−water (1+1), hexane−ethyl acetate (2+1), methanol−buffer solution(3+1)2) Reagent + water: Describe as reagent name 1 (V1+V2). In the case of reagents described inTable 1 in JIS K 0050, it means V1 volume of reagent name 1 is diluted by mixing with V2volume of water.
Example: hydrochloric acid (1+1), sulfuric acid (1+2), ammonia solution (1+3)
3) Solution + reagent: Describe as solution name a (concentration) - reagent name b [V1+V2].
In this case, it means V1 volume of solution name a of a certain concentration is mixed with
V2 volume of reagent name b.
Example: sodium hydroxide solution (4 g/L) − methanol [1+4]4) Diluted reagent + reagent: Describe as reagents name a (V1+V2) - reagent name b [V3+V4].
In this case, V3 volume of the solution in which V1 volume of reagent name a described inTable 1 in JIS K 0050 diluted by mixing with V2 volume of water, is mixed with V4 volumeof reagent name b.
Example: hydrochloric acid (1+100) − methanol [2+3]h) Preparation of a calibration curve: “Put A mL - B mL of the standard solution in volumetricflasks step-by-step.” means the procedure to put a volume of 4 - 6 steps (2) in the range from A
mL to B mL of the standard solution in respective volumetric flasks step-by-step.
Prepare a calibration curve every time a test is conducted. Also, when the same test item ismeasured under the same conditions for multiple samples continuously, measure the standard
solution at regular intervals to check the indicated value.
i) Washing of apparatus: Wash containers with a detergent and tap water before usage and wash
sufficiently with water of A2 specified in JIS K 0577 or water that is confirmed not to affect aquantification value. In case of sampling a sample to test a metallic element and organic
materials, after previous washing, dip with nitric acid (1+9) or hydrochloric acid (1+9) asappropriate and further wash sufficiently with water of A2, A3 or A4.
j) Handling of reagents and liquid waste, etc.: Handle with care and in compliance with relevantlaws and regulations. When treatment methods are specified in respective test items, comply
with the methods.
k) Referential matters related to the validity of testing methods: Information related to thevalidity of respective testing methods such as quantification range (minimum limits ofquantification, etc.), mean recovery, repeatability, intermediate precision and reproducibility is
described in a Comment, etc. Note that the numerical values such as Minimum Limit of
Quantification, etc. are not standards to be targeted but examples.
Note (1) When the dilution factor is large, accuracy should be secured by procedures such as
repeating the dilution procedure.
(2) Set according to the specification and operation method of the measurement instrumentused. There is no need to include the minimum and the maximum values of thecalibration curb range described in the Testing Methods for Fertilizers.
3Testing Methods for Fertilizers(2021)

(3)
a)

Water
Water: Water used in the Testing Methods for Fertilizers herein is water of A2 specified in JIS
K 0557 or water that is confirmed not to affect a quantitation value. However, when otherwise
specified in respective test items, use the specified water.

(4)a)

Reagents
Reagents: When the reagent is JIS-specified, use one of highest quality among those marked
with the JIS symbol; when none of the reagent is marked with the JIS symbol, use one of qualitythat will not cause a problem in the test. Use reference materials for volumetric analysis
specified in JIS K 8005 for the standardization of titration solutions. Note that ethanol (95)
specified in JIS K 8102 to prepare indicators, etc. can be replaced with ethanol (99.5) specified
in JIS K 8101 and ethanol-water (19+1) prepared with water.
b) Reference materials: The preparation of standard solutions or standardization of titration
solutions using reference materials 1) - 2) below other than materials specified in respective
testing items is possible.
1) Reference materials provided by National Metrology Institute: Reference materials
traceable to International System of Unit (SI) provided by National Metrology Institute (NMI:
National Institute of Advanced Industrial Science and Technology NMIJ, NIST, BAM, etc.)
which signed CIPM MRA (Global Mutual Recognition Arrangement based on the Meter
Convention)2) Reference materials for volumetric analysis: Reference materials for volumetric analysis
specified in JIS K 8005.
c) Standard Solutions: In the cases of specifying in the comment in respective testing items, thepreparation of standard solutions for a calibration curve using the solution which is traceable to
the National Metrology of 1) - 3) below other than specified in respective testing items ispossible. However, use standard solutions which do not cause a problem in the test with thekinds and concentration of chemical compounds or added acid used. In addition, in (2.1) a)
Main components or major components, calculate main components or major components
using conversion factors specified in the comment of respective items.
1) Standard Solutions provided by National Metrology Institute: Standard solutions traceable
to International System of Unit provided by National Metrology Institute (NMI: National
Institute of Advanced Industrial Science and Technology NMIJ, NIST, BAM, etc.) which signed
CIPM MRA.
2) JCSS (Japan Calibration Service System) Standard Solutions: Standard solutions preparedby JCSS (Japan Calibration Service System) the registered provider for Chemical Analysis,
Atomic Absorption Spectrometry, ICP or Ion Chromatography traceable to specific referencematerials based on Measurement Act Article 134. In addition, it is recommended to use standard
solutions which indicate the uncertainty of concentration and factors.
3) Standard Solutions traceable to National Metrology: Standard Solutions traceable to
National Metrology (National Institute of Advanced Industrial Science and Technology NMIJ,NIST, BAM reference materials, etc. traceable to International System of Unit) provided by
National Metrology Institutes which signed CIPM MRA, but at the same time they are standard
solutions for Chemical Analysis, Atomic Absorption Spectrometry, ICP or Ion Chromatography
prepared by the providers who obtained the certification of ISO Guide 34(JIS Q 0034：
General requirements for the competence of reference material producers). In addition, it isrecommended to use standard solutions which indicate the uncertainty of concentration andfactors.
d) Titrant: A Titrant described in 1) is usable if it is specified in the comment of a testing item. In
4

Testing Methods for Fertilizers(2021)

addition, the titrant may be diluted to a predetermined concentration as necessary. In this case,however, dilution treatment should be conducted when it is used and factors of the titrant before
dilution should be applied.
1) Titrant conforming to ISO/IEC 17025: A Titrant which is prepared and standardized andwhose factors are calculated by a laboratory which obtained an accreditation (accredited range:
JIS K 8001 JA.5 solutions for titration) based on ISO/IEC 17205. In addition, it is recommended
to use titrant which indicates the uncertainty of concentration and factors.
e) Concentration of reagent solution: Unless otherwise specified, the mass concentration isexpressed as g/L or mg/L, while the molar concentration is expressed as mol/L or mmol/L. The
concentration of the standard solution is expressed as the mass in 1 mL (mg/mL, µg/mL or
ng/mL) except for the ion-selective electrode method.
f) Concentration in parenthesis shown after the name of reagent solution: It indicates that thesolution is about that concentration except the standard solution. For example, sodiumhydroxide solution (0.1 mol/L) means that it is about 0.1 mol/L sodium hydroxide solution.
Also, the concentration shown in front of the name of solution means that it is the accurate
concentration. However, the concentration is generally expressed as a round figure; calculate
the factor separately.
(5) Apparatusa) Glass apparatus: Unless otherwise specified, use glass apparatus specified in JIS R 3503 andJIS R 3505. Also, when a heating procedure is involved, use borosilicate glass-1 specified in
JIS R 3503.
b) Non-glass apparatus: Unless otherwise specified, use plastic apparatus.
c) Desiccants for desiccators: Unless otherwise specified, use silica gel.
d) Porcelain crucibles and porcelain evaporating dishes: Use ones specified in JIS R 1301 andJIS R 1302.
e) Platinum crucibles and platinum evaporating dishes: Use ones specified in JIS H 6201 andJIS H 6202.
f) Filter paper: Use that specified in JIS P 3801. However, the type of filter paper is specified in
respective test items.
g) Absorbance measurement (absorptiometric analysis) absorbance cells: Unless otherwise
specified, use ones of 10 mm in optical path length.

5

Testing Methods for Fertilizers(2021)

1.2

Validity check of testing methods

The Testing Methods for Fertilizers are methods which have been discussed and approved by the TechnicalCommittee for Fertilizers etc. or include some methods in the Official Methods of Analysis of Fertilizers (1992)
whose performance has been evaluated and style was rewritten according to the Testing Methods for Fertilizers.
The Testing Methods for Fertilizers will be revised by adding, modifying, or deleting testing methods with theapproval of the Technical Committee for Fertilizers etc. due to the needs such as progress in analyticaltechniques and changing social situation.
The procedure for the testing methods validity check is shown in Annex A of this Testing Methods for
Fertilizers. This procedure was made based on 7.2.2 Validation of methods in JIS Q 17025 “General
requirements for the competence of testing and calibration laboratories” or 2.4 Tests for validation
requirements in “Guidelines for the design and implementation of surveillance and monitoring and for theevaluation and publication of the results” which was issued by the Ministry of Agriculture, Forestry and
Fisheries and with reference to the guideline of Codex Alimentarius Commission (CAC), IUPAC protocol andthe guideline of AOAC INTERNATIONAL, etc. Validated testing methods are methods which are conductedaccording to this procedure and confirmed to conform to the standards such as required accuracy (trueness andprecision), quantification range (maximum and minimum limits of quantification) and so on.
In addition, according to the validation levels in Table 1, an individual testing method is classified from TypeA to Type E in Table 2.
Table 1
Symbol of Validation, etc.
Def-M (Defining method)
Def-C (Defining calculation)
Def-E (Defining extraction)
HCV (Harmonized collaborative
validation)
MLV(Multi laboratory validation)
SLV (Single laboratory validation)
RNV (Research non validated)
Table 2

Testing method validation level
Validation method, etc.
Procedures of a testing method define measurement items. No
relation to a validation level.
Only calculation methods in a testing method define measurement
items. The part of the definition has no relation to a validation level.
Only extraction procedures in a testing method define measurement
items. The part of the definition has no relation to a validation level.
Evaluation by a collaboration test using samples of no less than 5concentrations in no less than 8 laboratories with a testing method
validation method regarded as an international standard (Guideline of
AOAC-International, IUPAC protocol, etc.).
Evaluation of validation using multiple laboratories, though it does notsatisfy MLV (H) criteria.
Evaluation in a single laboratory using a testing method validation
method regarded as an international standard (IUPAC/ISO/AOACInternational harmonized guideline, etc.).
A testing method that does not carry out the validation by SLV or
higher level.

Classification of an individual testing method

Symbol of
Validation level
Classification
Type A A defined testing method
A testing method whose evaluation results by HCV and SLV satisfies the requirements ofType B"Appendix: The procedure to validate characteristics of testing methods".
A testing method whose evaluation results by MLV and SLV satisfies the requirements ofType C"Appendix: The procedure to validate characteristics of testing methods".
A testing method whose evaluation results by SLV satisfies the requirements of "Appendix: The
Type D
procedure to validate characteristics of testing methods".
Type EA testing method that does not carry out the validation by SLV or higher level.

6

Testing Methods for Fertilizers(2021)

1.3 Procedure of testing methods
1.3.1 Competence evaluation of laboratory
When an individual testing method is used, it is recommended that the following competence
evaluation of a laboratory is conducted.
As for the testing methods of Type A, Type B and Type C, conduct a replicate testing with fivesamples, whose measured component concentration is known and to which certified referencematerials or standard solutions are added, to confirm trueness and precision in advance. As for thetesting methods of Type D and Type E, conduct a validity check in a single laboratory anew.
In order to ensure the reliability of a series of testing, conduct internal quality control (internal
quality assurance control, internal precision control) for each testing by a duplicate testing withsamples, whose measured component concentration is known, to confirm trueness and precision.
If it is possible, participate in an external quality assessment (external precision control,
competence test) in order to evaluate the consistency with testing results of other laboratories andconfirm the evaluation by z score.
1.3.2 Evaluation of test result
The results of a testing method which substitutes for the Testing Methods for Fertilizers can beused if it conforms to criteria required in validation of a testing method. However, in case where theresult of the testing method does not agree with the result of the Testing Methods for Fertilizers (1),the testing result of the latter is used to make a final judgement. In addition, if multiple methods aredescribed for a testing component, it is recommended that the result of a testing method for final
judgement is adopted in the following order: Type A, Type B, Type C, Type D and Type E.
Note (1) Refer to the separate sheet: “Target of trueness and criteria of precision in respective
concentration levels” or “the reproducibility of respective testing methods” in order todetermine if there is mutual agreement.

7Testing Methods for Fertilizers(2021)

2.
Handling of samples
2.1 Sampling
Refer to the “Sampling Method of Fertilizers (2020)”.
References
1)
Incorporated Administrative Agency Food and Agricultural Materials Inspection Center:
Sampling Method of Fertilizers (2020)
2)
JIS M 8100: Particulate materials - General rules for methods of sampling (1992)
3)
JIS K 0060: Sampling method of industrial wastes (1992)
4)
JIS Z 8816: Particulate materials − General requirements for methods of sampling (2001)
5)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p. 12 - 17, Yokendo, Tokyo (1988)

8

Testing Methods for Fertilizers(2021)

2.2 Storage of samples(1) Summary
Put a sample in a container suitable for its characteristics and form and seal it tightly, and then store
the sample at room temperature (10 ºC - 30 ºC) or cold temperature. Care should be taken not tofreeze it when it is stored at cold temperature.
(2) Apparatus and instruments: Apparatus and instruments are shown below.
a) Refrigerator: A refrigerator that can be adjusted to 1 ºC - 8 ºC.
b) Storage container for a sample: A storage container for a sample should be clean, strong andcompletely sealed airtight. In particular, in case it contains sludge for raw materials, thecontainer should be made of non-degradable, non-absorbable material. Additionally, it should
be airtight, water-proof, vapor-proof and non-corrosive.
(3) Procedure: Conduct storage as shown below.
a) Store a relatively stable sample in a tightly sealed container to avoid direct sunlight.
b) Store a sample in a desiccator, etc. by tightly sealing it if test results are affected by moistureabsorption.
c) Store a sample in a tightly sealed container in a dark place at 1 ºC - 8 ºC if it is easily deteriorated
by moisture.

9

Testing Methods for Fertilizers(2021)

2.3
(1)
a)
b)
c)

Preparation of test samples
Summary
Prepare a test sample by pre-drying, reducing, and grinding laboratory samples as necessary.
Conduct pre-drying if a laboratory sample is moist and hard to grind.
A laboratory sample made from such fertilizers as a fluid fertilizer and a particle-fertilizer thatis sufficiently homogeneous can be used as a test sample.
d) If contamination by apparatus affects a test result, procedures such as pre-drying, reduction andgrinding are prohibitede) Note that part of a test sample should not scatter, nor should surrounding fine particles or otheralien substances be mixed with the test sample being prepared10

Testing Methods for Fertilizers(2021)

2.3.1 Pre-drying(1) Summary
This procedure is applicable to fertilizers whose laboratory sample is moist and hard to grind. The
symbol of the procedure is 2.3.1-2017 or PD.-1.
Conduct pre-drying using a drying apparatus, and measure the loss on drying in this procedure. In
addition, calculate a conversion factor (actual article), if necessary, to convert the component content
obtained in respective tests to the component content in a laboratory sample (actual article).
(2)a)

Apparatus and instruments: Apparatus and instruments are shown below.
Drying apparatus:
A drying apparatus that can be adjusted to the pre-drying temperature at± 2 ºC.
b) Sample drying dish: Measure the mass to the order of 0.1g in advance. Additionally, usematerials of a quality that do not affect the measurement of test components.

(3)a)

Procedure: Conduct pre-drying as shown below.
Put 250 g - 1 kg of a laboratory sample in a sample drying dish, spread uniformly and measure
the mass to the order of 0.1g.
b) Place a sample drying dish containing a laboratory sample in a drying apparatus and dry (1).
c) Remove a sample drying dish from a drying apparatus and leave at rest at room temperature
until it is balanced with atmospheric temperature (2).
d) After leaving at rest, measure the mass of c) to the order of 0.1 g.
e) Calculate loss on drying in the pre-drying by the following formula (1). If necessary, calculate
a conversion factor (actual article) by the following formula (2).
Loss on drying (% (mass fraction)) = ((W1 - A)/W1) × 100 ………. (1)Conversion factor (actual article) = A/W1
W1：
A：………… (2)Mass (g) of the sampled laboratory sample
Mass (g) of the laboratory sample after drying

Note (1) Examples of drying temperature and drying time: About 70 hours at 40 ºC, no less than
5 hours at 65 ºC.
(2) An example of time to leave at rest: About 20 minutes
Comment 1 When calculating major components in a laboratory sample (actual article) such ascompost and sludge fertilizers, etc. where the test sample is prepared conducting predrying, convert component contents in the analytical sample obtained in respective
tests by the following formula.
Component content in a laboratory sample (actual article) = B ×C
B： Component content in an analytical sample obtained in each test
C： Conversion factor (actual article)
References
1) Mariko AIZAWA, Yuji SHIRAI, Yasushi SUGIMURA, Yuichi TAKAHASHI, Jun OKI,
Yukio FUKUCHI and Norio HIKICHI: Evaluation of Pre-drying Procedure to Prepare
Test Samples from Sludge Fertilizer, Research Report of Fertilizer Vol. 1, p. 122 - 128(2008)
11

Testing Methods for Fertilizers(2021)(4)

Flow sheet for pre-drying
is shown below.

The flow sheet for the pre-drying of a moist laboratory sample

12

Testing Methods for Fertilizers(2021)

2.3.2
Reduction (Separation)(1) Summary
This procedure is applicable to fertilizers. The symbol of the procedure is 2.3.2-2017 or Red.-1.
In order to distinguish a test sample from a sample for granularity test and physical characteristics
test, etc., reduce (separate) a laboratory sample with an increment reduction method, a riffle sampler
method or a conical quartering method.
(2)a)

Apparatus
Scoop for increment reduction:
A scoop for increment reduction specified in the“Sampling Method of Fertilizers (2020)”.
b) Riffle sampler: A riffle sampler specified in the “Sampling Method of Fertilizers (2020)”.

(3)a)

Procedure: Conduct reduction (separation) as shown below.
Increment reduction method: Refer to the “Sampling Method of Fertilizers (2020)” 4.2 (2)Increment reduction method.
b) Riffle sampler method: Refer to the “Sampling Method of Fertilizers (2020)” 4.2 (3) Riffle
sampler method.
c) Conical quartering method: Refer to the “Sampling Method of Fertilizers (2020)” 4.2 (4)Conical quartering method
References
1)
Incorporated Administrative Agency Food and Agricultural Materials Inspection Center:
Sampling Method of Fertilizers (2020)
2)
JIS M 8100: Particulate materials - General rules for methods of sampling (1992)
3)
JIS K 0060: Sampling method of industrial wastes (1992)
4)
JIS Z 8816: Particulate materials − General requirements for methods of sampling (2001)

13

Testing Methods for Fertilizers(2021)

2.3.3
Grinding(1) Summary
This procedure is applicable to fertilizers. The symbol of the procedure is 2.3.3-2017 or GRD.-1.
In order to prepare a homogeneous test sample, grind a laboratory sample with an adequate grinder
until it completely passes through the designated granularity.
(2)a)

Apparatus and instruments: Apparatus and instruments are shown below.
Grinder: Use a grinder (3) of a type and suitability for the granularity and the physicalcharacteristics (1) of a laboratory sample. In addition, the grinder apparatus which come into
contact with a laboratory sample should be made of materials (2) which do not affect theanalytical value.
b) Primary grinder: A grinder (4) that can primarily grind a large lump.
c) Cutter machine: A cutter that can cut long stems, etc.
d) Sieve: A sieve for the test specified in JIS Z 8801-1 or JIS Z 8801-2 or equivalents.
Note (1) The physical characteristics of a laboratory sample are defined by their solidity,
toughness, specific gravity and adhesiveness.
(2) (Ex.) Do not use stainless steel apparatus when preparing a test sample for chromium or
nickel.
(3) A centrifuging type grinder, a cutting mill, a vibration mill type grinder, etc.
(4) A blender with an attachable blade, etc.

(3) Procedure: Conduct grinding as shown below.
(3.1) Fertilizers except ones specified in (3.2): Conduct as specified in 6.4 of JIS M 8100 and as
shown below.
a) Break or cut a laboratory sample with a primary grinder or a cutting machine as necessary.
b) Grind with a grinding machine until it completely passes through a sieve of 500 µm - 1 mm
aperture.
c) Mix ground samples to make the test sample.
Comment 1 If the sampling amount of an analytical sample is less than 1 g, use a test sample which
will completely pass through 500 µm aperture sieve. In addition, in case a test sample
which suits the aforementioned condition cannot be obtained due to a deliquescentlaboratory sample, etc., make one by crushing a test sample with a mortar and pestle,
which completely passes through 1 mm aperture sieve.
(3.2) Fused phosphate fertilizer, silicate slag fertilizer, etc.: Conduct as specified in 6.4 of JIS M
8100 and as shown below.
a) Grind a laboratory sample with a vibration mill type grinder.
b) Transfer the ground laboratory sample to a sieve of 212 µm apertures.
c) Incline the sieve about 20 degrees, supporting it with one hand or a bent arm, and tap the sieveframe with the other hand at the rate of about 120 times per minute. During the procedure, place
the sieve in a horizontal position at the rate of 4 times per minute, rotate it 90 degrees and tap
the sieve frame firmly one or two times.
d) When fine powder attaches to the back side of a sieve screen, remove it gently from the backside to make minus sieve.
e) Regarding the plus sieve of a sample, make them pass through by repeating the procedure in a)- d).
f) Combine and mix the sample passed to make the test sample.
14

Testing Methods for Fertilizers(2021)

Comment 2 Conduct the procedures in (3.2) to obtain observed value of citric acid-soluble main
components in a stable manner. For examples of applicable laboratory samples, fusedmatters such as fused phosphate and silicate slag fertilizer, fertilizers made from fusedmaterials and calcined phosphate fertilizer, etc. are listed.
Comment 3 The procedures in b) - d) are the procedures in 6.1.3 (1.4) of JIS Z 8815.
References
1)
JIS Z 8801-1: Test sieves - Part 1: Test sieves of metal wire cloth (2019)
2)
JIS Z 8801-2: Test sieves - Part 2: Test sieves of metal wire cloth (2020)
3)
JIS M 8100: Particulate materials - General rules for methods of sampling (1992)

15

Testing Methods for Fertilizers(2021)

3.
General tests
3.1 Moisture or moisture content
3.1.a Loss on drying method with drying apparatus(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type A (Def-M)
and its symbol is 3.1.a-2017 or Mois.a-1.
Use drying apparatus under conditions suitable for the kind of fertilizers to be measured to heatanalytical samples to measure loss on drying and obtain moisture in an analytical sample or the
moisture content of a quality labeling standard of a special fertilizer (herein after referred to as“moisture”). Additionally, calculate a conversion factor (drying matter) to convert component content
obtained by respective tests to component content in a drying matter as necessary.
This testing method corresponds to loss on heating in the Official Methods of Analysis of Fertilizers(1992).
(2) Apparatus and instruments: Apparatus and instruments are shown below.
a) Drying apparatus: Drying apparatus that can be adjusted to the test temperature ± 2 ºC.
b) Ground-in stoppered weighing bottles (1): Low-form weighing bottles, 50 mm × 30 mm,
specified in JIS R 3503. Dry by heating in advance in a drying apparatus at 75 ºC - 130 ºC,
stand to cool in a desiccator, and measure the mass to the order of 1 mg.
Note (1) Aluminum weighing dishes described in the Handbook of the Feed Analysis Standards-2009- can also be used.
(3)a)

Measurement: Conduct measurement as shown below.
Put 2 g-5 g of an analytical sample in a ground-in stoppered weighing bottle, spread so that the
thickness is no more than 10 mm, and measure the mass to the order of 1 mg.
b) Place the ground-in stoppered weighing bottle containing the analytical sample in a drying
apparatus at 100 ºC ± 2 ºC, and heat for 5 hours (2).
c) After heating, fit the stopper into the ground-in stoppered weighing bottle, and immediately
move to a desiccator to let it stand to cool.
d) After standing to cool, remove the ground-in stoppered weighing bottle from the desiccator,and measure the mass to the order of 1 mg.
e) Calculate loss on drying in the analytical sample by the following formula (1) as moisture. If
necessary, calculate a conversion factor (actual article) by the following formula (2).
Loss on drying (% (mass fraction)) = ((W1 - A)/W1) × 100 ………. (1)Conversion factor (drying matter) = W1/A………………………… (2)W1： Mass (g) of the sampled analytical sample
A： Mass (g) of the analytical sample after drying
Note (2) Heat simultaneously the slightly moved or removed stopper of the ground-in stoppered
weighing bottle.
Comment 1 When pre-drying a laboratory sample such as compost and sludge fertilizers to
prepare a test sample, calculate the moisture of the laboratory sample (actual article)
by the following formula:

16

Testing Methods for Fertilizers(2021)

Moisture (% (mass fraction)) in the laboratory sample (actual article) = B + C × ((100 B)/100)
B： Loss on drying (% (mass fraction)) of the laboratory sample (actual article) by the
pre-drying procedure
C： Loss on drying (% (mass fraction)) in the analytical sample by moisture measurement
Comment 2 When calculating harmful content in a drying matter of sludge fertilizers, etc.,
convert component content in a test sample obtained from respective tests by thefollowing formula.
Component content in a drying matter = D ×E
D： Component content in an analytical sample obtained in each test
E： Conversion factor (drying matter)
Comment 3 Use drying conditions in Table 1 for fertilizers of the types shown below:
Table 1
Type of fertilizers
Superphosphate of lime, triple
superphosphate of lime, or fertilizer
containing theseAmmonium sulfate, sodium nitrate, andpotassium salts
Urea and urea-containing fertilizer
Silica gel fertilizer and fertilizer
containing silica gel, and silica hydrogel
fertilizer

Drying conditions
Sampling
amount ofDryinganalyticaltemperaturesamples
About 5 g

100 ºC ± 2 ºC

Drying time

3 hours

About 5 g

Until a constant
130 ºC ± 2 ºC
weight isachieved.
75 ºC ± 2 ºC
4 hours

About 5 g

180 °C±5 °C

2 g- 5 g

3 hours

Comment 4 For samples containing volatile matters, subtract the volatile matter content by thefollowing a) and b) from loss on drying to obtain moisture.
a) Fertilizers containing guano or diammonium hydrogen phosphate, etc.: Determine
total nitrogen in the test sample, and in the analytical sample after the drying
procedure; convert the difference between the quantitation values into ammonia (NH3)to make the volatile matter content.
b) Potassium hydrogen carbonate: Determine carbon dioxide in the test sample, and in
the analytical sample after the drying procedure; the difference between thequantitation values is the volatile matter content.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p. 20 - 23, Yokendo, Tokyo (1988)
2)
Society for the Study of Feed Analysis Standards: Methods of Analysis of Feeds and17

Testing Methods for Fertilizers(2021)

3)(4)Feed Additives-2009-I, p. 37 - 39, Incorporated Administrative Agency Food andAgricultural Materials Inspection Center, Saitama (2009)
JIS Z 0701： Silica gel desiccants for packaging (1997)

Flow sheet for moisture: The flow sheet for moisture in fertilizers is shown below:

18

Testing Methods for Fertilizers(2021)

3.1.b Loss on drying method by moisture analyzers(1) Summary
The testing method is applicable to sludge fertilizers, compost, and organic fertilizers, etc. This
testing method is classified as Type B and its symbol is 3.1.b-2017 or Mois.b-1.
Use a moisture analyzer in the heat drying method to measure loss on drying and obtain moisturein an analytical sample or the moisture content of a quality labeling standard of a special fertilizer(herein after referred to as “moisture”). Additionally, calculate a conversion factor (drying matter) toconvert component content obtained by respective tests to component content in a drying matter asnecessary.
In addition, the performance of this testing method is shown in Comment 3.
(2)a)

Instruments: Instruments are as shown below:
Moisture analyzer: A moisture analyzer consisted of a heat source to heat an analyticalsample (halogen lamp, infrared heater, ceramic heater, etc.) and a balance (1) with calibration
function.

Note (1) There is a method to calibrate with calibration weights or a method to calibrate
automatically with built-in weights.
(3)

a)
b)
c)
d)

Measurement: Conduct measurement as shown below. However, conduct in advance acomparative test with 3.1.a Loss on drying with drying apparatus using sludge fertilizers,
compost, and organic fertilizers, etc., to confirm that there is no difference in the quantitation
value of moisture.
Put about 5 g of an analytical sample in a ground-in stoppered weighing bottle, spread so thatthe thickness is no more than 10 mm, and measure the mass to the order of 1 mg.
Heat at 100 ºC (2), until a constant weight is achieved.
After the end of heating (2), measure the mass to the order of 1 mg.
Calculate loss on drying in the analytical sample by the formula (1) as moisture. If necessary,calculate a conversion factor (drying matter) by the formula (2).
Loss on drying (% (mass fraction)) = ((W1 - A)/W1) × 100
Conversion factor (drying matter) = W1/A…. (1)…. (2)

W1： Mass (g) of the sampled analytical sample
A： Mass (g) of the analytical sample after drying
Note (2)The setup of the drying program and the determination parameter for the end of heating(constant weight) is according to the specification and the operation method of the
moisture analyzer used.

Comment 1 When pre-drying is conducted, calculate the moisture of the laboratory sample (actual
article) by the following formula:
Moisture (% (mass fraction)) in the laboratory sample (actual article) = B + C × ((100 B)/100)
B： Loss on drying (% (mass fraction)) of the laboratory sample (actual article) by the
pre-drying procedure
C： Loss on drying (% (mass fraction)) in the analytical sample by moisture measurement
19Testing Methods for Fertilizers(2021)

Comment 2 When calculating harmful content in a drying matter of sludge fertilizers, etc.,
convert component content in a test sample obtained from respective tests by thefollowing formula.
Component content in a drying matter = D × E
D： Component content in an analytical sample obtained in each test
E： Conversion factor (drying matter)
Comment 3 Table 1 shows the results of the comparison of the measurement values by loss on
drying method with drying apparatus and the measurement values by loss on drying
method with a moisture analyzer using organic fertilizers, compost and sludge
fertilizers in order to evaluate trueness.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 2.

20

Testing Methods for Fertilizers(2021)

References
1)
Takeshi UCHIYAMA and Chiyo SAKASEGAWA: Validation of a Heating Method Usinga Moisture Analyzer for Moisture Content in Sludge Fertilizer. Research Report of
Fertilizer Vol. 1, p. 1- 5 (2008)
2)
Takeshi UCHIYAMA and Yuji SHIRAI: Determination of Moisture Content in Sludge
Fertilizer by a Heating Method Using Moisture Analyzer: A Collaborative Study.
Research Report of Fertilizer Vol. 1, p. 6 - 11 (2008)
3)
Satono AKIMOTO and Sakiko TAKAHASHI: Validation of a Heating Method Using a
Moisture Analyzer for Moisture Content in Sludge Fertilizer. Research Report of
Fertilizer Vol. 2, p. 1 - 5 (2009)(4)

Flow sheet for moisture: The flow sheet for moisture in sludge fertilizers, compost, andorganic fertilizers, etc. is shown below:

21Testing Methods for Fertilizers(2021)

3.2 Ash content
3.2.a Ignition residue method(1) Summary
The method is applicable to organic fertilizers and fertilizers containing organic matters. This testing
method is classified as Type A (Def-M) and its symbol is 3.2.a-2017 or Ash.a-1.
The method ignites an analytical sample with an electric furnace and measures residue on ignition to
obtain ash content in an analytical sample.
(2) Apparatus and instruments: Apparatus and instruments are shown below.
a) Electric furnace: Electric furnace that can be adjusted to 550ºC ± 5 ºC.
b) Crucible: After heating a porcelain crucible for chemical analysis specified in JIS R 1301
with an electric furnace at 550 ºC ± 5 ºC, stand to cool in a desiccator in advance and measure
the mass to the order of 1 mg.
(3)
a)
b)
c)
d)
e)
f)

Measurement: Conduct measurement as shown below.
Put about 2 g of an analytical sample into a crucible, and measure the mass to the order of 1 mg.
Place it into an electric furnace, heat gently until carbonized (1).
Heat at 550 ºC ± 5 ºC for no less than 4 hours (1).
After heating, move the crucible into a desiccator and let it stand to cool.
After standing to cool, remove the crucible from the desiccator and measure the mass to theorder of 1 mg.
Calculate the residue on ignition in the analytical sample by the following formula to make ash
content.
Residue on ignition (% (mass fraction)) = (A/W) × 100
W： Mass (g) of the sampled analytical sample
A： Mass (g) of the ignited analytical sample

Note

(4)

(1)

Example of carbonizing and incineration procedure: After raising the temperaturefrom room temperature to about 250 °C in 30 minutes to 1 hour, continue heating forabout 1 hour and further raise to 550 °C in 1 to 2 hours.

Flow sheet for ash content: The flow sheet for ash content in fertilizers is shown below:

22Testing Methods for Fertilizers(2021)

3.3 pH
3.3.a Glass electrode method(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type A (Def-M)
and its symbol is 3.3.a-2017 or pH.a-1.
Measure the pH of fertilizers with a pH meter using a glass electrode.
(2)a)

Reagent: Reagents are as shown below.
Oxalate pH standard solution: Oxalate pH standard solution class 2 traceable to National
Metrology.
b) Phthalate pH standard solution: Phthalate pH standard solution class 2 traceable to
National Metrology.
c) Neutral phosphate pH standard solution: Neutral phosphate pH standard solution class 2
traceable to National Metrology.
d) Borate pH standard solution: Borate pH standard solution class 2 traceable to National
Metrology.
e) Carbonate pH standard solution:
Carbonate pH standard solution class 2 traceable to
National Metrology.
Comment 1 Respective pH standard solutions stored for long time should not be used since the pH
value may change during storage period. In particular, note that borate pH standard
solution and carbonate pH standard solution easily absorb carbon dioxide in the air, sothat the pH values deteriorate.
The pH standard solution that was used once or left exposed to the air should not be
used.

(3)
a)

Instruments: Instruments are as shown below:
pH meter: Use type II specified in JIS Z 8802.

Comment 2 Conduct the calibration of a pH meter as indicated in JIS Z 8802. Actual calibration
operation is according to the operation procedure of the pH meter used formeasurement.
When the pH of a sample solution is no more than 7, use neutral phosphate pH standard
solution and oxalate pH standard solution, or phthalate pH standard solution. When it
exceeds 7, use neutral phosphate pH standard solution and borate pH standard solution,or carbonate pH standard solution.
(4) Test procedures(4.1) Preparation of sample solution: Conduct preparation of a sample solution as shown below.
(4.1.1) Fertilizers except inorganic fertilizersa) Put a predetermined amount of an analytical sample (1) into a ground-in stopper flask and add
water 5 - 10 times the volume (2).
b) Mix with a magnetic stirrer, filter with Type 3 filter paper to make a sample solution.
Note (1) In the case of a moist laboratory sample, it is recommended to use a sample that is not
pre-dried.
(2) If the sample solution becomes hard to measure because of gelling due to the influenceof flocculants in sludge fertilizer, etc., increase the volume of water to be added.

23

Testing Methods for Fertilizers(2021)(4.1.2) Inorganic fertilizersa) Transfer a predetermined amount of an analytical sample (1) into a ground-in stopper flask andadd water 100 times the volume.
b) Mix with a magnetic stirrer, filter with Type 3 filter paper to make a sample solution.
Comment 3 The procedure in (4.1.1) is the same as 3.4.a (4.1). Additionally, the sample
solution prepared in 4.2.4.a (4.1) can be used instead of the sample solution preparedby (4.1.2).
(4.2) Measurement: Conduct the measurement as indicated in JIS Z 8802 and as shown below. Actual
calibration operation is according to the operation procedure of the pH meter used formeasurement.
a) Wash the read station of a calibrated pH meter repeatedly no less than 3 times with water andwipe out with clean and soft paper, etc.
b) Put a sample solution into a beaker (3), dip the read station in the solution and measure the pH
value.
Note (3) It is necessary to put sufficient volume of sample solution to keep a measurement value
stable.
Comment 4 If a pH meter has a temperature correction dial or a digital switching, measure the pH
value after adjusting the graduation of the pH meter with the temperature of a sample.
References
1)
JIS Z 8802：(5)

Methods for determination of pH of aqueous solutions (2011)

Flow sheet for pH value: The flow sheet for pH value in fertilizers is shown below.

Predetermined volume
Ground-in stopper flask.
of analytical sample← Water 5 -10 times or 100 times the volume
Stirring
Filtration
Measurement

Type 3 filter paper
pH meterFigure Flow sheet for pH in fertilizers.

24Testing Methods for Fertilizers(2021)

3.4 Electrical conductivity
3.4.a Measurement method with an electrical conductivity meter(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type A (Def-M)
and its symbol is 3.4.a-2017 or EC.a-1.
Measure the electrical conductivity of organic fertilizers such as compost or sludge fertilizers with
an electrical conductivity meter.
(2)a)

Reagent: Reagents are as shown below.
Potassium chloride: Grind potassium chloride used for measurement of electrical conductivity
specified in JIS K 8121 with an agate mortar to powder and heat for 4 hours at 500 ºC ± 5 ºC,
and then stand to cool in a desiccator.
b) Potassium chloride standard solution (1): Measure predetermined volume (2) of potassium
chloride of a) on a weighing dish, dissolve in a small amount of water, transfer it into a 1000mL volumetric flask, and add up to the marked line with water.
Note (1) Store potassium chloride standard solution in a polyethylene or borosilicate glass bottle
and seal the bottle.
(2) The volume that is recommended for an instrument or a cell used.
Comment 1 Potassium chloride standard solution used once or left in the air should not be used.

(3)a)

Instruments: Instruments are as shown below:
Electrical conductivity meter: An electrical conductivity meter specified
0130

in

JIS

K

Comment 2 Check the indicated value as shown in 6.2 in JIS K 0130 as necessary. Actual procedure
to check is according to the operation procedure of the electrical conductivity meterused for measurement.
(4) Test procedures(4.1) Preparation of sample solution: Conduct preparation of a sample solution as shown below.
a) Put the predetermined volume of an analytical sample (3) into a ground-in stopper flask and add
water 10 times the equivalent volume of dry matter (4).
b) Mix with a magnetic stirrer, filter with Type 3 filter paper to make a sample solution.
Note (3) In the case of a moist laboratory sample, it is recommended to use a sample that is not
pre-dried.
(4) If the sample solution becomes hard to measure because it is gelled by the influence offlocculants in sludge fertilizer, etc., increase the volume of water added. However, thisfact should be expressed in the test result.
Comment 3 The procedure in (4.1) is the same as 3.3.a (4.1.1).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0130 and as shown below.
Actual measurement operation is according to the operation procedure of the electricalconductivity meter used for measurement.
a) Wash the read station of an electrical conductivity meter repeatedly no less than 3 times withwater.
b) Put a sample solution into a beaker (5), dip the read station and measure electrical conductivity.
25

Testing Methods for Fertilizers(2021)

Note (5) It is necessary to put sufficient volume of sample solution to keep a measurement value
stable.
References
1)
JIS K 0130：General rules for electrical conductivity measuring method (2008)(5)

Flow sheet for electrical conductivity: The flow sheet for electrical conductivity is showed
below.

26

Testing Methods for Fertilizers(2021)

3.5 Granularity
3.5.a Dry-type sieving testing method(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type A (Def-M)
and its symbol is 3.5.a-2017 or P-size.a-1.
Measure the particle diameter distribution of solid fertilizers with a dry-type sieving analysis.
(2) Apparatus: Apparatus are shown below.
a) Sieve: A sieve for testing specified in JIS Z 8815b) Clogging removal brush: A brush which is adequately hard for the apertures and does notdamage the sieving screen.
c) Weighing dish: A container that can contain about 250 g of a sample. Measure the mass tothe order of 0.1g in advance.
(3)

Dry-type sieving analysis procedure: Conduct sieving analysis corresponding to the aperturesize of a sieve used as indicated in JIS Z 8815 and as shown below.
(3.1) More than 1mm and no more than 4mma) Stack a large aperture sieve on an acceptor so that the large sieve is on top.
b) Measure a laboratory sample to the order of 0.1g and put it in the sieve at the top section.
c) After putting a stopper on it, hold the stacked sieves with both hands, and vibrate (1) them backand forth along a unidirectional and horizontal plane at about 60 times per minute with about
70 mm amplitude.
d) Put respective plus and minus sieves in a weighing dish (2).
Note (1) Conduct more circular motion at the rate of about 3 revolutions per minute as necessary.
(2) Turning over the back side of a sieve, remove the clogged particles from the sieve screenwith a clogging removal brush and combine them with the plus sieve.
(3.2) Less than or equal to 1mma) Stack a large aperture sieve on an acceptor so that the large sieve is on top.
b) Measure the laboratory sample or minus sieve of (3.1) c) to the order of 0.1g and put it in thesieve at the top section.
c) After putting a stopper on it, incline the stacked sieves about 20 degrees, supporting with one
hand or a bent arm, and tap the sieve frame with the other hand at the rate of about 120 times
per a minute.
d) During the procedure in c), place the sieve in a horizontal position at the rate of 4 times per
minute, rotate it 90 degrees and tap the sieve frame firmly one or two times.
e) Put respective plus and minus sieves (3) in a weighing dish (2).
Note (3) When fine powder attaches to the back side of a sieve screen, remove them gently fromthe back side with a clogging removal brush and combine them with the minus sieve(4)

Measurement of granularity distribution: Calculate the granularity distribution in ananalytical sample as shown below.
a) Measure respective mass of plus and minus sieves to the order of 0.1g.
b) Calculate “plus sieve percentage” and “minus sieve percentage” with the following formula andround the results to the first decimal place.
c) Confirm that the sum of the mass of the plus sieve and the mass of the minus sieve with thesmallest aperture is in the range of ± 2 % of the mass of sample measured in (3.1) b) or (3.2)b).
27

Testing Methods for Fertilizers(2021)

Mass percentage of plus sieve or minus sieve (%) (R) = (A/T) × 100
A： Mass of plus sieve or minus sieve (g)T： Sum of the mass of plus and minus sieve (g)References
1)
JIS Z 8815： Test sieving - General requirements (1994).
2)
JIS K 0069： testing methods for sieving of chemical products (1992).
(5)

Flow sheet for granularity: The flow sheet of granularity of solid fertilizers is shown below.

Laboratory sample
or Test sample

Measure the mass to the order of 0.1g

Dry-type sieving
Mass measurement ofrespective plus sieveand minus sieve

Measure the mass to the order of 0.1g

Figure Flow sheet for granularity of solid fertilizers

28Testing Methods for Fertilizers(2021)

3.6 Oil content
3.6.a Diethyl ether extraction method(1) Summary
This testing method is applicable to organic fertilizers. This testing method is classified as Type A(Def-M) and its symbol is 3.6.a-2017 or Oil.a-1.
Extract an analytical sample with diethyl ether using a Soxhlet extractor and measure the extract
to obtain oil content in an analytical sample. The oil content contains not only fat but also fat-soluble
pigments (carotenoid, chlorophyll, etc.), wax, and free fatty acids, etc.
(2) Reagent: Reagents are as shown below.
a) Diethyl ether: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Drying apparatus: Drying apparatus that can be adjusted to the test temperature ± 2 ºC.
b) Soxhlet extractor: An inter-changeable Soxhlet extractor, cooling apparatus and weighing
bottles (Example: JIS R 3503, attached figure 71)c) Water bath: A water bath that can be adjusted to about 60 ºCd) Weighing bottle: A flat bottle flask connectable to a Soxhlet extractor. After heating with adrying apparatus at 100 ºC - 105 ºC in advance, stand to cool in a desiccator and measure themass to the order of 1mg.
e) Cylindrical filter paper: A cylindrical filter paper made of cellulose. Example: 22 mm
external diameter, 20 mm internal diameter, 90 mm total length (1).
(4)
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)

Measurement: Conduct measurement as shown below.
Weigh 2 g - 5 g of an analytical sample to the order of 1mg, and put it in a cylindrical filter
paper.
Place absorbent cotton on the upper end of an analytical sample (2), as if gently pushing it, andheat it at 100 ºC - 105 ºC for 2 hours.
As soon as heating is complete, move the cylindrical filter paper to a desiccator and stand to
cool.
After standing to cool, put it in a Soxhlet extractor and connect it to a cooling apparatus.
Put adequate volume of diethyl ether (3) in a weighing bottle, connect it to the Soxhlet extractor
and heat (4) it for 8 hours to extract.
Recover the diethyl ether (5).
Disconnect the weighing bottle from the Soxhlet extractor and vaporize the diethyl ether (6).
Heat the weighing bottle (7) at 100 ºC - 105 ºC for 3 hours.
As soon as heating is complete, move the weighing bottle to the desiccator and stand to cool.
After standing to cool, remove the weighing bottle from the desiccator and measure the mass
to the order of 1mg.
Calculate oil content with the following formula.
Oil content (% (mass fraction)) = (B/A) × 100
A： Mass (g) of the sampled analytical sample
B： Mass of extract of diethyl ether (g)Note (1) Select a scale according to the volume of a Soxhlet extractor.
(2) The purpose is to prevent overflow at the upper end of an analytical sample.
29

Testing Methods for Fertilizers(2021)(3) The amount of diethyl ether depends on the volume of a weighing bottle.
(4) Adjust the temperature for diethyl ether to circulate 16 - 20 times per hour. (Target
temperature is about 60 ºC)(5) Remove the cylindrical filter paper from the Soxhlet extractor. In the case of a cockattached Soxhlet extractor, open the cock and recover it.
(6) It is dangerous if diethyl ether resides in a weighing bottle when the bottle is put in adrying apparatus.
(7) Wipe the outside of a weighing bottle since there is a risk of garbage or stain sticking toit.
References
1)
Japan Oil Chemist ‘Society: Standard Method for the Analysis of Fats, Oils and RelatedMaterials (2003), 1.5 Oil content p. 1 - 2, Incorporated Foundation Japan Oil Chemist‘Society, Tokyo (2009)
2)
Feed Analysis Standard Task Force: Feed Analysis Method/Handbook -2009 - I, p. 37 39, Incorporated Administrative Agency, Food and Agriculture Materials Inspection
Center, Saitama (2009)(5)

Flow sheet for oil content: The flow sheet for oil content in organic fertilizers is shown below:
2 g- 5 ganalytical sample
Pre-drying

Weigh to the order of 1mg to a cylindrical filter paper
100 ºC - 105 ºC, for 2 hours

Soxhlet extractor
Extraction

Diethyl ether, heating, for 8 hours

Weighing bottle
Heating

100 ºC - 105 ºC, for 3 hours

Standing to cool

Desiccator

Measurement

Measure the mass to the order of 1mg

Figure Flow sheet for oil content in organic fertilizers.

30Testing Methods for Fertilizers(2021)

4.
Main components, guaranteed components, etc.
4.1 Nitrogen4.1.1 Total nitrogen4.1.1.a Kjeldahl method(1) Summary
This testing method is applicable to fertilizers containing no nitrate nitrogen. This testing method
is classified as Type C and its symbol is 4.1.1.a-2017 or T-N.a-1.
Add sulfuric acid, potassium sulfate and copper (II) sulfate pentahydrate to an analytical sample,
pretreat by Kjeldahl method to change total nitrogen (T-N) to ammonium ion, and add a sodiumhydroxide solution to subject to steam distillation. Collect isolated ammonia with 0.25 mol/L sulfuric
acid and measure surplus sulfuric acid by (neutralization) titration using a 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution to obtain the total nitrogen (T-N) in an analytical sample. Or collectisolated ammonia with a boric acid solution and measure ammonium ion by (neutralization) titration
using 0.25 mol/L sulfuric acid to obtain the total nitrogen (T-N) in an analytical sample. This testing
method corresponds to the sulfuric acid method in the Official Methods of Analysis of Fertilizers(1992). In addition, the performance of this testing method is shown in Comment 8.
(2)
a)

Reagent: Reagents are as shown below.
0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in a polyethylene
bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding in small
portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mL of thesupernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve ina small amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100
mL of water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture solution,and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the color of the31Testing Methods for Fertilizers(2021)

solution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following formula(1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula (2):Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of 0.25
mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water tomake 1000 mL.
e) Catalyst (5): Mix potassium sulfate specified in JIS K 8962 and copper (II) sulfate pentahydrate(6)specified in JIS K 8983 in the ratio of 9 to 1.
f) Sodium hydroxide solution (200 g/L - 500 g/L) (1):Dissolve 100 g - 250 g of sodiumhydroxide specified in JIS K 8576 in water to make 500 mL.
g) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
i) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in JIS K
8897 in 100 mL of ethanol (95) specified in JIS K 8102.
j) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
k) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green specified in
JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100 mL),
add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid) solution
in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
(5) A tablet is commercially available.
(6) Crush into powder as appropriate.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
32

Testing Methods for Fertilizers(2021)(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Steam distillation apparatusb) Digestion flask: Kjeldahl flaskc) Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.
(4) Test procedures(4.1) Kjeldahl digestion: Conduct digestion as shown below.
a) Weigh 0.5 g - 5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL - 500-mL
digestion flask.
b) Add 5 g - 10 g of catalyst, and further add 20 mL - 40 mL of sulfuric acid, shake to mix (7) andheat gently.
c) After bubbles cease to form, heat until white smoke of sulfuric acid evolves.
d) Ignite until organic matters are completely digested (8).
e) After standing to cool, add a small amount of water, mix well by shaking, transfer to a 250-mL- 500-mL volumetric flask with water (9), and further mix by shaking.
f) After cooling is complete, add water up to the marked line to make a digestion solution.
Note (7) Leaving at rest overnight is preferable.
(8) When the solution has finished changing color, heat further for no less than 2 hours.
(9) When the entire sample solution volume is used in measurement, it is not necessary totransfer it to a volumetric flask.
Comment 3 A digestion solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
Comment 4 In the case of fish meal containing amino acids that are not easily digested, use 0.5 g 1 g analytical sample, 10 g catalyst and 30 mL - 40 mL sulfuric acid.
Comment 5 In the case of nitrolime, moisten by adding a small amount of water before theprocedure in (4.1) b). Care should be taken because bubbles are produced by theaddition of sulfuric acid.
(4.2) Distillation: Conduct distillation as shown below. Specific distillation procedures are according
to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (10) of 0.25 mol/L sulfuric acid in an acceptor (11), add a few dropsof methyl red−methylene blue mixture solution, and connect this acceptor to a steam distillation
apparatus. Or, put a predetermined amount (10) of boric acid solution (40 g/L) in an acceptor (11),add a few drops of methyl red−bromocresol green mixture solution, and connect this acceptor
to a steam distillation apparatus.
b) Put a predetermined amount of the digestion solution in a 300-mL distillation flask, add a properamount of sodium hydroxide solution (200 g/L - 500 g/L) (12), and immediately connect this
distillation flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at a
distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in theacceptor with a small amount of water, and pool the washing with the distillate.
Note (10) 5 mL - 20 mL
33

Testing Methods for Fertilizers(2021)(11) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL beakerwith which the distillate outlet of the steam distillation apparatus can be immersed in
0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(12) An amount sufficient to make the solution strong alkalinity. A blue color will appear.
(4.3) Measurement: Conduct measurement as shown below.
(4.3.1) When 0.25 mol/L sulfuric acid is used in (4.2):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of
the solution becomes gray-green (4).
b) Calculate the total nitrogen (T-N) in the analytical sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (V8/V9) × (14.007/W3) × (100/1000)= (B × V6 － V7) × C1 × f1 × (V8/V9) × (1.4007/W3)
B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V8： Constant volume (mL) of the digestion solution in (4.1) f)
V9： Aliquot volume (mL) of the digestion solution subjected to distillation in (4.2)b)
W3： Mass (g) of the analytical sample(4.3.2) When a boric acid solution (40 g/L) is used in (4.2):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (13).
b) Calculate the total nitrogen (T-N) in the analytical sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (V11/V12) × (14.007/W2) × (100/1000)= V10 × C2 × 2 × f2 × (V11/V12) × (2.8014/W2)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV11： Constant volume (mL) of the digestion solution in (4.1) f)
V12： Aliquot volume (mL) of the digestion solution subjected to distillation in (4.2)b)
W2： Mass (g) of the analytical sample
Note (13) The endpoint is reached when the color changes from green to light red.
Comment 6 The titration procedures in (2) a) Standardization, (2) c) Standardization and (4.3)
can be conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.
34

Testing Methods for Fertilizers(2021)

Comment 7 The nitrogen content in the analytical sample can be measured by using an automatic
nitrogen analyzer (Kjeldahl digestion method) instead of the test procedure in (4). The
setup of the program and the parameter of the analyzer as well as vessels etc. areaccording to the specification and the operation method of the automatic nitrogen
analyzer used. However, conduct in advance a comparative test with the test procedurein (4) using fertilizers containing no nitrate nitrogen, to confirm that there is nodifference in the quantitation value of total nitrogen.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 98.5 % - 100.6 %and 97.1%-99.2 % as total nitrogen (T-N) respectively.
The results of the collaborative study (limited to reported values with the Kjeldahl
method) to determine a certified reference material fertilizer were analyzed by using athree-level nesting analysis of variance. Table 1 shows the calculation results ofreproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 % (mass fraction) for solid fertilizers and about 0.02 % (mass fraction)
for fluid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p. 27 - 31, Yokendo, Tokyo (1988)
2)
Feed Analysis Standard Task Force: Feed Analysis Method/Handbook -2009 - I, p. 28 33, Incorporated Administrative Agency, Food and Agriculture Materials Inspection
Center, Saitama (2009)3)
Takashi KUBOTA, Tomoko OSHIDA, Kozue YANAI, Yuzuru INOUE, Seiji MATSUI,Takaharu MATSUMOTO, Eiichi ISHIKURO and Akemi YASUI: Improvement of theConditions for the Determination of Total Nitrogen in Fish Meal in Kjeldahl Method and
Its Comparison with Dumas Method, Bunsekikagaku, 60, p. 67 - 74 (2011)
4)
Kimie KATO, Masaki CHIDA and Erina WATANABE: Verification of Performance
Characteristics of Testing Method for Total Nitrogen Content in Fertilizer by Kjeldahl
method, Research Report of Fertilizer, Vol. 5, p. 156 - 166 (2012)35

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total nitrogen: The flow sheet for total nitrogen in fertilizers is shown below:

36Testing Methods for Fertilizers(2021)

4.1.1.b Combustion method(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 4.1.1.b-2017 or T-N.b-1.
Thermally decompose nitrogen compounds in an analytical sample using a total nitrogen analyzer by
the combustion method to produce nitrogen gas and nitroxide gas. Reduce the nitroxide gas tonitrogen, and measure the nitrogen gas content with a thermal conductivity detector to obtain the total
nitrogen (T-N) in an analytical sample. This testing method is also referred to as a modified Dumas’
method. In addition, the performance of this testing method is shown in Comment 4.
(2)a)

Instruments: Instruments are as shown below:
Total nitrogen analyzer by the combustion method: A total nitrogen analyzer configuredon the basis of the principle of the combustion method (modified Dumas’ method).
1) Turn on the total nitrogen analyzer by the combustion method (1), and adjust so that stableindicated values can be obtained.
(i) Combustion gas: Oxygen having purity no less than 99.99 % (volume percentage)(ii) Carrier gas: Helium having purity no less than 99.99 % (volume percentage)(3)

Measurement: Conduct measurement as shown below. However, confirm in advance using
an analytical sample that there is no difference from the measured value of total nitrogenobtained according to 4.1.1.a, 4.1.1.c, 4.1.1.d or 4.1.1.e.
a) Measurement conditions for the total nitrogen analyzer by the combustion method: Set up
the measurement conditions for the total nitrogen analyzer considering the following:
Combustion temperature: No less than 870 ºCb) Calibration curve preparation
1) Turn on the total nitrogen analyzer by the combustion method (1), and adjust so that stableindicated values can be obtained.
2) Weigh a predetermined amount of the standard for calibration curves (2) to the order of 0.1 mg
into a combustion vessel.
3) Insert the combustion vessel into the total nitrogen analyzer by the combustion method, andread the indicated value.
4) Conduct the procedure in 3) for another combustion vessel for a blank test, and read theindicated value.
5) Prepare a curve for the relationship between the nitrogen content and the indicated value of thestandard for calibration curves and the blank test for calibration curves.
c) Sample measurement
1) Weigh a predetermined amount of an analytical sample (3) to the order of 0.1 mg into a
combustion vessel.
2) Insert the combustion vessel containing the analytical sample to the total nitrogen analyzer by
the combustion method, and read the indicated value.
3) Obtain the nitrogen content from the calibration curve, and calculate total nitrogen in theanalytical sample.
Note (1) The setup of the program and the parameter of the analyzer are according to thespecification and the operation method of the total nitrogen analyzer by the combustion
method used.
(2) Standard for calibration curves: DL-Aspartic acid (purity no less than 99 % (massfraction)), EDTA (purity no less than 99 % (mass fraction)), hippuric acid (purity no lessthan 98 % (mass fraction)) or other reagents having equivalent purity recommended by
the total nitrogen analyzer by the combustion method used.
37

Testing Methods for Fertilizers(2021)(3) The sampling amount of an analytical sample is as shown in Table 1. In addition, set the
sampling amount of an analytical sample upon consideration of the estimated content of
total nitrogen in the test sample and the measurement range of the total nitrogen analyzer
by the combustion method.
Comment 1 Sample an analytical sample from a test sample prepared in 2.3.3 Grinding (3.1) bygrinding with a mill until it completely passes through a sieve of 500 µm aperture orfrom a test sample prepared in 2.3.3 Grinding Comment 1.

Comment 2 Compound fertilizers, designated blended fertilizers and nitrolime may have highcontents of phosphoric acid (P2O5), alkali metals (Na, K), alkaline earth metals (Ca,Mg), etc., causing contamination of packing or damage in quartz parts, etc. To avoid
their influences, it is recommended to add tungsten oxide (elemental analysis reagent
or heat-treated reagent) to completely cover the analytical sample.
Comment 3 When a sample with a low content of organic compounds, such as compound fertilizers
and designated blended fertilizers etc., and thus with low combustion efficiency ismeasured, it is recommended to add sucrose to the analytical sample so that the carbon
content will be comparable to the standard for calibration curves. Additionally, confirm
in advance that sucrose to be used has a nitrogen content that does not affect themeasured value of total nitrogen of the analytical sample.
Comment 4 Table 2, in order to evaluate trueness, shows the results of the comparison of
measurement values by the Combustion method and the Kjeldahl method with sludge
fertilizers, organic fertilizers, and inorganic fertilizers, etc.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 3.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 % (mass fraction) for fluid fertilizers for home gardening and about
0.05 % (mass fraction) for the other fertilizers.

38Testing Methods for Fertilizers(2021)

References
1)
Mariko AIZAWA, Yasushi SUGIMURA, Yuichi TAKAHASHI, Jun OKI, Yukio
FUKUCHI, Yuji SHIRAI and Norio HIKICHI: Validation of a Combustion Method for
Determination of Total Nitrogen Content in Sludge Fertilizer. Research Report of
Fertilizer Vol. 1, p. 12 - 17, (2008)
2)
Mariko AIZAWA and Yuji SHIRAI: Determination of Total Nitrogen content in Sludge
39Testing Methods for Fertilizers(2021)

3)
4)
5)
6)
(4)

Fertilizer by a Combustion Method: A Collaborative Study. Research Report of Fertilizer
Vol. 1, p. 18 - 24, (2008)
Mariko AIZAWA and Yuji SHIRAI: Validation of a Combustion Method for
Determination of Total Nitrogen Content in Organic Fertilizer. Research Report of
Fertilizer Vol. 2, p. 6 - 11, (2009)
Mariko AIZAWA and Yuji SHIRAI: Validation of a Combustion Method for
Determination of Total Nitrogen Content in Inorganic Fertilizer. Research Report of
Fertilizer Vol. 3, p. 1 - 10, (2010)
Mariko AIZAWA, Yuko SEKINE and Yuji SHIRAI: Determination of Total Nitrogen
Content in Fertilizer by a Combustion Method: A Collaborative Study. Research Reportof Fertilizer Vol. 3, p. 11 - 18, (2010)
Kazumi UCHIYAMA and Yoshio MAEBASHI: Effective Analysis of Organic Trace
Element, p. 99, Mimizuku-sha, Tokyo (2008)

Flow sheet for total nitrogen: The flow sheet for total nitrogen in fertilizers is shown below:

40Testing Methods for Fertilizers(2021)

Reference: Chromatograms of the standard for calibration curves and an analytical sample areshown below:

1)Standard for calibration curves (DL-aspartic acid)2)

Analytical sample (sludge fertilizer)

Reference figures:

Chromatograms of total nitrogen.

Measurement conditions for total nitrogen analyzer by the combustion method
Combustion gas: Highly pure oxygen, purity no less than 99.9999 % (volume
fraction), flow rate 200 mL/min
Carrier gas: Highly pure helium, purity no less than 99.9999 % (volume fraction),flow rate 80 mL/min
Separation column: A silica gel stainless column (1m)
Detector: Thermal conductivity detector (TCD)
Measurement cycle: Purge time = 60 seconds, circulation combustion time = 200
seconds, measurement time = 100 seconds
Current value of Detector: 160 mA
Temperature conditions: Reaction furnace temperature: 870 ºC
Reaction furnace temperature: 600 °C
Column oven temperature: 70 °C
Detector temperature: 100 °C
41

Testing Methods for Fertilizers(2021)

4.1.1.c Devarda’s alloy – Kjeldahl method(1) Summary
The method is applicable to the fertilizers that contain nitrate nitrogen (N-N) and guarantee total
nitrogen. This testing method is classified as Type E and its symbol is 4.1.1.c-2017 or T-N.c-1.
Add hydrochloric acid (1+1) and tin (II) chloride dihydrate to an analytical sample and further add
devarda’s alloy to reduce nitrate nitrogen (N-N), and then add sulfuric acid (1+1), pretreat by Kjeldahl
method to change total nitrogen (T-N) to ammonium ion and add sodium hydroxide to subject tosteam distillation. Collect isolated ammonia with 0.25 mol/L sulfuric acid and measure surplus
sulfuric acid by (neutralization) titration using a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to
obtain the total nitrogen (T-N) in an analytical sample. Or collect isolated ammonia with a boric acidsolution and measure ammonium ion by (neutralization) titration using 0.25 mol/L sulfuric acid toobtain the total nitrogen (T-N) in an analytical sample. This testing method corresponds to thedevarda’s alloy - sulfuric acid method in the Official Methods of Analysis of Fertilizers (1992).
(2)a)

Reagent: Reagents are as shown below.
0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in JIS
K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, then put about
2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve in a small amountof water, transfer to a 250-mL volumetric flask, and add water up to the marked line (1). Put apredetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask, add a few dropsof bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate with a 0.1 mol/L - 0.2
mol/L sodium hydroxide solution until the color of the solution becomes green. Calculate thefactor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by the following formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100 mLof water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL - 300mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture solution, and titratewith a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following formula (1). Or, calculate thefactor of 0.25 mol/L sulfuric acid by the following formula (2):42Testing Methods for Fertilizers(2021)

Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of 0.25
mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water tomake 1000 mL.
e) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
f) Tin (II) chloride dihydrate: A JIS Guaranteed Reagent specified in JIS K 8136 or a reagentof mercury analysis grade or equivalent quality.
g) Devarda’s alloy: A reagent of nitrogen analysis grade specified in JIS K 8653 or a reagent ofequivalent quality.
h) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodium hydroxide
specified in JIS K 8576 in water to make 500 mL.
i) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
j) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
k) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in JIS K
8897 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
m) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green specified in
JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
n) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100 mL),
add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid) solution
in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
(3)
a)
b)
c)

Apparatus and instruments: Apparatus and instruments are shown below.
Steam distillation apparatus
Digestion flask: Kjeldahl flask
Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.

43

Testing Methods for Fertilizers(2021)

Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
(4) Test procedures(4.1) Reduction and Kjeldahl digestion: Conduct reduction and digestion as shown below:a) Weigh 0.5 g - 1 g (no more than the equivalents of N-N 50 mg) of an analytical sample to theorder of 1 mg, and put it in a 300-mL- 500-mL digestion flask (5)b) Add 60 mL of hydrochloric acid (1+1) and 2 g of tin (II) chloride dihydrate, and shake to mix
and leave at rest for about 20 minutes.
c) Add 3.5 g of devarda’s alloy and leave at rest for about 40 minutes while sometimes shaking tomix.
d) Add 70 mL of sulfuric acid (1+1) and one boiling stone as necessary, and heat at low
temperature (6).
e) As soon as white smoke start evolving, strengthen heating gradually and further continue
heating for about 90 minutes.
f) After standing to cool, add 100 mL - 200 mL of water, mix well by shaking, transfer to a 250mL - 500-mL volumetric flask with water, and further mix by shaking (7).
g) After cooling is complete, add water up to the marked line to make a digestion solution.
Note (5) In the case of direct distillation, a 500-mL Kjeldahl flask connectable to a steam
distillation apparatus is preferable.
(6) If the bubbles foam strongly and excessively, suspend heating for a little while.
(7) When the entire sample solution volume is used in measurement, it is not necessary to
precisely adjust.
(4.2) Distillation: Conduct distillation as shown below. Specific distillation procedures are according
to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (8) of 0.25 mol/L sulfuric acid in an acceptor, (9) add a few drops ofmethyl red−methylene blue mixture solution, and connect this acceptor to a steam distillation
apparatus. Or, put a predetermined amount (8) of boric acid solution (40 g/L) in an acceptor (9),add a few drops of methyl red−bromocresol green mixture solution, and connect this acceptor
to a steam distillation apparatus.
b) Put a predetermined amount of the digestion solution in a 300-mL distillation flask, add a properamount of sodium hydroxide solution (200 g/L - 500 g/L) (10), and connect this distillation flask
to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at a
distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in theacceptor with a small amount of water, and pool the washing with the distillate.
Note (8) 5 mL - 20 mL(9) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL beakerwith which the distillate outlet of the steam distillation apparatus can be immersed in
0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(10) An amount sufficient to make the solution strong alkalinity. A blue color will appear.
44

Testing Methods for Fertilizers(2021)(4.3) Measurement: Conduct measurement as shown below.
(4.3.1) When 0.25 mol/L sulfuric acid is used in (4.2):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of
the solution becomes gray-green (4).
b) Calculate the total nitrogen (T-N) in the analytical sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (V8/V9) × (14.007/W2) × (100/1000)= (B × V6 － V7) × C1 × f1 × (V8/V9) × (1.4007/W2)
B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V8： Constant volume (mL) of the digestion solution in (4.1) g)
V9： Aliquot volume (mL) of the digestion solution subjected to distillation in (4.2)b)
W2： Mass (g) of the analytical sample(4.3.2) When a boric acid solution (40 g/L) is used in (4.2):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (11).
b) Calculate the total nitrogen (T-N) in the analytical sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (V11/V12) × (14.007/W3) × (100/1000)= V10 × C2 × f2 × (V11/V12) × (2.8014/W3)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV11： Constant volume (mL) of the digestion solution in (4.1) g)
V12： Aliquot volume (mL) of the digestion solution subjected to distillation in (4.2)b)
W3： Mass (g) of the analytical sample
Note (11) The endpoint is reached when the color changes from green to light red.
Comment 3 The titration procedures in (2) a) Standardization, (2) c) Standardization and (4.3)
can be conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.31- 33, Yokendo, Tokyo (1988)
45

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total nitrogen: The flow sheet for total nitrogen in fertilizers is shown below:

46

Testing Methods for Fertilizers(2021)

4.1.1.d Reduced iron - Kjeldahl method(1) Summary
The method is applicable to the fertilizers that contain nitrate nitrogen (N-N) and guarantee total
nitrogen. This testing method is classified as Type E and its symbol is 4.1.1.d-2017 or T-N.d-1.
Add water, reduced iron and sulfuric acid (1+1) to an analytical sample to reduce nitrate nitrogen (NN) and heat at low temperature, and then add sulfuric acid and pretreat by Kjeldahl method to change
total nitrogen (T-N) to ammonium ion, and add a sodium hydroxide solution to subject to steam
distillation. Collect isolated ammonia with 0.25 mol/L sulfuric acid and measure surplus sulfuric acidby (neutralization) titration using a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to obtain the
total nitrogen (T-N) in an analytical sample. Or collect isolated ammonia with a boric acid solution
and measure ammonium ion by (neutralization) titration using 0.25 mol/L sulfuric acid to obtain the
total nitrogen (T-N) in an analytical sample. This testing method corresponds to the reduced iron sulfuric acid method in the Official Methods of Analysis of Fertilizers (1992).
(2)a)

Reagent: Reagents are as shown below.
0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Transfer 5.5 mL -11
mL of the supernatant to a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in JIS
K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, then put
about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve in asmall amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100 mLof water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture solution,and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the color of thesolution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following formula(1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula (2):47

Testing Methods for Fertilizers(2021)

Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of 0.25
mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2×2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water tomake 1000 mL.
e) Reduced iron:
Nitrogen content is no more than 0.005 % (mass fraction)(5)f) Catalyst : Mix potassium sulfate specified in JIS K 8962 and copper (II) sulfate pentahydrate(6)specified in JIS K 8983 in the ratio of 9 to 1.
g) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodium hydroxide
specified in JIS K 8576 in water to make 500 mL.
h) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
i) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
j) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in JIS K
8897 in 100 mL of ethanol (95) specified in JIS K 8102.
k) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
l) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green specified in
JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
m) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100mL), add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid) solution
in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
(5) A tablet is commercially available.
(6) Crush into powder as appropriate.
(3)
a)
b)
c)

Instruments: Instruments are as shown below:
Steam distillation apparatus
Digestion flask: Kjeldahl flask
Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.

48

Testing Methods for Fertilizers(2021)

Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
(4) Test procedures(4.1) Reduction and Kjeldahl digestion: Conduct reduction and digestion as shown below:a) Weigh 0.5 g - 1 g of an analytical sample to the order of 1 mg, and put it in a 300-mL - 500-mL
digestion flask.
b) Add 30 mL of water and mix well.
c) As soon as 5 g of reduced iron and 30mL of sulfuric acid (1+1) are added, insert a long stem
funnel to a digestion flask and shake to mix gently while cooling the outside of the container
under flowing water (7).
d) Leave at rest for about 5 minutes (8), boil in a low flame for about 15 minutes.
e) After standing to cool, add 5 g - 10 g of catalyst, 30 mL of sulfuric acid and, if necessary, one
boiling stone, heat gradually until water evaporates and white smoke of sulfuric acid evolves(9).
f) Ignite until it is completely digested (10).
g) After standing to cool, add a small amount of water, mix well by shaking, transfer to a 250-mL- 500-mL volumetric flask with water, and further mix by shaking.
h) After cooling is complete, add water up to the marked line to make a digestion solution.
Note (7) A sudden reaction generates heat, and unreacted nitric acid vaporizes or digests to makenitrogen oxide etc. through which process losses occur easily. Careful and efficient
operation should be taken(8) Until a sudden reaction is settled.
(9) If the bubbles foam strongly and excessively, suspend heating for a little while.
(10) When the solution has finished changing color, heat further for no less than 2 hours.
(4.2) Distillation: Conduct distillation as shown below. Specific distillation procedures are according
to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (11) of 0.25 mol/L sulfuric acid in an acceptor (12), add a few dropsof methyl red−methylene blue mixture solution, and connect this acceptor to a steam distillation
apparatus. Or, put a predetermined amount (11) of boric acid solution (40 g/L) in an acceptor (12),add a few drops of methyl red−bromocresol green mixture solution, and connect this acceptor
to a steam distillation apparatus.
b) Put a predetermined amount of the digestion solution in a 300-mL distillation flask, add a properamount of sodium hydroxide solution (200 g/L - 500 g/L) (13), and connect this distillation flask
to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at a
distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in theacceptor with a small amount of water, and pool the washing with the distillate.
Note (11) 5 mL - 20 mL(12) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL beakerwith which the distillate outlet of the steam distillation apparatus can be immersed in
0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
49

Testing Methods for Fertilizers(2021)(13) An amount sufficient to make the solution strong alkalinity. A blue or reddish-browncolor will appear.
(4.3) Measurement: Conduct measurement as shown below.
(4.3.1) When 0.25 mol/L sulfuric acid is used in (4.2):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of
the solution becomes gray-green (4).
b) Calculate the total nitrogen (T-N) in the analytical sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (V8/V9) × (14.007/W2) × (100/1000)= (B × V6 － V7) × C1 × f1 × (V8/V9) × (1.4007/W2)
B：

Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V8： Constant volume (mL) of the digestion solution in (4.1) h)
V9： Aliquot volume (mL) of the digestion solution subjected to distillation in (4.2)b)
W2： Mass (g) of the analytical sample(4.3.2) When a boric acid solution (40 g/L) is used in (4.2):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (14).
b) Calculate the total nitrogen (T-N) in the analytical sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (V11/V12) × (14.007/W3) × (100/1000)= V10 × C2 × f2 × (V11/V12) × (2.8014/W3)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV11： Constant volume (mL) of the digestion solution in (4.1) h)
V12： Aliquot volume (mL) of the digestion solution subjected to distillation in (4.2)b)
W3： Mass (g) of the analytical sample
Note (14) The endpoint is reached when the color changes from green to light red.
Comment 3 The titration procedures in (2) a) Standardization, (2) c) Standardization and (4.3)
can be conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.
References
50

Testing Methods for Fertilizers(2021)

1)(5)

Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.33- 34, Yokendo, Tokyo (1988)

Flow sheet for total nitrogen: The flow sheet for total nitrogen in fertilizers is shown below:

51

Testing Methods for Fertilizers(2021)

Digestion
Solution
Aliquot
Distillation flask(predetermined volume)← Sodium hydroxide (200 g/L - 500 g/L)
Receiver: 200-mL - 300-mL Erlenmeyer flask or beakerA predetermined amount of 0.25-mol/L sulfuric acid and a few
Steam distillation
drops of methyl red-methylene blue mixture solution, or aapparatus
predetermined amount of boric acid solution (40 g/L), several
drops of methyl red - bromocresol green mixture solution
Steam distillation

Distillation rate: 5 mL/min - 7 mL/min

Stop distilling
120 mL – 160 mL distillate← Water (wash the part of the distillation apparatus
that came in contact with the solution in the receiver)0.1mol/L - 0.2 mol/L sodium hydroxide solution (until the
Titration
solution becomes gray-green), or
0.25 mol/L sulfuric acid (until the solution becomes light red)
Figure 2 Flow sheet for total nitrogen in fertilizers (Distillation and measurement procedure).

52

Testing Methods for Fertilizers(2021)

4.1.1.e Calculation with ammoniacal nitrogen and nitrate nitrogen(1) Summary
This testing method is applicable to the fertilizers that contain ammoniacal nitrogen (A-N) and nitrate
nitrogen (N-N), and that does not contain the fertilizers guaranteeing total nitrogen (T-N). This testing
method is classified as Type A (Def-C) and its symbol is 4.1.1.e-2017 or T-N.e-1.
Calculate total nitrogen (T-N) by adding the ammoniacal nitrogen (A-N) obtained in 4.1.2 to thenitrate nitrogen (N-N) obtained in 4.1.3.
(2) The calculation of total nitrogena) Calculate the total nitrogen (T-N) in the test sample by the following formula:
Total nitrogen (T-N) (% (mass fraction)) in the test sample= (A-N) ＋ (N-N)
A-N： Ammoniacal nitrogen (% (mass fraction)) in the analytical sample (1)obtained by 4.1.2
N-N： Nitrate nitrogen (% (mass fraction)) in the analytical sample (1) obtained by
4.1.3
Note (1) A-N and N-N use raw data without rounding numerical value

53

Testing Methods for Fertilizers(2021)

4.1.2 Ammoniacal nitrogen
4.1.2.a Distillation method(1) Summary
The testing method is applicable to the fertilizers that contain ammonium salt. However, in somecases, it is not applicable to the fertilizers that contain such compounds as nitrolime that digests byheating. This testing method is classified as Type B and its symbol is 4.1.2.a-2021 or A-N.a-2.
Add water to an analytical sample or extract an analytical sample with hydrochloric acid (1+23),
further add magnesium oxide or a sodium hydroxide solution to make the solution alkalinity andsubject it to steam distillation. Collect isolated ammonia with 0.25 mol/L sulfuric acid and measuresurplus sulfuric acid by (neutralization) titration using a 0.1 mol/L - 0.2 mol/L sodium hydroxide
solution to obtain ammoniacal nitrogen (A-N) in an analytical sample. Or collect isolated ammonia
with a boric acid solution and measure ammonium ion by (neutralization) titration using 0.25 mol/L
sulfuric acid to obtain ammoniacal nitrogen (A-N) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 7 to Comment 10.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in JIS
K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, then put
about 2.5g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve in asmall amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Magnesium oxide: A JIS Guaranteed Reagent specified in JIS K 8432 or a reagent ofequivalent quality.
c) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
d) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
e) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100 mLof water in advance, stir well, and add water to make 1000 mL.
54

Testing Methods for Fertilizers(2021)

Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL - 300mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture solution, and titratewith a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the color of the solution becomesgray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following formula (1). Or, calculate thefactor of 0.25 mol/L sulfuric acid by the following formula (2):Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of 0.25
mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2×2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf)

Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water tomake 1000 mL.
g) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodium hydroxide
specified in JIS K 8576 in water to make 500 mL.
h) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
i) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
j) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in JIS K
8897 in 100 mL of ethanol (95) specified in JIS K 8102.
k) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
l) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green specified in
JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
m) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100 mL),
add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid) solution
in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) e) can be replaced with 0.25 mol/L sulfuric acid55

Testing Methods for Fertilizers(2021)

conforming to ISO/IEC 17025.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 250-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) Steam distillation apparatusc) Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.
(4) Test procedures(4.1) Sample solution preparation: Prepare a sample solution as shown below:(4.1.1) Addition of watera) Weigh 0.25 g - 2g (5) (the equivalents of 20 mg - 100 mg as N) of an analytical sample to theorder of 1 mg, and put it in a 300-mL - 500-mL distillation flaskb) Add about 25 mL of water to make a sample solution.
(4.1.2) Extraction using a vertical rotating mixera) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumaetricflask.
b) Add about 150 mL of hydrochloric acid (1+23) and mix at a rate of 30 - 40 revolutions/min forabout 30 minutes.
c) Add water to the marked line to make a sample solution.
(4.1.3) Extraction using a vertical reciprocating shakera) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 150 mL of hydrochloric acid (1+23) and mix at a rate of 300 reciprocations/min(amplitude of 40 mm) for about 30 minutes.
c) Add water to the marked line to make a sample solution.
Note (5) The sampling amount of the analytical sample is 5 g when there is less nitrogen content
in the fertilizers such as a home garden-use fertilizer.
Comment 3 When it is a fertilizer which contains ammonium urate, humus acid ammonium or
nitrate nitrogen, etc., or when it is not a fertilizer in which phosphate, ammonium andmagnesium coexist, conduct the procedure in (4.1.1.1) a) - c) in 4.2.4.a, the procedurein (4.1.1.2) a) - c) in 4.2.4.a or the procedure in (4.1.2) a) - c) in 4.2.4.a and put apredetermined amount of suspension (the equivalents of 20 mg - 100 mg as N) in a
300-mL - 500-mL distillation flask to make a sample solution.
(4.2) Distillation: Conduct distillation as shown below. Specific distillation procedures are according
to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (6) of 0.25 mol/L sulfuric acid in an acceptor (7), add a few dropsof methyl red−methylene blue mixture solution, and connect this acceptor to a steam distillation
56

Testing Methods for Fertilizers(2021)

apparatus. Or, put a predetermined amount (6) of boric acid solution (40 g/L) in an acceptor (7),add a few drops of methyl red−bromocresol green mixture solution, and connect this acceptor
to a steam distillation apparatus.
b) Add (9) no less than 2 g of magnesium oxide (8) to the distillation flask containing the sample
solution prepared in (4.1.1), and connect this distillation flask to a steam distillation apparatus.
Or, put a predetermined amount (the equivalents of 20 mg - 100 mg as N) of the sample solution
prepared in (4.1.2) or (4.1.3) in a 300-mL distillation flask, add (9) no less than 5 g of magnesiumoxide (8), and connect this distillation flask to a steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at a
distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in theacceptor with a small amount of water, and pool the washing with the distillate.
Note (6) 5 mL - 20 mL(7) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL beakerwith which the distillate outlet of the steam distillation apparatus can be immersed in
0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(8) An amount sufficient to make the solution strong alkalinity.
(9) Add a small amount of silicone oil as necessary.
Comment 4 When the sample does not contain organic matters or urea, a proper amount of
sodium hydroxide solution (200 g/L - 500 g/L) (8) can be added instead of magnesiumoxide.
(4.3) Measurement: Conduct measurement as shown below.
(4.3.1) When 0.25 mol/L sulfuric acid is used in (4.2):(4.3.1.1) In the case the sample solution was prepared by the procedure in (4.1.1)
a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of
the solution becomes gray-green (4).
b) Calculate the ammoniacal nitrogen (A-N) in the analytical sample by the following formula:Ammoniacal nitrogen (A-N) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (14.007/W2) × (100/1000)= (B × V6 － V7) × C1 × f1 × (1.4007/W2)
B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
W2： Mass (g) of the analytical sample(4.3.1.2) In the case the sample solution was prepared by the procedure in (4.1.2) or (4.1.3)
a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of
the solution becomes gray-green (4).
57

Testing Methods for Fertilizers(2021)b) Calculate the ammoniacal nitrogen (A-N) in the analytical sample by the following formula:Ammoniacal nitrogen (A-N) (% (mass fraction)) in the analytical sample＝(B×V8－V9)×C1×f1×(250/V10)×(14.007/W3)×(100/1000)＝(B×V8－V9)×C1×f1×(250/V10)×(1.4007/W3)
B： Volume of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution equivalent to 1 mL of
0.25 mol/L sulfuric acidV8： Volume of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V9： Volume (mL) of sodium hydroxide solution needed for titration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f 1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V10： Aliquot volume (mL) of the sample solution subjected to distillation in (4.2) b)
W3： Mass (g) of the analytical sample(4.3.2) When a boric acid solution (40 g/L) is used in (4.2):(4.3.2.1) In the case the sample solution was prepared by the procedure in (4.1.1)
a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (10).
b) Calculate the ammoniacal nitrogen (A-N) in the analytical sample by the following formula:Ammoniacal nitrogen (A-N) (% (mass fraction)) in the analytical sample= V11 × C2 × 2 × f2 × (14.007/W4) × (100/1000)= V11 × C2 × f2 × (2.8014/W4)
V11： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acid
W4： Mass (g) of the analytical sample(4.3.2.2) In the case the sample solution was prepared by the procedure in (4.1.2) or (4.1.3)
a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (10).
b) Calculate the ammoniacal nitrogen (A-N) in the analytical sample by the following formula:Ammoniacal nitrogen (A-N) (% (mass fraction)) in the analytical sample＝V12×C2×2×f2×(250/V13)×(14.007/W5)×(100/1000)＝V12×C2×f2×(250/V13)×(2.8014/W5)
V12： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acid
V13： Aliquot volume (mL) of the sample solution subjected to distillation in (4.2) b)
W5： Mass (g) of the analytical sample
Note (10) The endpoint is reached when the color changes from green to light red.
58

Testing Methods for Fertilizers(2021)

Comment 5 If it is hard to confirm the endpoint due to the carbon dioxide resulting from carbonate
in the extract when magnesium oxide is used, it is recommended to boil the extract
for 1-2 minute(s) after distilling and cool, and then titrate.
Comment 6 The titration procedures in (2) a) Standardization, (2) e) Standardization and (4.3)
can be conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.
Comment 7 Recovery testing was conducted to evaluate trueness of the extraction procedure(4.1.1) using a preparation sample. As a result, the mean recovery rates at the content
level of 10 % (mass fraction) - 21 % (mass fraction) and 1 % (mass fraction) were
100.2 % - 100.8 % and 102.5 % as ammoniacal nitrogen (A-N) respectively.
Comment 8 The comparison of the measurement value (yi: 0.27 % (mass fraction) - 21.34 %(mass fraction)) of the extraction procedure using a vertical rotating mixer (4.1.2)
and the measurement value (xi) of the extraction procedure (4.1.1) was conducted toevaluate trueness of the extraction procedure (4.1.2) and the extraction procedure(4.1.3) using fertilizers (22 samples). As a result, a regression equation was y = 0.188+ 0.990x, and its correlation coefficient (r) was 0.998. In addition, the comparison of
the measurement value (yi) and the measurement value (xi) of 4.1.2.b formaldehyde
method was conducted using fertilizers (13 samples). As a result, a regression
equation was y = −0.255 + 1.041x, and its correlation coefficient (r) was 0.999.
Similarly, the comparison of the measurement value (yi: 0.25 % (mass fraction) 21.44 % (mass fraction)) of the extraction procedure using a vertical reciprocating
shaker (4.1.3) and the measurement value (xi) of the extraction procedure (4.1.1) was
conducted using fertilizers (22 samples). As a result, a regression equation was y =0.193 + 0.990x, and its correlation coefficient (r) was 0.999. Further, the comparisonof the measurement value (yi) and the measurement value (xi) of 4.1.2.bformaldehyde method was conducted. As a result, a regression equation was y =−0.220 + 1.039x, and its correlation coefficient (r) was 0.998.
Comment 9 In order to evaluate precision of the extraction procedure (4.1.1), results from acollaborative study for test method validation and its analysis are shown in Table 1.
Further, the results of the collaborative study (limited to reported values with
Distillation method) to determine a certified reference material fertilizer wereanalyzed by using a three-level nesting analysis of variance. Table 2 shows thecalculation results of reproducibility, intermediate precision and repeatability. In
addition, in order to evaluate precision of the extraction procedure (4.1.2) and theextraction procedure (4.1.3), the results of the repeatability tests on different days
using ammonium sulfate fertilizer, by-product organic fertilizer, compound fertilizer,
magnesium ammonium phosphate, mixed compost compound fertilizer, by-productcompound fertilizer, and composted sludge fertilizer were analyzed by the one-way
analysis of variance. Table 3 shows the calculation results of intermediate precisionand repeatability.
Comment 10 The minimum limit of quantification of the extraction procedure (4.1.1) was
estimated to be about 0.1 % (mass fraction) for solid fertilizers and about 0.01 %(mass fraction) for fluid fertilizers, that of the extraction procedure (4.1.2) was
estimated to be about 0.07 % (mass fraction) for solid fertilizers and about 0.003 %(mass fraction) for fluid fertilizers, and that of the extraction procedure (4.1.3) was
estimated to be about 0.1 % (mass fraction) for solid fertilizers and about 0.005 %(mass fraction) for fluid fertilizers.

59Testing Methods for Fertilizers(2021)

Table 3Analysis results of the repeatability tests on different days of ammoniacal nitrogen
Extraction method

Sample nameT est days of
repeatability(T ) 1)

2)

sr

3)

(%)
0.39

Mean

Ammonium sulfate

5

(%)
20.52

Compound fertilizer

5

8.85

Byproduct organic fertilizer

5

Vertical reciprocating shaker Ammonium sulfate

Vertical rotating mixer

4)
3)

5)

RSD r
(%)

6)

s I(T)

3)

7)

RSD I(T)
(%)

1.9

(%)
0.39

0.05

0.5

0.06

0.7

0.53

0.01

1.4

0.02

4.3

5

20.79

0.15

0.7

0.15

0.7

Compound fertilizer

5

8.70

0.29

3.3

0.29

3.3

Byproduct organic fertilizer

5

0.53

0.02

3.4

0.04

8.4

1) The number of test days conducting a duplicate test

1.95) Repeatability relative standard deviation

2) Mean ([Number of test days (T )] × [Number of duplicate testing (2)]) 6) Intermediate standard deviation
3) Mass fraction7) Intermediate relative standard deviation

4) Repeatability standard deviation

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers
60

Testing Methods for Fertilizers(2021)

2)

3)(Details), p.36- 37, Yokendo, Tokyo (1988)
Kimie KATO, Masaki CHIDA and Erina WATANABE: Verification of Performance
Characteristics of Testing Method for Ammonia Nitrogen Content in Fertilizer byDistillation Method, Research Report of Fertilizer, Vol. 6, p. 130 - 138 (2013)
Erika HIRATA, Hideo SOETA, Hidemi YOSHIMURA and Keiji YAGI: Performance
Evaluation of Determination Method for Nitrogen in Fertilizer: Harmonized
Collaborative Validation, Research Report of Fertilizer, Vol. 12, p. 84 – 93 (2019)(5) Flow sheet for ammoniacal nitrogen: The flow sheet for ammoniacal nitrogen in fertilizers isshown below.
0.25 g - 2 g analyticalsampleWeigh the equivalents of 20 mg - 100 mg as N to the order of 1 mg in
a 300-mL distillation flask← 25 mL of water
Sample solution
Figure 1-1 Flow sheet for ammoniacal nitrogen in fertilizers (Extraction procedure (4.1.1))

2.5 g analytical sample

Weigh to the order of 1 mg in a 250-mL volumetric flask← About 150 mL of hydrochloric acid (1+23)
Shaking to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Sample solution
Figure 1-2 Flow sheet for ammoniacal nitrogen in fertilizers (Extraction procedure (4.1.2))

2.5 g analytical sample

Weigh to the order of 1 mg in a 250-mL volumetric flask← About 150 mL of hydrochloric acid (1+23)
Shaking to mix

Vertical reciprocating shaker (300 reciprocations/min, amplitude of 40 mm), for 30 minutes← Water (up to the marked line)
Sample solution
Figure 1-3 Flow sheet for ammoniacal nitrogen in fertilizers (Extraction procedure (4.1.3))

61

Testing Methods for Fertilizers(2021)

Sample solution

Sample solution prepared by the extraction procedure in (4.1.1)

Sample solution

Sample solution prepared by the extraction procedure in (4.1.2) or the extraction procedure in (4.1.3)

Aliquot

Equivalents of 20 mg - 100 mg as A, 300-mL distillation flask← No less than 2 g of magnesium oxide in the case of the extraction procedure in (4.1.1)
No less than 5 g of magnesium oxide in the case of the extraction procedure in (4.1.2) or the extraction procedure in (4.1.3)← A small amount of defoaming agent as necessary

Steam distillation
apparatus

Receiver: 200-mL - 300-mL Erlenmeyer flask or beakerA predetermined amount of 0.25-mol/L sulfuric acid and a few dropsof methyl red-methylene blue mixture solution, or a predeterminedamount of boric acid solution (40 g/L), several drops of methyl red bromocresol green mixture solution

Steam distillation

Distillation rate: 5 mL/min～7 mL/min

Stop distilling

120 mL – 160 mL distillate← Water (wash the part of the distillation apparatus that came in contact with the solution in the receiver)

Titration

0.1-mol/L - 0.2-mol/L sodium hydroxide solution (until the solution
becomes gray-green), or 0.25-mol/L sulfuric acid (until the solution
becomes light red)

Figure 2 Flow sheet for ammoniacal nitrogen in fertilizers (Distillation and measurement procedure)62

Testing Methods for Fertilizers(2021)

4.1.2.b Formaldehyde method(1) Summary
The testing method is applicable to the fertilizers which do not contain a large amount of flora andfauna sample. This testing method is classified as Type C and its symbol is 4.1.2.b-2017 or A-N.b-1.
After adding water or hydrochloric acid (1+20) to an analytical sample to extract ammonium ion, add
an aluminum chloride solution, add a potassium hydroxide solution drop by drop and precipitate
phosphoric acid and excessive aluminum to make a sample solution. Adjust the sample solution toslight acidity, add a formaldehyde solution and measure ammonium ion by complexometric titration
with 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to obtain the ammoniacal nitrogen (A-N) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 8.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve ina small amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f)= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Potassium chloride solution (1 mol/L) (1): Dissolve 75 g of potassium chloride specified in JIS
K 8121 in water to make 1000 mL.
c) Aluminum chloride solution (1 mol/L) (1): Dissolve 240 g of aluminum chloride (III)hexahydrate specified in JIS K 8114 in water to make 1000 mL.
d) Potassium hydroxide solution (170 g/L) (1): Dissolve 170 g of potassium hydroxide in water
to make 1000 mL.
e) Formaldehyde solution: Add one volume of water to one volume of the 36 % (mass fraction)- 38 % (mass fraction) formaldehyde specified in JIS K 8872.
f) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
g) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, and add water to make 100 mL.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
63Testing Methods for Fertilizers(2021)

i)

100 mL of ethanol (95) specified in JIS K 8102.
Bromothymol blue solution (1 g/100 mL): Dissolve 1 g of bromothymol blue specified in JIS
K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, and add water to make 100 mL.

Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 Thymol blue can be dissolved if it is sodium salt. The thymol blue specified in JIS K
8643 is slightly hard to dissolve in ethanol and hard to dissolve in water. Therefore,
add about 2.15 mL of sodium hydroxide solution (0.1 mol/L) per 0.1 g of thymol
blue to neutralize, and then prepare the thymol blue solution (1 g/100 mL) throughthe same procedure as (2) i).
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Ammonium saltsa) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Compound fertilizersa) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 300 mL of hydrochloric acid (1 + 20) and shake to mix at the rate of 30 - 40
revolutions/min for about 30 minutes.
c) Add an aluminum chloride solution (1 mol/L) (2) to the solution and add a few drops of methyl
red solution (1mol/L) as an indicator. After that, add immediately potassium hydroxide (170g/L) while shaking the flask until the color of the solution changes to light yellow (3).
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (2) Add 3 mL of aluminum chloride per 0.04 g of P or 0.1 g of P2O5 in the sample solution.
(3) Form precipitate of aluminum hydroxide and aluminum phosphate to separate thephosphate.
Comment 4 In the procedure of (4.1.1) a) and (4.1.2) a), it is also allowed to weigh 2.5g of ananalytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask
Comment 5 When it is not a fertilizer in which phosphate, ammonium and magnesium coexist,
64Testing Methods for Fertilizers(2021)

about 400 mL of potassium chloride solution (1 mol/L) can be used instead of about
300 mL of hydrochloric acid (1+20) in the procedure of (4.1.2) b).
Comment 6 In the case of the compound fertilizers containing bentonite, after shaking to mix using
about 300 mL of hydrochloric acid (1+20) or about 400 mL of potassium chloride
solution (1 mol/L) according to Comment 5 in (4.1.2) b), add water to the marked line,
filter with Type 3 filter paper and transfer 50 ml - 100 mL to a 250-mL volumetricflask, and then conduct the procedure in (4.1.2) c) - e).
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined amount of sample solution (the equivalents of 50 mg as A-N) in a 300-mL
volumetric flask (4).
b) Add water to the solution to make about 100 mL.
c) Add one or two drop(s) of methyl red solution (0.1 g/100 mL) and add hydrochloric acid
(1+200) until the color of the solution changes to light pink.
d) Add 10 mL of formaldehyde solution.
e) Add one or two drop(s) of thymol blue solution (1 g/100 mL) and titrate with 0.1 mol/L - 0.2
mol/L sodium hydroxide solution until the color of the solution changes to blue (5).
f) As a blank test, put 100 mL of water in another 300-mL Erlenmeyer flask and conduct theprocedure in c) - e).
g) Calculate the ammoniacal nitrogen (A-N) in the analytical sample by the following formula:Ammoniacal nitrogen (A-N) (% (mass fraction)) in the analytical sample= (VS － VB) × C × f × (V4/V5) × (14.007/W2) × (100/1000)= (VS － VB) × C × f × (V4/V5) × (1.4007/W2)
VS： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration in (4.2) e)
VB： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration of the blank test in (4.2) f)
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V4： Constant volume (mL) of the sample solution in (4.1.1) c) or (4.1.2) d)
V5： Aliquot volume (mL) of the sample solution in (4.2) a)
W2： Mass (g) of the analytical sample
Note (4) The volume to be transferred should be up to 100 mL.
(5) The endpoint is reached when the color changes from green to light red. It is easy toobserve the change of color under fluorescent light.
Comment 7 The titration procedures in (2) a) Standardization and (4.2) e) - f) can be conductedby an automatic titrator. The setup of the titration program, the determination
parameter for the endpoint and vessels such as acceptors are according to thespecification and the operation method of the automatic titrator used.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 21 %(mass fraction) and 1 % (mass fraction) were 100.4 % - 101.0 % and 100.1 % asammoniacal nitrogen (A-N) respectively.
The results of the collaborative study (limited to reported values by Formaldehyde
method) to determine a certified reference material fertilizer were analyzed by using athree-level nesting analysis of variance. Table 1 shows the calculation results of65

Testing Methods for Fertilizers(2021)

reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.03 % (mass fraction) for solid fertilizers and about 0.02 % (mass fraction)
for fluid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.39- 42, Yokendo, Tokyo (1988)
2)
Kimie KATO, Masaki CHIDA and Erina WATANABE: Verification of Performance
Characteristics of Testing Method for Ammonia Nitrogen Content in Fertilizer byFormaldehyde Method, Research Report of Fertilizer Vol. 6, p. 139 - 147 (2013)(5)

Flow sheet for ammoniacal nitrogen: The flow sheet for ammoniacal nitrogen in fertilizers isshown below.
5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask(ammonium salts)← About 400 mL of water
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for ammoniacal nitrogen in fertilizers (Extraction procedure (4.1.1))

66

Testing Methods for Fertilizers(2021)

5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask(compound fertilizer)← About 300 mL of hydrochloric acid (1 + 20)
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Aluminum chloride solution (1 mol/L)← One or two drop(s) of methyl red← Potassium hydroxide solution (170 g/L)
(Until the solution changes to light yellow)← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for ammoniacal nitrogen in fertilizers (Extraction procedure (4.1.2))

Sample solution
Up to the equivalents of 50 mg as A-N,300-mL Erlenmeyer flask← Add water to make about 100 mL of solution← One or two drop(s) of methyl red (0.1 g/100 mL)← Hydrochloric acid (1+200) [light pink]← 10 mL of formaldehyde solution← One or two drop (s) of thymol blue solution (1 g/100 mL)
0.1 mol/L - 0.2 mol/L sodium hydroxide solution
Titration(until the solution becomes blue)
Aliquot

Figure 2 Flow sheet for ammoniacal nitrogen in fertilizers (Measurement procedure)

67

Testing Methods for Fertilizers(2021)

4.1.3 Nitrate nitrogen
4.1.3.a Devarda’s alloy - distillation method(1) Summary
The testing method is applicable to the fertilizer containing nitrate. However, it is not applicable tofertilizers containing urea, nitrolime and organic matters that digest by heating and isolate ammonia.
This testing method is classified as Type E and its symbol is 4.1.3.a-2017 or N-N.a-1.
Add water to an analytical sample to dissolve ammoniacal nitrogen (A-N) and nitrate nitrogen (NN), and further add devarda’s alloy and sodium hydroxide to subject it to steam distillation. In thisprocess, nitrate nitrogen (N-N) is reduced to ammonia. Collect isolated ammonia with 0.25 mol/L
sulfuric acid and measure surplus sulfuric acid by (neutralization) titration using 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution to obtain nitrogen content (N-N+A-N) in an analytical sample. Or collectisolated ammonia with a boric acid solution and measure ammonium ion by (neutralization) titration
using 0.25 mol/L sulfuric acid to obtain nitrogen content (N-N+A-N) in an analytical sample. Subtract
separately obtained the ammoniacal nitrogen (A-N) by 4.1.2 to calculate nitrate nitrogen (N-N). This
testing method corresponds to the devarda’s alloy method in the Official Methods of Analysis of
Fertilizers (1992).
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve ina small amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100 mLof water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture solution,and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the color of the68Testing Methods for Fertilizers(2021)

solution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following formula(1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula (2):Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of 0.25
mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water tomake 1000 mL.
e) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodium hydroxide
specified in JIS K 8576 in water to make 500 mL.
f) Devarda’s alloy: A reagent of nitrogen analysis grade specified in JIS K 8653 or a reagent ofequivalent quality.
g) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, and add water to make 100 mL.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
i) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in JIS K
8897 in 100 mL of ethanol (95) specified in JIS K 8102.
j) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
k) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green specified in
JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100 mL),
add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid) solution
in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.

69

Testing Methods for Fertilizers(2021)(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Steam distillation apparatusb) Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.
(4) Test procedures(4.1) Sample solution preparation: Prepare a sample solution as shown below:a) Weigh 0.25 g - 1 g (5) (the equivalents of 20 mg - 100 mg as N) of an analytical sample to theorder of 1 mg, and put it in a 300-mL - 500-mL distillation flaskb) Add about 25 mL of water to make a sample solution.
Note (5) Conduct the procedure in Comment 3 when there is much nitrogen content in thefertilizers such as simple salt fertilizers.
Comment 3 In the case of nitrate fertilizer, etc. containing much nitrogen content, weigh 2 g - 5gof an analytical sample to the order of 1 mg, put it into a 250- mL volumetric flask,
dissolve it in water, and further add water up to the marked line. Put predeterminedvolume of suspension (the equivalents of 20 mg -100 mg as N) into a 300- mL - 500mL distillation flask.
(4.2)

Distillation: Conduct distillation as shown below. Specific distillation procedures areaccording to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (6) of 0.25 mol/L sulfuric acid in an acceptor (7), add a few drops ofmethyl red−methylene blue mixture solution, and connect this acceptor to a steam distillation
apparatus. Or, put a predetermined amount (6) of boric acid solution (40 g/L) in an acceptor (7),add a few drops of methyl red−bromocresol green mixture solution, and connect this acceptor
to a steam distillation apparatus.
b) Add (10) no less than 3 mg of devarda’s alloy and adequate volume of sodium hydroxide (200g/L - 500 g/L) (8) (9) and connect this distillation flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at a
distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in theacceptor with a small amount of water, and pool the washing with the distillate.
Note (6) 5 mL - 20 mL(7) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL beakerwith which the distillate outlet of the steam distillation apparatus can be immersed in
0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(8) Sudden reaction makes bubbles foam drastically and the bubbles overflow from a
distillation flask. Therefore, it is required to add an alkali solution gradually and mix
quietly.
(9) An amount sufficient to make the solution strong alkalinity.
(10) Add a small amount of silicone oil as necessary.

(4.3) Measurement: Conduct measurement as shown below.
(4.3.1) When 0.25 mol/L sulfuric acid is used in (4.2):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of
the solution becomes gray-green (4).
b) Calculate nitrogen content (N-N+A-N) in the analytical sample by the following formula:70

Testing Methods for Fertilizers(2021)c)

Subtract the ammoniacal nitrogen (A-N) separately obtained in 4.1.2 from the obtained nitrogencontent (N-N+A-N) to calculate nitrate nitrogen (N-N) (11) (12).
Nitrogen content (N-N+A-N) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (14.007/W2) × (100/1000)= (B × V6 － V7) × C1 × f1 × (1.4007/W2)
B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration in (4.3) a)
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
W2： Mass (g) of the analytical sample

Note (11) The nitrogen content (N-N+A-N) and ammoniacal nitrogen (A-N) use raw data without
rounding the numerical value.
(12) When no ammoniacal nitrogen (A-N) is contained, the nitrogen content (N-N+A-N)
calculated in (4.3) b) is regarded as nitrate nitrogen (N-N).
(4.3.2) When a boric acid solution (40 g/L) is used in (4.2):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (13).
b) Calculate nitrogen content (N-N+A-N) in the analytical sample by the following formula:c) Subtract the ammoniacal nitrogen (A-N) separately obtained in 4.1.2 from the obtained nitrogencontent (N-N+A-N) to calculate nitrate nitrogen (N-N) (11) (12).
Nitrogen content (N-N+A-N) (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (14.007/W3) × (100/1000)= V10 × C2 × f2 × (2.8014/W3)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acid
W3： Mass (g) of the analytical sample
Note (13) The endpoint is reached when the color changes from green to light red.
Comment 4 The titration procedures in (2) a) Standardization, (2) c) Standardization and (4.3)
can be conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.

71

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.49- 50, Yokendo, Tokyo (1988)(5) Flow sheet for nitrate nitrogen: The flow sheet for nitrate nitrogen in fertilizers is shown below.

0.25 g - 1 g
Weigh the equivalents of 20 mg - 100 mg as N to the order of 1 mg
analytical sample
into a 300-mL distillation flask.
← 25 mL of water← No less than 3 g of devarda's alloy← Sodium hydroxide solution (200 g/L - 500 g/L)
← A small amount of silicone oil as necessary
Receiver: 200-mL - 300-mL Erlenmeyer flask or beakerA predetermined amount of 0.25-mol/L sulfuric acid and a few
Steam distillation
drops of methyl red-methylene blue mixture solution, or aapparatus
predetermined amount of boric acid solution (40 g/L), several
drops of methyl red - bromocresol green mixture solution
Steam distillation

Distillation rate: 5 mL/min - 7 mL/min

Stop distilling
120 mL - 160 mL distillate← Water (wash the part of the distillation apparatus
that came in contact with the solution in the receiver)
0.1 mol/L - 0.2 mol/L sodium hydroxide solution (until the
Titration
solution becomes gray-green), or
0.25 mol/L sulfuric acid (until the solution becomes light red)
Figure Flow sheet for nitrate nitrogen in fertilizers

72

Testing Methods for Fertilizers(2021)

4.1.3.b Reduced iron- distillation method(1) Summary
The testing method is applicable to the fertilizer containing nitrate. However, it is not applicable tofertilizers containing urea, nitrolime and organic matters that digest by heating and isolate ammonia.
This testing method is classified as Type E and its symbol is 4.1.3.b-2017 or N-N.b-1.
Add water to an analytical sample to dissolve ammoniacal nitrogen (A-N) and nitrate nitrogen (NN), and add reduced iron and a sulfuric acid solution to boil lightly. In this process, nitrate nitrogen(N-N) is reduced to ammonia. And further add a sodium hydroxide solution to distillate. Collectisolated ammonia with 0.25 mol/L sulfuric acid and measure surplus sulfuric acid by (neutralization)
titration using 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to obtain nitrogen content (N-N+AN) in an analytical sample. Or collect isolated ammonia with a boric acid solution and measureammonium ion by (neutralization) titration using 0.25 mol/L sulfuric acid to obtain nitrogen content(N-N+A-N) in an analytical sample. Subtract separately obtained the ammoniacal nitrogen (A-N) by
4.1.2 to calculate nitrate nitrogen (N-N). This testing method corresponds to the reduced iron methodin the Official Methods of Analysis of Fertilizers (1992).
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve ina small amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100 mLof water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture solution,and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the color of thesolution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L sodium
73Testing Methods for Fertilizers(2021)

hydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following formula(1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula (2):Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of 0.25
mol/L sulfuric acid=V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water tomake 1000 mL.
e) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodium hydroxide
specified in JIS K 8576 in water to make 500 mL.
f) Reduced iron: Nitrogen content is no more than 0.005 % (mass fraction)g) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified in
JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, and add water to make 100 mL.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
i) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in JIS K
8897 in 100 mL of ethanol (95) specified in JIS K 8102.
j) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
k) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green specified in
JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100mL), add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid) solution
in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
(3) Instruments: Instruments are as shown below:a) Steam distillation apparatusb) Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam74

Testing Methods for Fertilizers(2021)

distillation apparatus.
(4) Test procedures(4.1) Preparation of sample solution: Conduct preparation of a sample solution as shown below.
a) Weigh 0.5 g - 1 g (5) (the equivalents of 20 mg - 100 mg as N) of an analytical sample to theorder of 1 mg, and put it in a 300-mL - 500-mL distillation flaskb) Add about 30 mL of water and mix well.
c) As soon as adding 5 g of reduced iron and 10 mL of sulfuric acid (1+1), insert a long stem
funnel to a distillation flask and shake to mix gently while cooling the outside of the container
under flowing water (6).
d) After leaving at rest for about 5 minutes (7), heat gradually by low temperature and boil in a low
flame for about 15 minutes, and then stand to cool to make a sample solution.
Note (5) Conduct the procedure in Comment 3 when there is much nitrogen content in thefertilizers such as simple salt fertilizers.
(6) Sudden reaction generates heat, and unreacted nitric acid vaporizes or digests to makenitrogen oxide etc. through which process losses occur easily. Careful and efficient
operation should be taken(7) Until a sudden reaction is settled.
Comment 3 In the case of nitrate fertilizer, etc. containing much nitrogen content, weigh 2 g - 5gof an analytical sample to the order of 1 mg, put it into a 250- mL volumetric flask,
dissolve it in water, and further add water up to the marked line. Put predeterminedvolume of suspension (the equivalents of 20 mg - 100 mg as N) into a 300-mL - 500mL distillation flask.
(4.2) Distillation: Conduct distillation as shown below. Specific distillation procedures are according
to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (8) of 0.25 mol/L sulfuric acid in an acceptor (9), add a few drops ofmethyl red−methylene blue mixture solution, and connect this acceptor to a steam distillation
apparatus. Or, put a predetermined amount (8) of boric acid solution (40 g/L) in an acceptor (9),add a few drops of methyl red−bromocresol green mixture solution, and connect this acceptor
to a steam distillation apparatus.
b) Add adequate volume of sodium hydroxide (200 g/L - 500 g/L) (10) and connect this distillation
flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at a
distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in theacceptor with a small amount of water, and pool the washing with the distillate.
Note (8) 5 mL - 20 mL(9) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL beakerwith which the distillate outlet of the steam distillation apparatus can be immersed in
0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(10) An amount sufficient to make the solution strong alkalinity.
(4.3) Measurement: Conduct measurement as shown below.
(4.3.1) When 0.25 mol/L sulfuric acid is used in (4.2) a),a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of75

Testing Methods for Fertilizers(2021)

the solution becomes gray-green (4).
b) Calculate nitrogen content (N-N+A-N) in the analytical sample by the following formula:c) Subtract the ammoniacal nitrogen (A-N) separately obtained in 4.1.2 from the obtained nitrogencontent (N-N+A-N) to calculate nitrate nitrogen (N-N) (11) (12).
Nitrogen content (N-N+A-N) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (14.007/W2) × (100/1000)= (B × V6 － V7) × C1 × f1 × (1.4007/W2)
B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
W2： Mass (g) of the analytical sample
Note (11) The nitrogen content (N-N+A-N) and ammoniacal nitrogen (A-N) use raw data
without rounding the numerical value.
(12) When no ammoniacal nitrogen (A-N) is contained, the nitrogen content (N-N+A-N)
calculated in (4.3) b) is regarded as nitrate nitrogen (N-N).
(4.3.2) When a boric acid solution (40 g/L) is used in (4.2) a):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomes lightred (13).
b) Calculate nitrogen content (N-N+A-N) in the analytical sample by the following formula:c) Subtract the ammoniacal nitrogen (A-N) separately obtained in 4.1.2 from the obtained nitrogencontent (N-N+A-N) to calculate nitrate nitrogen (N-N) (11) (12).
Nitrogen content (N-N+A-N) (% (mass fraction)) in the analytical sample=V10 × C2 × 2 × f2 × (14.007/W3) × (100/1000)=V10 × C2 × f2 × (2.8014/W3)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acid
W3： Mass (g) of the analytical sample
Note (13) The endpoint is reached when the color changes from green to light red.
Comment 4 The titration procedures in (2) a) Standardization, (2) c) Standardization and (4.3)
can be conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.

76

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.48- 49, Yokendo, Tokyo (1988)(5)

Flow sheet for nitrate nitrogen: The flow sheet for nitrate nitrogen in fertilizers is shown
below.
0.5 g – 1 g
Weigh the equivalents of 20 mg - 100 mg of N to the order of 1 mg,
analytical sample
and put it into a 300-mL distillation flask.
←About 30 mL of water←5 g of reduced iron←About 10 mL of sulfuric acid (1+1)
Insert a long stem funnel immediately to a distillation flask and shake
Mixtureto mix gently while cooling the outside of the container under flowing water
Leaving at rest
Heating

For about 5 minutes (until a strong reaction is settled)
Boil in a low flame for about 15 minutes

Standing to cool
←Sodium hydroxide (200 g/L - 500 g/L)
Receiver: 200-mL - 300-mL Erlenmeyer flask or beakerA predetermined amount of 0.25-mol/L sulfuric acid and a few
Steam distillation
drops of methyl red-methylene blue mixture solution, or aapparatus
predetermined amount of boric acid solution (40 g/L), several
drops of methyl red - bromocresol green mixture solution
Steam distillation

Distillation rate: 5 mL/min - 7 mL/min

Stop distilling
120 mL - 160 mL distillate← Water (wash the part of the distillation apparatus
that came in contact with the solution in the receiver)
0.1 mol/L - 0.2 mol/L sodium hydroxide solution (until the
Titration
solution becomes gray-green), or
0.25 mol/L sulfuric acid (until the solution becomes light red)
Figure Flow sheet for nitrate nitrogen in fertilizers

77Testing Methods for Fertilizers(2021)

4.1.3.c Phenol sulfuric acid method(1) Summary
The testing method is applicable to the fertilizer containing nitrate. It is also applicable to thefertilizers containing chemical compounds such as urea, nitrolime and organic matters that digest by
heating and isolate ammonia. This testing method is classified as Type B and its symbol is 4.1.3.c2021 or N-N.c-2.
Add a copper sulfate - silver sulfate solution, calcium hydroxide and basic magnesium carbonate
to an analytical sample, extract nitrate nitrogen (N-N) as well as removing chloride and organic
matters, and measure the absorbance of nitro phenol ammonium sulfate formed by the reaction withphenol sulfuric acid and an ammonia solution to calculate nitrate nitrogen (N-N) in an analyticalsample. In addition, the performance of this testing method is shown in Comment 3.
(2) Reagent: Reagents are as shown below.
a) Nitrate standard solution (N-N 5 mg/mL) (1): Heat potassium nitrate (no less than 99.9 (%)(mass fraction) in purity) at 110 ºC for no less than 1 hour, and after standing to cool in a
desiccator, put 36.09 g in a weighing dish. Dissolve in a small amount of water, transfer to a
1000-mL volumetric flask, and add water up to the marked line.
b) Nitrate standard solution (N-N 0.01 mg/mL): Dilute predetermined volume of nitrate
standard solution (N-N 5 mg/mL) with water to prepare a nitrate standard solution (N-N 0.01
mg/mL).
c) Copper sulfuric - silver sulfuric solution (1): Dissolve 5 g of copper (II) sulfate pentahydrate
specified JIS K 8983 in 900 mL of water, and dissolve while adding 4 g of silver sulfate
specified in JIS K 8965 to make 1000 mL (2).
d) Phenol sulfuric acid: Dissolve 15 g of phenol specified in JIS K 8798 in 100 mL of sulfuric
acid specified in JIS K 8965, heat in a water bath at 80 ºC - 100 ºC for two hours and then let it
stand to cool (2).
e) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS
K 8085 or a reagent of equivalent quality.
f) Calcium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8575 or a reagent ofequivalent quality.
g) Basic magnesium carbonate: Basic magnesium carbonate that contains no nitrate nitrogen.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in an amber bottle.
Comment 1

Instead of the nitrate standard solution in (2), a nitrate standard solution for acalibration curve may be prepared using nitrate nitrogen (NO3-N 0.1 mg/mL or 1
mg/mL) traceable to National Metrology.

(3) Instruments: Instruments are as shown below:a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 250-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) Spectrophotometer: A spectrophotometer specified in JIS K 0115c) Water bath: Water bath that can be adjusted to no less than 80 ºC
78Testing Methods for Fertilizers(2021)(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample(4.1.1.1) Vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add about 200 mL of copper sulfuric - silver sulfuric solution and shake to mix at 30 - 40
revolutions /min for about 20 minutes.
c) Add about 1 g of calcium hydroxide and about 1 g of basic magnesium carbonate and shake tomix at 30 - 40 revolutions /min for about 10 minutes.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution (3).
(4.1.1.2) Vertical reciprocating shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add about 200 mL of copper sulfuric - silver sulfuric solution, and shake to mix at 300
reciprocations/min (amplitude of 40 mm) for about 20 minutes.
c) Add about 1 g of calcium hydroxide and about 1 g of basic magnesium carbonate and shake tomix at 300 reciprocations/min (amplitude of 40 mm) for about 10 minutes.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution (3).
(4.1.2) Fluid test samplea) Weigh 0.4 g of an analytical sample to the order of 1 mg, and put it in a 100-mL volumetric flask.
b) Add about 80 mL of copper sulfuric - silver sulfuric solution, and shake to mix.
c) Add about 0.4 g of calcium hydroxide and about 0.4 g of basic magnesium carbonate, and shaketo mix (4).
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution (3).
Note (3) As soon as the sample solution is prepared, conduct the procedure in (4.2) a).
(4) Shake horizontally for at least five times, and turn upside down once. Repeat that about
10 times. Keep shaking until precipitation originating from the analytical sample, copper
sulfuric - silver sulfuric solution, calcium hydroxide or basic magnesium carbonate is
not present and fully dispersed.
Comment 2 If the filtrate of (4.1.1.1), (4.1.1.2), (4.1.2) e) is colored, add no more than 0.5 g ofactive carbon and filter with Type 3 filter paper to make a sample solution.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of sample solution (the equivalents of 0.01 mg - 0.1 mg as N-N)
into a small evaporating dish (4).
b) Evaporate water on a water bath at no less than 80 ºC to exsiccate.
c) After standing to cool, swiftly add 2 mL of phenol sulfuric acid (5) and then rotate theevaporating dish so that the whole residue comes in contact with the acid.
d) After leaving at rest for about 10 minutes, add 20 mL of water (6).
e) After standing to cool, transfer it with water to a 100- mL volumetric flask.
79

Testing Methods for Fertilizers(2021)f)

Add an ammonia solution (1+2), until the color of a solution changes to light yellow, to allow
it to be weak alkalinity, and further add 3 mL of ammonia solution (1+3) (7).
g) After cooling is complete, add water up to the marked line and leave at rest for 30 minutes.
Note (4) A round-bottom glass or porcelain evaporating dish is preferable.
(5) Add at the center of a small evaporating dish with Komagome pipet.
(6) If residue does not dissolve easily, grind it with a glass rod.
(7) As no color appears from a blank test solution for a calibration curve preparation, add
almost the same volume of ammonia solution (1+2) as the nitrate standard solution.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of spectrophotometer: Set up the measurement conditions ofspectrophotometer considering the following.
Detection wavelength: 410 nmb) Calibration curve preparation
1) Put 1 mL - 10 mL of nitrate standard solution (N-N 0.01 mg/mL) in small evaporating dishes(4)step-by-step.
2) Conduct the same procedure as (4.2) b) - g) to make the nitrate standard solution for thecalibration curve preparation.
3) Put 40 mL of water in a 100-mL volumetric flask, and shake to mix while gently adding 2 mLof phenol sulfuric acid. Let it stand to cool and conduct the same procedure as (4.2) f) - g) to
make the blank test solution for calibration curve.
4) Measure absorbance at a wavelength 410 nm of the nitrate standard solution for the calibration
curve preparation using the blank test solution for the calibration curve preparation as thecontrol.
5) Prepare the calibration curve of concentration of the nitrate nitrogen and absorbance of thenitrate standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) g), measure absorbance by the same procedure as b) 4).
2) Obtain the nitrate nitrogen (N-N) content from the calibration curve and calculate nitrate
nitrogen (N-N) in the analytical sample.
Comment 3 Tripricates recovery testing was conducted to evaluate trueness using a preparation
sample. As a result, the mean recovery rates at the content level of 16 % (mass fraction)and 1 % (mass fraction) - 3% (mass fraction) were 103.4 % and 101.1 % - 100.9 % asnitrate nitrogen (N-N) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1.
The comparison of the measurement value (yi: 0.04 % - 16.48 % (mass fraction)) of
extraction by a vertical reciprocating shaker and the measurement value (xi) ofextraction by a vertical rotating mixer was conducted using sodium nitrate (2 samples),lime nitrate (1 sample), fluid nitrogen fertilizer (2 samples), coating compound
fertilizer (1 sample), compound fertilizer (5 samples), fluid compound fertilizer (4samples), blended fertilizer (3 samples), home garden-use compound fertilizer (2samples), and compost (1 sample). As a result, a regression equation was y = 0.0059 +0.9995x, and its correlation coefficient (r) was 0.9999.
The results of repeated analyses on different days using a compound fertilizer andhome garden-use compound fertilizer were analyzed by the one-way analysis ofvariance. Table 2 shows the estimation results of intermediate precision and80Testing Methods for Fertilizers(2021)

repeatability.
The comparison of the measurement value (yi: 1.15% - 8.48 % (mass fraction)) of
simple extraction and the measurement value (xi) of extraction by a vertical rotating
mixer was conducted using fluid nitrogen fertilizer (3 samples), fluid compound
fertilizer (7 samples), and home garden-use compound fertilizer (4 samples). As aresult, a regression equation was y = −0.0098 + 0.9967x, and its correlation coefficient(r) was 0.9999.
The results of repeated analyses on different days using a fluid nitrogen fertilizer andfluid compound fertilizer were analyzed by the one-way analysis of variance. Table 2
shows the estimation results of intermediate precision and repeatability.
Comment 4 The minimum limit of quantification of the extraction procedure (4.1.1) was estimatedto be about 0.01 % (mass fraction) for solid fertilizers and about 0.002 % (massfraction) for fluid fertilizers, and that of the extraction procedure (4.1.2) was estimatedto be about 0.003 % (mass fraction) for fluid fertilizers.

Table 2Estimation results of repeatability and intermediate precision
Days of
Repeatability
Intermediate precision
2)
Mean
4）
5）
6）
7）
repeatability
Sample namesr
RSD rs I（T）RSD I（T）
3)
(%)
1）
3）
3）
（％）
（％）
（％）
（％）
T
Compound fertilizer
5
15.89
0.07
0.5
0.1
0.8
Home garden-use
5
4.23
0.01
0.3
0.01
0.3
fertilizer
Compost
5
0.03
0.001
3.5
0.01
0.03
Fluid nitrogen
5
1.62
0.01
0.4
0.01
1.0
fertilizer
Fluid compound
5
8.43
0.05
0.6
0.06
0.7
fertilizer
1) The number of days conducting duplicate analysis
4) Repeatability standard deviation
2) Mean ([Number of days of repeatability (T )] × [Number 5) Repeatability relative standard deviationof duplicates (2)])6) Intermediate standard deviation
3) Mass fraction7) Intermediate relative standard deviation81

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.52- 55, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)3)
Kimie KATO, Masaki CHIDA and Erina WATANABE: Verification of Performance
Characteristics of Testing Method for Nitrate Nitrogen Content in Fertilizer by Phenol
Sulfuric Acid Method, Research Report of Fertilizer Vol. 6, p. 148 - 155 (2013)4)
Erika HIRATA, Hideo SOETA, Hidemi YOSHIMURA and Keiji YAGI: Performance
Evaluation of Determination Method for Nitrogen in Fertilizer: Harmonized
Collaborative Validation, Research Report of Fertilizer, Vol. 12, p. 84 – 93 (2019)(5) Flow sheet for nitrate nitrogen: The flow sheet for nitrate nitrogen in fertilizers is shown
below.
1 g analytical sample
Weigh to the order of 1 mg in a 250-mL volumetric flask← About 200 mL of copper sulfate - silver sulfate solution
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 20 minutes← About 1 g of calcium hydroxide← About 1 g of basic magnesium carbonate
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 10 minutes
Water
(up
to
the marked line)←
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for nitrate nitrogen in fertilizers (Extraction procedure (4.1.1.1))

1 g analytical sample
Weigh to the order of 1 mg in a 250-mL volumetric flask← About 200 mL of copper sulfate - silver sulfate solution
Shaking to mix
Vertical reciprocating shaker (300 reciprocations/min, amplitude of 40 mm), for 20 minutes← About 1 g of calcium hydroxide← About 1 g of basic magnesium carbonate
Shaking to mix
Vertical reciprocating shaker (300 reciprocations/min, amplitude of 40 mm), for 10 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for nitrate nitrogen in fertilizers (Extraction procedure (4.1.1.2))82

Testing Methods for Fertilizers(2021)
0.4 g analytical sample
Weigh to the order of 1 mg in a 100-mL volumetric flask← About 80 mL of copper sulfate - silver sulfate solution
Shaking to mix← About 0.4 g of calcium hydroxide← About 0.4 g of basic magnesium carbonate
Shaking to mix← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-3 Flow sheet for nitrate nitrogen in fertilizers (Extraction procedure (4.1.2))

83

Testing Methods for Fertilizers(2021)

4.2 Phosphoric acid
4.2.1 Total phosphoric acid
4.2.1.a Ammonium vanadomolybdate absorptiometric analysis(1) Summary
This testing method is applicable to fertilizers containing organic matters. This testing method isclassified as Type B and its symbol is 4.2.1.a-2017 or T-P.a-1.
Add sulfuric acid, potassium sulfate and copper (II) sulfate pentahydrate to an analytical sample.
Pretreat by Kjeldahl digestion, incineration-hydrochloric acid boiling or aqua regia digestion toconvert total phosphorus to phosphate ion, and measure the absorbance of phosphovanadomolybdatesalt formed by the reaction with ammonium vanadate (V), hexaammonium heptamolybdate and nitricacid, to obtain total phosphoric acid (T-P2O5) in an analytical sample. In addition, the performance of
this testing method is shown in Comment 9.
(2) Reagent: Reagents are as shown below.
a) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
b) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
d) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS K
8085 or a reagent of equivalent quality.
e) Catalyst (1): Mix potassium sulfate specified in JIS K 8962 and copper (II) sulfate pentahydrate(2)
specified in JIS K 8983 in the ratio of 9 to 1.
f) Coloring reagent solution (3) (4): Dissolve 1.12 g of ammonium vanadate (V)(5) specified in JIS
K 8747 in water, add 250 mL of nitric acid, then add 27 g of hexaammonium heptamolybdate
tetrahydrate (6) specified in JIS K 8905 dissolved in water, and further add water to make 1000mL (7).
g) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
h) Phosphoric acid standard solution (P2O5 10 mg/mL) (3): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
i) Phosphoric acid standard solution (P2O5 0.5 mg/mL) (3): Put 50 mL of phosphoric acidstandard solution (P2O5 10 mg/mL) in a 1000-mL volumetric flask, add 2 mL - 3 mL of nitricacid, and add water up to the marked line.
Note (1) A tablet is commercially available.
(2) Crush into powder as appropriate.
(3) This is an example of preparation; prepare an amount as appropriate.
(4) This corresponds to reagent “a” reagent solution in the Official Methods of Analysis of
Fertilizers (1992).
(5) This corresponds to ammonium metavanadate in the Official Methods of Analysis of
Fertilizers (1992).
(6) This corresponds to ammonium molybdate in the Official Methods of Analysis of
Fertilizers (1992).
(7) Store in an amber bottle.
84

Testing Methods for Fertilizers(2021)

Comment 1 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate the total phosphoric acid (T-P2O5) in an analytical sample bymultiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.3) by a conversion factor (2.2914).
Comment 2 When using a sample solution obtained in the procedure in (4.1.3) h) for themeasurement of cadmium, nickel, chromium or lead, sulfuric acid and hydrochloric
acid in (2) should be a reagent of harmful metal analysis grade, microanalysis grade orequivalents.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Spectrophotometer: A spectrophotometer specified in JIS K 0115b) Electric furnace: An electric furnace that can be adjusted to 550 ºC ± 5 ºC.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
d) Digestion flask: Kjeldahl flask(4) Test procedures(4.1) Sample solution preparation: Prepare a sample solution as shown below:(4.1.1) Kjeldahl digestiona) Weigh 0.5 g - 5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL digestion
flask.
b) Add 5 g - 10 g of catalyst, and further add 20 mL - 40 mL of sulfuric acid, shake to mix andheat gently.
c) After bubbles cease to form, heat until white smoke of sulfuric acid evolves.
d) Ignite until organic matters are completely digested (8).
e) After standing to cool, add a small amount of water, mix well by shaking, transfer to a 250-mL- 500-mL volumetric flask with water, and further mix by shaking.
f) After cooling is complete, add water up to the marked lineg) Filter with Type 3 filter paper to make a sample solution.
Note (8) When the solution has finished changing color, heat further for no less than 2 hours.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Incineration-hydrochloric acid boilinga) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (9).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (9).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After cooling is complete, transfer to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
85

Testing Methods for Fertilizers(2021)

Note (9) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 550 °C in 1 to 2 hours.
Comment 4 Do not conduct the procedures in (4.1.2) b) - c) in the case of fertilizers not containing
organic matters.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.1.3) Incineration-aqua regia digestiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (10).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (10).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (11), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated (12).
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (13) to the digest, cover
the tall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL volumetric flask with water, add water up to themarked line, and filter with Type 3 filter paper to make a sample solution.
Note (10) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about
1 hour and further raise to 450 °C in 1 to 2 hours.
(11) The watch glass can be removed.
(12) When exsiccating it, phosphoric acid may not dissolve completely and theconcentration may become a low value in the procedure in g).
(13) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetricflask is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be
added.
Comment 6 Do not conduct the procedures in (4.1.3) b) - c) in the case of fertilizers not containing
organic matters.
Comment 7 A sample solution obtained in the procedure in (4.1.3) is also applicable to thecomponents shown in Annex B.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 6 mg as P2O5)
in a 100-mL volumetric flask.
b) Add 1 - 2 drop(s) of phenolphthalein solution (1 g/100 mL), and neutralize by adding ammonia
solution (1+1) until the color of the solution becomes light red-purple (14).
c) Add nitric acid (1+10) until the light red-purple color of the solution disappears to make itslightly acidic, and add a proper amount of water (15).
d) Add 20 mL of coloring reagent solution, and further add water up to the marked line, and thenleave at rest for about 30 minutes.
Note (14) It is not necessary to add a phenolphthalein solution (1 g/100 mL) when determination
86Testing Methods for Fertilizers(2021)

can be done by the color change of copper ion (light blue → blue-purple).
(15) Without the addition of water, precipitate may be produced when a coloring reagent
solution is added.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of spectrophotometer: Set up the measurement conditions ofspectrophotometer considering the following.
Detection wavelength: 420 nmb) Calibration curve preparation
1) Put 1 mL - 12 mL of phosphoric acid standard solution (P2O5 0.5 mg/mL) in 100-mL volumetricflasks step-by-step.
2) Add a proper amount of water (15), and conduct the same procedure as (4.2) d) to make the P2O5
0.5 mg/100 mL - 6 mg/100 mL phosphoric acid standard solutions for the calibration curve
preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 420 nm of the phosphoric acid standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control (16).
5) Prepare the calibration curve of the phosphoric acid concentration and absorbance of thephosphoric acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) d), measure absorbance by the same procedure as b) 4) (16).
2) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate total
phosphoric acid (T-P2O5) in the analytical sample.
Note (16) Measure within 6 hours after adding the coloring reagent solution in the procedure in(4.2) d).
Comment 8 After the procedure in (4.2) a), it is possible to measure another measurement solutionof citrate-soluble phosphoric acid at the same time by adding 4 mL of nitrate acid (1+1)
and 2 mL of Petermans citrate solution and by conducting the procedures from (4.2)d) to (4.3) in 4.2.2.a (using b reagent solution in the Official Methods of Analysis of
Fertilizers (1992)).
After the procedure in (4.2) a), it is possible to measure another measurement solutionof citrate-soluble phosphoric acid at the same time by adding 4 mL of nitrate acid (1+1)
and 17 mL of citric acid solution and by conducting the procedures from (4.2) d) to(4.3) in 4.2.3.a (using b reagent solution in the Official Methods of Analysis of
Fertilizers (1992)).
Comment 9 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % - 20 % (mass fraction) and
1 % (mass fraction) - 5 % (mass fraction) were 99.4 % - 100.2 % and 101.0 % - 105.7 %as total phosphoric acid (T-P2O5) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1. In addition, the results of thecollaborative study to determine a certified reference material fertilizer were analyzed
by using a three-level nesting analysis of variance. Table 2 shows the calculation
results of reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to87

Testing Methods for Fertilizers(2021)

be about 0.04 % (mass fraction) for solid fertilizers and about 0.01 % (mass fraction)
for fluid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.108- 114, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)3)
Kimie KATO, Masayuki YOSHIMOTO and Yuji SHIRAI: Systematization of
Determination Methods of Major Components in Sludge Fertilizer, Compost and Organic
Fertilizer, Research Report of Fertilizer, Vol. 3 p. 107 - 116 (2010)4)
Yoshiyuki SUNAGA, Yasushi SUGIMURA, Ichiro YOSHIDA and Hidenori KONISHI:
Verification of Performance Characteristics of Testing Methods for Phosphorus Content
in Fertilizer by Ammonium Vanadomolybdate Absorption Photometry, Research Reportof Fertilizer Vol. 5, p. 167 - 179 (2012)5)
Toshio HIRABARA, Shin ABE, and Masahiro ECHI: Performance Evaluation of
Determination Method for Phosphoric Acid in fertilizer: Harmonized Collaborative
Validation, Research Report of Fertilizer, Vol. 12, p. 94 – 108 (2019)88

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total phosphoric acid: The flow sheet for total phosphoric acid in fertilizers isshown below:

89Testing Methods for Fertilizers(2021)

90

Testing Methods for Fertilizers(2021)

4.2.1.b Quinoline gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing organic matters. It is suitable for thefertilizers with relatively a high content of phosphoric acid. This testing method is classified as
Type E and its symbol is 4.2.1.b-2017 or T-P.b-1.
Add sulfuric acid, potassium sulfate and copper (II) sulfate pentahydrate to an analytical sample.
Pretreat by the Kjeldahl digestion method to convert the total phosphoric acid (T-P2O5) to phosphateion, and measure the mass of quinolinium phosphomolybdate formed by the reaction with quinoline,
molybdic acid and nitric acid to obtain the total phosphoric acid (T-P2O5) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
b) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
c) Sodium molybdate solution (1): Dissolve 70 g of sodium molybdate dihydrate in 150 mL ofwater.
d) Quinoline solution (1): Add 5 mL of quinolone specified in JIS K 8279 to the mixture solutionof 35 mL of nitric acid and 100 mL of water.
e) Quimosiac solution (1): Add 60 g of citric acid monohydrate specified in JIS K 8283 to the
mixture solution of 85 mL nitric acid and 150 mL of water to dissolve. Add gradually total
volume of the sodium molybdate solution to mix. Add gradually the total volume of thequinoline solution while mixing the solution. After leaving at rest overnight, filter the total
volume with Type 3 filter paper. Add 280 mL of acetone specified in JIS K 8034, and further
add water to make 1000 mL.
f) Catalyst (2): Mix potassium sulfate specified in JIS K 8962 and copper (II) sulfate pentahydrate(3)
specified in JIS K 8983 in the ratio of 9 to 1.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A tablet is commercially available.
(3) Crush into powder as appropriate.
(3)
a)
b)
c)

Apparatus and instruments: Apparatus and instruments are shown below.
Water bath: Water bath that can be adjusted to 60 ºC - 65 ºC.
Drying apparatus:
A drying apparatus that can be adjusted to 220 ºC ± 5 ºC.
Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 220 ºC ± 5 ºC in advance and measure the mass tothe order of 1 mg.
d) Digestion flask: Kjeldahl flask(4) Test procedures(4.1) Kjeldahl digestion: Conduct digestion as shown below.
a) Weigh 0.5 g - 5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL digestion
flask.
b) Add 5 g - 10 g of catalyst, and further add 20 mL - 40 mL of sulfuric acid, shake to mix andheat gently.
c) After bubbles cease to form, heat until white smoke of sulfuric acid evolves.
d) Ignite until organic matters are completely digested (4).
e) After standing to cool, add a small amount of water, mix well by shaking, transfer to a 250-mL- 500-mL volumetric flask with water.
91

Testing Methods for Fertilizers(2021)f) After cooling is complete, add water up to the marked lineg) Filter with Type 3 filter paper to make a sample solution.
Note (4) When the solution has finished changing color, heat further for no less than 2 hours.
Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 10 mg - 30 mg as P2O5 and no more than 5 mL
as sulfuric acid) of sample solution in a 300-mL tall beaker.
b) Add 5 mL of nitric acid and add water to make about 80 mL.
c) Cover with a watch glass. After boiling for about 3 minutes, wash the watch glass and the inside
the tall beaker with water and add water to make about 100 mL.
d) Immediately, add 50mL of quimosiac solution, heat for about 15 minutes while sometimes
mixing in a water bath at 60 ºC - 65 ºC to produce the precipitate of quinonium
phosphomolybdate.
e) After standing to cool down to room temperature while sometimes mixing, filter under reducedpressure with a crucible type glass filter, wash the tall beaker 3 times with water and transfer
the whole precipitate into a crucible type glass filter, and further wash 7 - 8 times with water.
f) Put the precipitate together with the crucible type glass filter in a drying apparatus and heat at
220 ºC ± 5 ºC for about 30 minutes.
g) As soon as heating is complete, move it into a desiccator and let it stand to cool.
h) After standing to cool, remove the crucible type glass filter from the desiccator and measure themass to the order of 1 mg.
i) Calculate total phosphoric acid (T-P2O5) in the analytical sample by the following formula.
Total phosphoric acid (T-P2O5) (% (mass fraction)) in an analytical sample=A × 0.03207 × (V1/V2) × (1/W) × 100
A： Mass (g) of the precipitate in h)
W： Mass (g) of the analytical sample
V1： Constant volume (mL) of sample solution
V2： Aliquot volume (mL) of the sample solution in a)
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.98- 106, Yokendo, Tokyo (1988)

92

Testing Methods for Fertilizers(2021)(5) Flow sheet for total phosphoric acid: The flow sheet for total phosphoric acid in fertilizers isshown below:

93Testing Methods for Fertilizers(2021)

4.2.2 Citrate-soluble phosphoric acid
4.2.2.a Ammonium vanadomolybdate absorptiometric analysis(1) Summary
This testing method is applicable to fertilizers that do not contain matter not colored by hydrolysis
with nitrate acids such as phosphonic acid. This testing method is classified as Type B and its symbol
is 4.2.2.a-2017 or S-P.a-1.
Extract by adding water to an analytical sample, then extract by adding an ammonium citric acidsolution, and combine respective pre-determined amounts of extract (equivalent volume). Heat after
adding nitric acid (1+1), hydrolyze nonorthophosphoric acid to orthophosphate ion and measure theabsorbance of phosphovanadomolybdate salt formed by the reaction with ammonium vanadate (V),hexaammonium heptamolybdate and nitric acid to obtain ammonia alkaline ammonium citratesoluble phosphoric acid (citrate-soluble phosphoric acid (S-P2O5)) in an analytical sample. In addition,
the performance of this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
b) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS K
8085 or a reagent of equivalent quality.
c) Petermans citrate solution: Add 173 g of citric acid monohydrate specified in JIS K 8283 inwater to dissolve and add gradually an ammonia solution equivalent to 42 g of nitrogen while
cooling. After cooling is complete, add water to make 1000 mL. Additionally, check that the
specific gravity of the solution is 1.082 - 1.083 (15 ºC) and the nitrogen content per 1 mL is 42
mg.
d) Coloring reagent solution (1) (2): Dissolve 1.12 g of ammonium vanadate (V)(3) specified in JIS
K 8747 in water, add 150 mL of nitric acid, then add 50 g of hexaammonium heptamolybdate
tetrahydrate (4) specified in JIS K 8905 dissolved in water, and further add water to make 1000mL (5).
e) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium
dihydrogenphosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand tocool in a desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water,transfer to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to themarked line.
f) Phosphoric acid standard solution (P2O5 0.5 mg/mL) (1): Put 50 mL of phosphoric acidstandard solution (P2O5 10 mg/mL) in a 1000-mL volumetric flask, add 2 mL - 3 mL of nitricacid, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to reagent “b” reagent solution in the Official Methods of Analysis of
Fertilizers (1992).
(3) This corresponds to ammonium metavanadate in the Official Methods of Analysis of
Fertilizers (1992).
(4) This corresponds to ammonium molybdate in the Official Methods of Analysis of
Fertilizers (1992).
(5) Store in an amber bottle. However. the reagent solution cannot tolerate long termpreservation.
Comment 1 The coloring reagent solution in d) can also be prepared by the following method.
Dissolve 2.24 g of ammonium vanadate (V) (3) specified in JIS K 8747 in water, add
300 mL of nitric acid, and add water to make 1000 mL. Separately, add 100 g of94

Testing Methods for Fertilizers(2021)

hexaammonium heptamolybdate tetrahydrate (4) specified in JIS K 8905 while
dissolving in water, and further add water to make 1000 mL. In the case of usage, mix
equal volumes of the two solutions.
Comment 2 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate citrate-soluble phosphoric acid (S-P2O5) in an analytical sample bymultiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.3) by a conversion factor (2.2914).
(3) Instruments: Instruments are as shown below:a) Water bath: Water bath that can be adjusted to 65 ºC ± 2 ºC.
b) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
c) Spectrophotometer: A spectrophotometer specified in JIS K 0115
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a small mortar.
b) Add about 20 mL - 25 mL of water, grind and filter (6) the supernatant with Type 6 filter paper
into a 250-mL volumetric flask.
c) Further, after repeating procedure in b) 3 times, transfer non-dissolved matter in the small
mortar onto a filter paper with water and wash with water until the filtrate becomes about 200mL.
d) Add a small amount of nitric acid to the filtrate, and further add water up to the marked line to
make a sample solution (1).
e) Transfer the non-dissolved matter on the filter paper together with the filter paper to another250- mL (7) volumetric flask, and add 100 mL of Petermans citrate solution and stopple. Then
shake to mix until the filter paper breaks down.
f) Heat the volumetric flask in e) in water bath at 65 ºC ± 2 ºC for 1 hour while shaking to mix
every 15 minutes.
g) After immediate cooling is complete, add water up to the marked lineh) Filter with Type 3 filter paper to make a sample solution (2).
Note (6) It is recommended to use a long stem funnel.
(7) It is recommended to use a 250-mL short-neck volumetric flask.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
Comment 4 When the determination is affected by the coloring of the sample solution of d) and h),
put the predetermined volume (8) of the sample solution (1) and the sample solution (2)in a 100-mL volumetric flask, add a few drops of hydrochloric acid (1+1) to acidify,
then add no more than 0.1 g of active carbon. After leaving at rest for a little while,
add water up to the marked line and filter with Type 3 filter paper. The filtrate is to be
the mixture solution for the sample solution of (4.2) a). Additionally, as phosphorus
contained in active carbon has the possibility to elute and affects the determination
value, a blank test is required.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount (the equivalents of 0.5 mg - 6 mg as P2O5 and no more than theequivalents of 2 mL of Petermans citrate solution) (8) of the sample solution (1) and the sample
95

Testing Methods for Fertilizers(2021)

solution (2) in a 100-mL volumetric flask.
b) Add the solution to make Petermans citrate solution equivalent to 2 mL.
c) Add 4 mL of nitric acid (1+1) (9), and heat to boil (10).
d) After cooling is complete, add a proper amount of water (11).
e) Add 20 mL of coloring reagent solution, and further add water up to the marked line, and thenleave at rest for about 30 minutes (9).
Comment 5 The volumetric flask used in the procedure in a) should be distinguished as a flask to
be used for phosphate coloring operation and should not be used for other purposes.
Note (8) The transferred volume of the sample solution (1) and the sample solution (2) should beequivalent.
(9) When the solution is muddled by adding nitric acid (1+1), conduct centrifugation with
about 1700 × g centrifugal force (12) for about five minutes after the procedure in e).
(10) When it does not contain nonorthophosphoric acid, the boiling operation is notnecessary.
(11) Without the addition of water, precipitate may be produced when a coloring reagent
solution is added.
(12) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of spectrophotometer: Set up the measurement conditions ofspectrophotometer considering the following.
Detection wavelength: 420 nmb) Calibration curve preparation
1) Put 1 mL - 12 mL of phosphoric acid standard solution (P2O5 0.5 mg/mL) in 100-mL volumetricflasks step-by-step.
2) Add 2 mL of Petermans citrate solution, 4 mL of nitric acid (1+1) and a proper amount of water(11), and conduct the same procedure as (4.2) e) to make the P2O5 0.5 mg/100 mL - 6 mg/100
mL phosphoric acid standard solutions for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 420 nm of the phosphoric acid standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control (13).
5) Prepare the calibration curve of the phosphoric acid concentration and absorbance of thephosphoric acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) e), measure absorbance by the same procedure as b) 4) (13).
2) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate citratesoluble phosphoric acid (S-P2O5) in the analytical sample.
Note (13) Measure within 2 hours after adding the coloring reagent solution.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 99.4 % - 100.6 %and 98.6 % - 103.0 % as citrate-soluble phosphoric acid (S-P2O5) respectively.
96

Testing Methods for Fertilizers(2021)

In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1. In addition, the results of thecollaborative study to determine a certified reference material fertilizer were analyzed
by using a three-level nesting analysis of variance. Table 2 shows the calculation
results of reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.08 % (mass fraction).

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.108- 114, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
97

Testing Methods for Fertilizers(2021)

3)

4)

(5)

Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)
Akira SHIMIZU and Shin ABE: Verification of Performance Characteristics of Testing
Method for Citrate-Soluble Phosphorus Content by Ammonium Vanadomolybdate
Absorption Photometry, Research Report of Fertilizer Vol. 5, p. 180 - 189 (2012)
Toshio HIRABARA, Shin ABE, and Masahiro ECHI: Performance Evaluation of
Determination Method for Phosphoric Acid in fertilizer: Harmonized Collaborative
Validation, Research Report of Fertilizer, Vol. 12, p. 94 – 108 (2019)

Flow sheet for citrate soluble phosphoric acid: The flow sheet for citrate soluble phosphoricacid in fertilizers is shown below:
2.5 g analytical sample

Repeat 3 times

Weigh to the order of 1 mg to a small mortar← About 20 mL - 25 mL water
Grinding

Supernatant filtration

Type 6 filter paper, 250-mL volumetric flask＜Residue＞
Transfer
Transfer residue to a filter paper← Washing with water, until filtrate reaches about 200 mL＜Residue＞＜Filtrate＞← A small amount of nitric acid
← Water (up to the marked line)
Sample solution (1)Transfer
Together with filter paper, 250-mL volumetric flask
100
ml
of
Petermans
citrate solution←
Shaking to mix
Stopple and shake to mix until a filter paler breaks down
Heating

At 65 ºC ± 2 ºC for 1 hour while shaking to mix every 15 minutes.

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution (2)Figure 1 Flow sheet for citrate-soluble phosphoric acid in fertilizers (Extraction procedure)98

Testing Methods for Fertilizers(2021)

99

Testing Methods for Fertilizers(2021)

4.2.2.b Quinoline gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing no Phosphorous acid, etc. It is suitable
for the fertilizers with relatively a high content of phosphoric acid. This testing method is classified
as Type E and its symbol is 4.2.2.b-2017 or S-P.b-1.
Extract by adding water to an analytical sample, then extract by adding an ammonium citric acidsolution, and combine respective pre-determined amounts of extract (equivalent volume). Heat after
adding nitric acid and water, hydrolyze nonorthophosphoric acid to orthophosphate ion and measure
the mass of quinolinium phosphomolybdate formed by the reaction with quinoline, molybdic acidand nitric acid to obtain ammonia alkaline ammonium citrate-soluble phosphoric acid (citrate-soluble
phosphoric acid (S-P2O5)) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
b) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS K
8085 or a reagent of equivalent quality.
c) Petermans citrate solution: Add 173 g of citric acid monohydrate specified in JIS K 8283 inwater to dissolve and add gradually an ammonia solution equivalent to 42 g of nitrogen while
cooling. After cooling is complete, add water to make 1000 mL. Additionally, check that the
specific gravity of the solution is 1.082 - 1.083 (15 ºC) and the nitrogen content per 1 mL is 42
mg.
d) Sodium molybdate solution: Dissolve 70 g of sodium molybdate dihydrate in 150 mL ofwater.
e) Quinoline solution: Add 5 mL of quinolone specified in JIS K 8279 to the mixture solutionof 35 mL of nitric acid and 100 mL of water.
f) Quimosiac solution: Add 60 g of citric acid monohydrate specified in JIS K 8283 to the
mixture solution of 85 mL nitric acid and 150 mL of water to dissolve. Add gradually total
volume of the sodium molybdate solution to mix. Add gradually the total volume of thequinoline solution while mixing the solution. After leaving at rest overnight, filter the total
volume with Type 3 filter paper. Add 280 mL of acetone specified in JIS K 8034, and further
add water to make 1000 mL.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Water bath: Water bath that can be adjusted to 65 °C ± 2 °C and 60 ºC - 65 ºC.
b) Drying apparatus: A drying apparatus that can be adjusted to 220 °C ± 5 ºC.
c) Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 220 ºC ± 5 ºC in advance and measure the mass tothe order of 1 mg.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a small mortar.
b) Add about 20 mL - 25 mL of water, grind well and filter (1) the supernatant with Type 6 filter
paper into a 250-mL volumetric flask.
c) Further, after repeating procedure in b) 3 times, transfer non-dissolved matter in the small
mortar onto a filter paper with water and wash with water until the filtrate becomes about 200mL.
d) Add a small amount of nitric acid to the filtrate, and further add water up to the marked line to
make a sample solution (1).
100

Testing Methods for Fertilizers(2021)e)

Transfer the non-dissolved matter on the filter paper together with the filter paper to another250- mL volumetric flask (2), and add 100 mL of Petermans citrate solution and stopple. Then
shake to mix until the filter paper breaks down completely.
f) Heat the volumetric flask in e) in water bath at 65 ºC ± 2 ºC for 1 hour while shaking to mix
every 15 minutes.
g) After immediate cooling is complete, add water up to the marked lineh) Filter with Type 6 filter paper to make a sample solution (2).
Note (1) It is recommended to use a long stem funnel.
(2) It is recommended to use a 250-mL short-neck volumetric flask.
Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined amount (the equivalents of 10 mg - 30 mg as P2O5 and no more than theequivalents of 2 mL of Petermans citrate solution) (3) of the sample solution (1) and the sample
solution (2) in a 300-mL tall beaker.
b) Add 5 mL of nitric acid and add water to make about 80 mL.
c) Cover with a watch glass. After boiling for about 3 minutes, wash the watch glass and the inside
the tall beaker with water and add water to make about 100 mL.
d) Immediately, add 50mL of quimosiac solution, heat for about 15 minutes while sometimes
mixing in a water bath at 60 ºC - 65 ºC to produce the precipitate of quinonium
phosphomolybdate.
e) After standing to cool down to room temperature while sometimes mixing, filter under reducedpressure with a crucible type glass filter, wash the tall beaker 3 times with water and transfer
the whole precipitate into a crucible type glass filter, and further wash 7 - 8 times with water.
f) Put the precipitate together with the crucible type glass filter in a drying apparatus and heat at
220 ºC ± 5 ºC for about 30 minutes.
g) As soon as heating is complete, move it into a desiccator and let it stand to cool.
h) After standing to cool, remove the crucible type glass filter from the desiccator and measure themass to the order of 1 mg.
i) Calculate citrate-soluble phosphoric acid (S-P2O5) in the analytical sample by the following
formula.
Citrate-soluble phosphoric acid (% (mass fraction)) in an analytical sample= A × 0.03207 × (V1/V2) × (1/W) × 100
A： Mass (g) of the precipitate in h)
W： Mass of an analytical sample (2.5 g)
V1： Constant volume (250 mL) of the sample solution
V2： Aliquot volume (mL) of the sample solution in a)
Note (3) The transferred volume of the sample solution (1) and the sample solution (2) should beequivalent.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.98- 106, Yokendo, Tokyo (1988)
101

Testing Methods for Fertilizers(2021)(5) Flow sheet for citrate soluble phosphoric acid: The flow sheet for citrate soluble phosphoricacid in fertilizers is shown below:
2.5 g analytical sample
Repeat 3 times

Weigh to the order of 1 mg to a small mortar← About 20 mL - 25 mL water
Grinding
Supernatant filtration

Type 6 filter paper, 250-mL volumetric flask＜Residue＞＜Residue＞

Transfer
Transfer residue to a filter paper← Wash with water, until filtrate reaches about 200 mL＜Filtrate＞← A small amount of nitric acid
← Water (up to the marked line)
Sample solution (1)Transfer
Together with filter paper, 250-mL volumetric flask← 100 ml Petermans citrate solution
Shaking to mix
Stopple and shake to mix until a filter paler breaks down
Heating

At 65 ºC ± 2 ºC for 1 hour while shaking to mix every 15 minutes.

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution (2)Figure 1 Flow sheet for citrate-soluble phosphoric acid in fertilizers(Extraction procedure)102

Testing Methods for Fertilizers(2021)

103

Testing Methods for Fertilizers(2021)

4.2.3 Citric acid-soluble phosphoric acid
4.2.3.a Ammonium vanadomolybdate absorptiometric analysis(1) Summary
This testing method is applicable to fertilizers that do not contain matter not colored by hydrolysis
with nitrate acids such as phosphonic acid. This testing method is classified as Type B and its symbol
is 4.2.3.a-2018 or C-P.a-2.
Extract by adding a citric acid solution to an analytical sample. Heat after adding nitric acid (1+1),hydrolyze nonorthophosphoric acid to orthophosphate ion and measure the absorbance ofphosphovanadomolybdate salt formed by the reaction with ammonium vanadate (V), hexaammonium
heptamolybdate and nitric acid to obtain citric acid-soluble phosphoric acid (C-P2O5) in an analyticalsample. In addition, the performance of this testing method is shown in Comment 9.
(2) Reagent: Reagents are as shown below.
a) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
b) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
c) Coloring reagent solution (1) (2): Dissolve 1.12 g of ammonium vanadate (V)(3) specified in JIS
K 8747 in water, add 150 mL of nitric acid, then add 50 g of hexaammonium heptamolybdate
tetrahydrate (4) specified in JIS K 8905 dissolved in water, and further add water to make 1000mL (5).
d) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
e) Phosphoric acid standard solution (P2O5 0.5 mg/mL) (1): Put 50 mL of phosphoric acidstandard solution (P2O5 10 mg/mL) in a 1000-mL volumetric flask, add 2 mL - 3 mL of nitricacid, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to reagent “b” reagent solution in the Official Methods of Analysis of
Fertilizers (1992).
(3) This corresponds to ammonium metavanadate in the Official Methods of Analysis of
Fertilizers (1992).
(4) This corresponds to ammonium molybdate in the Official Methods of Analysis of
Fertilizers (1992).
(5) Store in an amber bottle. However, the reagent solution cannot tolerate long termpreservation.
Comment 1 The coloring reagent solution in c) can also be prepared by the following method.
Dissolve 2.24 g of ammonium vanadate (V) (3) specified in JIS K 8747 in water, add
300 mL of nitric acid, and add water to make 1000 mL. Separately, add 100 g ofhexaammonium heptamolybdate tetrahydrate (4) specified in JIS K 8905 while
dissolving in water, and further add water to make 1000 mL. In the case of usage, mix
equal volumes of the two solutions.
Comment 2 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate citric acid-soluble phosphoric acid (C-P2O5) in an analytical sample
104Testing Methods for Fertilizers(2021)

by multiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.3) by a conversion factor (2.2914).
(3) Instruments: Instruments are as shown below:a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
c) Spectrophotometer: A spectrophotometer specified in JIS K 0115
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (6), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (6) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(7).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (6), and shake to mix by reciprocating
horizontally at 160 times /min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (7) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 For a by-product phosphate fertilizer, if the pH of the sample solution in (4.1.1) d) and(4.1.2) d) is neutral or basic, prepare a sample solution anew by replacing “1 g of ananalytical sample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of ananalytical sample”.
Comment 6 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
Comment 7 When the determination is affected by the coloring of the sample solution of (4.1.1) d)
105

Testing Methods for Fertilizers(2021)

and (4.1.2) d), transfer the predetermined volume of the sample solution to a 100-mL
volumetric flask, add a few drops of hydrochloric acid (1+1) to acidify, then add nomore than 0.1 g of active carbon. After leaving at rest for a little while, add water up
to the marked line and filter with Type 3 filter paper. The filtrate is prepared as the
sample solution of (4.2) a). Additionally, as phosphorus contained in active carbon has
the possibility to elute and affects the determination value, a blank test is required.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 6 mg as P2O5
and no more than the equivalents of 17 mL of citric acid solution) in a 100-mL volumetric flask.
b) Add the solution to make citric acid solution equivalent to 17 mL.
c) Add 4 mL of nitric acid (1+1) (8), and heat to boil (9).
d) After cooling is complete, add a proper amount of water (10).
e) Add 20 mL of coloring reagent solution, and further add water up to the marked line, and thenleave at rest for about 30 minutes.
Comment 8 The volumetric flask used in the procedure in a) should be distinguished as a flask to
be used for phosphate coloring operation and should not be used for other purposes.
Note (8) When the solution is muddled by adding nitric acid (1+1), conduct centrifugation with
about 1700 × g centrifugal force (11) for about five minutes after the procedure in e).
(9) When it does not contain nonorthophosphoric acid, the boiling operation is notnecessary.
(10) Without the addition of water, precipitate may be produced when a coloring reagent
solution is added.
(11) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 420 nmb) Calibration curve preparation
1) Put 1 mL - 12 mL of phosphoric acid standard solution (P2O5 0.5 mg/mL) in 100-mL volumetricflasks step-by-step.
2) Add 17 mL of a citric acid solution, then add 4 mL of nitric acid (1+1), further add a properamount of water (10) and conduct the same procedure as (4.2) e) to make the P2O5 0.5 mg/100
mL - 6 mg/100 mL phosphoric acid standard solution for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 420 nm of the phosphoric acid standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control (12).
5) Prepare the calibration curve of the phosphoric acid concentration and absorbance of thephosphoric acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) e), measure absorbance by the same procedure as b) 4) (12).
2) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate citric acid106

Testing Methods for Fertilizers(2021)

soluble phosphoric acid (C-P2O5) in the analytical sample.
Note (12) Measure within 2 hours after adding the coloring reagent solution.
Comment 9 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 96.6 % - 103.4 %and 102.0 % - 103.8 % as citric acid-soluble phosphoric acid (C-P2O5) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1. In addition, the results of thecollaborative study to determine a certified reference material fertilizer were analyzed
by using a three-level nesting analysis of variance. Table 2 shows the calculation
results of reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.03 % (mass fraction) for solid fertilizers and about 0.01 % (mass fraction)
for fluid fertilizers.

107Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.108- 114, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)3)
Yoshiyuki SUNAGA, Yasushi SUGIMURA, Ichiro YOSHIDA and Hidenori KONISHI:
Verification of Performance Characteristics of Testing Methods for Phosphorus Content
in Fertilizer by Ammonium Vanadomolybdate Absorption Photometry, Research Reportof Fertilizer Vol. 5, p. 167 - 179 (2012)4)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)5)
Toshio HIRABARA, Shin ABE, and Masahiro ECHI: Performance Evaluation of
Determination Method for Phosphoric Acid in fertilizer: Harmonized Collaborative
Validation, Research Report of Fertilizer, Vol. 12, p. 94 – 108 (2019)108

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble phosphoric acid: The flow sheet for citric acid-soluble
phosphoric acid in fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble phosphoric acid in fertilizers(Extraction procedure (4.1.1))

1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30 ºC ± 1 º
C, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble phosphoric acid in fertilizers(Extraction procedure (4.1.2))
Sample solution
Aliquot
100-mL volumetric flask(predetermined volume)← Citric acid solution, until it reaches the equivalents of 17 mL← 4 mL of nitric acid(1+1)
Heating
Boiling
Cooling← A proper amount of water← 20 mL of coloring reagent solution← Water (up to the marked line)
Leaving at rest
For about 30 minutes
Measurement

Spectrophotometer (420nm)

Figure 2 Flow sheet for citric acid-soluble phosphoric acid in fertilizers(Coloring and measurement procedure)109

Testing Methods for Fertilizers(2021)

4.2.3.b Ammonium vanadomolybdate absorptiometric analysis (Fertilizers containing
phosphorous acid or phosphite)(1) Summary
This testing method is applicable to the fertilizers containing phosphorous acid or phosphite. This
testing method is classified as Type B and its symbol is 4.2.3.b-2018 or C-P.b-2.
Extract by adding a citric acid solution to an analytical sample, add hydrochloric acid - sulfuric
acid to heat, and oxygenate phosphorous acid ion to orthophosphate ion, and then measure theabsorbance of phosphovanadomolybdate salt formed by the reaction with ammonium vanadate (V),hexaammonium heptamolybdate and nitric acid to obtain citric acid-soluble phosphoric acid (C-P2O5)
in an analytical sample. In addition, the performance of this testing method is shown in Comment 7.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
d) Coloring reagent solution (1) (2): Dissolve 1.12 g of ammonium vanadate (V)(3) specified in JIS
K 8747 in water, add 150 mL of nitric acid, then add 50 g of hexaammonium heptamolybdate
tetrahydrate (4) specified in JIS K 8905 dissolved in water, and further add water to make 1000mL (5).
e) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
f) Phosphoric acid standard solution (P2O5 0.5 mg/mL) (1): Put 50 mL of phosphoric acidstandard solution (P2O5 10 mg/mL) in a 1000-mL volumetric flask, add 2 mL - 3 mL of nitricacid, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to reagent “b” reagent solution in the Official Methods of Analysis of
Fertilizers (1992).
(3) This corresponds to ammonium metavanadate in the Official Methods of Analysis of
Fertilizers (1992).
(4) This corresponds to ammonium molybdate in the Official Methods of Analysis of
Fertilizers (1992).
(5) Store in an amber bottle. However, the reagent solution cannot tolerate long termpreservation.
Comment 1 The coloring reagent solution in d) can also be prepared by the following method.
Dissolve 2.24 g of ammonium vanadate (V) (3) specified in JIS K 8747 in water, add
300 mL of nitric acid, and add water to make 1000 mL. Separately, add 100 g ofhexaammonium heptamolybdate tetrahydrate (4) specified in JIS K 8905 while
dissolving in water, and further add water to make 1000 mL. In the case of usage, mix
equal volumes of the two solutions.
Comment 2 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
110

Testing Methods for Fertilizers(2021)

this case, calculate citric acid-soluble phosphoric acid (C-P2O5) in an analytical sample
by multiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.3) by a conversion factor (2.2914).
(3) Instruments: Instruments are as shown below:a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
c) Spectrophotometer: A spectrophotometer specified in JIS K 0115
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (6), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (6) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(7).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (6), and shake to mix by reciprocating
horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (7) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 For a by-product phosphate fertilizer, if the pH of the sample solution in (4.1.1) d) and(4.1.2) d) is neutral or basic, prepare a sample solution anew by replacing “1 g of ananalytical sample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of ananalytical sample”.
111Testing Methods for Fertilizers(2021)

Comment 6 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount (up to 25 mL, the equivalents of 0.5 mg - 6 mg as P2O5) of thesample solution in a 100-mL - 200-mL tall beaker.
b) Add 3 mL of hydrochloric acid and 1 mL of nitric acid.
c) Cover the tall beaker with a watch glass (8), heat on a hot plate or sand bath at 200 ºC - 250 ºC
and condense until the solution volume becomes about 2 mL (9).
d) After standing to cool, transfer it with water to a 100- mL volumetric flask (10).
e) Add the citric acid solution to make the equivalents of 17 mL of the citric acid and further add
2 mL of nitric acid (1+1).
f) Add 20 mL of coloring reagent solution, and further add water up to the marked line, and thenleave at rest for about 30 minutes.
Note (8) A watch glass should not be uncovered when bubbles form while heating because they
may splash.
(9) It is recommended to transfer 2 mL of water to a 100-mL - 200-mL tall beaker in advanceand confirm the volume.
(10) The volume of the solution after transferring should be up to about 50 mL.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 420 nmb) Calibration curve preparation
1) Put 1 mL - 12 mL of phosphoric acid standard solution (P2O5 0.5 mg/mL) in 100-mL volumetricflasks step-by-step.
2) Add 17 mL of a citric acid solution, then add 4 mL of nitric acid (1+1), further add a properamount of water (11). Conduct the same procedure as (4.2) f) to make the P2O5 0.5 mg/100 mL- 6 mg/100 mL phosphoric acid standard solutions for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 420 nm of the phosphoric acid standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control (12).
5) Prepare the calibration curve of the phosphoric acid concentration and absorbance of thephosphoric acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) f), measure absorbance by the same procedure as b) 4) (12).
2) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate citric acidsoluble phosphoric acid (C-P2O5) in the analytical sample.
Note (11) If water is not added, precipitate may form when adding the coloring reagent solution.
(12) Measure within 2 hours after adding the coloring reagent solution in the procedure in(4.2) f).
112

Testing Methods for Fertilizers(2021)

Comment 7 Additive recovery testing was conducted to evaluate trueness using solid fertilizers (10samples) containing the equivalents of 1.03 % (mass fraction) - 51.04 % (massfraction) as citric acid-soluble phosphoric acid. As a result, the mean recovery rate was
99 % - 100 %.
The results of the repeatability tests on different days using a solid preparation sample
to evaluate precision were analyzed by one-way analysis of variance. Table 1 shows
the calculation results of intermediate precision and repeatability.
Additionally, results from a collaborative study for test method validation and theiranalysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.05 % (mass fraction).

113

Testing Methods for Fertilizers(2021)

References1)
Toshiaki HIROI, Masayuki YAMANISHI Determination Method for Citric Acid-Soluble
Phosphorus in Solid Fertilizer Containing Phosphonate (Phosphite) using
Spectrophotometer, Research Report of Fertilizer, Vol. 9, p. 43 - 58 (2016)
2)
Masayuki YAMANISHI, Toshiaki HIROI and Fumika TAKATSU Determination Method
for Citric Acid-Soluble and Water-Soluble Phosphorus in Solid Fertilizer Containing
Phosphonic Acid or Phosphonate (Phosphite) using Spectrophotometer: A Collaborative
Study, Vol. 9, p. 59 - 68 (2016)3)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)(5)

Flow sheet for citric acid-soluble phosphoric acid containing phosphorus acid, etc.: The
flow sheet for citric acid-soluble phosphoric acid in fertilizers containing phosphorus acid, etc.isshown below:
1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1-1 Flow sheet for citric acid-soluble phosphoric acidin fertilizers containing phosphorus acid, etc. (Extraction procedure (4.1.1))

1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30 ºC ± 1 º
C, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1-2 Flow sheet for citric acid-soluble phosphoric acidin fertilizers containing phosphorus acid, etc. (Extraction procedure (4.1.2))

114

Testing Methods for Fertilizers(2021)

Sample solution
Aliquot
100-mL - 200-mL tall beaker(predetermined volume)← 3 mL of hydrochloric acid← 1 mL of nitric acid
MixingHeating

Cover with a watch glass, heat on a hot plate or sand bathat 200 ºC - 250 ºC, condense until the solution volume reaches about 2 mL

Standing to coolTransfer
100-mL volumetric flask, water (solution volume is up to about 50 mL)← Citric acid solution, until the equivalent of 17 mL← 2 mL of Nitric acid (1+1)← 20 mL of coloring reagent solution← Water (up to the marked line)
Leaving at rest
For about 30 minutes
Measurement

Spectrophotometer (420 nm)

Figure 2 Flow sheet for citric acid-soluble phosphoric acidin fertilizers containing phosphorus acid, etc. (Coloring and measurement procedure)115

Testing Methods for Fertilizers(2021)

4.2.3.c Quinoline gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing no phosphorous acid, etc. It is suitable
for the fertilizers with relatively a high content of phosphoric acid. This testing method is classified
as Type E and its symbol is 4.2.3.c-2017 or C-P.c-1.
Extract by adding a citric acid solution to an analytical sample. Heat after adding nitric acid andwater, hydrolyze nonorthophosphoric acid to orthophosphate ion and measure the mass ofquinolinium phosphomolybdate formed by the reaction with quinoline, molybdic acid and nitric acidto obtain citric acid-soluble phosphoric acid (C-P2O5) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
b) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
c) Sodium molybdate solution: Dissolve 70 g of sodium molybdate dihydrate in 150 mL ofwater.
d) Quinoline solution: Add 5 mL of quinoline specified in JIS K 8279 to the mixture solutionof 35 mL of nitric acid and 100 mL of water.
e) Quimosiac solution: Add 60 g of citric acid monohydrate specified in JIS K 8283 to the
mixture solution of 85 mL nitric acid and 150 mL of water to dissolve. Add gradually total
volume of the sodium molybdate solution to mix. Add gradually the total volume of thequinoline solution while mixing the solution. After leaving at rest overnight, filter the total
volume with Type 3 filter paper. Add 280 mL of acetone specified in JIS K 8034, and further
add water to make 1000 mL.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
b) Water bath: Water bath that can be adjusted to 60 ºC - 65 ºC.
c) Drying apparatus: A drying apparatus that can be adjusted to 220 ºC ± 5 ºC.
d) Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 220 ºC ± 5 ºC in advance and measure the mass tothe order of 1 mg.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.

116

Testing Methods for Fertilizers(2021)

Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
Comment 2 For a by-product phosphate fertilizer or a fertilizer containing a by-product phosphate,
if the pH of the sample solution of d) is neutral or basic, prepare a sample solution
anew by replacing “1 g of an analytical sample” in the procedure in a) with “0.5 g ofan analytical sample”.
Comment 3 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedure of (4.1) b).
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 10 mg - 30 mg as P2O5) of sample solution in a
300-mL tall beaker.
b) Add 5 mL of nitric acid and add water to make about 80 mL.
c) Cover with a watch glass. After boiling for about 3 minutes, wash the watch glass and the inside
the tall beaker with water and add water to make about 100 mL.
d) Immediately, add 50mL of quimosiac solution, heat for about 15 minutes while sometimes
mixing in a water bath at 60 ºC - 65 ºC to produce the precipitate of quinolinium
phosphomolybdate.
e) After standing to cool down to room temperature while sometimes mixing, filter under reducedpressure with a crucible type glass filter, wash the tall beaker 3 times with water and transfer
the whole precipitate into a crucible type glass filter, and further wash 7 - 8 times with water.
f) Transfer the precipitate together with the crucible type glass filter into a drying apparatus andheat at 220 ºC ± 5 ºC for about 30 minutes.
g) As soon as heating is complete, move it into a desiccator and let it stand to cool.
h) After standing to cool, remove the crucible type glass filter from the desiccator and measure themass to the order of 1 mg.
i) Calculate citric acid-soluble phosphoric acid (C-P2O5) in the analytical sample by the following
formula.
Citric acid-soluble phosphoric acid (C-P2O5) (% (mass fraction)) in an analytical sample= A × 0.03207 × (V1/V2) × (1/W) × 100
A： Mass (g) of the precipitate in h)
W： Mass of an analytical sample (1 g)
V1： Constant volume (250 mL) of the sample solution
V2： Aliquot volume (mL) of the sample solution in a)
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.98- 106, Yokendo, Tokyo (1988)

117

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble phosphoric acid: The flow sheet for citric acid-soluble
phosphoric acid in fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Shaking to mix
Constant-temperature vertical rotating mixer (30 - 40
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1 Flow sheet for citric acid-soluble phosphoric acid in fertilizers (Extraction procedure)118

Testing Methods for Fertilizers(2021)

4.2.3.d ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. It is also suitable for the fertilizers containing
phosphite. This testing method is classified as Type D and its symbol is 4.2.3.d-2018 or C-P.d-1.
Extract by adding a citric acid solution to an analytical sample, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the phosphorus at a wavelength of 178.287 nm toobtain citric acid-soluble phosphoric acid (citric acid-soluble phosphoric acid (C-P2O5)) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 8.
(2) Reagent: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
d) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
e) Phosphoric acid standard solution (P2O5 1 mg/mL) (1): Put 10 mL of phosphoric acid standard
solution (P2O5 10 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up
to the marked line.
f) Phosphoric acid standard solution (P2O5 20 µg/mL - 0.4 mg/mL) for the calibration curve
preparation (1): Put 2 mL - 40 mL of phosphoric acid standard solution (P2O5 1 mg/mL) in a
100-mL volumetric flask step by step and add hydrochloric acid (1+23) up to the marked line.
g) Phosphoric acid standard solution ((P2O5 5 µg/mL - 20 µg/mL) for the calibration curve
preparation (1): Put 5 mL - 20 mL of phosphoric acid standard solution (P2O5 0.1 mg/mL) in
a 100-mL volumetric flask step by step and add hydrochloric acid (1+23) up to the marked line.
h) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) - g).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate citric acid-soluble phosphoric acid (C-P2O5) in an analytical sample
by multiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.2) by a conversion factor (2.2914).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3)a)

Instruments: Instruments are as shown below:
ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0115
119

Testing Methods for Fertilizers(2021)

1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
ba) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
bb) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(3).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix by reciprocating
horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (3) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 For a by-product phosphate fertilizer, if the pH of the sample solution in (4.1.1) d) and(4.1.2) d) is neutral or basic, prepare a sample solution anew by replacing “1 g of ananalytical sample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of ananalytical sample”.
Comment 6 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometry used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 178.287 nm
120

Testing Methods for Fertilizers(2021)b) Calibration curve preparation
1) Spray the phosphoric acid standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 178.287 nm.
2) Prepare a curve for the relationship between the phosphoric acid concentration and the indicatedvalue of the phosphoric acid standard solution for the calibration curve preparation and theblank test solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 40 mg as P2O5)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate citric acidsoluble phosphoric acid (C-P2O5) in the analytical sample.
Comment 7 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 The comparison of the measurement value (yi：1.74 % (mass fraction) - 49.04 % (massfraction )) of ICP Optical Emission Spectrometry and the measurement value (xi) of
Ammonium vanadomolybdate absorptiometric analysis was conducted to evaluate
trueness using processed phosphorus fertilizers (2 samples), compound fertilizers (12samples), home garden-use compound fertilizers (1 sample), mixed compost
compound fertilizers (2 samples), mixed phosphate fertilizers (2 samples), designatedblended fertilizers (4samples), blended fertilizers (5 samples), byproduct compound
fertilizers (1 sample), byproduct phosphorus fertilizers (2 samples), organic compound
fertilizers (1 sample) and fused phosphate fertilizers (1 sample). As a result, a
regression equation was y=−0.0027+1.001x, and its correlation coefficient (r) was
1.000. In addition, additive recovery testing was conducted using a preparation sample.
As a result, the mean recovery rate at the additive level of 0.260 % (mass fraction) 49.99 % (mass fraction) was 96.3 % - 100.8 %.
The results of the repeatability tests on different days using compound fertilizers andblended fertilizers to evaluate precision were analyzed by one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different daysof citric acid-soluble phosphoric acid (Solid fertilizer)
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Compound fertilizer
7
20.90
0.13
0.6
0.18
0.9
Blended fertilizer
7
6.44
0.06
0.9
0.06
1.0
1) The number of test days conducting a duplicate test 6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
× the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

121

Testing Methods for Fertilizers(2021)

References
1)
Keisuke AOYAMA: Simultaneous Determination of Water-Soluble Principal Ingredients(W-P2O5, W-K2O, W-MgO, W-MnO and W-B2O3) in Liquid Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research
Report of Fertilizer, Vol. 8, p. 1 - 9 (2015)
2)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)3)
Shingo MATSUO:
Simultaneous Determination of Citrate-Soluble Principal
Ingredients (C-P2O5, C-K2O, C-MgO, C-MnO and C-B2O3) in Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research
Report of Fertilizer, Vol. 11, p. 14 – 28 (2018)122

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble phosphoric acid: The flow sheet for citric acid-soluble
phosphoric acid in fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Shaking to mix
Constant-temperature vertical rotating mixer (30 - 40
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble phosphoric acid in fertilizers(Extraction procedure (4.1.1))

1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30 ºC ± 1 º
C, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble phosphoric acid in fertilizers(Extraction procedure (4.1.2))

123

Testing Methods for Fertilizers(2021)

4.2.4 Water-soluble phosphoric acid
4.2.4.a Ammonium vanadomolybdate absorptiometric analysis(1) Summary
This testing method is applicable to fertilizers that do not contain matter not colored by hydrolysis
with nitrate acids such as phosphonic acid. This testing method is classified as Type B and its symbol
is 4.2.4.a-2017 or W-P.a-1.
Extract by adding water to an analytical sample, add nitric acid (1+1) to heat, and hydrolyze
nonorthophosphoric acid to orthophosphate ion, then measure the absorbance ofphosphovanadomolybdate salt formed by the reaction with ammonium vanadate (V), hexaammonium
heptamolybdate and nitric acid to obtain water-soluble phosphoric acid (W-P2O5) in an analyticalsample. In addition, the performance of this testing method is shown in Comment 9.
(2) Reagent: Reagents are as shown below.
a) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
b) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS K
8085 or a reagent of equivalent quality.
c) Coloring reagent solution (1) (2): Dissolve 1.12 g of ammonium vanadate (V)(3) specified in JIS
K 8747 in water, add 250 mL of nitric acid, then add 27 g of hexaammonium heptamolybdate
tetrahydrate (4) specified in JIS K 8905 dissolved in water, and further add water to make 1000mL (5).
d) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
e) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
f) Phosphoric acid standard solution (P2O5 0.5 mg/mL) (1): Put 50 mL of phosphoric acidstandard solution (P2O5 10 mg/mL) in a 1000-mL volumetric flask, add 2 mL - 3 mL of nitricacid, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to reagent “a” reagent solution in the Official Methods of Analysis of
Fertilizers (1992).
(3) This corresponds to ammonium metavanadate in the Official Methods of Analysis of
Fertilizers (1992).
(4) This corresponds to ammonium molybdate in the Official Methods of Analysis of
Fertilizers (1992).
(5) Store in an amber bottle.
Comment 1 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate water-soluble phosphoric acid (W-P2O5) in an analytical sample bymultiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.3) by a conversion factor (2.2914).
(3)a)

Instruments: Instruments are as shown below:
Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
124Testing Methods for Fertilizers(2021)aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
c) Spectrophotometer: A spectrophotometer specified in JIS K 0115
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample(4.1.1.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 2 In the procedure of (4.1.1.1) a), it is also allowed to weigh 2.5 g of an analytical sample
to the order of 1 mg, and put it in a 250-mL volumetric flask. In that case, add about
200 mL of water in the procedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.1.2) Vertical reciprocating shaker:a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 200 mL of water, and shake to mix by reciprocating vertically at 300 times/min(amplitude of 40 mm) for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.1.2) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 6 When the determination is affected by the coloring of the sample solution of (4.1.1.1)d), (4.1.1.2) d) and (4.1.2) d), put the predetermined volume of the sample solution in
a 100-mL volumetric flask, add a few drops of hydrochloric acid (1+1) to acidify, then
add no more than 0.1 g of active carbon. After leaving at rest for a little while, add
water up to the marked line and filter with Type 3 filter paper. The filtrate is preparedas the sample solution of (4.2) a). Additionally, as phosphorus contained in active
carbon has the possibility to elute and affects the determination value, a blank test isrequired.
125

Testing Methods for Fertilizers(2021)(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 6 mg as P2O5)
in a 100-mL volumetric flask.
b) Add 4 mL of nitric acid (1+1) (6), and heat to boil (7).
c) After cooling is complete, add 1 - 2 drop(s) of phenolphthalein solution (1 g/100 mL), andneutralize by adding ammonia solution (1+1) until the color of the solution becomes light redpurple (14).
d) Add nitric acid (1+10) until the light red-purple color of the solution disappears to make itslightly acidic, and add a proper amount of water (8).
e) Add 20 mL of coloring reagent solution, and further add water up to the marked line, and thenleave at rest for about 30 minutes (6).
Comment 7 The volumetric flask used in the procedure in a) should be distinguished as a flask to
be used for phosphate coloring operation and should not be used for other purposes.
Note (6) When the solution is muddled by adding nitric acid (1+1), conduct centrifugation with
about 1700 × g centrifugal force (9) for about five minutes after the procedure in e).
(7) When it does not contain nonorthophosphoric acid, the procedure in b) is not necessary.
(8) Without the addition of water, precipitate may be produced when a coloring reagent
solution is added.
(9) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 420 nmb) Calibration curve preparation
1) Put 1 mL - 12 mL of phosphoric acid standard solution (P2O5 0.5 mg/mL) in 100-mL volumetricflasks step-by-step.
2) Add a proper amount of water (8), and conduct the same procedure as (4.2) e) to make the P2O5
0.5 mg/100 mL - 6 mg/100 mL phosphoric acid standard solutions for the calibration curve
preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 420 nm of the phosphoric acid standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control (10).
5) Prepare the calibration curve of the phosphoric acid concentration and absorbance of thephosphoric acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) e), measure absorbance by the same procedure as b) 4) (10).
2) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate watersoluble phosphoric acid (W-P2O5) in the analytical sample.
Note (10) Measure within 6 hours after adding the coloring reagent solution in the procedure in(4.2) e).
126

Testing Methods for Fertilizers(2021)

Comment 8 After the procedure in (4.2) a), it is possible to measure another measurement solutionof citrate-soluble phosphoric acid at the same time by adding 2 mL of Petermans citratesolution and by conducting the procedures from (4.2) c) to (4.3) in 4.2.2.a (using b
reagent solution in the Official Methods of Analysis of Fertilizers (1992)).
After the procedure in (4.2) a), it is possible to measure another measurement solutionof citrate-soluble phosphoric acid at the same time by adding 17 mL of citric acidsolution and by conducting the procedures from (4.2) c) to (4.3) in 4.2.3.a (using b
reagent solution in the Official Methods of Analysis of Fertilizers (1992)).
Comment 9 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 100.5 % - 101.2 %and 99.0 % - 101.7 % as water-soluble phosphoric acid (W-P2O5) respectively. The
comparison of the measurement value (yi: 0.292 % (mass fraction) - 40.40 % (massfraction)) of extraction by a vertical reciprocating shaker and the measurement value(xi) of extraction by a vertical rotating mixer was conducted using fertilizers (12samples). As a result, a regression equation was y = −0.041 + 0.999x, and its correlation
coefficient (r) was 1.000. The comparison of the measurement value (yi: 1.92 % (massfraction) - 12.21 % (mass fraction)) of simple extraction and the measurement value(xi) of extraction by a vertical rotating mixer was conducted using fluid fertilizers (12samples). As a result, a regression equation was y = 0.005 + 1.005x, and its correlation
coefficient (r) was 0.999.
The results of the repeatability tests on different days using compound fertilizers,
designated blended fertilizer and fluid compound fertilizer (2 samples) to evaluate
precision were analyzed by one-way analysis of variance. Tables 1-1 and 1-2 show thecalculation results of intermediate precision and repeatability. Table 2 shows results
and analysis results from a collaborative study for testing method validation. In
addition, the results of the collaborative study to determine a certified referencematerial fertilizer were analyzed by using a three-level nesting analysis of variance.
Table 3 shows the calculation results of reproducibility, intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.03 % (mass fraction) for solid fertilizers and about 0.004 % (mass fraction)
for fluid fertilizers.

127Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.108- 114, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)3)
Yoshiyuki SUNAGA, Yasushi SUGIMURA, Ichiro YOSHIDA and Hidenori KONISHI:
128

Testing Methods for Fertilizers(2021)

4)
5)
6)

Verification of Performance Characteristics of Testing Method for Citrate-Soluble
Phosphorus Content by Ammonium Vanadomolybdate Absorption Photometry, Research
Report of Fertilizer Vol. 5, p. 167 - 179 (2012)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components in
Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20 (2016)
Shinji KAWAGUCHI: Extraction Method for the Water-soluble Principal Ingredientsin the Solid Fertilizer using a General-purpose Equipment, Research Report of Fertilizer,
Vol. 10, p. 1 - 8 (2017)
Toshio HIRABARA, Shin ABE, and Masahiro ECHI: Performance Evaluation of
Determination Method for Phosphoric Acid in fertilizer: Harmonized Collaborative
Validation, Research Report of Fertilizer, Vol. 12, p. 94 – 108 (2019)(5) Flow sheet for water-soluble phosphoric acid: The flow sheet for water-soluble
phosphoric acid: in fertilizers is shown below:
5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask(powdery)← Water, about 400 mL
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble phosphoric acid in fertilizers(Extraction procedure (4.1.1.1))

129

Testing Methods for Fertilizers(2021)

130

Testing Methods for Fertilizers(2021)

4.2.4.b Ammonium vanadomolybdate absorptiometric analysis (Fertilizers containing
phosphorous acid or phosphite)(1) Summary
This testing method is applicable to the fertilizers containing phosphorous acid or phosphite. This
testing method is classified as Type B and its symbol is 4.2.4.b-2017 or W-P.b-1.
Extract by adding water to an analytical sample, add hydrochloric acid - sulfuric acid to heat, andoxygenate phosphorous acid ion to orthophosphate ion, and then measure the absorbance ofphosphovanadomolybdate salt formed by the reaction with ammonium vanadate (V), hexaammonium
heptamolybdate and nitric acid to obtain water-soluble phosphoric acid (W-P2O5) in an analyticalsample. In addition, the performance of this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
c) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS K
8085 or a reagent of equivalent quality.
d) Coloring reagent solution (1) (2): Dissolve 1.12 g of ammonium vanadate (V)(3) specified in
JIS K 8747 in water, add 250 mL of nitric acid, then add 27 g of hexaammonium
heptamolybdate tetrahydrate(4) specified in JIS K 8905 dissolved in water, and further add
water to make 1000 mL (5).
e) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
f) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
g) Phosphoric acid standard solution (P2O5 0.5 mg/mL) (1): Put 50 mL of phosphoric acidstandard solution (P2O5 10 mg/mL) in a 1000-mL volumetric flask, add 2 mL - 3 mL of nitricacid, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to reagent “a” reagent solution in the Official Methods of Analysis of
Fertilizers (1992).
(3) This corresponds to ammonium metavanadate in the Official Methods of Analysis of
Fertilizers (1992).
(4) This corresponds to ammonium molybdate in the Official Methods of Analysis of
Fertilizers (1992).
(5) Store in an amber bottle.
Comment 1 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate water-soluble phosphoric acid (W-P2O5) in an analytical sample bymultiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.3) by a conversion factor (2.2914).
(3)

Instruments: Instruments are as shown below:
131Testing Methods for Fertilizers(2021)

a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 250-mL - 500mL volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
c) Spectrophotometer: A spectrophotometer specified in JIS K 0115
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample(4.1.1.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 2 In the procedure of (4.1.1.1) a), it is also allowed to weigh 2.5 g of an analytical sample
to the order of 1 mg, and put it in a 250-mL volumetric flask. In that case, add about
200 mL of water in the procedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.1.2) Vertical reciprocating shaker:a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 200 mL of water, and shake to mix by reciprocating vertically at 300 times/min(amplitude of 40 mm) for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.1.2) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount (the equivalents of 0.5 mg - 6 mg as P2O5) of the sample solution132

Testing Methods for Fertilizers(2021)

in a 100-mL - 200-mL tall beaker.
b) Add 3 mL of hydrochloric acid and 1 mL of nitric acid.
c) Cover the tall beaker with a watch glass, heat on a hot plate or sand bath at 200 ºC - 250 ºC andcondense (7) until the solution volume becomes about 2 mL (6).
d) After standing to cool, transfer it with water to a 100- mL volumetric flask (8).
e) Add 1 - 2 drop (s) of phenolphthalein solution (1 g/100 mL), and neutralize by adding ammonia
solution (1+1) until the color of the solution becomes light red-purple.
f) Add nitric acid (1+10) until the light red-purple color of the solution disappears to make itslightly acidic.
g) Add 20 mL of coloring reagent solution, and further add water up to the marked line, and thenleave at rest for about 30 minutes.
Note (6) It is recommended to transfer about 2 mL of water to a 100-mL - 200-mL tall beaker inadvance and confirm the volume.
(7) Care should be taken not to exsiccate it. When it exsiccates, the determined value
becomes lower than usual in some cases.
(8) The volume of the solution after transferring should be up to about 50 mL.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 420 nmb) Calibration curve preparation
1) Put 1 mL - 12 mL of phosphoric acid standard solution (P2O5 0.5 mg/mL) in 100-mL volumetricflasks step-by-step.
2) Add a proper amount of water (9), and conduct the same procedure as (4.2) g) to make the P2O5
0.5 mg/100 mL - 6 mg/100 mL phosphoric acid standard solutions for the calibration curve
preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 420 nm of the phosphoric acid standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control (10).
5) Prepare the calibration curve of the phosphoric acid concentration and absorbance of thephosphoric acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) g), measure absorbance by the same procedure as b) 4) (10).
2) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate watersoluble phosphoric acid (W-P2O5) in the analytical sample.
Note (9) If water is not added, precipitate may form when adding the coloring reagent solution.
(10) Measure within 6 hours after adding the coloring reagent solution in the procedure in(4.2) g).
Comment 6 Recovery testing was conducted to evaluate trueness using a fluid preparation sample.
As a result, the mean recovery rates at the content level of 30 % (mass fraction) - 50 %(mass fraction), 10 % (mass fraction) - 20 % (mass fraction), 4 % (mass fraction) and
0.2 % (mass fraction) were 101.1 % - 101.8 %, 101.1 % - 101.5 %, 100.8 % and133

Testing Methods for Fertilizers(2021)

102.5 % as water-soluble phosphoric acid (W-P2O5) respectively. In the case of using
a solid preparation sample, the average rate of recovery at the content level of 30 %(mass fraction) - 59 % (mass fraction), 12 % (mass fraction) - 21 % (mass fraction)and 1 % (mass fraction) - 9 % (mass fraction) are 99.5 % - 100.4 %, 99.3 % - 100.3 %,and 96.9 % - 100.4% respectively.
The results of the repeatability tests on different days using a solid preparation sample
to evaluate precision were analyzed by one-way analysis of variance. Table 1 shows
the calculation results of intermediate precision and repeatability.
Also, table 2-1 and 2-2 show results from a collaborative study for test method
validation using solid and fluid fertilizers and its analysis.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.04 % (mass fraction) for solid fertilizers and about 0.01 % (mass fraction)
for fluid fertilizers.

134Testing Methods for Fertilizers(2021)

References1)
Toshiaki HIROI, Masakazu SAIKI and Kimie KATO: Development and Validation ofSpectrophotometry for Determination of Water-Soluble Phosphoric acid in Liquid Mixed
Fertilizer Containing Phosphonic acid, Research Report of Fertilizer, Vol. 1 P. 25 - 33
(2008)
2)
Toshiaki HIROI, Masakazu SAIKI and Kimie KATO: Determination of Water-Soluble
Phosphoric Acid in Liquid Mixed Fertilizer Containing Phosphonic Acid bySpectrophotometry: A Collaborative Study, Research Report of Fertilizer, Vol. 1 p. 34 40 (2008)
3)
Fumihiro ABE, Noriyuki SASAKI and Toshio HIRABARA: Determination of WaterSoluble Phosphorus in Solid Fertilizer Containing Phosphonic Acid bySpectrophotometry, Research Report of Fertilizer, Vol. 8, p. 10 - 16 (2015)
4)
Masayuki YAMANISHI, Toshiaki HIROI and Fumika TAKATSU Determination Method
for Citric Acid-Soluble and Water-Soluble Phosphorus in Solid Fertilizer Containing
Phosphonic Acid or Phosphonate (Phosphite) using Spectrophotometer: A Collaborative
Study, Vol. 9, p. 59 - 68 (2016)(5)

Flow sheet for water-soluble phosphoric acid containing phosphorus acid, etc.: The flow
sheet for water-soluble phosphoric acid in fertilizers containing phosphorus acid, etc.is shown
below:
5 g analytical sample(powdery)

Weigh to the order of 1 mg into a 500-mL volumetric flask← Water, about 400 mL
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble phosphoric acid in fertilizers
containing phosphorus acid, etc. (Extraction procedure (4.1.1.1))

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Testing Methods for Fertilizers(2021)

136

Testing Methods for Fertilizers(2021)

137

Testing Methods for Fertilizers(2021)

4.2.4.c Quinoline gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing no phosphorous acid, etc. It is suitable forthe fertilizers with relatively a high content of phosphoric acid. This testing method is classified as
Type E and its symbol is 4.2.4.c-2017 or W-P.c-1.
Extract by adding water to an analytical sample. Heat after adding nitric acid and water, hydrolyze
nonorthophosphoric acid to orthophosphate ion and measure the mass of quinonium
phosphomolybdate formed by the reaction with quinoline, molybdic acid and nitric acid to obtainwater-soluble phosphoric acid (W-P2O5) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
b) Sodium molybdate solution: Dissolve 70 g of sodium molybdate dihydrate in 150 mL ofwater.
c) Quinoline solution: Add 5 mL of quinoline specified in JIS K 8279 to the mixture solutionof 35 mL of nitric acid and 100 mL of water.
d) Quimosiac solution: Add 60 g of citric acid monohydrate specified in JIS K 8283 to the
mixture solution of 85 mL nitric acid and 150 mL of water to dissolve. Add gradually total
volume of the sodium molybdate solution to mix. Add gradually the total volume of thequinoline solution while mixing the solution. After leaving at rest overnight, filter the total
volume with Type 3 filter paper. Add 280 mL of acetone specified in JIS K 8034, and further
add water to make 1000 mL.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Water bath: Water bath that can be adjusted to 60 ºC - 65 ºC.
c) Drying apparatus: A drying apparatus that can be adjusted to 220 ºC ± 5 ºC.
d) Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 220 ºC ± 5 ºC in advance and measure the mass tothe order of 1 mg.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30 - 40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 1 In the procedure in a), it is also allowed to weigh 2.5 g of an analytical sample to theorder of 1 mg, and put it into a 250-mL volumetric flask. In that case, add about 200
mL of water in the procedure in b).
Comment 2 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement:
Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 10 mg - 30 mg as P2O5 and no more than 20
mL as the total solution volume) of sample solution in a 300-mL tall beaker.
138

Testing Methods for Fertilizers(2021)b) Add 5 mL of nitric acid and add water to make 80 mL.
c) Cover with a watch glass. After boiling for about 3 minutes, wash the watch glass and the inside
the tall beaker with water and add water to make 100 mL.
d) Immediately, add 50mL of quimosiac solution, heat for about 15 minutes while sometimes
mixing in a water bath at 60 ºC - 65 ºC to produce the precipitate of quinolinium
phosphomolybdate.
e) After standing to cool down to room temperature while sometimes mixing, filter under reducedpressure with a crucible type glass filter, wash the tall beaker 3 times with water and transfer
the whole precipitate into a crucible type glass filter, and further wash 7 - 8 times with water.
f) Transfer the precipitate together with the crucible type glass filter into a drying apparatus andheat at 220 ºC ± 5 ºC for about 30 minutes.
g) As soon as heating is complete, move it into a desiccator and let it stand to cool.
h) After standing to cool, remove the crucible type glass filter from the desiccator and measure themass to the order of 1 mg.
i) Calculate water-soluble phosphoric acid (W-P2O5) by the following formula.
Water-soluble phosphoric acid (% (mass fraction)) in an analytical sample= A × 0.03207 × (V1/V2) × (1/W) × 100
A： Mass (g) of the precipitate in h)
W： Mass of an analytical sample (5 g)
V1： Constant volume (500 mL) of the sample solution
V2： Aliquot volume (mL) of the sample solution in a)
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.98- 114, Yokendo, Tokyo (1988)(5)

Flow sheet for water-soluble phosphoric acid The flow sheet for water-soluble phosphoricacid: in fertilizers is shown below:
5 g analytical sample
Weigh to the order of 1 mg to a 500-mL volumetric flask← About 400 mL of water
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for water-soluble phosphoric acid in fertilizers(Extraction procedure)

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Testing Methods for Fertilizers(2021)

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Testing Methods for Fertilizers(2021)

4.2.4.d ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. It is also suitable for the fertilizers containing
phosphorus acid (phosphite). This testing method is classified as Type D for solid fertilizers and TypeB for fluid fertilizers. Its symbol is 4.2.4.d-2019 or W-P.d-2.
Extract by adding water to an analytical sample, introduce it to an ICP Optical Emission Spectrometer(ICP-OES) and measure the phosphorus at a wavelength of 178.287 nm to obtain water-soluble
phosphoric acid W-P2O5) in an analytical sample. In addition, the performance of this testing method
is shown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Phosphoric acid standard solution (P2O5 10 mg/mL) (1): Heat potassium dihydrogen
phosphate specified in JIS K 9007 at 105 ºC ± 2 ºC for about 2 hours, let it stand to cool in a
desiccator, and weigh 19.17 g to a weighing dish. Dissolve in a small amount of water, transfer
to a 1000-mL volumetric flask, add 2 mL-3 mL of nitric acid, and add water up to the markedline.
d) Phosphoric acid standard solution (P2O5 1 mg/mL) (1): Put 10 mL of phosphoric acid standard
solution (P2O5 10 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up
to the marked line.
e) Phosphoric acid standard solution (P2O5 20 µg/mL - 0.4 mg/mL) for the calibration curve
preparation (1): Put 2 mL - 40 mL of phosphoric acid standard solution (P2O5 1 mg/mL) in a
100-mL volumetric flask step by step and add hydrochloric acid (1+23) up to the marked line.
f) Phosphoric acid standard solution ((P2O5 5 µg/mL - 20 µg/mL) for the calibration curve
preparation (1): Put 5 mL - 20 mL of phosphoric acid standard solution (P2O5 0.1 mg/mL) in a
100-mL volumetric flask step by step and add hydrochloric acid (1+23) up to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the phosphoric acid standard solution in (2), a phosphoric acid standard
solution for a calibration curve can be prepared using a phosphoric acid standard
solution (P 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case,calculate water-soluble phosphoric acid (W-P2O5) in an analytical sample bymultiplying the concentration (P) of a phosphoric acid standard solution for acalibration curve or a measured value obtained in (4.2) by a conversion factor (2.2914).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
141

Testing Methods for Fertilizers(2021)ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample(4.1.1.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 3 In the procedure of (4.1.1.1) a), it is also allowed to weigh 2.5g of an analytical sample
to the order of 1 mg, and put it in a 250-mL volumetric flask
Comment 4 A sample solution obtained in the procedure in (4.1.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.1.2) Vertical reciprocating shakera) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 200 mL of water, and shake to mix at 300 times/min (amplitude of 40 mm) for about
30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 5 A sample solution obtained in the procedure in (4.1.1.2) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (2) The sampling amount of the analytical sample is 10 g when there is less phosphoric acidcontent in the fertilizers such as a home garden-use fertilizer.
Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 178.287 nm
142

Testing Methods for Fertilizers(2021)b) Calibration curve preparation
1) Spray the phosphoric acid standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 178.287 nm.
2) Prepare a curve for the relationship between the phosphoric acid concentration and the indicatedvalue of the phosphoric acid standard solution for the calibration curve preparation and theblank test solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 40 mg as P2O5)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the phosphoric acid (P2O5) content from the calibration curve, and calculate watersoluble phosphoric acid (W-P2O5) in the analytical sample.
Comment 7 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 The comparison of the measurement value (yi：0.390 % (mass fraction) - 29.5 % (massfraction )) of ICP Optical Emission Spectrometry and the measurement value (xi) of
Ammonium vanadomolybdate absorptiometric analysis was conducted to evaluate
trueness using powdery test fertilizers (26 samples). As a result, a regression equation
was y=−0.115+0.977x, and its correlation coefficient (r) was 0.998. Similarly thecomparison of the measurement value (yi：0.179 % (mass fraction) - 10.88 % (massfraction )) and the measurement value (xi) was conducted using fluid fertilizers (12samples). As a result, a regression equation was y=−0. 022+1.008x, and its correlation
coefficient (r) was 0.999. In addition, additive recovery testing was conducted using
preparation fertilizers (5 samples). As a result, the mean recovery rate at the additive
level of 1.64 % (mass fraction) - 52.15 % (mass fraction) was 99.8 % - 103.0 %.
Additive recovery testing was conducted using a fluid compound fertilizer (1 brand)
and a home garden-use compound fertilizer (1 brand). As a result, the mean recovery
rates at the additive level of 10 % (mass fraction) and 1 % (mass fraction) were 98.1 %and 101.9 % respectively.
The results of the repeatability tests on different days using a home garden-use
compound fertilizer (solid), a blended fertilizer, a fluid compound fertilizer and a homegarden-use compound fertilizer (fluid) to evaluate precision were analyzed by the oneway analysis of variance. Table 1-1 and 1-2 show the calculation results ofintermediate precision and repeatability. Additionally, results from a collaborative
study for test method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.04 % (mass fraction) for solid fertilizers and about 0.02 % (mass fraction)
for fluid fertilizers.

143Testing Methods for Fertilizers(2021)
Table 1-1 Analysis results of the repeatability tests on different days of water-soluble phosphoric acid
(Solid fertilizer)
2)
4)
6)
5)
7)
Test days ofMeansrs I(T) RSD I(T)RSD rName of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Home garden-use compound fertilizer
5
28.91
0.54
1.9
0.54
1.9
(solid)Blended fertilizer
5
1.58
0.05
3.3
0.07
4.5
1) The number of test days conducting a duplicate test 6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
× the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

Table 1-2 Analysis results of the repeatability tests on different days of water-soluble phosphoric acid(Fluid fertilizer)
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Fluid compound fertilizer
Home garden-use compound fertilizer(fluid)Footnote: Refer to Table 2-1

7

10.83

0.10

0.9

0.14

1.3

7

0.829

0.008

0.9

0.015

1.8

Table 2 Analysis results of the collaborative study
for the test method validation of water-soluble phosphoric acid
4)

RSD r

3)

(%)

10
9.45
0.16
Preparation sample (Fluid) 1
Preparation sample (Fluid) 2
10
2.02
0.02
10
5.07
0.06
Preparation sample (Fluid) 3
Preparation sample (Fluid) 4
9
1.04
0.01
10
0.519
0.003
Preparation sample (Fluid) 5
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

Sample name

Number of1)laboratories

Mean

2)

sr

3)

(%)

(%)

5)

6)

RSD R

(%)

3)

(%)

1.7

0.29

3.0

1.2

0.04

2.0

1.1

0.09

1.9

0.8

0.04

3.5

0.6

0.013

2.5

sR

7)

References
1)
Keisuke AOYAMA: Simultaneous Determination of Water-Soluble Principal Ingredients(W-P2O5, W-K2O, W-MgO, W-MnO and W-B2O3) in Liquid Fertilizer using Inductively
144

Testing Methods for Fertilizers(2021)

2)
3)

(5)

Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research Report of
Fertilizer, Vol. 8, p. 1 - 9 (2015)
Norio FUNAKI: Simultaneous Determination of Water-soluble Principal Ingredients in
Fertilizer using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES),
Research Report of Fertilizer, Vol. 12, p. 28 – 51 (2019)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)

Flow sheet: The flow sheet for water-soluble phosphoric acid of the fluid mixed fertilizers isshown below:

5 g analytical sample
Weigh to the order of 1 mg to a 500-mL volumetric flask(powdery)← Water, about 400 mL
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble phosphoric acid in fluid fertilizers(Extraction procedure (4.1.1.1)
2.5 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask(powdery)← Water, about 200 mL
Vertical reciprocating shaker (300 reciprocations/min, amplitude
Shaking to mix
of 40 mm), for 30 minutes, 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for water-soluble phosphoric acid in fluid fertilizers(Extraction procedure (4.1.1.2)

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Testing Methods for Fertilizers(2021)

4.3 Potassium
4.3.1 Total potassium
4.3.1.a Flame atomic absorption spectrometry or flame photometry(1) Summary
This testing method is applicable to fertilizers containing organic matters. This testing method isclassified as Type B and its symbol is 4.3.1.a-2021 or T-K.a-2.
Pretreat an analytical sample with incineration-hydrochloric acid boiling or aqua regia digestion toconvert the total potassium into potassium ion, add an interference suppressor solution, and then sprayin an acetylene-air flame, and measure the atomic absorption with potassium at a wavelength of 766.5
nm or 769.9 nm to quantify the total potassium. Or, determine the intensity of the emission line at awavelength of 766.5 nm or 769.9 nm produced in flame to obtain the total potassium (T-K2O) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 8.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
c) Interference suppressor solution: Weigh 12.5 g of calcium carbonate specified in JIS K
8617 into a 2000-mL beaker, add a small amount of water, gradually add 105 mL ofhydrochloric acid, and heat for a little while. After cooling is complete, add water to make 1000mL.
d) Potassium standard solution (K2O 1 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.583 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line. Dissolve in a small amount of water, transfer to a
1000-mL volumetric flask, and add water up to the marked line.
e) Potassium standard solution (K2O 5 µg/mL - 50 µg/mL) for the calibration curve
preparation (2): Put 2.5 mL - 25 mL of potassium standard solution (K2O 1 mg/mL) in 500-mL
volumetric flasks step-by-step, add about 50 mL of interference suppressor solution (3), and add
water up to the marked line.
f) Blank test solution for the calibration curve preparation (1): Put about 50 mL of interference
suppressor solution in a 500-mL volumetric flask (3), and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This is an example of preparation in the case of a wavelength of 769.9 nm; prepare anamount appropriate for the actual condition.
(3) Add an interference suppressor solution that is 1/10 of the volume to be prepared.
Comment 1 Instead of the potassium standard solution in (2), a potassium standard solution for thecalibration curve preparation can be prepared by using a potassium standard solution(K 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate total
potassium (T-K2O) in the analytical sample by multiplying the concentration (K) of apotassium standard solution for calibration curve preparation or a measurement value(K) obtained in (4.2) by a conversion factor (1.2046).
Comment 2 When using a sample solution obtained in the procedure in (4.1.2) h) for themeasurement of cadmium, nickel, chromium or lead, sulfuric acid and hydrochloric
acid in (2) should be a reagent of harmful metal analysis grade, microanalysis grade orequivalents.
147

Testing Methods for Fertilizers(2021)(3) Instruments: Instruments are as shown below:a) Analytical instrument: An atomic absorption spectrometer or a flame photometer as shown
below:aa) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A potassium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
ab) Flame photometer:
1) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can be adjusted to 550 ºC ± 5 ºC.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Incineration-hydrochloric acid boilinga) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make about 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After standing to cool, transfer to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (4) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 550 °C in 1 to 2 hours.
Comment 3 Do not conduct the procedures in (4.1.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Incineration-aqua regia digestiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (5).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (5).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mL
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Testing Methods for Fertilizers(2021)

of nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (6), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (7) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL volumetric flask with water, add water up to themarked line, and filter with Type 3 filter paper to make a sample solution.
Note (5) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(6) The watch glass can be removed.
(7) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 5 Do not conduct the procedures in (4.1.2) b) - c) in the case of fertilizers not containing
organic matters.
Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer or flame photometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer or the flame photometer:
Set up the measurement conditions for the atomic absorption spectrometer or the flame
photometer considering the following:
Analytical line wavelength: 766.5 nm or 769.9 nmb) Calibration curve preparation
1) Spray the potassium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 766.5 nm or 769.9 nm.
2) Prepare a curve for the relationship between the potassium concentration and the indicatedvalue of the potassium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as K2O)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the potassium content from the calibration curve, and calculate total potassium (T-K2O)
in the analytical sample.
Comment 7 The analytical line wavelength may be set to 404.4 nm with lower sensitivity. At the
wavelength of 404.4 nm, the slit width needs to be reduced to separate neighboringlines. If the slit width is specified for the instrument, set the slit width to the specified
value. An example preparation of standard solutions for calibration curve preparation
for a wavelength of 404.4 nm is 3 µg/mL - 90 µg/mL as K2O, and the minimum limit
149

Testing Methods for Fertilizers(2021)

of quantification was estimated to be about 3 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 97.8 % - 100.1 %and 100.9 % - 103.1 % as total potassium acid (T-K2O) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1. In addition, the results of thecollaborative study to determine a certified reference material fertilizer were analyzed
by using a three-level nesting analysis of variance. Table 2 shows the calculation
results of reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.08 % (mass fraction) for solid fertilizers and about 0.03 % (mass fraction)
for fluid fertilizers.

References
150

Testing Methods for Fertilizers(2021)

1)
2)
3)
4)

Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.132- 138, Yokendo, Tokyo (1988)
Kimie KATO, Masayuki YOSHIMOTO and Yuji SHIRAI: Systematization of
Determination Methods of Major Components in Sludge Fertilizer, Compost and Organic
Fertilizer, Research Report of Fertilizer, Vol. 3 p. 107 - 116 (2010)
Yasuharu KIMURA and Hisanori ARAYA Verification of Performance Characteristicsof Testing Methods for Potassium Content in Fertilizer by Atomic Absorption
Spectrometry, Research Report of Fertilizer Vol. 5, p. 190 - 200 (2012)
Hisanori ARAYA and Kimie KATO: Performance Evaluation of Determination Methods
for Potassium in Fertilizer - Harmonized Collaborative Validation - Research Report of
Fertilizer, Vol. 12, p. 109 – 122 (2019)(5) Flow sheet for total potassium: The flow sheet for total potassium in fertilizers is shown below:

151

Testing Methods for Fertilizers(2021)

152

Testing Methods for Fertilizers(2021)

4.3.1.b Sodium tetraphenylborate gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing organic matters. It is suitable for
fertilizers containing relatively a high content of potassium. This testing method is classified as TypeD and its symbol is 4.3.1.b-2017 or T-K.b-1.
Pretreat an analytical sample by incineration and hydrochloric acid to convert the total potassium
into potassium ion, mask co-existing ammonium and other salts with formaldehyde andethylenediamine tetraacetate, and measure the mass of potassium tetraphenylborate formed by thereaction with tetraphenylborate to obtain the total potassium (T-K2O) in an analytical sample. In
addition, the performance of this testing method is shown in Comment 2.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Formaldehyde solution: A JIS Guaranteed Reagent specified in JIS K 8872 or a reagent ofequivalent quality.
c) Sodium hydroxide solution (200 g/L) (1): Dissolve 200 g of sodium hydroxide specified in JIS
K 8576 in water to make 1000 mL.
d) Aluminum chloride solution (1 mol/L) (1): Dissolve 12 g of aluminum chloride (III)hexahydrate specified in JIS K 8114 in water to make 100 mL.
e) Tetraphenylborate solution (1): Put 6.1 g of sodium tetraphenylborate specified in JIS K 9521
in a 250-mL volumetric flask, dissolve by adding about 200 mL of water and add 10 mL ofaluminum chloride solution. Add a methyl red solution (0.1 g/100 mL) as an indicator, andneutralize with a sodium hydroxide solution (200 g/L) until the color of the solution changes toyellow, and then add water up to the marked line. Filter with Type 3 filter paper and add 0.5 mLof sodium hydroxide solution (200 g/L) to the total filtrate. Filter with Type 3 filter paper in thecase of usage.
f) Tetraphenylborate washing solution (1): Dilute 40 mL of tetraphenylborate solution withwater to make 1000 mL.
g) Ethylenediaminetetraacetate - Sodium hydroxide solution (1): Dissolve 10 g ofethylenediaminetetraacetic acid disodium dihydrogen dihydrate specified in JIS K 8107 and 8
g of sodium hydroxide specified in JIS K 8576 in a proper amount of water. Add 6 mL - 10 mLof tetraphenylborate solution while mixing according to the potassium content coexisting as
impurity after standing to cool, and then add water to make 100 mL. After leaving at rest for
about 30 minutes while sometimes mixing, filter with Type 3 filter paper.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Electric furnace: An electric furnace that can be adjusted to 550 ºC ± 5 ºC.
b) Drying apparatus: A drying apparatus that can be adjusted to 120 ºC ± 2 ºC.
c) Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 120 ºC ± 2 ºC in advance and measure the mass tothe order of 1 mg.
d) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
153Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh about 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mLtall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (2).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (2).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After cooling, transfer to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (2) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 550 °C in 1 to 2 hours.
Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined amount (the equivalents of 15 mg - 30 mg as K2O) of the sample solution
in a 100-mL tall beaker.
b) Add water to the solution to reach 50 mL when the procedure in e) is complete.
c) Add hydrochloric acid (1+9), so that the hydrochloric acid becomes equivalent to 0.2 mL.
d) Add 5 mL of formaldehyde solution, and then add 5 mL of ethylenediamine tetraacetate−sodiumhydroxide solution.
e) Add necessary volume (3) of tetraphenylborate solution at the rate of one or two drop(s) per
second while mixing, and further add 4 mL of the same solution in the same manner.
f) Leave at rest for about 30 minutes while sometimes mixing to form the precipitate of potassium
tetraphenylborate.
g) Filter supernatant under reduced pressure with a crucible type glass filter, wash the tall beaker
5 times with 5 mL of tetraphenylborate washing solution and transfer the whole precipitate to
the crucible type glass filter and further wash 2 times with 2 ml of water.
h) Transfer the precipitate together with the crucible type glass filter into a drying apparatus andheat at 120 ºC ± 2 ºC for about 1hour.
i) As soon as heating is complete, move it into a desiccator and let it stand to cool.
j) After standing to cool, remove the crucible type glass filter from the desiccator and measure themass to the order of 1 mg.
k) Calculate total potassium (T-K2O) in the analytical sample by the following formula.
Total potassium (T-K2O) (% (mass fraction)) in an analytical sample= A × 0.1314 × (V1/V2)/W × 100
A： Mass (g) of the precipitate
V1： Constant volume (mL) of the sample solution in (4.1) g)
V2： Aliquot volume (mL) of the sample solution in (4.2) a)
W： Mass (g) of the analytical sample
154

Testing Methods for Fertilizers(2021)

Note (3) About 3 ml of tetraphenylborate solution per 10 mg of K2O is required to form theprecipitate of potassium tetraphenylborate
Comment 2 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 25 % (mass fraction) - 30 %(mass fraction) and 10 % (mass fraction) - 20 % (mass fraction) were 99.5 % - 100.8 %and 99.5 % - 100.6 % as total potassium acid (T-K2O) respectively.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.3 % (mass fraction) for solid fertilizers.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.122- 128, Yokendo, Tokyo (1988)
2)
Keiji YAGI, Aiko YANO and Hideo SOETA:
Verification of Performance
Characteristics of Testing Method for Nitrate Nitrogen Content in Fertilizer by Phenol
Sulfuric Acid Method, Research Report of Fertilizer Vol. 5, p. 201 - 211 (2012)(5)

Flow sheet for total potassium: The flow sheet for total potassium in fertilizers is shown
below:

155

Testing Methods for Fertilizers(2021)

156

Testing Methods for Fertilizers(2021)

4.3.2 Citric acid-soluble potassium
4.3.2.a Flame atomic absorption spectrometry or flame photometry(1) Summary
This testing method is applicable to fertilizers containing potassium silicate fertilizers, etc. This
testing method is classified as Type B and its symbol is 4.3.2.a-2021 or C-K.a-3.
Extract by adding a citric acid solution to an analytical sample, add an interference suppressor
solution, and then spray in an acetylene−air flame, and measure the atomic absorption with potassium
at a wavelength of 766.5 nm or 769.9 nm to quantify citric acid-soluble potassium (C-K2O). Or,
measure the intensity of the emission line at a wavelength of 766.5 nm or 769.9 nm produced in flame
to quantify citric acid-soluble potassium (C-K2O) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
c) Interference suppressor solution (1): Weigh 12.5 g of calcium carbonate specified in JIS K
8617 into a 2000-mL beaker, add a small amount of water, gradually add 105 mL ofhydrochloric acid, and heat for a little while. After standing to cool, add water to make 1000mL.
d) Potassium standard solution (K2O 1 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.583 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line.
e) Potassium standard solution (K2O 5 µg/mL - 50 µg/mL) for the calibration curve
preparation (2): Put 2.5 mL - 25 mL of potassium standard solution (K2O 1 mg/mL) in 500-mL
volumetric flasks step-by-step, add about 50 mL of interference suppressor solution (3), and add
water up to the marked line.
f) Blank test solution for the calibration curve preparation (1): Put about 50 mL of interference
suppressor solution in a 500-mL volumetric flask (3), and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This is an example of preparation in the case of a wavelength of 769.9 nm; prepare anamount appropriate for the actual condition.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the potassium standard solution in (2), a potassium standard solution for thecalibration curve preparation can be prepared by using a potassium standard solution(K 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate
citric acid-soluble potassium (C-K2O) in the analytical sample by multiplying theconcentration (K) of a potassium standard solution for calibration curve preparation ora measurement value (K) obtained in (4.2) by a conversion factor (1.2046).
(3) Instruments: Instruments are as shown below:a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
157

Testing Methods for Fertilizers(2021)

mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Analytical instrument: An atomic absorption spectrometer or a flame photometer as shown
below:ba) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A potassium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
bb) Flame photometer:
1) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (4), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (4) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(5).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (4), and shake to mix by reciprocating
horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (5) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 3 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 4 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved matters
158

Testing Methods for Fertilizers(2021)

after the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer or the flame photometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer or the flame photometer:
Set up the measurement conditions for the atomic absorption spectrometer or the flame
photometer considering the following:
Analytical line wavelength: 766.5 nm or 769.9 nmb) Calibration curve preparation
1) Spray the potassium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 766.5 nm or 769.9 nm.
2) Prepare a curve for the relationship between the potassium concentration and the indicatedvalue of the potassium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as K2O)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the potassium content from the calibration curve, and calculate citric acid-soluble
potassium (C-K2O) in the analytical sample.
Comment 5 The analytical line wavelength may be set to 404.4 nm with lower sensitivity. At the
wavelength of 404.4 nm, the slit width needs to be reduced more than for other wave
lengths to separate neighboring lines. If the slit width is specified for the instrument,
set the slit width to the specified value. An example preparation of standard solutions
for calibration curve preparation for a wavelength of 404.4 nm is 3 µg/mL - 90 µg/mL
as K2O, and the minimum limit of quantification was estimated to be about 3 µg/mL
in a measurement solution. However, it is necessary to understand in advance theconcentration range of calibration curve suitable for the instrument and prepare
standard solutions for calibration curve preparation.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 100.2 % - 101.7 %and 100.4 % - 101.8 % as citric acid-soluble potassium (C-K2O) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.05 % (mass fraction) for solid fertilizers and about 0.06 % (mass fraction)
for fluid fertilizers.

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Testing Methods for Fertilizers(2021)
Table 1 Analysis results of the collaborative study
for the test method validation of citric acid-soluble potassium
Number of Mean2) s r4) RSD r5)
Sample name1)
3)
3)
laboratories
(%)
(%)
(%)
10
37.98
0.77
2.0
Byproduct compound fertilizer
10
20.32
0.12
0.6
Potassium silicate fertilizer
10
10.59
0.16
1.5
Compound fertilizer A
10
4.79
0.02
0.4
Compound fertilizer B
Home garden-use compound fertilizer
9
1.95
0.01
0.6
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

6)

sR

7)

(%)

RSD R
(%)

1.00
0.32

2.6
1.6

0.28
0.12

2.6
2.5

0.03

1.7

3)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.136- 138, Yokendo, Tokyo (1988)
2)
Yasuharu KIMURA and Hisanori ARAYA Verification of Performance Characteristicsof Testing Methods for Potassium Content in Fertilizer by Atomic Absorption
Spectrometry, Research Report of Fertilizer Vol. 5, p. 190 - 200 (2012)3)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)
4)
Hisanori ARAYA and Kimie KATO: Performance Evaluation of Determination Methods
for Potassium in Fertilizer - Harmonized Collaborative Validation - Research Report of
Fertilizer, Vol. 12, p. 109 – 122 (2019)(5)

Flow sheet for citric acid-soluble potassium: The flow sheet for citric acid-soluble potassiumin fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← 150 mL citrate solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1-1 Flow sheet for citric acid-soluble potassium in fertilizers (Extract procedure 4.1.1)

160

Testing Methods for Fertilizers(2021)

1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← 150 mL citrate solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30 ºC ± 1 º
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1-2 Flow sheet for citric acid-soluble potassium in fertilizers (Extract procedure 4.1.2)

161

Testing Methods for Fertilizers(2021)

4.3.2.b Sodium tetraphenylborate gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing potassium silicate fertilizers, etc. This
testing method is classified as Type D and its symbol is 4.3.2.b-2017 or C-K.b-1.
Extract by adding a citric acid solution to an analytical sample, mask co-existing ammonium andother salts with formaldehyde and ethylenediamine tetraacetate and measure the mass of citric acidsoluble potassium (citric acid-soluble potassium (C-K2O)) and the mass of potassium
tetraphenylborate formed by the reaction with tetraphenylborate to obtain citric acid-soluble
potassium (C-K2O) in an analytical sample. In addition, the performance of this testing method isshown in Comment 3.
(2) Reagent: Reagents are as shown below.
a) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
b) Formaldehyde solution: A JIS Guaranteed Reagent specified in JIS K 8872 or a reagent ofequivalent quality.
c) Sodium hydroxide solution (200 g/L) (1): Dissolve 200 g of sodium hydroxide specified in JIS
K 8576 in water to make 1000 mL.
d) Aluminum chloride solution (1 mol/L) (1): Dissolve 12 g of aluminum chloride (III)hexahydrate specified in JIS K 8114 in water to make 100 mL.
e) Tetraphenylborate solution (1): Put 6.1 g of sodium tetraphenylborate specified in JIS K 9521
in a 250-mL volumetric flask, dissolve by adding about 200 mL of water and add 10 mL ofaluminum chloride solution. Add a methyl red solution (0.1 g/100 mL) as an indicator, andneutralize with a sodium hydroxide solution (200 g/L) until the color of the solution changes toyellow, and then add water up to the marked line. Filter with Type 3 filter paper and add 0.5 mLof sodium hydroxide solution (200 g/L) to the total filtrate. Filter with Type 3 filter paper in thecase of usage.
f) Tetraphenylborate washing solution (1): Dilute 40 mL of tetraphenylborate solution withwater to make 1000 mL.
g) Ethylenediaminetetraacetate - Sodium hydroxide solution (1): Dissolve 10 g ofethylenediaminetetraacetic acid disodium dihydrogen dihydrate specified in JIS K 8107 and 8
g of sodium hydroxide specified in JIS K 8576 in a proper amount of water. Add 6 mL - 10 mLof tetraphenylborate solution while mixing according to the potassium content coexisting as
impurity after standing to cool, and then add water to make 100 mL. After leaving at rest for
about 30 minutes while sometimes mixing, filter with Type 3 filter paper.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
b) Drying apparatus: A drying apparatus that can be adjusted to 120 ºC ± 2 ºC.
c) Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 120 ºC ± 2 ºC in advance and measure the mass tothe order of 1 mg.
(4)

Test procedure162

Testing Methods for Fertilizers(2021)(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
Comment 2 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedure of (4.1) b).
(4.2) Measurement: Conduct measurement as shown below.
a) Put 20 mL of sample solution in a 100-mL tall beaker.
b) Add water to the solution to reach 50 mL when the procedure in d) is complete.
c) Add 5 mL of formaldehyde solution, and then add 5 mL of ethylenediamine tetraacetate sodium hydroxide solution.
d) Add necessary volume (3) of tetraphenylborate solution at the rate of one or two drop(s) per
second while mixing, and further add 4 mL of the same solution in the same manner.
e) Leave at rest for about 30 minutes while sometimes mixing to form the precipitate of potassium
tetraphenylborate.
f) Filter supernatant under reduced pressure with a crucible type glass filter, wash the vessel 5
times with 5 mL of tetraphenylborate washing solution and transfer the whole precipitate to the
crucible type glass filter and further wash 2 times with 2 ml of water.
g) Put the precipitate together with the crucible type glass filter into a drying apparatus and heatat 120 ºC ± 2 ºC for about 1hour.
h) As soon as heating is complete, move it into a desiccator and let it stand to cool.
i) After standing to cool, remove the crucible type glass filter from the desiccator and measure themass to the order of 1 mg.
j) Calculate citric acid-soluble potassium (C-K2O) by the following formula in the analyticalsample.
Citric acid-soluble potassium (C-K2O) (% (mass fraction)) in an analytical sample=A×0.1314×(V1/V2)/W×100
A： Mass (g) of the precipitate
V1： Constant volume (mL) of the sample solution in (4.1) c)
V2： Aliquot volume (mL) of the sample solution in (4.2) a)
W： Mass (g) of the analytical sample
Note (3) About 3 ml of tetraphenylborate solution per 10 mg of K2O is required to form theprecipitate of potassium tetraphenylborate
Comment 3 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 25 % (mass fraction) - 30 %163

Testing Methods for Fertilizers(2021)(mass fraction) and 10 % (mass fraction) - 20 % (mass fraction) were 98.6 % - 100.6 %and 100.6 % - 100.7 % as citric acid-soluble potassium (C-K2O) respectively.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.6 % (mass fraction) for solid fertilizers.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.122- 128, Yokendo, Tokyo (1988)
2)
Keiji YAGI, Aiko YANO and Hideo SOETA:
Verification of Performance
Characteristics of Testing Method for Nitrate Nitrogen Content in Fertilizer by Phenol
Sulfuric Acid Method, Research Report of Fertilizer Vol. 5, p. 201 - 211 (2012)(5)

Flow sheet for the testing method: The flow sheet for citric acid-soluble potassium in
fertilizers is shown below:

1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← 150 mL citrate solution [about 30 ºC]
Constant temperature rotary shaker (30 - 40 revolutions/min)Shaking to mix
30 ºC ± 1 ºC, 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for citric acid-soluble potassium in fertilizers (Extraction procedure)

164

Testing Methods for Fertilizers(2021)

4.3.2.c Sodium tetraphenylborate volumetric analysis(1) Summary
This testing method is applicable to fertilizers containing potassium silicate fertilizer, etc. but notorganic matters. This testing method is classified as Type E and its symbol is 4.3.2.c-2017 or C-K.c1.
Extract by adding a citric acid solution to an analytical sample, mask co-existing ammonium andother salts with formaldehyde, and make potassium ion and tetraphenylborate react with each other.
Measure unconsumed tetraphenylborate by conducting a precipitate titration to obtain citric acidsoluble potassium (C-K2O) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
b) Formaldehyde solution: A JIS Guaranteed Reagent specified in JIS K 8872 or a reagent ofequivalent quality.
c) Sodium hydroxide solution (120 g/L) (1): Dissolve 30 g of sodium hydroxide specified in JIS
K 8576 in water to make 250 mL.
d) Tetraphenylborate solution (1): Put 12.2 g of sodium tetraphenylborate in a 1000-mL
volumetric flask, dissolve by adding about 800 mL of water and add 3 mL of sodium hydroxide(120 g/L) to the total filtrate, and further add water up to the marked line. Filter with Type 3
filter paper in the case of usage.
e) Benzalkonium chloride solution (3.3 g/500 mL) (1): Dissolve 3.3 g of benzalkonium chloride
in 500 mL of water.
f) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
g) Titan Yellow solution (0.04 g/100mL): Dissolve 0.04 g of Titan Yellow in 100 mL of water inthe case of usage.
h) Potassium standard solution (K2O 2 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 3.166 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Instruments: Instruments are as shown below:a) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
165

Testing Methods for Fertilizers(2021)

Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
Comment 2 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedure of (4.1) b).
(4.2) Precipitate formation: Form precipitate as shown below.
a) Put 5 mL - 15 mL (no more than the equivalents of 30 mg as K2O) of the extract in a 100-mL
volumetric flask.
b) Add water to the solution to make about 30 mL.
c) Add about 5 mL of formaldehyde solution and add 5 mL of sodium hydroxide solution (120g/L).
d) Add 25 mL of tetraphenylborate solution at the rate of one or two drop(s) per second while
shaking to mix.
e) After adding water up to the marked line, leave at rest for 10 minutes.
f) Filter with Type 3 filter paper to make a sample solution.
(4.3) Measurement: Conduct measurement as shown below.
a) Calibration curve preparation
1) Put 1 mL - 15 mL of potassium standard solution (K2O 2 mg/mL) in 100-mL volumetric flasks
step-by-step.
2) Conduct the same procedures as (4.2) b) - f) to make K2O 2 mg/100 mL - 30 mg/100 mL of thepotassium standard solutions for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Put 40 mL of the potassium standard solutions for the calibration curve preparation and theblank test solution for the calibration curve preparation in an Erlenmeyer flask respectively.
5) Add a few drops of Titan Yellow solution.
6) Titrate with a benzalkonium chloride solution (3.3 g/500 mL) until the color of the solutionchanges to light red (2).
7) Prepare a curve for the relationship between the potassium concentration and the volume of the
benzalkonium chloride solution (3.3 g/500 mL) required for the titration of the potassium
standard solutions for the calibration curve preparation and the blank test solution for thecalibration curve preparation.
b) Sample measurement
1) Put 40 mL of the sample solution of (4.2) f) in a 100-mL Erlenmeyer flask.
2) Conduct similarly as in a) 5) - 6) to obtain the volume of the benzalkonium chloride solution(3.3 g/500 mL) required for the titration.
3) Obtain the potassium content from the calibration curve, and calculate citric acid-soluble
potassium (C-K2O) in the analytical sample.
Note (2) If the solution temperature is no more than 20 ºC, the reaction does not advance in somecases. Therefore, it is recommended to heat the solution up to about 30 ºC.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.128- 132, Yokendo, Tokyo (1988)

166

Testing Methods for Fertilizers(2021)(5) Flow sheet for citric acid-soluble potassium: The flow sheet for citric acid-soluble potassiumin fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← 150 mL citrate solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hourStanding to cool
← Water (up to the marked line)
Filtration
Type 3 filter paper
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for citric acid-soluble potassium in fertilizers (Extraction procedure)

Sample solution
Aliquot (5 mL - 15 mL)

100-mL volumetric flask← Water (the volume to reach about 30 mL)← About 5 mL of formaldehyde solution← 5 mL of sodium hydroxide solution (120 g/L)
← 25 mL tetraphenylborate solution(one or two drop (s) per second while shaking to mix)
← Water (up to the marked line)
Leaving at rest
10 minutes
Filtration

Type 3 filter paper

Aliquot (40 mL)
100-mL Erlenmeyer flask← A few drops of titan yellow solution
Benzaikonium chloride solution (3.3 g/500 mL)
Titration(until the solution changes to light red)
Figure 2 Flow sheet for citric acid-soluble potassium in fertilizers (Measurement procedure)

167

Testing Methods for Fertilizers(2021)

4.3.2.d ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 4.3.2.d-2018 or C-K.d-1.
Extract by adding a citric acid solution to an analytical sample, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the potassium at a wavelength of 766.491 nm toobtain citric acid-soluble potassium (citric acid-soluble potassium (C-K2O)) in an analytical sample.
In addition, the performance of this testing method is shown in Comment 8.
(2) Reagent: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
d) Potassium standard solution (K2O 1 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.583 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line.
e) Potassium standard solution (K2O 20 µg/mL - 0.16 mg/mL) for the calibration curve
preparation (1): Put 2 mL - 16 mL of potassium standard solution (K2O 1 mg/mL) in 100-mL
volumetric flasks step-by-step, add about 25 mL of hydrochloric acid (1+5), and add water up
to the marked line.
f) Potassium standard solution (K2O 2 µg/mL - 20 µg/mL) for the calibration curve
preparation (1): Put 2 mL - 20 mL of potassium standard solution (K2O 0.1 mg/mL) in 100-mL
volumetric flasks step-by-step, add about 25 mL of hydrochloric acid (1+23), and add water up
to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the potassium standard solution in (2), a potassium standard solution for thecalibration curve preparation can be prepared by using a potassium standard solution(K 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate
citric acid-soluble potassium (C-K2O) in the analytical sample by multiplying theconcentration (K) of a potassium standard solution for calibration curve preparation ora measurement value (K) obtained in (4.2) by a conversion factor (1.2046).
Comment 2 There are two modes to observe emission from an ICP-OES, a horizontal observation
mode and an axial observation mode. The axial observation mode does not apply topotassium since interference is serious.
Comment 3 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
168

Testing Methods for Fertilizers(2021)

0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
ba) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
bb) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(3).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix by reciprocating
horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (3) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 6 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometry used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:169

Testing Methods for Fertilizers(2021)

Analytical line wavelength: 766.491 nmb) Calibration curve preparation
1) Spray the potassium standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 766.491 nm.
2) Prepare a curve for the relationship between the potassium concentration and the indicatedvalue of the potassium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Transfer a predetermined amount of the sample solution (the equivalents of 0.2 mg - 16 mg
as K2O) to a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the potassium content from the calibration curve, and calculate citric acid-soluble
potassium (C-K2O) in the analytical sample.
Comment 7 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 The comparison of the measurement value (yi：3.57 % (mass fraction) - 34.24 % (massfraction )) of ICP Optical Emission Spectrometry and the measurement value (xi) of
Flame atomic absorption spectrometry analysis was conducted to evaluate truenessusing compound fertilizers (9 samples), mixed compost compound fertilizers (2samples), designated blended fertilizers (1sample), blended fertilizers (4 samples), andbyproduct compound fertilizers (1 sample). As a result, a regression equation was y=−0.0058+1.0027x, and its correlation coefficient (r) was 0.999. In addition, additive
recovery testing was conducted using a preparation sample. As a result, the mean
recovery rate at the additive level of 0.329 % (mass fraction) - 63.18 % (mass fraction)
was 98.0 % - 100.3 %.
The results of the repeatability tests on different days using compound fertilizers andblended fertilizers to evaluate precision were analyzed by one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.09 % (mass fraction).

170

Testing Methods for Fertilizers(2021)

References
1)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)2)
Shingo MATSUO: Simultaneous Determination of Citrate-Soluble Principal Ingredients(C-P2O5, C-K2O, C-MgO, C-MnO and C-B2O3) in Fertilizer using Inductively Coupled
Plasma-Optical Emission Spectrometry (ICP-OES), Research Report of Fertilizer, Vol.
11, p. 14 – 28 (2018)171

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble potassium: The flow sheet for citric acid-soluble potassiumin fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← 150 mL citrate solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1-1 Flow sheet for citric acid-soluble potassium in fertilizers (Extract procedure 4.1.1)

1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← 150 mL citrate solution [about 30 ºC]
Shaking to mix

Horizontal reciprocating water bath shaker (160 reciprocations/min,
amplitude of 25 mm - 40 mm), at 30 ºC ± 1 ºC, for 1 hour

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution

Figure 1-2 Flow sheet for citric acid-soluble potassium in fertilizers (Extract procedure 4.1.2)

172

Testing Methods for Fertilizers(2021)

4.3.3 Water-soluble potassium
4.3.3.a Flame atomic absorption spectrometry or flame photometry(1) Summary
This testing method is applicable to fertilizers containing potassium salts. This testing method isclassified as Type B and its symbol is 4.3.3.a-2021 or W-K.a-2.
Extract by adding water to an analytical sample, add an interference suppressor solution, and thenspray in an acetylene−air flame, and measure the atomic absorption with potassium at a wavelengthof 766.5 nm or 769.9 nm to quantify water-soluble potassium (W-K2O). Or, determine the intensityof the emission line at a wavelength of 766.5 nm or 769.9 nm produced in flame to quantify watersoluble potassium (W-K2O) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 9.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution: Weigh 12.5 g of calcium carbonate specified in JIS K
8617 into a 2000-mL beaker, add a small amount of water, gradually add 105 mL ofhydrochloric acid, and heat for a little while. After cooling is complete, add water to make 1000mL.
c) Potassium standard solution (K2O 1 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.583 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line.
d) Potassium standard solution (K2O 5 µg/mL - 50 µg/mL) for the calibration curve
preparation (2): Put 2.5 mL - 25 mL of potassium standard solution (K2O 1 mg/mL) in 500-mL
volumetric flasks step-by-step, add about 50 mL of interference suppressor solution (3), and add
water up to the marked line.
e) Blank test solution for the calibration curve preparation (1): Put about 50 mL of interference
suppressor solution in a 500-mL volumetric flask (3), and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This is an example of preparation in the case of a wavelength of 769.9 nm; prepare anamount appropriate for the actual condition.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the potassium standard solution in (2), a potassium standard solution for thecalibration curve preparation can be prepared by using a potassium standard solution(K 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate
water-soluble potassium (W-K2O) in the analytical sample by multiplying theconcentration (K) of a potassium standard solution for calibration curve preparation ora measurement value (K) obtained in (4.2) by a conversion factor (1.2046).
(3) Instruments: Instruments are as shown below:a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min
173

Testing Methods for Fertilizers(2021)(amplitude of 40 mm).
b) Analytical instrument: An atomic absorption spectrometer or a flame photometer as shown
below:ba) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A potassium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
bb) Flame photometer:
1) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
c) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Compound fertilizers containing potassium salts and magnesia potassium sulfatea) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add about 200 mL of water, and cover with a watch glass and heat on a hot plate to boil forabout 15 minutes.
c) After immediate cooling is complete, transfer it to a 250- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Comment 2 In the procedure in a), a 250-mL volumetric flask can be used instead of a 300-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. Additionally, “cover with a watch
glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 250-mL volumetricflask with water” in the procedure in c).
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Compound fertilizers containing no magnesia potassium sulfate(4.1.2.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 In the procedure of (4.1.2.1) a), it is also allowed to weigh 2.5 g of an analytical sample
to the order of 1 mg, and put it in a 250-mL volumetric flask. In that case, add about
200 mL of water in the procedure in b).
Comment 5 A sample solution obtained in the procedure in (4.1.2.1) is also applicable to thecomponents shown in Annex B.
(4.1.2.2) Vertical reciprocating shaker:a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
174

Testing Methods for Fertilizers(2021)b) Add about 200 mL of water, and shake to mix by reciprocating vertically at 300 times/min(amplitude of 40 mm) for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 6 A sample solution obtained in the procedure in (4.1.2.2) is also applicable to thecomponents shown in Annex B.
(4.1.3) Fluid test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 7 A sample solution obtained in the procedure in (4.1.3) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer or flame photometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer or flame photometer: Set
up the measurement conditions for the atomic absorption spectrometer or flame photometerconsidering the following:
Analytical line wavelength: 766.5 nm or 769.9 nmb) Calibration curve preparation
1) Spray the potassium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 766.5 nm or 769.9 nm.
2) Prepare a curve for the relationship between the potassium concentration and the indicatedvalue of the potassium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as K2O)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the potassium content from the calibration curve, and calculate water soluble potassium(W-K2O) in the analytical sample.
Comment 8 The analytical line wavelength may be set to 404.4 nm with lower sensitivity. At the
wavelength of 404.4 nm, the slit width needs to be reduced to separate neighboringlines. If the slit width is specified for the instrument, set the slit width to the specified
value. An example preparation of standard solutions for calibration curve preparation
for a wavelength of 404.4 nm is 3 µg/mL - 90 µg/mL as K2O, and the minimum limitof quantification was estimated to be about 3 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 9 Recovery testing was conducted to evaluate trueness using a preparation sample. As a175

Testing Methods for Fertilizers(2021)

result, the mean recovery rates at the content level of 10 % (mass fraction) - 20 %(mass fraction) and 1 % (mass fraction) - 5 % (mass fraction) were 97.9 % - 100.2 %and 97.3 % - 100.6 % as water soluble potassium (W–K2O) respectively. The
comparison of the measurement value (yi: 2.69 % (mass fraction) - 26.64 % (massfraction)) of extraction by a vertical reciprocating shaker and the measurement value(xi) of extraction by a vertical rotating mixer was conducted to evaluate trueness of theextraction of solid fertilizers using fertilizers (12 samples). As a result, a regression
equation was y = 0.022 + 1.001x, and its correlation coefficient (r) was 1.000. The
comparison of the measurement value (yi: 2.69 % (mass fraction) - 26.64 % (massfraction)) of extraction by a vertical reciprocating shaker and the measurement value(xi) of extraction by a vertical rotating mixer was conducted to evaluate trueness of theextraction of fluid fertilizers using fertilizers (12 samples). As a result, a regression
equation was y = 0.022 + 1.001x, and its correlation coefficient (r) was 1.000.
The results of the repeatability tests on different days using compound fertilizers,
designated blended fertilizer and fluid compound fertilizer (2 samples) to evaluate
precision were analyzed by one-way analysis of variance. Table 1-1 and 1-2 show thecalculation results of intermediate precision and repeatability. Results from acollaborative study for test method validation and its analysis are shown in Table 3.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.04 % (mass fraction) for solid fertilizers and about 0.007 % (massfraction) for fluid fertilizers.

176

Testing Methods for Fertilizers(2021)

Table 2-2 Analysis results of the collaborative study
for the test method validation of water-soluble potassium(Compound fertilizers not containing magnesia potassium sulfate)
Number of Mean2) s r4) RSD r5) s R6) RSD R7)
Sample name1)
3)
3)
laboratories(%) (%)3)
(%)
(%)
(%)
10
26.72
0.15
0.6
0.25
0.9
Compound fertilizer 1
Compound fertilizer 2
10
20.79
0.14
0.7
0.27
1.3
10
15.25
0.11
0.7
0.27
1.8
Compound fertilizer 3
10
4.47
0.04
0.8
0.09
2.1
Compound fertilizer 4
Home garden-use compound
10
1.71
0.01
0.7
0.03
1.9
fertilizer
Footnote: Refer to table 2-1

177Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.136- 138, Yokendo, Tokyo (1988)
2)
Yasuharu KIMURA and Hisanori ARAYA
Verification of Performance
Characteristics of Testing Methods for Potassium Content in Fertilizer by Atomic
Absorption Spectrometry, Research Report of Fertilizer Vol. 5, p. 190 - 200 (2012)3)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components
in Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20(2016)
4)
Shinji KAWAGUCHI:
Extraction Method for the Water-soluble Principal
Ingredients in the Solid Fertilizer using a General-purpose Equipment , Research
Report of Fertilizer, Vol. 10, p. 1 - 8 (2017)
5)
Hisanori ARAYA and Kimie KATO: Performance Evaluation of Determination
Methods for Potassium in Fertilizer - Harmonized Collaborative Validation Research Report of Fertilizer, Vol. 12, p. 109 – 122 (2019)178

Testing Methods for Fertilizers(2021)(5)

Flow sheet for water-soluble potassium: The flow sheet for water-soluble potassium in
fertilizers is shown below:

5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask(compound fertilizer)← About 400 mL water
Shaking to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Type 3 filter paper

Filtration

Sample solution
Figure 1-2 Flow sheet for water-soluble potassium in fertilizers(Extraction procedure (4.1.2.1))

2.5 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask(compound fertilizer)← About 200 mL water
Vertical reciprocating shaker(300 times/min, with amplitude of
Shaking to mix
40 mm), for 30 minutes← Water (up to the marked line)
Type 3 filter paper
Filtration
Sample solution
Figure 1-3 Flow sheet for water-soluble potassium in fertilizers(Extraction procedure (4.1.2.2))

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Testing Methods for Fertilizers(2021)

4.3.3.b Sodium tetraphenylborate gravimetric analysis(1) Summary
This testing method is applicable to fertilizers containing potassium salts. This testing method isclassified as Type D and its symbol is 4.3.3.b-2017 or W-K.b-1.
Extract by adding water to an analytical sample, mask co-existing ammonium and other salts withformaldehyde and ethylenediamine tetraacetate and measure the mass of potassium tetraphenylborate
formed by the reaction with tetraphenylborate to obtain water-soluble potassium (W-K2O) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 5.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Formaldehyde solution: A JIS Guaranteed Reagent specified in JIS K 8872 or a reagent ofequivalent quality.
c) Sodium hydroxide solution (200 g/L) (1): Dissolve 200 g of sodium hydroxide specified in JIS
K 8576 in water to make 1000 mL.
d) Aluminum chloride solution (1 mol/L) (1): Dissolve 12 g of aluminum chloride (III)hexahydrate specified in JIS K 8114 in water to make 100 mL.
e) Tetraphenylborate solution (1): Put 6.1 g of sodium tetraphenylborate specified in JIS K 9521
in a 250-mL volumetric flask, dissolve by adding about 200 mL of water and add 10 mL ofaluminum chloride solution. Add a methyl red solution (0.1 g/100 mL) as an indicator, andneutralize with a sodium hydroxide solution (200 g/L) until the color of the solution changes toyellow, and then add water up to the marked line. Filter with Type 3 filter paper and add 0.5 mLof sodium hydroxide solution (200 g/L) to the total filtrate. Filter with Type 3 filter paper in thecase of usage.
f) Tetraphenylborate washing solution (1): Dilute 40 mL of tetraphenylborate solution withwater to make 1000 mL.
g) Ethylenediaminetetraacetate - Sodium hydroxide solution (1): Dissolve 10 g ofethylenediaminetetraacetic acid disodium dihydrogen dihydrate specified in JIS K 8107 and 8
g of sodium hydroxide specified in JIS K 8576 in a proper amount of water. Add 6 mL - 10 mLof tetraphenylborate solution while mixing according to the potassium content coexisting as
impurity after standing to cool, and then add water to make 100 mL. After leaving at rest for
about 30 minutes while sometimes mixing, filter with Type 3 filter paper.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Drying apparatus: A drying apparatus that can be adjusted to 120 ºC ± 2 ºC.
c) Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let it
stand to cool in a desiccator after heating at 120 ºC ± 2 ºC in advance and measure the mass tothe order of 1 mg.
d) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Compound fertilizers containing potassium salts and magnesia potassium sulfate
181

Testing Methods for Fertilizers(2021)a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add about 200 mL of water, and cover with a watch glass and heat on a hot plate to boil forabout 15 minutes.
c) After immediate cooling is complete, transfer it to a 250- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Comment 1 In the procedure in a), a 250-mL volumetric flask can be used instead of a 300-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. Additionally, “cover with a watch
glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 250-mL volumetricflask with water” in the procedure in c).
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Compound fertilizers containing no magnesia potassium sulfatea) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 3 In the procedure in a), it is also allowed to weigh 2.5 g of an analytical sample to theorder of 1 mg, and put it into a 250-mL volumetric flask. In that case, add about 200
mL of water in the procedure in b).
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined amount (the equivalents of 15 mg - 30 mg as K2O) of the sample solution
in a 100-mL tall beaker.
b) Add water to the solution to reach 50 mL when the procedure in e) is complete.
c) Add 2 mL of hydrochloric acid (1+9).
d) Add 5 mL of formaldehyde solution, and then add 5 mL of ethylenediamine tetraacetate sodium hydroxide solution.
e) Add necessary volume (2) of tetraphenylborate solution at the rate of one or two drop(s) per
second while mixing, and further add 4 mL of the same solution in the same manner.
f) Leave at rest for about 30 minutes while sometimes mixing to form the precipitate of potassium
tetraphenylborate.
g) Filter supernatant under reduced pressure with a crucible type glass filter, wash the vessel 5
times with 5 mL of tetraphenylborate washing solution and transfer the whole precipitate to the
crucible type glass filter and further wash 2 times with 2 ml of water.
h) Transfer the precipitate together with the crucible type glass filter into a drying apparatus
adjusted to 120 ºC ± 2 ºC and heat for 1 hour.
i) As soon as heating is complete, move it into a desiccator and let it stand to cool.
j) After standing to cool, remove the ground-in stoppered weighing bottle from the desiccator, andmeasure the mass to the order of 1 mg.
k) Calculate water soluble potassium (W-K2O) in the analytical sample by the following formula.
Water-soluble potassium (W-K2O) (% (mass fraction)) in an analytical sample
182

Testing Methods for Fertilizers(2021)=A × 0.1314 × (V1/V2)/W × 100
A： Mass (g) of the precipitate
V1： Constant volume (mL) of the sample solution in (4.1.1) d) or (4.1.2) c)
V2： Aliquot volume (mL) of the sample solution in (4.2) a)
W： Mass (g) of the analytical sample
Note (2) About 3 ml of tetraphenylborate solution per 10 mg of K2O is required to form theprecipitate of potassium tetraphenylborate
Comment 5 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 30 % (mass fraction) - 50 %(mass fraction) and 10 % (mass fraction) - 20 % (mass fraction) were 100.2 % 100.8 % and 99.3 % - 102.2 % as water soluble potassium (W-K2O) respectively.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.7 % (mass fraction) for solid fertilizers.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.122- 128, Yokendo, Tokyo (1988)
2)
Keiji YAGI, Aiko YANO and Hideo SOETA: Verification of Performance Characteristicsof Testing Method for Nitrate Nitrogen Content in Fertilizer by Phenol Sulfuric Acid
Method, Research Report of Fertilizer Vol. 5, p. 201 - 211 (2012)(5)

Flow sheet for water-soluble potassium: The flow sheet for water-soluble potassium in
fertilizers is shown below:

183

Testing Methods for Fertilizers(2021)

5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask(compound fertilizer)← About 400 mL of water
Shake to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2

Flow sheet for water-soluble potassium in fertilizers(Extraction procedure (4.1.2))

184

Testing Methods for Fertilizers(2021)

4.3.3.c Sodium tetraphenylborate volumetric analysis(1) Summary
This testing method is applicable to fertilizers containing potassium salt but not organic matters.
This testing method is classified as Type E and its symbol is 4.3.3.c-2017 or W-K.c-1.
Extract by adding water to an analytical sample, mask co-existing ammonium and other salts withformaldehyde, and make potassium ion and tetraphenylborate react with each other. Measureunconsumed tetraphenylborate by conducting a precipitate titration to obtain water-soluble potassium(W-K2O) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Formaldehyde solution: A JIS Guaranteed Reagent specified in JIS K 8872 or a reagent ofequivalent quality.
b) Sodium hydroxide solution (120 g/L) (1): Dissolve 30 g of sodium hydroxide specified in JIS
K 8576 in water to make 250 mL.
c) Tetraphenylborate solution (1): Put 12.2 g of sodium tetraphenylborate in a 1000-mL
volumetric flask, dissolve by adding about 800 mL of water and add 3 mL of sodium hydroxide(120 g/L) to the total filtrate, and further add water up to the marked line. Filter with Type 3
filter paper in the case of usage.
d) Benzalkonium chloride solution (3.3 g/500 mL) (1): Dissolve 3.3 g of benzalkonium chloride
in 500 mL of water.
e) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
f) Titan Yellow solution (0.04 g/100mL): Dissolve 0.04 g of Titan Yellow in 100 mL of water inthe case of usage.
g) Potassium standard solution (K2O 2 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 3.166 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Compound fertilizers containing potassium salts and magnesia potassium sulfatea) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add about 200 mL of water, and cover with a watch glass and heat on a hot plate to boil forabout 15 minutes.
c) After immediate cooling is complete, transfer it to a 250- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make an extract.
Comment 1 In the procedure in a), a 250-mL volumetric flask can be used instead of a 300-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. Additionally, “cover with a watch
glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 250-mL volumetric
185

Testing Methods for Fertilizers(2021)

flask with water” in the procedure in c).
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Compound fertilizers containing no magnesia potassium sulfatea) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make an extract.
Comment 3 In the procedure in a), it is also allowed to weigh 2.5 g of an analytical sample to theorder of 1 mg, and put it in a 250-mL volumetric flask. In that case, add about 200 mLof water in the procedure in b).
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Precipitate formation: Form precipitate as shown below.
a) Put 5 mL - 15 mL (no more than the equivalents of 30 mg as K2O) of the extract in a 100-mL
volumetric flask.
b) Add water to the solution to make about 30 mL.
c) Add about 5 mL of formaldehyde solution and add 5 mL of sodium hydroxide solution (120g/L).
d) Add 25 mL of tetraphenylborate solution at the rate of one or two drop (s) per second while
shaking to mix.
e) After adding water up to the marked line, leave at rest for 10 minutes.
f) Filter with Type 3 filter paper to make a sample solution.
(4.3) Measurement: Conduct measurement as shown below.
a) Calibration curve preparation
1) Put 1 mL - 15 mL of potassium standard solution (K2O 2 mg/mL) in 100-mL volumetric flasks
step-by-step.
2) Conduct the same procedures as (4.2) b) - f) to make K2O 2 mg/100 mL - 30 mg/100 mL of thepotassium standard solutions for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
4) Put 40 mL of the potassium standard solutions for the calibration curve preparation and theblank test solution for the calibration curve preparation in an Erlenmeyer flask respectively.
5) Add a few drops of Titan Yellow solution.
6) Titrate with a benzalkonium chloride solution (3.3 g/500 mL) until the color of the solutionchanges to light red (2).
7) Prepare a curve for the relationship between the potassium concentration and the volume of the
benzalkonium chloride solution (3.3 g/500 mL) required for the titration of the potassium
standard solutions for the calibration curve preparation and the blank test solution for thecalibration curve preparation.
b) Sample measurement
1) Put 40 mL of the sample solution of (4.2) f) in a 100-mL Erlenmeyer flask.
2) Conduct similarly as in a) 5) - 6) to obtain the volume of the benzalkonium chloride solution(3.3 g/500 mL) required for the titration.
3) Obtain the potassium content from the calibration curve, and calculate water soluble potassium186Testing Methods for Fertilizers(2021)(W-K2O) in the analytical sample.
Note (2) If the solution temperature is no more than 20 ºC, the reaction does not advance in somecases. Therefore, it is recommended to heat the solution up to about 30 ºC.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.128- 132, Yokendo, Tokyo (1988)(5)

Flow sheet for water-soluble potassium: The flow sheet for water-soluble potassium in
fertilizers is shown below:

5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask(compound fertilizer)← About 400 mL of water
Shake to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2

Flow sheet for water-soluble potassium in fertilizers(Extraction procedure (4.1.2))

187

Testing Methods for Fertilizers(2021)

188

Testing Methods for Fertilizers(2021)

4.3.3.d ICP Optical Emission Spectrometry(1) Summary
This testing method is classified as Type D for solid fertilizers and Type B for fluid fertilizers.
Its symbol is 4.3.3.d-2019 or W-K.d-2.
Add water to an analytical sample to extract, introduce it to an ICP Optical Emission Spectrometer(ICP-OES) and measure the potassium at a wavelength of 766.491 nm, etc. to obtain water-soluble
potassium (W-K2O) in the analytical sample. In addition, the performance of this testing method isshown in Comment 11.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Potassium standard solution (K2O 1 mg/mL) (1): Heat potassium chloride specified in JIS K
8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.583 g
into a weighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetricflask, and add water up to the marked line.
d) Potassium standard solution (K2O 20 µg/mL - 0.16 mg/mL) for the calibration curve
preparation (1): Put 2 mL - 16 mL of potassium standard solution (K2O 1 mg/mL) in 100-mL
volumetric flasks step-by-step, add about 25 mL of hydrochloric acid (1+5), and add water up
to the marked line.
e) Potassium standard solution (K2O 2 µg/mL - 20 µg/mL) for the calibration curve
preparation (1): Put 2 mL - 20 mL of potassium standard solution (K2O 0.1 mg/mL) in 100-mL
volumetric flasks step-by-step, and add hydrochloric acid (1+23) to the marked line.
f) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the potassium standard solution in (2), a potassium standard solution for thecalibration curve preparation can be prepared by using a potassium standard solution(K 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate
water-soluble potassium (W-K2O) in the analytical sample by multiplying theconcentration (K) of a potassium standard solution for calibration curve preparation ora measurement value (K) obtained in (4.2) by a conversion factor (1.2046).
Comment 2 There are two modes to observe emission from an ICP-OES, a horizontal observation
mode and an axial observation mode. The axial observation mode does not apply topotassium since interference is serious.
Comment 3 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
ab) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
189

Testing Methods for Fertilizers(2021)ac) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample (Solid compound fertilizers containing potassium salts and magnesia
potassium sulfate)a) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add about 200 mL of water, and cover with a watch glass and heat on a hot plate to boil forabout 15 minutes.
c) After immediate cooling is complete, transfer it to a 250- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Comment 4 In the procedure in a), a 250-mL volumetric flask can be used instead of a 300-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. Additionally, “cover with a watch
glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 250-mL volumetricflask with water” in the procedure in c).
Comment 5 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Powdery test sample (Solid compound fertilizers not containing potassium salts andmagnesia potassium sulfate)(4.1.2.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 6 In the procedure of (4.1.2.1) a), it is also allowed to weigh 2.5 g of an analytical sample
to the order of 1 mg, and put it in a 250-mL volumetric flask. In that case, add about
200 mL of water in the procedure in b).
Comment 7 A sample solution obtained in the procedure in (4.1.2.1) is also applicable to thecomponents shown in Annex B.
(4.1.2.2) Vertical reciprocating shakera) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 200 mL of water, and shake to mix at 300 times/min (amplitude of 40 mm) for about
30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 8 A sample solution obtained in the procedure in (4.1.2.2) is also applicable to thecomponents shown in Annex B.
190

Testing Methods for Fertilizers(2021)(4.1.3) Fluid test samplea) Weigh 1 mg of an analytical sample (2) to the order of 1 g, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (2) The sampling amount of the analytical sample is 10 g when there is less potassium
content in the fertilizers such as a home garden-use fertilizer.
Comment 9 A sample solution obtained in the procedure in (4.1.3) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement according to JIS K 0116 and as shown below. Specificmeasurement procedures are according to the operation method of the ICP Optical Emission
Spectrometry used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 766.491 nm or 769.896 nm (3)b) Calibration curve preparation
1) Spray the potassium standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at an analytical line wavelength.
2) Prepare a curve for the relationship between the potassium concentration and the indicatedvalue of the potassium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.2 mg - 16 mg as K2O)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the potassium content from the calibration curve, and calculate water soluble potassium(W-K2O) in the analytical sample.
Note (3) 769.896 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 766.491 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 10 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 11 The comparison of the measurement value (yi: 3.30 % (mass fraction) - 35.22 %(mass fraction)) of ICP Optical Emission Spectrometry and the measurement value (xi)of Flame atomic absorption spectrometry was conducted to evaluate trueness using
powdery test fertilizers (25 samples). As a result, a regression equation was y = −0.233+ 1.018x, and its correlation coefficient (r) was 0.997. Similarly the comparison of the191

Testing Methods for Fertilizers(2021)

measurement value (yi: 0.641 % (mass fraction) - 7.23 % (mass fraction)) and themeasurement value (xi) was conducted using fluid fertilizers (12 samples). As a result,a regression equation was y = −0.021 + 0.969x, and its correlation coefficient (r) was
0.999. In addition, additive recovery testing was conducted using preparation
fertilizers (7 samples). As a result, the mean recovery rate at the additive level of
1.09 % (mass fraction) - 63.18 % (mass fraction) was 98.4 % - 102.4 %. Additionally,
additive recovery testing was conducted using a fluid compound fertilizer (1 brand)
and a home garden-use compound fertilizer (1 brand). As a result, the mean recovery
rates at the additive level of 5 % (mass fraction) and 0.4 % (mass fraction) were
102.3 % and 104.0 % respectively.
The results of the repeatability tests on different days using potassium sulfate,
potassium bicarbonate, a home garden-use compound fertilizer (solid fertilizer), a
blended fertilizer, a fluid compound fertilizer and a home garden-use compound
fertilizer (fluid fertilizer) to evaluate precision were analyzed by the one-way analysis
of variance. Table 1-1 and 1-2 show the calculation results of intermediate precisionand repeatability. Additionally, results from a collaborative study for test method
validation and their analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.08 % (mass fraction) for solid fertilizers and about 0.05 % (mass fraction)
for fluid fertilizers.

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Testing Methods for Fertilizers(2021)

References
1)
Keisuke AOYAMA: Simultaneous Determination of Water-Soluble Principal
Ingredients (W-P2O5, W-K2O, W-MgO, W-MnO and W-B2O3) in Liquid Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research
Report of Fertilizer, Vol. 8, p. 1 - 9 (2015)
2)
Norio FUNAKI: Simultaneous Determination of Water-soluble Principal Ingredients in
Fertilizer using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES),
Research Report of Fertilizer, Vol. 12, p. 28 – 51 (2019)
3)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)

193

Testing Methods for Fertilizers(2021)(5)

Flow sheet for water-soluble potassium: The flow sheet for water-soluble potassium in thefluid fertilizers is shown below:

5 g analytical sample
Weigh to the order of 1 mg to a 500-mL volumetric flask(Compound fertilizer)← Water, about 400 mL
Shaking to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for water-soluble potassium in fluid fertilizers(Extraction procedure (4.1.2.1))

2.5 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask(Compound fertilizer)← Water, about 200 mL
Vertical reciprocating shaker (300 times/min,Shaking to mix
40 mm of amplitude) For 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-3 Flow sheet for water-soluble potassium in fluid fertilizers(Extraction procedure (4.1.2.2))

194

Testing Methods for Fertilizers(2021)

1 g analytical sample(Fluid)Weigh to the order of 1 mg to a 100-mL volumetric flask← Water, about 50 mL
Shaking to mix← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-4 Flow sheet for water-soluble potassium in fluid fertilizers(Extraction procedure (4.1.3))
Sample solution
Aliquot
100-mL volmetric flask(predetermined volume)← 25 mL of hydrochloric acid (1+5)← Water (up to the marked line)
Measurement
ICP Optical Emission Spectrometer (766.491nm)
Figure 2 Flow sheet for water-soluble potassium in fluid fertilizers(Measurement procedure)

195

Testing Methods for Fertilizers(2021)

4.4 Silicic acid
4.4.1 Acid and base-soluble silicic acid
4.4.1.a Potassium fluoride method(1) Summary
This testing method is applicable to fertilizers containing no silica gel fertilizers. This testing method
is classified as Type B and its symbol is 4.4.1.a-2019 or S-Si.a-2.
Extract by adding hydrochloric acid (1+23) to an analytical sample, add hydrochloric acid, potassium
fluoride solution and potassium chloride and cool in a refrigerator, and then filter after forming
precipitate as potassium silicofluoride (K2SiF6). Put the precipitate in water and heat, and titratedissolved potassium silicofluoride (K2SiF6) with 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to
obtain the hydrochloric acid (1+23) soluble silicic acid (acid and base-soluble silicic acid (S-SiO2))
in an analytical sample. In addition, the performance of this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in JIS
K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, then put
about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve in asmall amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed for titration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Potassium chloride: A JIS Guaranteed Reagent specified in JIS K 8121 or a reagent ofequivalent quality.
d) Potassium chloride solution (1): Add 250 mL of ethanol specified in JIS K 8101 to 750 mL ofwater to mix, and add 150 mL of potassium chloride to dissolve. Add a few drops of methyl red
solution (0.1 g/100 mL) as an indicator and add hydrochloric acid drop by drop until the colorof the solution becomes red to make it acidic. After leaving at rest for 1 day, neutralize with the
0.1 mol/L - 0.2 mol/L sodium hydroxide solution.
e) Potassium fluoride solution (1): Dissolve 58 g of potassium fluoride specified in JIS K 8815 in1000 mL of water (2).
f) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
196

Testing Methods for Fertilizers(2021)

100 mL of ethanol (95) specified in JIS K 8102.
g) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in a container made of polymer that contains no silicon.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Hot plate: A hot plate or a water bath, etc. which can raise the liquid temperature up to 80 ºC.
c) Beaker made of polymer: A beaker made of polyethylene, etc. of a quality of material which
prevents silicic acid from eluting in the measurement procedure in (4.2).
d) Filter made of polymer: A Gooch crucible made of polymer (compatible filter diameter: 25mm) or a funnel for reduced pressure filtering made of polymer (compatible filter diameter: 21mm) A Gooch crucible made of polyethylene, etc. of a quality of material which prevents silicic
acid from eluting in the measurement procedure in (4.2).
Comment 2 A funnel for reduced pressure filtering made of polymer (compatible filter diameter:
21 mm) is sold under the name Polyethylene Kiriyama Funnel PSB-21.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of hydrochloric acid (1+23) heated up to about 30 ºC (3), and shake to mix at 30 40 revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (3) Since processed slag phosphoric acid fertilizers and mixed phosphoric acid fertilizers,
etc. stick to the bottom of a volumetric flask easily, shake to mix the volumetric flask
gently and disperse an analytical sample into the hydrochloric acid (1+23).
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shaker
197

Testing Methods for Fertilizers(2021)a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(4).
b) Add about 150 mL of hydrochloric acid heated up to about 30 ºC (3), and shake to mix byreciprocating horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC)
for 1 hour.
c) After immediate cooling is complete, add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Note (4) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 20 mg - 50 mg as SiO2 and no more than 25
mL of liquid volume) in a 200-mL beaker made of polymer.
b) Add about 10 mL of hydrochloric acid and about 15 mL of potassium fluoride solution, andfurther add about 2 g of potassium chloride to dissolve, and then cool in a refrigerator for about
30 minutes or more (5) to form the precipitate of potassium fluoride.
c) Filter under reduced pressure with a filter made of polymer (6) topped with Type 6 filter paper,and wash the container 3 times with a potassium chloride solution, then transfer the whole
precipitate into the filter, and further wash 6 - 7 times with a small amount of potassium chloride
solution (7).
d) Transfer the precipitate on the filter together with the filter paper into a 300-mL tall beaker withwater, and further add water to make about 200 mL and heat it and raise the liquid temperature
up to 70 ºC - 80 ºC on a hot plate, etc.
e) Add a few drops of phenolphthalein solution (1 g/100 mL) to the sample solution as an indicatorand titrate with the 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of thesolution becomes light red.
f) Calculate acid and base-soluble silicic acid (S-SiO2) by the following formula.
Acid and base-soluble silicic acid (S-SiO2) (% (mass fraction)) in an analytical sample= V4 × C × f × (V5/V6) × (15.021/W2) × (100/1000)
V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V5： Constant volume (mL) of the extract in (4.1) c)
V6： Aliquot volume (mL) of the extract in (4.2) a)
W2： Mass (g) of the analytical sample
Note (5) To be no more than 10 ºC(6) Filter paper pulp can be stuffed to restrain precipitate from outflowing.
(7) Until the filtrate becomes neutral.
Comment 5 (2) a) Standardization and (4.2) e) Titration procedure can be conducted by anautomatic titrator. The setup of the titration program, the determination parameter for198

Testing Methods for Fertilizers(2021)

the endpoint and vessels such as acceptors are according to the specification and theoperation method of the automatic titrator used.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 25 % (mass fraction) - 40 %(mass fraction) and 10 % (mass fraction) were 98.4 % - 100.5 % and 101.0 % as acidsoluble silicic acid (S-SiO2) respectively.
The comparison of the measurement value (yi: 13.24 % (mass fraction) - 37.08 % (massfraction)) of extraction by a horizontal reciprocating water bath shaker and themeasurement value (xi) of extraction by a constant-temperature vertical rotating mixer
was conducted to evaluate trueness using fertilizers (25 samples). As a result, a
regression equation was y = −0.250 + 0.987x, and its correlation coefficient (r) was
0.999. In addition, the results of the repeatability tests on different days using silicate
slag fertilizers and mixed phosphorus fertilizer to evaluate precision were analyzed by
one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study for testing
method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.3 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different days of acid and base-soluble silicic acid
Name of sample

2)

Test days of
repeatability (T)Silicate slag fertilizer
Mixed phosphorus fertilizer
1) The number of test days conducting a duplicate test
2) Mean (the number of test days(T )×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

5
5

Mean
1)

(%)

3)

37.22
11.82

sr

4)

(%)

5)

3)

RSD r
(%)

6)

(%)

RSD I(T)
(%)

3)

0.15
0.4
0.17
0.4
0.09
0.8
0.16
1.4
6) Intermediate standard deviation
7) Intermediate relative standard
deviation

Table2 Analysis results of the collaborative study
for the test method validation of acid and base-soluble silicic acid
4)
6)
2)
5)
Number of
sr
sR
Mean
RSD r
Sample name
1)
3)
3)
3)
laboratories
(%)
(%)
(%)
(%)
Silicate slag fertilizer
11
34.66 0.19
0.6
0.53
Mixed phosphorus fertilizer
11
21.35
1.0
1.0
0.45
Processed slag phosphate fertilizer
10
28.92
1.0
1.0
0.65
Mixed potassium fertilizer
11
16.15 0.90
0.9
0.44
Autoclaved lightweight concrete powdery fertilizer
11
25.00
0.7
0.7
0.46
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

199s I(T)

7)

RSD R
(%)
1.5
2.1
2.2
2.7
1.9

7)

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.144- 146, Yokendo, Tokyo (1988)
2)
Yasushi MIYASHITA Verification of Performance Characteristics of Testing Method
for Soluble Silicic Acid in Fertilizer by Potassium Fluoride Method, Research Report of
Fertilizer Vol. 7, p. 123 - 130 (2014)3)
Toshiharu YAGI and Kenta SAKUMA: Extraction Method for the Silicic Acid in the
Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 12, p.
1 – 9 (2019)4)
Kenta SAKUMA, Tarou MOTOKI and Toshiharu YAGI: Performance Evaluation of
Determination Methods for Soluble Silicic Acid and Water-soluble Silicic Acid in
Fertilizer: Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13,
p. 62 – 75 (2020)
5)

Flow sheet for acid-soluble silicic acid: The flow sheet for acid and base-soluble silicic acidin fertilizers is shown below:

1 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask.
← About 150 mL hydrochloric acid (1+23) [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for acid and base-soluble silicic acid in fertilizers(Extraction procedure (4.1.1))

200

Testing Methods for Fertilizers(2021)

Sample solution
Aliquot
200-mL beaker made of polymer(predetermined amount)← About 10 mL hydrochloric acid
← About 15mL potassium fluoride solution← About 2 g of potassium chloride
Cooling
For 30 minutes or more in a refrigerator
Filtration
under reduced pressure
Transfer

Filter made of polymer, Type 6 filter paper
Precipitate to the filter,3 times with a small mount of potassium chloride solution←Wash 6 - 7 times with a small mount of potassium chloride solution
Transfer
300-mL tall beaker, water← Water (until the liquid volume reaches about 200 mL)
Heating
70 ºC - 80 ºC← A few drops of phenolphthalein solution (1 g/100 mL)
0.1 mol/L - 0.2 mol/L sodium hydroxide solution
Titration(Until the solution becomes light red)
Figure 2 Flow sheet for acid and base-soluble silicic acid in fertilizers(Measurement procedure)201

Testing Methods for Fertilizers(2021)

4.4.1.b Potassium fluoride method (Silica gel fertilizers, etc.)(1) Summary
This testing method is applicable to silica gel fertilizers and silica hydrogel fertilizers. This testing
method is classified as Type B and its symbol is 4.4.1.b-2017 or S-Si.b-1.
Extract by adding sodium hydroxide (20 g/L) to an analytical sample, add hydrochloric acid,potassium fluoride solution and potassium chloride and cool in a refrigerator, and then filter after
forming precipitate as potassium silicofluoride (K2SiF6). Put the precipitate in water and heat, andtitrate dissolved potassium silicofluoride (K2SiF6) with 0.1 mol/L - 0.2 mol/L sodium hydroxide
solution to obtain the sodium hydroxide solution (20 g/L)) soluble silicic acid (acid and base-soluble
silicic acid (S-SiO2)) in an analytical sample. In addition, the performance of this testing method isshown in Comment 3.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve ina small amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed for titration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
c) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
d) Potassium chloride: A JIS Guaranteed Reagent specified in JIS K 8121 or a reagent ofequivalent quality.
e) Potassium chloride solution (1): Add 250 mL of ethanol specified in JIS K 8101 to 750 mL ofwater to mix, and add 150 mL of potassium chloride to dissolve. Add a few drops of methyl red
solution (0.1 g/100 mL) as an indicator and add hydrochloric acid drop by drop until the colorof the solution becomes red to make it acidic. After leaving at rest for 1 day, neutralize with the
0.1 mol/L - 0.2 mol/L sodium hydroxide solution.
f) Potassium fluoride solution (1): Dissolve 58 g of potassium fluoride specified in JIS K 8815 in1000 mL of water (2).
202

Testing Methods for Fertilizers(2021)

g) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
h) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in a container made of polyethylene, etc. that contains no silicon.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Water bath: A water bath that can be adjusted to 65 ºC ± 2 ºC.
b) Hot plate, etc.: A hot plate or a water bath, etc. which can raise the liquid temperature up to 80ºC.
c) Volumetric flask and beaker made of polymer: A flask and a beaker that are made ofpolyethylene, etc. of a quality of material which prevents silicic acid from eluting in the extract
procedure in (4.1) and in the measurement procedure in (4.2).
d) Filter made of polymer: A Gooch crucible made of polymer (compatible filter diameter: 25mm) or a funnel for reduced pressure filtering made of polymer (compatible filter diameter: 21mm) A Gooch crucible made of polyethylene, etc. of a quality of material which prevents silicic
acid from eluting in the measurement procedure in (4.2).
Comment 2 A funnel for reduced pressure filtering made of polymer (compatible filter diameter:
21 mm) is sold under the name Polyethylene Kiriyama Funnel PSB-21.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask
made of polymer.
b) Add about 150 mL of sodium hydroxide solution (20 g/L) heated up to about 65 ºC, and heatfor 1 hour while shaking to mix at every 10 minutes in a water bath at 65 ºC ± 2 ºC.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 20 mg - 50 mg as SiO2 and no more than 25
mL of liquid volume) in a 200-mL beaker made of polymer.
b) Add about 10 mL of hydrochloric acid and about 15 mL of potassium fluoride solution, andfurther add about 2 g of potassium chloride to dissolve, and then cool in a refrigerator for about
30 minutes (3) to form the precipitate of potassium fluoride.
c) Filter under reduced pressure with a filter made of polymer (4) topped with Type 6 filter paper,and wash the container 3 times with a potassium chloride solution, then transfer the whole
precipitate into the filter, and further wash 6 - 7 times with a small amount of potassium chloride
solution (5).
d) Transfer the precipitate on the filter together with the filter paper into a 300-mL tall beaker withwater, and further add water to make about 200 mL and heat it and raise the liquid temperature
up to 70 ºC - 80 ºC on a hot plate, etc.
e) Add a few drops of phenolphthalein solution (1 g/100 mL) as an indicator and titrate with the203

Testing Methods for Fertilizers(2021)f)

0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomes lightred.
Calculate base-soluble silicic acid (S-SiO2) by the following formula.
Base-soluble silicic acid (S-SiO2) (% (mass fraction)) in an analytical sample= V4 × C × f × (V5/V6) × (15.021/W2) × (100/1000)
V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V5： Constant volume (mL) of the extract in (4.1) c)
V6： Aliquot volume (mL) of the extract in (4.2) a)
W2： Mass (g) of the analytical sample

Note (3) To be no more than 10 ºC(4) Filter paper pulp can be stuffed to restrain precipitate from outflowing.
(5) Until the filtrate becomes neutral.
Comment 3 Table 1 shows results and analysis results from a collaborative study for testing method
validation.

References
1)
Takeshi HASHIMOTO, Akira SHIMIZU and Kaori OKADA:
Validation of a Methodof Potassium Fluoride for Determination of Sodium Hydroxide-Soluble Silicic Acid in
Silica Gel Fertilizer, Research Report of Fertilizer, Vol. 3, p. 19 - 24 (2010)
2)
Akira SHIMIZU, Shin ABE and Jun ITO:
Determination of Solubility Silicic Acid in
Silica gel Fertilizer and Silica gel-including Fertilizer by Potassium Fluoride Method: A
Collaborative Study, Research Report of Fertilizer, Vol. 5, p. 31 - 40 (2012)
204

Testing Methods for Fertilizers(2021)

5)

Flow sheet for acid and base-soluble silicic acid: The flow sheet for acid and base-soluble
silicic acid in silica gel fertilizers, etc. is shown below:
1g
Weigh to the order of 1 mg
analytical sample
into a 250-mL volumetric flask made of polymer.
← About 150 mL sodium hydroxide (20 g/L) [about 65 ºC]
Heating

65 ºC ± 2 ºC, 1 hour, shaking to mix every 10 minutes

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for acid and base-soluble silicic acid in silica gel fertilizers(Extraction procedure)

Sample solution
Aliquot
200-mL beaker made of polymer(predetermined amount)← About 10 mL hydrochloric acid
← About 15mL potassium fluoride solution← About 2 g of potassium chloride
Cooling
For 30 minutes or more in a refrigerator
Filtration
under reduced pressure
Transfer

Filter made of polymer, Type 6 filter paper
Precipitate to the filter,3 times with a small mount of potassium chloride solution←Wash 6 - 7 times with a small mount of potassium chloride solution
Transfer
300-mL tall beaker, water← Water (until the liquid volume reaches about 200 mL)
Heating
70 ºC - 80 ºC← A few drops of phenolphthalein solution (1 g/100 mL)
0.1 mol/L - 0.2 mol/L sodium hydroxide solution
Titration(Until the solution becomes light red)
Figure 2 Flow sheet for acid and base-soluble silicic acid in silica gel fertilizers(Measurement procedure)205

Testing Methods for Fertilizers(2021)

4.4.1.c Potassium fluoride method (Fertilizers containing silica gel fertilizers)(1) Summary
This testing method is applicable to fertilizers containing silica gel fertilizers. This testing method isclassified as Type B and its symbol is 4.4.1.c-2017 or S-Si.c-1.
Mix the equivalent volumes of the extract which is extracted by adding hydrochloric acid (1+23) toan analytical sample and the liquid by extracting non-dissolved matter on a filter paper with sodiumhydroxide (20 g/L), and add hydrochloric acid, a potassium fluoride solution and potassium chloride.
Cool it in a refrigerator, and then filter after forming precipitate as potassium silicofluoride (K2SiF6).
Put the precipitate in water and heat, and titrate dissolved potassium silicofluoride (K2SiF6) with 0.1
mol/L - 0.2 mol/L sodium hydroxide solution to obtain acid and base-soluble silicic acid (S-SiO2) inan analytical sample. In addition, the performance of this testing method is shown in Comment 3.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g to a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve ina small amount of water, transfer to a 250-mL volumetric flask, and add water up to the marked
line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer flask,
add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titrate witha 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f)= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% ) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution transferred
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
c) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
d) Potassium chloride: A JIS Guaranteed Reagent specified in JIS K 8121 or a reagent ofequivalent quality.
e) Potassium chloride solution (1): Add 250 mL of ethanol specified in JIS K 8101 to 750 mL ofwater to mix, and add 150 mL of potassium chloride to dissolve. Add a few drops of methyl red
solution (0.1 g/100 mL) as an indicator and add hydrochloric acid drop by drop until the colorof the solution becomes red to make it acidic. After leaving at rest for 1 day, neutralize with the
0.1 mol/L - 0.2 mol/L sodium hydroxide solution.
f) Potassium fluoride solution (1): Dissolve 58 g of potassium fluoride specified in JIS K 8815 in206

Testing Methods for Fertilizers(2021)

1000 mL of water (2).
g) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
h) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in a container made of polymer that contains no silicon.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
(3) Instruments: Instruments are as shown below:a) Water bath: A water bath that can be adjusted to 65 ºC ±2 ºC.
b) Hot plate, etc.: A hot plate or a water bath, etc. which can raise the liquid temperature up to 80ºC.
c) Volumetric flask and beaker made of polymer: A flask and a beaker that are made ofpolyethylene, etc. of a quality of material which prevents silicic acid from eluting in the extract
procedure in (4.1) and in the measurement procedure in (4.2).
d) Filter made of polymer: A Gooch crucible made of polymer (compatible filter diameter: 25mm) or a funnel for reduced pressure filtering made of polymer (compatible filter diameter: 21mm) A Gooch crucible made of polyethylene, etc. of a quality of material which prevents silicic
acid from eluting in the measurement procedure in (4.2).
Comment 2 A funnel for reduced pressure filtering made of polymer (compatible filter diameter:
21 mm) is sold under the name Polyethylene Kiriyama Funnel PSB-21.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add 150 mL of hydrochloric acid (1+23) warmed up to about 30 ºC, and warm it in a water
bath at 30 ºC ± 2 ºC while stirring every 10minutes with a glass rod for 1 hour.
c) After immediate cooling is complete, filter with Type 6 filter paper to a 250-mL volumetricflask as an acceptor. Wash the tall beaker with water, then transfer the whole residue on the filter
paper and add water up to the marked line to make a sample solution (1).
d) Put the non-dissolved matter on the filter paper together with the filter paper in a 250- mL
volumetric flask made of polymer.
e) Add 150 mL of sodium hydroxide solution heated up to about 65 ºC, and heat for 1 hour while
shaking to mix at every 10 minutes in a water bath at 65 ºC ± 2 ºC.
f) After immediate cooling is complete, add water up to the marked line and filter with Type 3
filter paper to make a sample solution (2).
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 20 mg - 50 mg as SiO2) (3) of the sample
solution (1) and (2) in a 200-mL beaker made of polymer.
b) Add about 10 mL of hydrochloric acid and about 15 mL of potassium fluoride solution, andfurther add about 2 g of potassium chloride to dissolve, and then cool in a refrigerator for about
30 minutes or more (4) to form the precipitate of potassium fluoride.
c) Filter under reduced pressure with a filter made of polymer (5) topped with Type 6 filter paper,
207

Testing Methods for Fertilizers(2021)

and wash the container 3 times with a potassium chloride solution, then transfer the whole
precipitate into the filter, and further wash 6 - 7 times with a small amount of potassium chloride
solution (6).
d) Transfer the precipitate on the filter together with the filter paper into a 300-mL tall beaker withwater, and further add water to make about 200 mL and heat it and raise the liquid temperature
up to 70 ºC - 80 ºC on a hot plate, etc.
e) Add a few drops of phenolphthalein solution (1 g/100 mL) as an indicator and titrate with the
0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomes lightred.
f) Calculate acid and base-soluble silicic acid (S-SiO2) by the following formula.
Acid and base-soluble silicic acid (S-SiO2) (% (mass fraction)) in an analytical sample= V4 × C × f × (V5/V6) × (15.021/W2) × (100/1000)
V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Estimated concentration (mol/L) of sodium hydroxide solution (0.1 mol/L - 0.2
mol/L)
f： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V5： Constant volume (mL) of the sample solution in (4.1) c)
V6： Aliquot volume (mL) of the sample solution in (4.2) a)
W2： Mass (g) of the analytical sample
Note (3) The transferred volume of the sample solution (1) and the sample solution (2) should beequivalent.
(4) To be no more than 10 ºC(5) Filter paper pulp can be stuffed to restrain precipitate from outflowing.
(6) Until the filtrate becomes neutral.
Comment 3 Table 1 shows results and analysis results from a collaborative study for testing method
validation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.6 % (mass fraction).

208

Testing Methods for Fertilizers(2021)

References
1)
Akira SHIMIZU, Jun ITO and Shin ABE:
Method Validation of Potassium Fluoride
Method for Determination of Acid-Soluble and Base-Soluble Silicic Acid in Fertilizer
containing Silica gel, Research Report of Fertilizer, Vol. 4, p. 1 - 8 (2011)2)
Akira SHIMIZU: Method Validation of Potassium Fluoride Method for Determinationof Acid-Soluble and Base-Soluble Silicic Acid in Fertilizer containing Silica Gel,
Research Report of Fertilizer, Vol. 6, p. 1 - 8 (2013)3)
Shinji KAWAGUCHI and Akira SHIMIZU:
Determination of Soluble Silicic Acid in
Fertilizers Containing Silica Gel Fertilizer by Potassium Fluoride Method: A
Collaborative Study, Research Report of Fertilizer Vol. 7, p. 36 - 42 (2014)

209

Testing Methods for Fertilizers(2021)(5)

Flow sheet for acid and base-soluble silicic acid: The flow sheet for acid and base-soluble
silicic acid in fertilizers including silica gel fertilizers is shown below:
1g
Weigh to the order of 1 mg
analytical sample
into a 300-mL tall beaker← About 150 mL hydrochloric acid (1+23) [30 ºC]
1 hour in water bath at 30 ºC ± 2 ºC
Warming(Stir at every 10 minutes)
Cooling
Filtration(supernatant)<Residue>

Immediately
Type 6 filter paper, a 250-mL volumetric flask

Transfer
Move the whole residue to a filter paper← Wash with water<Filtrate>← Wash (up to the marked line)
Sample solution (1)Transfer

250-mL volumetric flask made of polyer,
together wiyh a filter paper

Cooling
Immediately
Add
about
150
mL of sodium hydroxide solution (20 g/L) [65ºC] to stople←
Shake to mix
Until the filter paper completely breaks down
Heating

65 ºC ± 2 ºC, while shaking to mix
at every 10 minutes for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution (2)Figure 1 Flow sheet for acid and base-soluble silicic acid in fertilizers(Extraction procedure)

210

Testing Methods for Fertilizers(2021)

211

Testing Methods for Fertilizers(2021)

4.4.1.d Perchloric acid method(1) Summary
This testing method is applicable to fertilizers containing no silica gel fertilizers. This testing method
is classified as Type E and its symbol is 4.4.1.d-2017 or S-Si.d-1.
Extract by adding hydrochloric acid (1+23) to an analytical sample, add perchloric acid and heat, andthen measure the formed silicic acid anhydride to obtain hydrochloric acid (1+23) soluble silicic acid(acid and base-soluble silicic acid (S-SiO2)) in an analytical sample.
(2) Reagentsa) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Perchloric acid: A JIS Guaranteed Reagent specified in JIS K 8223 or a reagent of equivalentquality.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
b) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
c) Electric furnace: An electric furnace that can be adjusted to 1000 ºC - 1100 ºC.
d) Crucible: After heating a chemical analysis porcelain crucible specified in JIS R 1301 in anelectric funnel at 1000 ºC - 1100 ºC, let it stand to cool in a desiccator and measure the mass tothe order of 1 mg.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of hydrochloric acid (1+23) heated up to about 30 ºC, and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Comment 1 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume in a 100-mL tall beaker.
b) Add about 10 mL of perchloric acid and heat on a hot plate.
c) When white smoke from the perchloric acid starts evolving, cover with a watch glass, then heatfor 15 - 20 minutes to form precipitate of silicone dioxide.
d) After standing to cool, add about 50 mL of hydrochloric acid (1+4) and cover with a watch glassand heat at 70 ºC - 80 ºC on a hot plate for several minutes.
e) Immediately after heating, filter with Type 5-C filter paper, wash the container with heatedhydrochloric acid (1+10) and transfer the whole precipitate to a filter paper.
f) Wash the precipitate and the filter paper 2 times with heated hydrochloric acid (1+10), andfurther wash several times with hot water (1).
g) Put the precipitate together with the filter paper into the crucible.
h) Put the crucible into a drying apparatus and dry at about 120 ºC for 1 hour.
i) After standing to cool, put the crucible into an electric funnel and heat gently to char (2).
212Testing Methods for Fertilizers(2021)j) Ignite at 1000 ºC - 1100 ºC for 1 hour (2).
k) After ignition, move the crucible to a desiccator and let it stand to cool.
l) After standing to cool, remove the crucible from the desiccator and measure the mass to theorder of 1 mg.
m) Calculate acid and base-soluble silicic acid (S-SiO2) by the following formula.
Acid and base-soluble silicic acid (S-SiO2) (% (mass fraction)) in an analytical sample= A × (V1/V2)/W × 100
A： Mass (g) of the precipitate
W： Mass (g) of the analytical sample
V1： Constant volume (mL) of the sample solution in (4.1) c)
V2： Aliquot volume (mL) of the sample solution in (4.2) a)
Note (1) Wash until no reaction by chloride appears in the filtrate.
(2) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 1000 °C - 1100 °C in 1 to 2 hours.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.143- 144, Yokendo, Tokyo (1988)
5)

Flow sheet for acid and base-soluble silicic acid: The flow sheet for acid and base-soluble
silicic acid in fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
← About 150 mL of hydrochloric acid (1+23) [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1

Flow sheet for acid and base-soluble silicic acid in fertilizers (Extraction procedure)213

Testing Methods for Fertilizers(2021)

214

Testing Methods for Fertilizers(2021)

4.4.2
Water-soluble silicic acid
4.4.2.a Potassium fluoride method(1) Summary
This testing method is applicable to liquid potassium silicate fertilizers. This testing method isclassified as Type B and its symbol is 4.4.2.a-2019 or W-Si.a-2.
Extract by adding water to an analytical sample, add hydrochloric acid, a potassium fluoride solution
and potassium chloride and cool in a refrigerator, and then filter after forming precipitate as potassium
silicofluoride (K2SiF6). Put the precipitate in water and heat, and titrate dissolved potassium
silicofluoride (K2SiF6) with 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to obtain the watersoluble silicic acid (W-SiO2) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 by adding
in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5 mL -11 mLof the supernatant in a ground-in stoppered storage container, and add 1000 mL of water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours, thenput about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg. Dissolve
in a small amount of water, transfer to a 250-mL volumetric flask, and add water up to themarked line (1). Put a predetermined amount of the solution in a 200-mL - 300-mL Erlenmeyer
flask, add a few drops of bromothymol blue solution (0.1 g/100 mL) as an indicator, and titratewith a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of the solution becomesgreen. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution by thefollowing formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f)= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C)
W1： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Potassium chloride: A JIS Guaranteed Reagent specified in JIS K 8121 or a reagent ofequivalent quality.
d) Potassium chloride solution (1): Add 250 mL of ethanol specified in JIS K 8101 to 750 mL ofwater to mix, and add 150 mL of potassium chloride to dissolve. Add a few drops of methyl red
solution (0.1 g/100 mL) as an indicator and add hydrochloric acid drop by drop until the colorof the solution becomes red to make it acidic. After leaving at rest for 1 day, neutralize with the
0.1 mol/L - 0.2 mol/L sodium hydroxide solution.
e) Potassium fluoride solution (1): Dissolve 58 g of potassium fluoride specified in JIS K 8815 in1000 mL of water (2).
f) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
215

Testing Methods for Fertilizers(2021)

100 mL of ethanol (95) specified in JIS K 8102.
g) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in a container made of polymer that contains no silicon.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced with a 0.1
mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Hot plate, etc.: A hot plate or a water bath, etc. which can raise the liquid temperature up to
80 ºC.
c) Beaker made of polymer: A beaker made of polyethylene, etc. of a quality of material which
prevents silicic acid from eluting in the extract procedure in (4.1) and in the measurement
procedure in (4.2).
d) Filter made of polymer: A Gooch crucible made of polymer (compatible filter diameter: 25mm) or a funnel for reduced pressure filtering made of polymer (compatible filter diameter: 21mm) A Gooch crucible made of polyethylene, etc. of a quality of material which prevents silicic
acid from eluting in the measurement procedure in (4.2).
Comment 2 A funnel for reduced pressure filtering made of polymer (compatible filter diameter:
21 mm) is sold under the name Polyethylene Kiriyama Funnel PSB-21.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 3 In the procedure of (4.1.1) a) and (4.1.2) a), it is also allowed to weigh 2.5 g of ananalytical sample to the order of 1 mg, and put it into a 250-mL volumetric flask. In
that case, add about 200 mL of water in the procedure in b).
Comment 4 The procedure in (4.1.1) is the same as the procedure in (4.1.1.1) in 4.2.4.a.
(4.1.2) Simple manual extractiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 20 mg - 50 mg as SiO2 and no more than 25
mL of liquid volume) in a 200-mL beaker made of polymer.
216

Testing Methods for Fertilizers(2021)b) Add about 10 mL of hydrochloric acid and about 15 mL of potassium fluoride solution, andfurther add about 2 g of potassium chloride to dissolve, and then cool in a refrigerator for about
30 minutes or more (3) to form the precipitate of potassium fluoride.
c) Filter under reduced pressure with a filter made of polymer (4) topped with Type 6 filter paper,and wash the container 3 times with a potassium chloride solution, then transfer the whole
precipitate into the filter, and further wash 6 - 7 times with a small amount of potassium chloride
solution (5).
d) Transfer the precipitate on the filter together with the filter paper into a 300-mL tall beaker withwater, and further add water to make about 200 mL and heat it and raise the liquid temperature
up to 70 ºC - 80 ºC on a hot plate, etc.
e) Add a few drops of phenolphthalein solution (1 g/100 mL) to the sample solution as an indicatorand titrate with the 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the color of thesolution becomes light red.
f) Calculate water soluble silicic acid (W-SiO2) by the following formula.
Water soluble silicic acid (W-SiO2) (% (mass fraction)) in an analytical sample= V4 × C × f × (V5/V6) × (15.021/W2) × (100/1000)
V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V5： Constant volume (mL) of the extract in (4.1) c)
V6： Aliquot volume (mL) of the extract in (4.2) a)
W2： Mass (g) of the analytical sample
Note (3) To be no more than 10 ºC(4) Filter paper pulp can be stuffed to restrain precipitate from outflowing.
(5) Until the filtrate becomes neutral.
Comment 5 The titration procedures in (2) a) Standardization and (4.2) e) Titration can be
conducted by an automatic titrator. The setup of the titration program, thedetermination parameter for the endpoint and vessels such as acceptors are according
to the specification and the operation method of the automatic titrator used.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 30 % (mass fraction) and 12 %(mass fraction) - 20% (mass fraction) were 100.7 % and 99.5 % - 100.5 as watersoluble silicic acid (W-SiO2) respectively.
The results of the repeatability tests on different days using a liquid potassium silicate
fertilizer by extraction with a vertical rotating mixer or simple manual extraction toevaluate precision were analyzed by the one-way analysis of variance. Table 1 shows
the calculation results of intermediate precision and repeatability. Additionally, resultsfrom a collaborative study for testing method validation and its analysis are shown in
Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 % (mass fraction).

217

Testing Methods for Fertilizers(2021)
Table 1 Analysis results of the repeatability tests on different days of water-soluble silicic acid
Extraction
methodName of sample

2)

Test days of
repeatability (T)VerticalLiquid potassium silicate fertilizer 1
rotating mixer Liquid potassium silicate fertilizer 2
Simple manual Liquid potassium silicate fertilizer 1
extraction
Liquid potassium silicate fertilizer 2
1) The number of test days conducting a duplicate test
2) Mean (the number of test days(T )×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

7
7
5
5

Mean
1)

(%)

3)

4)

sr

(%)

3)

5)

RSD r
(%)

6)

s I(T)(%)

3)

RSD I(T)
(%)

7)

24.01
0.07
0.3
0.08
0.4
16.07
0.03
0.2
0.04
0.3
25.28
0.06
0.2
0.13
0.5
15.98
0.12
0.8
0.15
1.0
6) Intermediate standard deviation
7) Intermediate relative standard deviation

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.144- 146, Yokendo, Tokyo (1988)
2)
Shinji KAWAGUCHI: Verification of Performance Characteristics of Testing Method for
Water-Soluble Silicic Acid in Fertilizer by Potassium Fluoride Method, Research Reportof Fertilizer, Vol. 8, p. 174 - 181 (2015)3)
Toshiharu YAGI and Kenta SAKUMA: Extraction Method for the Silicic Acid in the
Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 12, p.
1 – 9 (2019)4)
Kenta SAKUMA, Tarou MOTOKI and Toshiharu YAGI: Performance Evaluation of
Determination Methods for Soluble Silicic Acid and Water-soluble Silicic Acid in
Fertilizer: Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13,
p. 62 – 75 (2020)
218

Testing Methods for Fertilizers(2021)

5)

Flow sheet for water-soluble silicic acid: The flow sheet for water-soluble silicic acid in
fertilizers is shown below:
5 g analytical sample
Weigh to the order of 1 mg to a 500-mL volumetric flask.
← About 400 mL of water
Shaking to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble silicic acid in fertilizers (Extraction procedure (4.1.1))

5 g analytical sample
Weigh to the order of 1 mg to a 500-mL volumetric flask.
← About 400 mL of water
Shaking to mix← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for water-soluble silicic acid in fertilizers (Extraction procedure

Sample solution
Aliquot
200-mL beaker made of polymer(predetermined amount)← About 10 mL hydrochloric acid
← About 15mL potassium fluoride solution← About 2 g of potassium chloride
Cooling
For 30 minutes or more in a refrigerator
Filtration
under reduced pressure
Transfer

Filter made of polymer, Type 6 filter paper
Precipitate to the filter,3 times with a small mount of potassium chloride solution←Wash 6 - 7 times with potassium chloride solution
Transfer
300-mL tall beaker, water← Water (until the liquid volume reaches about 200 mL)
Heating
70 ºC - 80 ºC← A few drops of phenolphthalein solution (1 g/100 mL)
0.1 mol/L - 0.2 mol/L sodium hydroxide solution
Titration(Until the solution becomes light red)
Figure 2 Flow sheet for water-soluble silicic acid in fertilizers (Measurement procedure)

219

Testing Methods for Fertilizers(2021)

4.5 Lime, calcium and alkalinity
4.5.1 Total lime
4.5.1.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers containing organic matters. This testing method isclassified as Type B and its symbol is 4.5.1.a-2017 or T-Ca.a-1.
Pretreat an analytical sample with incineration - hydrochloric acid boiling or aqua regia digestion,
add an interference suppressor solution, and then spray in an acetylene−air flame, and measure theatomic absorption with calcium at a wavelength of 422.7 nm to quantify total lime (T-CaO) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 7.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Calcium standard solution (CaO 1 mg/mL) (1): Heat calcium carbonate specified in JIS K
8617 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.785 g
into a weighing dish. Transfer to a 1000-mL volumetric flask with a small amount of water, add
20 mL of hydrochloric acid (1+3) to dissolve, and add water up to the marked line.
d) Calcium standard solution (CaO 5 µg/mL - 50 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL - 25 mL of a calcium standard solution (CaO 1 mg/mL) in 500-mL
volumetric flasks step-by-step, add about 50 mL of interference suppressor solution (3), and add
water up to the marked line (4).
e) Blank test solution for the calibration curve preparation (1): Put about 50 mL of interference
suppressor solution in a 500-mL volumetric flask (3), and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
(4) For storage, use a sealable container made of materials which are not likely to dissolve
calcium, such as borosilicate glass-1 specified in JIS R 3503 or Teflon.
Comment 1 Instead of the calcium standard solution in (2), a calcium standard solution for thecalibration curve preparation can be prepared by using a calcium standard solution (Ca1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate total
lime (T-CaO) in the analytical sample by multiplying the concentration (Ca) of thecalcium standard solution for calibration curve preparation or a measurement value(Ca) obtained in (4.2) by a conversion factor (1.3992).
Comment 2 When using a sample solution obtained in the procedure in (4.1.2) h) for themeasurement of cadmium, nickel, chromium or lead, sulfuric acid and hydrochloric
acid in (2) should be a reagent of harmful metal analysis grade, microanalysis grade orequivalents.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
220

Testing Methods for Fertilizers(2021)

1) Light source: A calcium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can be adjusted to 550 ºC ± 5 ºC.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Incineration-hydrochloric acid boilinga) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (5).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (5).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After standing to cool, transfer the solution to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (5) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 550 °C in 1 to 2 hours.
Comment 3 Do not conduct the procedures in (4.1.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Incineration-aqua regia digestiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (6).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (6).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (7), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (8) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL volumetric flask with water, add water up to themarked line, and filter with Type 3 filter paper to make a sample solution.
Note (6) Example of charring and incineration procedure:
221

After raising the temperature from

Testing Methods for Fertilizers(2021)

room temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(7) The watch glass can be removed.
(8) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 5 Do not conduct the procedures in (4.1.2) b) - c) in the case of fertilizers not containing
organic matters.
Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 422.7 nmb) Calibration curve preparation
1) Spray the calcium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 422.7 nm.
2) Prepare a curve for the relationship between the calcium concentration and the indicated valueof the calcium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as CaO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the calcium content from the calibration curve, and calculate total lime (T-CaO) in theanalytical sample.
Comment 7 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 15 % (mass fraction) and 1 %(mass fraction) were 101.8 % and 97.9% as total lime (T-CaO) respectively. In orderto evaluate precision, results from a collaborative study for test method validation andits analysis are shown in Table 1.
In addition, the results of the collaborative study to determine a certified referencematerial fertilizer were analyzed by using a three-level nesting analysis of variance.
Table 2 shows the calculation results of reproducibility, intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.05 % (mass fraction).

222

Testing Methods for Fertilizers(2021)

Table 1 Analysis results of the collaborative study
for the test method validation of total lime
Number of Mean2) s r4) RSD r5) s R6) RSD R7)
Sample name
1)
3)
3)
3)
laboratories
(%)
(%)
(%)
(%)
(%)
Industrial sludge fertilizer

10

36.35

0.50

1.4

0.33

2.4

Compost

9

13.69

0.23

1.7

0.25

2.3

Compound fertilizer

10

10.53

0.09

0.8

0.24

2.4

Composted sludge fertilizer A

8

2.02

0.02

0.9

0.04

2.6

Composted sludge fertilizer B
101) Number of laboratories used in analysis
2) Mean (n = number of laboratories ×
number of samples (2))3) Mass fraction
4) Repeatability standard deviation

1.55
0.04
2.3
0.03
4.3
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

Table 2 Analysis results of the collaborative study to determine total limeof a certified reference material fertilizer
Name of certified
reference material fertilizer

Number oflaboratory (p )

Mean
1)

(%)

2)

3)

FAMIC-C-12
11
5.82
1) The number of laboaratories used for analysis
conducting flame atomic absorbance spectrometry2) Mean (the number of laboratory(p )×test days(2)×the number of replicate testing(3))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

sr

4)

(%)

3)

0.07

RSD r
(%)

5)

s I(T)

6)

(%)

3)

RSD I(T)
(%)

7)

8)

sR

(%)

3)

9)

RSD R
(%)

1.2
0.11
2.0
0.29
5.0
6) Intermediate standard deviation
7) Intermediate relative standard deviation
8) Reproducibility standard deviation
9) Reproducibility relative standard deviation

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.156- 158, Yokendo, Tokyo (1988)
2)
Kimie KATO, Masayuki YOSHIMOTO and Yuji SHIRAI: Systematization of
Determination Methods of Major Components in Sludge Fertilizer, Compost and Organic
Fertilizer, Research Report of Fertilizer, Vol. 3 p. 107 – 116 (2010)3)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Calcium Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 183 - 192 (2013)
4)
Hisanori ARAYA and Kimie KATO: Performance Evaluation of Determination Method
for Total Lime and Soluble Lime in Fertilizer: Harmonized Collaborative Validation,
Research Report of Fertilizer, Vol. 13, p. 76 – 86 (2020)

223

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total lime: The flow sheet for total lime in fertilizers is shown below:
5 g analytical sample
Charring
Incineration

Weigh to the order of 1 mg into a 200-mL- 300-mL tall beaker.
Heat gently
Ignite at 550 ºC ± 5 ºC, no less than 4 hours

Standing to coolRoom temperature← Small amount of water, moisten the residue← About 10 mL of hydrochloric acid
← Water (up to about 20 mL)
Heating
Cover with a watch glass, and boil for 5 minutes.
Standing to coolRoom temperature

Transfer
250-mL - 500-mL volumetric flask, water← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for total lime in fertilizers.
(Incineration-hydrochloric acid boiling prorcedure (4.1.1))

224

Testing Methods for Fertilizers(2021)

5g
analytical sample
Charring
Incineration

Weigh to the order of 1 mg into a 200-mL - 300-mL tall beaker.
Heat gently
Ignite at 450 ºC ± 5 ºC for 8 - 16 hours

Standing to coolRoom temperature← A small amount of water← About 10 mL of nitric acid
← About 30 mL of hydrochloric acid
Heating
Cover with a watch glass to digest
Heating

Slightly move the watch glass and remove acid

Standing to coolRoom temperature← 25 mL - 50 mL of hydrochloric acid (1+5)
Heating
Cover with a watch glass to dissolve
Standing to coolRoom temperature

Transfer
100-mL - 200-mL volumetric flask, water← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for total lime in fertilizers(Incineration-aqua regia digestion procedure (4.1.2))
Sample solution
Aliquot
100-mL volumetric flask(predetermined amount)←About 10 mL interference suppressor solution← Water (up to the marked line)
Measurement
Atomic absorption spectrometer
Figure 2 Flow sheet for total lime in fertilizers (Measurement)

225

Testing Methods for Fertilizers(2021)

4.5.2 Acid-soluble lime
4.5.2.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers that guarantee alkalinity. This testing method isclassified as Type B and its symbol is 4.5.2.a-2017 or S-Ca.a-1.
Add hydrochloric acid (1+23) to an analytical sample, boil to extract, and add an interference
suppressor solution, and then spray in an acetylene−air flame, and measure the atomic absorption
with calcium at a wavelength of 422.7 nm to quantify hydrochloric acid (1+23) soluble lime (acidsoluble lime (S-CaO)) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (2): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(1)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Calcium standard solution (CaO 1 mg/mL) (2): Put calcium carbonate specified in JIS K 8617
in a drying apparatus, heat at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator,
and weigh 1.785 g into a weighing dish. Transfer to a 1000-mL volumetric flask with a small
amount of water, add 20 mL of hydrochloric acid (1+3) to dissolve, and add water up to themarked line.
d) Calcium standard solution (CaO 5 µg/mL - 50 µg/mL) for the calibration curve
preparation (2): Put 2.5 mL - 25 mL of a calcium standard solution (CaO 1 mg/mL) in 500-mL
volumetric flasks step-by-step, add about 50 mL of interference suppressor solution (3), and add
water up to the marked line (4).
e) Blank test solution for the calibration curve preparation (2): Put about 50 mL of interference
suppressor solution in a 500-mL volumetric flask (3), and add water up to the marked line (4).
Note (1) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(2) This is an example of preparation; prepare an amount as appropriate.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
(4) For storage, use a sealable container made of materials which are not likely to dissolve
calcium, such as borosilicate glass-1 specified in JIS R 3503 or Teflon.
Comment 1 Instead of the calcium standard solution in (2), a calcium standard solution for thecalibration curve preparation can be prepared by using a calcium standard solution (Ca1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate acidsoluble lime (S-CaO) in the analytical sample by multiplying the concentration (Ca)of the calcium standard solution for calibration curve preparation or a measurement
value (Ca) obtained in (4.2) by a conversion factor (1.3992).
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A calcium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene
226

Testing Methods for Fertilizers(2021)(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2 g of an analytical sample to the order of 1 mg, and put it in a 500-mL tall beaker.
b) Add about 20 mL of hydrochloric acid (1+23), cover with a watch glass, and boil on a hot plate
for about 5 minutes (5).
c) After immediate cooling is complete, transfer it to a 250-mL - 500-mL volumetric flask withwater.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (5) Be aware that an analytical sample should not solidify in the bottom of a beaker.
Comment 2 In the case of a by-product magnesia fertilizer or a fertilizer containing a by-productmagnesia, if the pH of the sample solution of d) is neutral or basic, prepare a sample
solution anew by replacing “2 g of an analytical sample” in the procedure in a) with
“1 g - 1.5 g of an analytical sample”.
Comment 3 In the procedure in a), a 500-mL volumetric flask can be used instead of a 500-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. In addition, “cover with a watch
glass” in b) is replaced by “place a funnel”, and “transfer it to a 250-mL - 500 mL
volumetric flask with water” in the procedure in c) is skipped.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 422.7 nmb) Calibration curve preparation
1) Spray the calcium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 422.7 nm.
2) Prepare a curve for the relationship between the calcium concentration and the indicated valueof the calcium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as CaO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the calcium content from the calibration curve, and calculate acid-soluble lime (S-CaO)in the analytical sample.
Comment 5 Recovery testing was conducted to evaluate trueness using a preparation sample. As a227

Testing Methods for Fertilizers(2021)

result, the mean recovery rates at the content level of 20 % (mass fraction) and 1 %(mass fraction) were 100.9 % and 101.1% as acid-soluble lime (S-CaO) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.05 % (mass fraction).
Table 1 Analysis results of the collaborative study
for the test method validation of acid-soluble lime
Sample name

Number of1)laboratories

4)

2)

sr

3)

(%)
0.70
0.46
0.38
0.08
0.04

Mean
(%)

3)

Slaked lime
10
65.95
Calcined phosphorus fertilizer
1030.31
Slag silicate fertilizer
10
29.49
Blended fertilizer
9
7.77
Mimic fertilizer
80.8231) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

RSD r
(%)
1.1
1.5
1.3
1.0
4.6

5)

6)

sR

3)

(%)
2.22
0.79
0.88
0.27
0.05

7)

RSD R
(%)
3.4
2.6
3.0
3.5
6.6

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.167- 169, Yokendo, Tokyo (1988)
2)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Calcium Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 183 - 192 (2013)
4)
Hisanori ARAYA and Kimie KATO: Performance Evaluation of Determination Method
for Total Lime and Soluble Lime in Fertilizer: Harmonized Collaborative Validation,
Research Report of Fertilizer, Vol. 13, p. 76 – 86 (2020)

228

Testing Methods for Fertilizers(2021)(5)

Flow sheet for acid-soluble lime: The flow sheet for acid-soluble lime in fertilizers is shown
below:
2 g analytical sample
Weigh to the order of 1 mg into a 500-mL tall beaker.
← About 200 mL of hydrochloric acid (1+23)
Heating
Cover with a watch glass, and boil for 5 minutes.
Cooling

Immediately

Transfer
Water, 250-mL - 500-mL volumetric flask← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for acid-soluble lime in fertilizers (Extraction procedure)

Sample solution
Aliquot
100-mL volumetric flask(predetermined amount)←About 10 mL interference suppressor solution← Water (up to the marked line)
Measurement
Atomic absorption spectrometer
Figure 2 Flow sheet for acid-soluble lime in fertilizers (Measurement procedure)

229

Testing Methods for Fertilizers(2021)

4.5.3 Citric acid-soluble lime
4.5.3.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 4.5.3.a-2020 or C-Ca.a-1.
Extract by adding citric acid solution to an analytical sample, and add an interference suppressor
solution, and then spray in an acetylene-air flame, and measure the atomic absorption with calcium
at a wavelength of 422.7 nm to quantify citric acid-soluble lime (C-CaO) in an analytical sample.
In addition, the performance of this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid:
A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent of equivalent quality.
b) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
c) Interference suppressor solution (1): Weigh 152.1 g of strontium chloride hexahydrate
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually 420
mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
d) Calcium standard solution (CaO 1 mg/mL): Heat calcium carbonate specified in JIS K 8617
at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.785 g into aweighing dish. Transfer to a 1000-mL volumetric flask with a small amount of water, add 20
mL of hydrochloric acid (1+3) to dissolve, and add water up to the marked line.
e) Calcium standard solution (CaO 100 mg/mL) (1): Put 10 mL of calcium standard solution(CaO 1 mg/mL) in a 100-mL flask and add water up to the marked line.
f) Calcium standard solution (CaO 1 µg/mL - 7 µg/mL) for the calibration curve preparation(1): Put 5 mL - 35 mL of a calcium standard solution (CaO 100 µg/mL) in 500-mL volumetricflasks step-by-step, add about 30 mL of a citric acid solution (2) and about 50 mL of aninterference suppressor solution (3), and add water up to the marked line (4).
g) Blank test solution for the calibration curve preparation (1): Put about 30 mL of a citric acidsolution (2) and about 50 mL of an interference suppressor solution in a 50-mL volumetric flask(3), and add water up to the marked line (4).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Add a citric acid solution that is 6/100 of the volume to be prepared.
(3) Add an interference suppressor solution that is 1/10 of the volume to be prepared.
(4) For storage, use a sealable container made of materials which are not likely to dissolve
calcium, such as borosilicate glass-1 specified in JIS R 3503 or Teflon.
Comment 1 Instead of the calcium standard solution in (2), a calcium standard solution for thecalibration curve preparation can be prepared by using a calcium standard solution(CaO 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate
citric acid-soluble lime (C-CaO) in the analytical sample by multiplying theconcentration (Ca) of the calcium standard solution for calibration curve preparation
or a measurement value (Ca) obtained in (4.2) by a conversion factor (1.3992).
(3) Instruments: Instruments are as shown below:aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be230

Testing Methods for Fertilizers(2021)

adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A calcium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (5), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (5) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(6).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (5), and shake to mix by reciprocating
horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (6) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 3 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 4 For a calcareous fertilizer, etc., if the pH of the sample solution in (4.1.1) d) and (4.1.2)d) is neutral or basic, prepare a sample solution anew by replacing “1 g of an analyticalsample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of an analyticalsample”.
Comment 5 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, check non-dissolved matters status after theprocedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
231

Testing Methods for Fertilizers(2021)

a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 422.7 nmb) Calibration curve preparation
1) Spray the calcium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 422.7 nm.
2) Prepare a curve for the relationship between the calcium concentration and the indicated valueof the calcium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 0.7 mg as CaO
and no more than the equivalents of 6mL of citric acid solution) in a 100-mL volumetric flask.
2) Add the solution to make a citric acid solution equivalent to 6 mL.
3) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
4) Subject to the same procedure as in b) 1) to read the indicated value.
5) Obtain the calcium content from the calibration curve, and calculate citric acid-soluble lime (CCaO) in the analytical sample.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 30 % (mass fraction), 1 % - 15 %(mass fraction) and 0.2 % (mass fraction) were 99 %, 101 % - 98 % and 96 % as citricacid-soluble lime (C-CaO) respectively.
The results of the repeatability tests on different days using calcium carbonate anddesignated blended fertilizer (1 brand) to evaluate precision were analyzed by the oneway analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability.
Additionally, results from a collaborative study for testing method validation and its
analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different days of citric acid-soluble lime
Name of sample
Calcium carbonate

2)

Test days of
repeatability T
5

Average
1)

4)

sr

3)

(%)

55.77

0.47

(%)

Designated blended fertilizer
54.7561) The number of test days conducting a duplicate test
2) Mean (the number of test days(T )×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

232

3)

5)

6)

RSD r
(%)

s I(T)

0.8

0.47

(%)

3)

7)

RSD I(T)
(%)
0.8

0.091
1.9
0.114
2.4
6) Intermediate standard deviation
7) Intermediate relative standard deviation

Testing Methods for Fertilizers(2021)
Table 2 Analysis results of the collaborative study for the test method validation of citric acid-soluble lime
2)
4
5
6
7
Number ofMeansr ）RSD r ）sR ）RSD R ）
Sample namelaboratories
3）
3）
3）
（%）
（%）
（%）
（%）
（%）
1)
Designated blended fertilizer

11

3.14

0.07

2.3

0.09

2.7

Composted sludge fertilizer

12

5.82

0.07

2.4

0.14

2.4

Compound fertilizer

12

12.30

0.24

2.0

0.58

4.7

Fish cakes powder

12

15.60

0.25

1.6

0.51

3.2

18.84
31.89
40.78

0.19
1.0
0.75
4.0
0.40
1.3
0.60
1.9
0.18
0.4
0.78
1.9
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

Gypsum12
Mixed phosphorus fertilizer
11
Silicate slag fertilizer
111) Number of laboratories used in analysis
2) Mean (n = [Number of laboratories]
× [Number of samples (2)])3) Mass fraction

References
1)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Calcium Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 183 – 192 (2013)
2)
Madoka KATO, Masayuki YAMANISHI and Yuji SHIRAI: Determination of Citric AcidSoluble CaO in Fertilizer by AAS and ICP-OES, Research Report of Fertilizer, Vol. 13,
p. 36 - 49 (2020)

233

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble lime: The flow sheet for citric acid-soluble lime in fertilizers
is shown below:
1g
Weigh 1 g to the order of 1 mg into a 250-mL volumetric flask
analytical sample← 150 mL of citric acid solution [about 30ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shake to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble lime in fertilizers (Extraction procedure (4.1.1))

1g
Weigh 1 g to the order of 1 mg into a 250-mL volumetric flask
analytical sample← 150 mL of citric acid solution [about 30ºC]
Horizontal reciprocating water bath shaker (160 reciprocations/min,
Shake to mix
amplitude of 25 mm - 40 mm), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble lime in fertilizers (Extraction procedure (4.1.2))

234

Testing Methods for Fertilizers(2021)

4.5.3.b ICP Optical Emission Spectrometry(1)Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 4.5.3.b-2020 or C-Ca.b-1.
Extract by adding a citric acid solution to an analytical sample, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the calcium at a wavelength of 393.366 nm to obtaincitric acid-soluble lime (C-CaO)) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mLd) Calcium standard solution (CaO 1 mg/mL): Heat calcium carbonate specified in JIS K 8617
at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and weigh 1.785 g into aweighing dish. Transfer to a 1000-mL volumetric flask with a small amount of water, add 20
mL of hydrochloric acid (1+3) to dissolve, and add water up to the marked line.
e) Calcium standard solution (CaO 0.1 mg/mL): Put 10 mL of calcium standard solution (CaO
1 mg/mL) in a 100-mL flask and add hydrochloric acid (1+23) up to the marked line.
f) Calcium standard solutions (CaO 1 µg/mL – 20µg /mL) for the calibration curve
preparation (1): Put 1 mL - 20 mL of calcium standard solution (CaO 0.1 mg/mL) in 100-mL
volumetric flasks step-by-step, and add hydrochloric acid (1+23) up to the marked line.
g) Calcium standard solutions (CaO 0.1 µg/mL – 1 µg /mL) for the calibration curve
preparation (1): Put 1 mL - 10 mL of calcium standard solution (CaO 10 µg/mL) in 100-mL
volumetric flasks step-by-step, and add hydrochloric acid (1+23) up to the marked line.
h) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e), f) and g).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the calcium standard solution in (2), a calcium standard solution for thecalibration curve preparation can be prepared by using a calcium standard solution (1mg/ mL or 10 mg/mL) traceable to National Metrology. In this case, calculate citricacid-soluble lime (C-CaO) in the analytical sample by multiplying the concentration(Ca) of the calcium standard solution for calibration curve preparation or ameasurement value (Ca) obtained in (4.2) by a conversion factor (1.3992).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to235

Testing Methods for Fertilizers(2021)

30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(3).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix by reciprocating
horizontally at 160 times/min with amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Note (3) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 For a calcareous fertilizer, if the pH of the sample solution in (4.1.1) d) and (4.1.2) d)is neutral or basic, prepare a sample solution anew by replacing “1 g of an analyticalsample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of an analyticalsample”.
Comment 6 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, check non-dissolved matters status after theprocedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometry used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up the236

Testing Methods for Fertilizers(2021)

measurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 393.366 nmb) Calibration curve preparation
1) Spray the calcium standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at a wavelength of 393.366 nm.
2) Prepare a curve for the relationship between the calcium concentration and the indicated valueof the calcium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 14 µg - 1.4 mg as CaO)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the calcium content from the calibration curve, and calculate citric acid-soluble lime (CCaO) in the analytical sample.
Comment 7 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 30 % (mass fraction), 1 % - 15 %(mass fraction) and 0.2 % (mass fraction) were 98 %, 103 % - 101 % and 104 % ascitric acid-soluble lime (C-CaO) respectively.
The results of the repeatability tests on different days using calcium carbonate anddesignated blended fertilizer (1 brand) to evaluate precision were analyzed by the oneway analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.3 % (mass fraction).

237

Testing Methods for Fertilizers(2021)

References
1)
Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development
Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research
Report of Fertilizer, Vol. 9, p. 1 - 9 (2016)
2)
Shingo MATSUO: Simultaneous Determination of Citrate-Soluble Principal Ingredients(C-P2O5, C-K2O, C-MgO, C-MnO and C-B2O3) in Fertilizer using Inductively Coupled
Plasma-Optical Emission Spectrometry (ICP-OES), Research Report of Fertilizer, Vol.
11, p. 14 – 28 (2018)
3)
Madoka KATO, Masayuki YAMANISHI and Yuji SHIRAI: Determination of Citric AcidSoluble CaO in Fertilizer by AAS and ICP-OES, Research Report of Fertilizer, Vol. 13,
p. 36 - 49 (2020)

238

Testing Methods for Fertilizers(2021)(5)

Flow sheet for the testing method: The flow sheet for citric acid-soluble lime in fertilizers isshown below:
1.00 g500-mL volumetric flask
analytical sample← About 400 mL of water
Shaking to mix

Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble calcium in fertilizers (Extraction procedure (4.1.1))

1g
Weigh 1 g to the order of 1 mg into a 250-mL volumetric flask
analytical sample← 150 mL of citric acid solution [about 30ºC]
Horizontal reciprocating water bath shaker (160 reciprocations/min,
Shake to mix
amplitude of 25 mm - 40 mm), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble lime in fertilizers (Extraction procedure (4.1.2))

239

Testing Methods for Fertilizers(2021)

4.5.4 Water-soluble calcium
4.5.4.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers that indicate calcium content as a response modifier.
This testing method is classified as Type D and its symbol is 4.5.3.a-2017 or W-Ca.a-1.
Extract by adding water to an analytical sample, and add an interference suppressor solution, and thenspray in an acetylene−air flame, and measure the atomic absorption with calcium at a wavelength of
422.7 nm to quantify water-soluble calcium (W-Ca) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 3(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Calcium standard solution (Ca 1 mg/mL): Calcium standard solution (Ca 1 mg/mL) traceable
to National Metrology.
d) Calcium standard solution (Ca 5 µg/mL - 50 µg/mL) for the calibration curve preparation(1): Put 2.5 mL - 25 mL of a calcium standard solution (Ca 1 mg/mL) in 500-mL volumetricflasks step-by-step, add about 50 mL of interference suppressor solution (3), and add water up
to the marked line (4).
e) Blank test solution for the calibration curve preparation (1): Put about 50 mL of interference
suppressor solution in a 500-mL volumetric flask (3), and add water up to the marked line (4).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
(4) For storage, use a sealable container made of materials which are not likely to dissolve
calcium, such as borosilicate glass-1 specified in JIS R 3503 or Teflon.
Comment 1 Instead of the calcium standard solution in (2), a calcium standard solution for thecalibration curve preparation can be prepared by using a calcium standard solution (Ca10 mg/mL) traceable to National Metrology.
Comment 2 Instead of the calcium standard solution in (2), a calcium standard solution (CaO 5µg/mL - 50 µg/mL) for the calibration curve preparation prepared in (2) in 4.5.1.a canbe used. In this case, calculate water-soluble calcium (W-Ca) in the analytical sample
by multiplying the concentration (CaO) of a calcium standard solution for calibration
curve preparation or a measurement value (CaO) obtained in (4.2) by a conversion
factor (0.7147).
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A calcium hollow cathode lamp
2) Gas: Gas for heating by flame240

Testing Methods for Fertilizers(2021)(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (5) The sampling amount of the analytical sample is 10 g when the content in the analyticalsample is less than 0.01 % (mass fraction) as water-soluble calcium.
Comment 3 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 422.7 nmb) Calibration curve preparation
1) Spray the calcium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 422.7 nm.
2) Prepare a curve for the relationship between the calcium concentration and the indicated valueof the calcium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as Ca) in
a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the calcium content from the calibration curve, and calculate water-soluble calcium (WCa) in the analytical sample.
Comment 3 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rate at the content level of 1 % (mass fraction) - 5 % (massfraction) was 98.1 % - 101.1% as water-soluble calcium (W-Ca) respectively.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.07 % (mass fraction) for solid fertilizers and about 0.04 % (mass fraction)
for fluid fertilizers.
241

Testing Methods for Fertilizers(2021)

References
1)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Calcium Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 183 - 192 (2013)(5)

Flow sheet for water-soluble calcium: The flow sheet for water-soluble calcium in fertilizers
is shown below:242

Testing Methods for Fertilizers(2021)

4.5.4.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type B and its symbol is 4.5.3.b-2017 or W-Ca.b-1.
Add water to an analytical sample to extract, introduce it to an ICP Optical Emission Spectrometer(ICP-OES) and measure the calcium at a wavelength of 393.366 nm to obtain water-soluble calcium(W-Ca). In addition, the performance of this testing method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Calcium standard solution (Ca 1 mg/mL): Calcium standard solution (Ca 1 mg/mL) traceable
to National Metrology.
d) Calcium standard solution (Ca 0.1 mg/mL) (1): Put 10 mL of calcium standard solution (Ca 1
mg/mL) in a 100-mL flask and add hydrochloric acid (1+23) up to the marked line.
e) Calcium standard solutions (Ca 1 µg/mL - 20µg /mL) for the calibration curve preparation(1): Put 1 mL - 20 mL of calcium standard solution (Ca 0.1 mg/mL) in 100-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) up to the marked line.
f) Calcium standard solutions (Ca 0.1 µg/mL - 1 µg/mL) for the calibration curve
preparation (1): Put 1 mL - 10 mL of calcium standard solution (Ca 10 µg/mL) for thecalibration curve preparation in 100-mL volumetric flasks step-by-step, and add hydrochloric
acid (1+23) up to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the calcium standard solution in (2), a calcium standard solution for thecalibration curve preparation can be prepared by using a calcium standard solution (Ca10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0115
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
243

Testing Methods for Fertilizers(2021)

Note (2) The sampling amount of the analytical sample is 10 g when the content in the analyticalsample is less than 0.01 % (mass fraction) as water-soluble calcium.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 393.366 nm or 317.933 nm (3)b) Calibration curve preparation
1) Spray the calcium standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at an analytical line wavelength.
2) Prepare a curve for the relationship between the calcium concentration and the indicated valueof the calcium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Ca)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the calcium content from the calibration curve, and calculate water-soluble calcium (WCa) in the analytical sample.
Note (3) 317.933 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 393.366 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 4 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 5 The comparison of the measurement value (yi：0.095 % (mass fraction) - 10.93 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of flame atomic absorbance spectrometry was conducted to evaluate trueness using
fluid fertilizers (12 samples). As a result, a regression equation was y=0.005+0.978x,and its correlation coefficient (r) was 0.999. Additionally, additive recovery testing
was conducted using a fluid compound fertilizer (1 brand) and a home garden-use
compound fertilizer (1 brand). As a result, the mean recovery rates at the additive levelof 0.01 % (mass fraction) and 0.1 % (mass fraction) were 105.9 % and 106.4 %respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a home garden-use compound fertilizer to evaluate precision were analyzed by the244Testing Methods for Fertilizers(2021)

one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study for test
method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0005 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different days of water-soluble calcium(Fluid fertilizer)
4)
6)
2)
5)
7)
Test days ofsrs I(T)Mean
RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability T
(%)
(%)
(%)
(%)
(%)
Fluid compound fertilizer
7
2.14
0.02
0.7
0.05
2.1
Home garden-use compound fertilizer
7
0.103
0.001
0.9
0.001
1.0
(fluid)1) The number of test days conducting a duplicate test
6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

References
1)
Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development245

Testing Methods for Fertilizers(2021)

2)

(5)

Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research
Report of Fertilizer, Vol. 9, p. 1 - 9 (2016)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)
Flow sheet: The flow sheet for water-soluble calcium of the fluid fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg to a 100-mL volumetric flask← Water, about 50 mL
Shaking to mix← Water (up to the marked line)
Filtration
Sample solution
Figure 1 The flow sheet for water-soluble calcium in fluid fertilizers(Extraction procedure)

Sample solution
Aliquot
100-mL volmetric flask(predetermined volume)← 25 mL of hydrochloric acid (1+5)← Water (up to the marked line)
Measurement
ICP Optical Emission Spectrometer (393.366 nm)
Figure 2 The flow sheet for water-soluble calcium in fluid fertilizers(Measurement procedure)246

Testing Methods for Fertilizers(2021)

4.5.5 Alkalinity
4.5.5.a Ethylenediamine tetraacetate method(1) Summary
This testing method is applicable to fertilizers that guarantee alkalinity. This testing method isclassified as Type E and its symbol is 4.5.4.a-2017 or AL.a-1.
Add hydrochloric acid (1+23) to an analytical sample, boil to extract, and mask with 2,2’,2”nitrilotriethanol and a potassium cyanide solution, add a 0.01 mol/L ethylenediamine tetraacetatestandard solution, and conduct a chelatometric titration with a 0.01 mol/L magnesium standard
solution to obtain alkalinity (AL). Or after masking, conduct a chelatometric titration with an
ethylenediamine tetraacetate standard solution to obtain alkalinity (AL) in an analytical sample.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
c) Ascorbic acid: A JIS Guaranteed Reagent specified in JIS K 9502 or a reagent of equivalentquality.
d) 2,2’,2”-nitrilotriethanol (1): A JIS Guaranteed Reagent specified in JIS K 8663 or a reagent ofequivalent quality.
e) Acetone: A JIS Guaranteed Reagent specified in JIS K 8034 or a reagent of equivalent quality.
f) Ammonia solution: A JIS Guaranteed (NH3 28 % (mass fraction)) reagent specified in JIS K
8085 or a reagent of equivalent quality.
g) 0.01 mol/L ethylenediamine tetraacetate standard solution: Dissolve 3.72 g ofethylenediaminetetraacetic acid dihydrogen disodium dihydrate in water to make 1000 mL.
Standardization: Wash zinc reference material for volumetric analysis specified in JIS K 8005
with hydrochloric acid (1+3), water, ethanol (99.5) specified in JIS K 8101, and diethyl ether
specified in JIS K 8103 successively, and immediately leave at rest in a desiccator for about
12 hours under no more than 2 kPa to dry, and then weigh about 0.65 mg to the order of 0.1
mg, put it in a 1000-mL volumetric flask, add about 10 mL of hydrochloric acid to dissolve
and then add water up to the marked line. Put 25 mL of the solution in a 200-mL - 300-mL
Erlenmeyer flask, add about 15 mL of water and about 5 mL of ammonium chloride buffer
solution, and titrate with a 0.01 mol/L ethylenediamine tetraacetate standard solution, while
adding Eriochrome Black T solution as an indicator, until the color of the solution becomesblue. Calculate the factor of a 0.01 mol/L ethylenediamine tetraacetate standard solution by
the following formula.
Factor of 0.01 mol/L ethylenediamine tetraacetate standard solution (f1)
= W1 × (A/100) × (1/65.409) × (V1/V2) × (1000/V3) × (1/C1)= W1 × A× (1/65.409) × (0.25/V3)
W： Mass (g) of d zinc sampled
A： Purity (% (mass fraction)) of zinc
V1： Aliquot volume (25 mL) of zinc solution
V2： Constant volume (1000 mL) of zinc solution
V3： Volume (mL) of 0.01 mol/L ethylenediamine tetraacetate standard solution needed
for titration
C1: Set concentration (0.01 mol/L) of 0.01 mol/L ethylenediamine tetraacetate standard
solution
247

Testing Methods for Fertilizers(2021)h) 0.01 mol/L magnesium standard solution: Put 0.24 g of magnesium specified in JIS K 8875
into a 1000-mL beaker, add about 10 mL of hydrochloric acid to dissolve, add a proper amountof water, and while adding a methyl red solution (0.1 g/100 mL) as an indicator, neutralize with
an ammonia solution (1+3) until the color of the solution becomes yellow, and then add water
to make 1000 mL.
Standardization: Put 25 mL of 0.01 mol/L magnesium standard solution in a 200-mL - 300mL Erlenmeyer flask, add about 15 mL of water and about 5 mL of ammonium chloride buffer
solution, and while adding an Eriochrome Black T solution as an indicator, titrate with 0.01
mol/L ethylenediamine tetraacetate standard solution until the color of the solution becomesblue. Calculate the factor of a 0.01 mol/L magnesium standard solution by the following
formula.
Factor of 0.01 mol/L magnesium standard solution (f2)
= (C1 × f1 × V4) × (1/V5) × (1/C2)= (f1 × V4) × (1/V5)
C1： Set concentration (0.01 mol/L) of 0.01 mol/L ethylenediamine tetraacetatestandard solution
C2： Set concentration (0.01 mol/L) of 0.01 mol/L magnesium standard solution
f1： Factor of 0.01 mol/L ethylenediamine tetraacetate standard solution
V4： Volume (mL) of 0.01 mol/L ethylenediamine tetraacetate standard solution needed
for titration
V5： Aliquot volume (mL) of 0.01 mol/L magnesium standard solutioni)Ammonium chloride solution: Dissolve 70 g of ammonium chloride specified in JIS K 8116
and 570 mL of ammonia solution in water to make 1000 mL.
j) 2-aminoethanol solution: Add 400 mL of water to 150 mL of 2-aminoethanol specified in
JIS K 8109, add gradually hydrochloric acid to a pH 10.6.
k) Potassium cyanide solution: Dissolve 100 g of potassium cyanide specified in JIS K 8443
in water to make 1000 mL.
l) Eriochrome Black T solution: Dissolve 0.5 g of Eriochrome Black T specified in JIS K 8736
and 4.5 g of hydroxyl-ammonium chloride in methanol−water (95+5) to make 100 mL.
m) Methyl red solution (0.1 g/100 mL): Dissolve 0.10 g of methyl red specified in JIS K 8896 in
100 mL of ethanol (95) specified in JIS K 8102.
n) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
o) Citric acid solution (2): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
Note (1) The reagent corresponds to triethanolamine in the Official Methods of Analysis of
Fertilizers (1992).
(2) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of a 0.01 mol/L ethylenediamine tetraacetate standard solution in (2) g), a 0.1
mol/L ethylenediaminetetraacetic acid dihydrogen disodium solution conforming to
ISO/IEC 17025 can be used.
(3) Instruments: Instruments are as shown below:a) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
248

Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2 g of an analytical sample to the order of 1 mg, and put it in a 500-mL tall beaker.
b) Add about 200mL of hydrochloric acid (1+23), cover with a watch glass, and boil on a hot plate
for about 5 minutes (3).
c) After immediate cooling is complete, transfer it to a 250-mL- 500 -mL volumetric flask withwater.
d) Immediately add water up to the marked line (4).
e) Filter with Type 3 filter paper to make a sample solution.
Note (3) Be aware that an analytical sample should not solidify in the bottom of a beaker.
(4) Conduct the procedure in Comment 5 when there is much manganese content in thefertilizers.
Comment 2 In the case of a by-product magnesia fertilizer, if the pH of the sample solution of d)is neutral or basic, prepare a sample solution anew by replacing “2 g of an analyticalsample” in the procedure in a) with “1 g - 1.5 g of an analytical sample”.
Comment 3 In the procedure in a), a 500-mL volumetric flask can be used instead of a 500-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. In addition, “cover with a watch
glass” in b) is replaced by “place a funnel”, and “transfer it to a 250-mL - 500 mL
volumetric flask with water” in the procedure in c) is skipped.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
Comment 5 Put a predetermined volume of filtrate in (4.1) e) in a 200-mL tall beaker, add a dropof methyl red solution as an indicator and add ammonia water (28 % (mass fraction))
specified in JIS K 8085 drop by drop until the color of the solution changes lightyellowish red from purplish red. Add 20 mL of ammonium peroxodisulfate aqueous
solution (20 g/100mL) to boil (5). Immediately transfer it to a 100-mL - 200-mL
volumetric flask with water. After immediate cooling is complete, add water up to themarked line. Filter with Type 3 filter paper to make a sample solution.
Note (5) Precipitation of manganese oxide, etc. is formed.
(4.2) Measurement: Conduct measurement as shown below. Two examples of titration are shown as
follows.
(4.2.1) Measurement (A): Titration with a magnesium standard solution (0.01 mol/L)a) Put a predetermined volume (the equivalents of 5 mg - 20 mg as CaO + MgO) of sample solution
in a 200-mL - 300-mL Erlenmeyer flask.
b) Add a proper amount of water, add a drop of methyl red solution as an indicator and add sodiumhydroxide solution (5 g/100 mL) drop by drop to neutralize until the color of the solution
becomes yellow.
c) Add 0.1 g of ascorbic acid, 1 ml - 10 mL of 2,2’,2”-nitrilotriethanol−water (1+3) and 1 mL - 10
mL of potassium cyanide solution (6).
d) Add a predetermined volume of 0.01 mol/L ethylenediamine tetraacetate standard solution (7).
e) Add 20 mL of ammonium chloride solution or 2-aminoethanol solution.
f) Add several drops of Eriochrome Black T solution, and titrate with a 0.01 mol/L magnesium
standard solution until the color of the solution becomes red.
g) Calculate the alkalinity (AL) content in an analytical sample by the following formula.
249

Testing Methods for Fertilizers(2021)

Alkalinity (AL) (% (mass fraction)) in an analytical sample= ((C1 × f1 × V6/1000) － (C2 × f2 × V7/1000)) × (56.077/W2) × (V8/V9) × 100= ((f1 × V6) － (f2 × V7)) × (56.077/W2) × (V3/V4) × (1/1000)
C1： Set concentration (0.01 mol/L) of 0.01 mol/L ethylenediamine tetraacetatestandard solution
C2： Set concentration (0.01 mol/L) of 0.01 mol/L magnesium standard solution
f1： Factor of 0.01 mol/L ethylenediamine tetraacetate standard solution
f2： Factor of 0.01 mol/L magnesium standard solution
V6： Additive volume (mL) of 0.01 mol/L ethylenediamine tetraacetate standard
solution
V7： Volume (mL) of 0.01 mol/L magnesium standard solution needed for titration
V8： Constant volume (mL) of the sample solution in (4.1) d)
V9： Aliquot volume (mL) of the sample solution subjected to titration in (4.2.1) a).
W2： Mass (g) of the analytical sample
Note (6) If manganese is present, replace “1 mL - 10 mL of potassium cyanide solution” with “1g- 5g of potassium cyanide”.
(7) Add excess volume since 1.8 mL of ethylenediamine tetraacetate standard solution (0.01
mol/L) is required for 1 mg of CaO.
(4.2.2)

Measurement (B): Titration with an ethylenediamine tetraacetate standard solution (0.01
mol/L)
a) Put a predetermined volume (the equivalents of 5 mg - 20 mg as CaO + MgO) of sample solution
in a 200-mL - 300-mL Erlenmeyer flask.
b) Add a proper amount of water and 5 mL of citric acid solution (8), add a drop of methyl red
solution as an indicator and add sodium hydroxide solution (5 g/100 mL) drop by drop to
neutralize until the color of the solution becomes yellow.
c) Add 0.1 g of ascorbic acid, 1 ml - 10 mL of 2,2’,2”-nitrilotriethanol−water (1+3) and 1 mL - 10
mL of potassium cyanide solution (6).
d) Add 20 mL of ammonium chloride solution or 2-aminoethanol solution.
e) Add several drops of an Eriochrome Black T solution, and immediately titrate with a 0.01 mol/L
ethylenediamine tetraacetate standard solution until the color of the solution becomes bluegreen.
f) Calculate the alkalinity (AL) content in an analytical sample by the following formula.
Alkalinity (AL) (% (mass fraction)) in an analytical sample= (C1 × f1 × V10/1000) × (56.077/W3) × (V11/V12) × 100= (f1 × V10) × (56.077/W3) × (V11/V12) × (１/1000)
C1： Set concentration (0.01 mol/L) of 0.01 mol/L ethylenediamine tetraacetatestandard solution
f1： Factor of 0.01 mol/L ethylenediamine tetraacetate standard solution
V10： Volume (mL) of 0.01 mol/L ethylenediamine tetraacetate standard solution needed
for titration
V11： Constant volume (mL) of the sample solution in (4.1) d)
V12： Aliquot volume (mL) of the sample solution subjected to titration in (4.2.2) a).
W3： Mass (g) of the analytical sample
Note (8) When the sample solution does not contain phosphate, silicate, etc., it is not necessary250

Testing Methods for Fertilizers(2021)

to add citric acid.
Comment 6 Care should be fully taken in the case of using potassium cyanide and its solution inaccordance with the Safety Data Sheet (SDS). In addition, observe laws and ordinances
concerned such as the Poisonous and Deleterious Substance Control Law.
Criteria of the abolition in the Poisonous and Deleterious Substance Control Law (forreference): Add a sodium hydroxide solution to make it alkalinity more than pH 11,
and further add an oxidizer (sodium hypochlorite, bleaching powder) solution to
conduct oxidative degradation processes. After dissolving CN ingredient, neutralize
with sulfuric acid, and discard it after diluting it with a large amount of water. Takeenough time to dissolve the CN ingredient with alkalinity.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.162- 164, Yokendo, Tokyo (1988)(5)

Flow sheet for alkalinity: The flow sheet for alkalinity in fertilizers is shown below:

2 g analytical sample
Weigh to the order of 1 mg to a 500-mL tall beaker← About 200 mL of hydrochloric acid (1+23)
Heating
Cover with a watch glass and boil for 5 minutes
Cooling

Immediately

Transfer
250-mL - 500-mL volumetric flask← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for alkalinity in fertilizers (Extraction procedure)251

Testing Methods for Fertilizers(2021)

252

Testing Methods for Fertilizers(2021)

4.5.5.b Calculation with acid-soluble lime and acid-soluble magnesia(1) Summary
This testing method is applicable to fertilizers that guarantee alkalinity (AL). This testing method
is classified as Type A (Def-C) and its symbol is 4.5.4.b-2017 or AL.b-1.
Multiply the acid-soluble magnesia (S-MgO) obtained in 4.6.2 by the factor (1.3934) and add tothe acid-soluble lime (S-CaO) obtained in 4.5.2 to calculate alkalinity (AL) in an analytical sample.
(2) Calculation of alkalinitya) Calculate the alkalinity (AL) in a teat sample by the following formula.
Alkalinity (AL) (% (mass fraction)) in an analytical sample= (S-CaO)＋1.3914 × (S-MgO)
S-CaO： Acid-soluble lime (% (mass fraction)) (1) obtained in 4.5.2 in an analyticalsampleS-MgO： Acid-soluble magnesia (% (mass fraction)) (1) obtained in 4.6.2 in ananalytical sample
Note (1) S-CaO and S-MgO use raw data without rounding numerical value

253

Testing Methods for Fertilizers(2021)

4.6 Magnesia
4.6.1 Total magnesia
4.6.1.a Flame atomic absorption spectrometry(1) Summary
The testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 4.6.1.a-2021 or T-Mg.a-2.
Pretreat an analytical sample with incineration and hydrochloric acid or nitric acid−hydrochloric
acid (1+3), add an interference suppressor solution, and then spray in an acetylene−air flame, andmeasure the atomic absorption with magnesium at a wavelength of 285.2 nm to quantify totalmagnesia (T-MgO) in an analytical sample. In addition, the performance of this testing method isshown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A JIS Guaranteed Reagent specified in JIS K 8541 or a reagent of equivalentquality.
c) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
d) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
e) Magnesium standard solution (MgO 1 mg/mL) (1): Weigh 0.603 g of magnesium (powder)specified in JIS K 8876 into a weighing dish. Transfer to a 1000-mL volumetric flask with asmall amount of water, add about 10 mL of hydrochloric acid to dissolve, and add water up to
the marked line.
f) Magnesium standard solution (MgO 0.1 mg/mL) (1): Put 10 mL of magnesium standard
solution (MgO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
g) Magnesium standard solution (MgO 1 µg/mL-10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of magnesium standard solution (MgO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
h) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution in a 250-mL volumetric flask (3), and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the magnesium standard solution in (2), a magnesium standard solution forthe calibration curve preparation can be prepared by using a magnesium standard
solution (Mg 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate total magnesia (T-MgO) in the analytical sample by multiplying theconcentration (Mg) of the magnesium standard solution for calibration curve
preparation or a measurement value (Mg) obtained in (4.2) by a conversion factor(1.6583).
Comment 2 When using a sample solution obtained in the procedure in (4.1.2) h) for themeasurement of cadmium, nickel, chromium or lead, sulfuric acid and hydrochloric
acid in (2) should be a reagent of harmful metal analysis grade, microanalysis grade or254

Testing Methods for Fertilizers(2021)

equivalents.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A magnesium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can be adjusted to 450 °C ± 5 °C or 550 ºC ± 5 ºC.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Incineration-hydrochloric acid boilinga) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After standing to cool, transfer the solution to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (4) Example of charring and incineration procedure: After raising the temperature from room
temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1 hourand further raise to 550 °C in 1 to 2 hours.
Comment 3 Do not conduct the procedures in (4.1.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Incineration-aqua regia digestiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (5).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (5).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (6), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (7) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
255

Testing Methods for Fertilizers(2021)h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water up
to the marked line, and filter with Type 3 filter paper to make a sample solution.
Note (5) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about
1 hour and further raise to 450 °C in 1 to 2 hours.
(6) The watch glass can be removed.
(7) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 5 Do not conduct the procedures in (4.1.2) b) - c) in the case of fertilizers not containing
organic matters.
Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.

(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 285.2 nmb) Calibration curve preparation
1) Spray the magnesium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 285.2 nm.
2) Prepare a curve for the relationship between the magnesium concentration and the indicatedvalue of the magnesium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MgO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the magnesium content from the calibration curve, and calculate the total magnesia (TMgO) in the analytical sample.
Comment 7 The analytical line wavelength may be set to 202.5 nm with lower sensitivity. An
example preparation of standard solutions for calibration curve preparation for awavelength of 202.5 nm is 0.07 µg/mL - 5 µg/mL as MgO, and the minimum limit ofquantification was estimated to be about 0.07 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range of calibration
curve suitable for the instrument and prepare standard solutions for calibration curve
preparation.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 5 % (mass fraction), 1 % (massfraction) and 0.2 % (mass fraction) were 102.4 %, 101.7 % and 103.0 % as totalmagnesia (T-MgO) respectively.
256

Testing Methods for Fertilizers(2021)

The results of the repeatability tests on different days using swine manure compost,composted sludge fertilizer and poultry manure ash (1 sample for each) to evaluate
precision were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability. Additionally, resultsfrom a collaborative study for test method validation and its analysis are shown in Table
2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different days of total magnesia
4)
6)
2)
5)
7)
Test days ofsrs I(T)Mean
RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability T
(%)
(%)
(%)
(%)
(%)
Swine manure compost
5
3.14
0.03
1.1
0.05
1.5
Composted sludge fertilizer
5
0.84
0.01
1.2
0.01
1.3
Poultry manure ash
5
3.97
0.03
0.7
0.04
1.1
1) The number of test days conducting a duplicate test
6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

References
1)
Erika HIRATA，Hideo SOETA，Hidemi YOSHIMURA，Keiji YAGI: Determination of
Total Magnesium in Compost and Sludge Fertilizer by Atomic Absorption Spectrometry- Research Report of Fertilizer Vol. 11, p. 29 - 38 (2018)2)
Kenji YAGI, Takuya KOBORI, Hideo SOETA and Hidemi YOSHIMURA: Performance
Evaluation of Determination Method for Magnesium in Fertilizer: Harmonized
Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 87 – 101 (2020)

257

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total magnesia: The flow sheet for total magnesia in fertilizers is shown below:

258

Testing Methods for Fertilizers(2021)

259

Testing Methods for Fertilizers(2021)

4.6.2 Acid-soluble magnesia
4.6.2.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers containing by-product magnesia fertilizers andfertilizers that guarantee alkalinity. This testing method is classified as Type B and its symbol is
4.6.2.a-2021 or S-Mg.a-2.
Add hydrochloric acid (1+23) to an analytical sample, boil to extract and add an interference
suppressor solution, and then spray in an acetylene−air flame, and measure the atomic absorption
with magnesium at a wavelength of 285.2 nm to obtain hydrochloric acid (1+23) soluble magnesia(acid-soluble magnesia (S-MgO)) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Magnesium standard solution (MgO 1 mg/mL) (1): Weigh 0.603 g of magnesium (powder)specified in JIS K 8876 into a weighing dish. Transfer to a 1000-mL volumetric flask with asmall amount of water, add about 10 mL of hydrochloric acid to dissolve, and add water up to
the marked line.
d) Magnesium standard solution (MgO 0.1 mg/mL) (1): Put 10 mL of magnesium standard
solution (MgO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
e) Magnesium standard solution (MgO 1 µg/mL-10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of magnesium standard solution (MgO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
f) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution used in the procedure e) in a 250-mL volumetric flask (3), and add water up
to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the magnesium standard solution in (2), a magnesium standard solution forthe calibration curve preparation can be prepared by using a magnesium standard
solution (Mg 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate acid-soluble magnesia (S-MgO) in the analytical sample bymultiplying the concentration (Mg) of a magnesium standard solution for calibration
curve preparation or a measurement value (Mg) obtained in (4.2) by a conversion
factor (1.6583).
(3)a)

Instruments: Instruments are as shown below:
Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A magnesium hollow cathode lamp260

Testing Methods for Fertilizers(2021)

2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2 g of an analytical sample to the order of 1 mg, and put it in a 500-mL tall beaker.
b) Add about 200mL of hydrochloric acid (1+23), cover with a watch glass, and boil on a hot plate
for about 5 minutes (4).
c) After immediate cooling is complete, transfer it to a 250-mL - 500 -mL volumetric flask withwater.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (4) Be aware that an analytical sample should not solidify in the bottom of a beaker.
Comment 2 In the case of a by-product magnesia fertilizer or a fertilizer containing a by-productmagnesia, if the pH of the sample solution of d) is neutral or basic, prepare a sample
solution anew by replacing “2 g of an analytical sample” in the procedure in a) with
“1 g - 1.5 g of an analytical sample”.
Comment 3 In the procedure in a), a 500-mL volumetric flask can be used instead of a 500-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. In addition, “cover with a watch
glass” in b) is replaced by “place a funnel”, and “transfer it to a 250-mL - 500 mL
volumetric flask with water” in the procedure in c) is skipped.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 285.2 nmb) Calibration curve preparation
1) Spray the magnesium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 285.2 nm.
2) Prepare a curve for the relationship between the magnesium concentration and the indicatedvalue of the magnesium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MgO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the magnesium content from the calibration curve, and calculate the acid-soluble
magnesia (S-MgO) in the analytical sample.
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Testing Methods for Fertilizers(2021)

Comment 5 The analytical line wavelength may be set to 202.5 nm with lower sensitivity. An
example preparation of standard solutions for calibration curve preparation for awavelength of 202.5 nm is 0.07 µg/mL - 5 µg/mL as MgO, and the minimum limit ofquantification was estimated to be about 0.07 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 15 % (mass fraction) and 1 %(mass fraction) were 101.7 % and 99.5% as acid-soluble magnesia (S-MgO)
respectively. In order to evaluate precision, results from a collaborative study for test
method validation and its analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 % (mass fraction) for solid fertilizers and about 0.05 % (mass fraction)
for fluid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.167- 169, Yokendo, Tokyo (1988)
2)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Magnesia Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 193 - 202 (2013)3)
Kenji YAGI, Takuya KOBORI, Hideo SOETA and Hidemi YOSHIMURA: Performance
Evaluation of Determination Method for Magnesium in Fertilizer: Harmonized
Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 87 – 101 (2020)

262

Testing Methods for Fertilizers(2021)(5)

Flow sheet for acid-soluble magnesia: The flow sheet for acid-soluble magnesia in fertilizers
is shown below:

263

Testing Methods for Fertilizers(2021)

4.6.3 Citric acid-soluble magnesia
4.6.3.a Flame atomic absorption spectrometry(1) Summary
This test method is applicable to fertilizers containing magnesia hydroxide fertilizers, etc. This
testing method is classified as Type B and its symbol is 4.6.3.a-2021 or C-Mg.a-3.
Extract by adding a citric acid solution to an analytical sample and add an interference suppressor
solution, and then spray in an acetylene−air flame, and measure the atomic absorption withmagnesium at a wavelength of 285.2 nm to obtain citric acid-soluble magnesia (C-MgO) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 9.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
c) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
d) Magnesium standard solution (MgO 1 mg/mL) (1): Weigh 0.603 g of magnesium (powder)specified in JIS K 8876 into a weighing dish. Transfer to a 1000-mL volumetric flask with asmall amount of water, add about 10 mL of hydrochloric acid to dissolve, and add water up to
the marked line.
e) Magnesium standard solution (MgO 0.1 mg/mL) (1): Put 10 mL of magnesium standard
solution (MgO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
f) Magnesium standard solution (MgO 1 µg/mL-10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of magnesium standard solution (MgO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
g) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution used in the procedure f) in a 250-mL volumetric flask (3), and add water up
to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the magnesium standard solution in (2), a magnesium standard solution forthe calibration curve preparation can be prepared by using a magnesium standard
solution (Mg 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate citric acid-soluble magnesia (C-MgO) in the analytical sample bymultiplying the concentration (Mg) of a magnesium standard solution for calibration
curve preparation or a measurement value (Mg) obtained in (4.2) by a conversion
factor (1.6583).
(3) Instruments: Instruments are as shown below:a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating264

Testing Methods for Fertilizers(2021)

mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A magnesium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (4), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (4) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(5).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (4), and shake to mix by reciprocating
at amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) at 160 times/min for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (5) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 3 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 4 For a by-product magnesia fertilizer, if the pH of the sample solution in (4.1.1) d) and(4.1.2) d) is neutral or basic, prepare a sample solution anew by replacing “1 g of ananalytical sample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of ananalytical sample”.
Comment 5 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
Comment 6 In some silicate slag fertilizers, the variation of measurement value of citric acid265

Testing Methods for Fertilizers(2021)

soluble magnesia (C-MgO) may be observed according to the time variation of heatingstate after adding a citric acid solution. Therefore, in the case of silicate slag fertilizers,
it is necessary to conduct the procedures of (4.1.1) c) - d) and (4.1.2) c) - d) as quickly
as possible after confirming the time of shaking to mix in the procedure in (4.1.1) b)and (4.1.2) b).
Comment 7 In the case of a fertilizer containing Kieserite (magnesia sulfate fertilizers), wash thenon-dissolved matters with water obtained while preparing the sample solution ofwater-soluble magnesia in (4.1) in 4.6.4.a to put it in a 250 mL volumetric flask, andthen prepare a sample solution by the procedures in (4.1.1) b) - d) and (4.1.2) b) - d).
Mix the magnesia obtained in (4.2) regarding this sample solution with the watersoluble magnesia in 4.6.4.a regarding the said fertilizers to make citric acid-soluble
magnesia.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 285.2 nmb) Calibration curve preparation
1) Spray the magnesium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 285.2 nm.
2) Prepare a curve for the relationship between the magnesium concentration and the indicatedvalue of the magnesium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MgO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the magnesium content from the calibration curve, and calculate the citric acid-soluble
magnesia (C-MgO) in the analytical sample.
Comment 8 The analytical line wavelength may be set to 202.5 nm with lower sensitivity. An
example preparation of standard solutions for calibration curve preparation for awavelength of 202.5 nm is 0.07 µg/mL - 5 µg/mL as MgO, and the minimum limit ofquantification was estimated to be about 0.07 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 9 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rate at the content level of 1 % (mass fraction) - 5 % (massfraction) was 98.9 % - 100.3 % as citric acid-soluble magnesia (C-MgO).
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1. The results of the collaborative study
to determine a certified reference material fertilizer were analyzed by using a threelevel nesting analysis of variance. Table 2 shows the calculation results ofreproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to266

Testing Methods for Fertilizers(2021)

be about 0.06 % (mass fraction) for solid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.167- 169, Yokendo, Tokyo (1988)
2)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Magnesia Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 193 - 202 (2013)3)
Souichi IGARASHI and Yasuharu KIMURA: Effect of Time during Extraction Operation
on Measurements of Citric Acid-Soluble Magnesium in Silicate Slag Fertilizer Vol. 7, p.
145 - 156 (2014)
4)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)5)
Kenji YAGI, Takuya KOBORI, Hideo SOETA and Hidemi YOSHIMURA: Performance
Evaluation of Determination Method for Magnesium in Fertilizer: Harmonized
Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 87 – 101 (2020)
267

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble magnesia: The flow sheet for citric acid-soluble magnesia
in fertilizers is shown below:
1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker← About 150 mL of citrate solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble magnesia in fertilizers(Extraction procedure (4.1.1))
1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker← About 150 mL of citrate solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble magnesia in fertilizers (Extraction procedure (4.1.2))

268

Testing Methods for Fertilizers(2021)

4.6.3.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 4.6.3.b-2018 or C-Mg.b-1.
Extract by adding a citric acid solution to an analytical sample, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the magnesium at a wavelength of 279.553 nm toobtain citric acid-soluble magnesia (citric acid-soluble magnesia (C-MgO)) in an analytical sample.
In addition, the performance of this testing method is shown in Comment 10.
(2) Reagent: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
d) Magnesium standard solution (MgO 1 mg/mL) (1): Weigh 0.603 g of magnesium (powder)specified in JIS K 8876 into a weighing dish. Transfer to a 1000-mL volumetric flask with asmall amount of water, add about 10 mL of hydrochloric acid to dissolve, and add water up to
the marked line.
e) Magnesium standard solution (MgO 0.1 mg/mL): Put 10 mL of magnesium standard solution(MgO 1 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to themarked line.
f) Magnesium standard solution (MgO 2 µg/mL - 10 µg/mL) for the calibration curve
preparation (1): Put 2 mL-16 mL of magnesium standard solution (MgO 0.1 mg/mL) in 100mL volumetric flasks step-by-step, and add hydrochloric acid (1+23) up to the marked line.
g) Magnesium standard solution (MgO 0.2 µg/mL - 2 µg/mL) for the calibration curve
preparation (1): Put 2 mL - 20 mL of magnesium standard solution (MgO 10 µg/mL) for thecalibration curve preparation in 100-mL volumetric flasks step-by-step, and add hydrochloric
acid (1+23) up to the marked line.
h) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) - g).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the magnesium standard solution in (2), a magnesium standard solution forthe calibration curve preparation can be prepared by using a magnesium standard
solution (Mg 1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate citric acid-soluble magnesia (C-MgO) in the analytical sample bymultiplying the concentration (Mg) of a magnesium standard solution for calibration
curve preparation or a measurement value (Mg) obtained in (4.2) by a conversion
factor (1.6583).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometry: An optical emission spectrometer specified in JIS K
269

Testing Methods for Fertilizers(2021)

0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
ba) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
bb) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(3).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix by reciprocating
at amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) at 160 times/min for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (3) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 For a by-product magnesia fertilizer, if the pH of the sample solution in (4.1.1) d) and(4.1.2) d) is neutral or basic, prepare a sample solution anew by replacing “1 g of ananalytical sample” in the procedures in (4.1.1) a) and (4.1.2) a) with “0.5 g of ananalytical sample”.
Comment 6 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, check the status of the non-dissolved matters after
the procedures of (4.1.1) b) and (4.1.2) b).
Comment 7 In some silicate slag fertilizers, the variation of measurement value of citric acidsoluble magnesia (C-MgO) may be observed according to the time variation of heating
270

Testing Methods for Fertilizers(2021)

state after adding a citric acid solution. Therefore, in the case of silicate slag fertilizers,
it is necessary to conduct the procedures of (4.1.1) c) - d) and (4.1.2) c) - d) as quickly
as possible after confirming the time of shaking to mix in the procedure in (4.1.1) b)and (4.1.2) b).
Comment 8 In the case of a fertilizer containing Kieserite (magnesia sulfate fertilizers), wash thenon-dissolved matters with water obtained while preparing the sample solution ofwater-soluble magnesia in (4.1) in 4.6.4.a to put it in a 250 mL volumetric flask, andthen prepare a sample solution by the procedures in (4.1.1) b) - d) and (4.1.2) b) - d).
Mix the magnesia obtained in (4.2) regarding this sample solution with the watersoluble magnesia in 4.6.4.a regarding the said fertilizers to make citric acid-soluble
magnesia.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 279.553 nmb) Calibration curve preparation
1) Spray the magnesium standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 279.553 nm.
2) Prepare a curve for the relationship between the magnesium concentration and the indicatedvalue of the magnesium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.02 mg - 1.6 mg as
MgO) in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the magnesium content from the calibration curve, and calculate the citric acid-soluble
magnesia (C-MgO) in the analytical sample.
Comment 9 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 10 The comparison of the measurement value (yi：1.59 % (mass fraction) - 15.06 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of Flame atomic absorption spectrometry was conducted to evaluate trueness using
processed phosphorus fertilizers (2 samples), compound fertilizers (11 samples),silicate slag fertilizer (1 sample), mixed compost compound fertilizer (1 sample),mixed phosphorus fertilizers (2 samples), designated blended fertilizer (1 sample),blended fertilizers (5 samples), byproduct compound fertilizer (1 sample), organic
compound fertilizer (1 sample), and fused phosphate fertilizer (1 sample). As a result,a regression equation was y=0.0271+1.0124x, and its correlation coefficient (r) was
0.999. In addition, additive recovery testing was conducted using a preparation sample.
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Testing Methods for Fertilizers(2021)

As a result, the mean recovery rate at the additive level of 0.232 % (mass fraction) 18.81 % (mass fraction) was 94.9 % - 102.7 %.
The results of the repeatability tests on different days using compound fertilizers andblended fertilizers to evaluate precision were analyzed by one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.03 % (mass fraction).

References
1)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)2)
Shingo MATSUO: Simultaneous Determination of Citrate-Soluble Principal Ingredients(C-P2O5, C-K2O, C-MgO, C-MnO and C-B2O3) in Fertilizer using Inductively Coupled
Plasma-Optical Emission Spectrometry (ICP-OES), Research Report of Fertilizer, Vol.
11, p. 14 – 28 (2018)(5)

Flow sheet for citric acid-soluble magnesia: The flow sheet for citric acid-soluble magnesia
in fertilizers is shown below:
1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker.

← About 150 mL of citrate solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble magnesia in fertilizers (Extraction procedure (4.1.1))

272

Testing Methods for Fertilizers(2021)

1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker.

← About 150 mL of citrate solution [about 30 ºC]
Shaking to mix

Horizontal reciprocating water bath shaker (160 reciprocations/min,
amplitude of 25 mm - 40 mm), at 30 ºC ± 1 ºC, for 1 hour

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble magnesia in fertilizers (Extraction procedure (4.1.2))

273

Testing Methods for Fertilizers(2021)

4.6.4 Water-soluble magnesia
4.6.4.a Flame atomic absorption spectrometry(1) Summary
This test method is applicable to fertilizers containing magnesia sulfate fertilizers, etc. This testing
method is classified as Type B and its symbol is 4.6.4.a-2021 or W-Mg.a-2.
Add water to an analytical sample and boil to extract. Add an interference suppressor solution, thenspray in an acetylene−air flame and measure the atomic absorption with magnesium at a wavelengthof 285.2 nm to obtain water-soluble magnesia (W-MgO) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Magnesium standard solution (MgO 1 mg/mL) (1): Weigh 0.603 g of magnesium (powder)specified in JIS K 8876 into a weighing dish. Transfer to a 1000-mL volumetric flask with asmall amount of water, add about 10 mL of hydrochloric acid to dissolve, and add water up to
the marked line.
d) Magnesium standard solution (MgO 0.1 mg/mL) (1): Put 10 mL of magnesium standard
solution (MgO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
e) Magnesium standard solution (MgO 1 µg/mL - 10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of magnesium standard solution (MgO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
f) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution used in the procedure d) in a 250-mL volumetric flask (3), and add water up
to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the magnesium standard solution in (2), a magnesium standard solution forthe calibration curve preparation can be prepared by using a magnesium standard
solution (Mg 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate water-soluble magnesia (W-MgO) in the analytical sample bymultiplying the concentration (Mg) of a magnesium standard solution for calibration
curve preparation or a measurement value (Mg) obtained in (4.2) by a conversion
factor (1.6583).
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A magnesium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene274Testing Methods for Fertilizers(2021)(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 400-mL tall beaker.
b) Add 400 mL of water, and cover with a watch glass to boil on a hot plate for about 30 minutes(5).
c) After immediate cooling is complete, transfer it to a 500- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (4) Be aware that an analytical sample should not solidify in the bottom of a beaker.
Comment 2 The procedure in (4.1.1) is the same as the procedure in (4.1.1) in 4.6.4.b.
Comment 3 In the procedure in a), a 500-mL volumetric flask can be used instead of a 500-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. Additionally, “cover with a watch
glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 500-mL volumetricflask with water” in the procedure in c).
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample (5) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (5) The sampling amount of the analytical sample is 10 g when there is less magnesia
content in the fertilizers such as a home garden-use fertilizer.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 285.2 nmb) Calibration curve preparation
1) Spray the magnesium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 285.2 nm.
2) Prepare a curve for the relationship between the magnesium concentration and the indicatedvalue of the magnesium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement275

Testing Methods for Fertilizers(2021)

1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MgO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the magnesium content from the calibration curve, and calculate the water-soluble
magnesia (W-MgO) in the analytical sample.
Comment 5 The analytical line wavelength may be set to 202.5 nm with lower sensitivity. An
example preparation of standard solutions for calibration curve preparation for awavelength of 202.5 nm is 0.07 µg/mL - 5 µg/mL as MgO, and the minimum limit ofquantification was estimated to be about 0.07 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 1 % (mass fraction) - 5 % (massfraction) were 100.4 % - 100.9 % as water-soluble magnesia (W-MgO) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.07 % (mass fraction).

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.167- 169, Yokendo, Tokyo (1988)
2)
Souichi IGARASHI and Yasuharu KIMURA: Verification of Performance Characteristicsof Testing Methods for Magnesia Content in Fertilizer by Atomic Absorption
Spectrometry: Research Report of Fertilizer Vol. 6, p. 193 - 202 (2013)3)
Kenji YAGI, Takuya KOBORI, Hideo SOETA and Hidemi YOSHIMURA: Performance276

Testing Methods for Fertilizers(2021)

Evaluation of Determination Method for Magnesium in Fertilizer: Harmonized
Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 87 – 101 (2020)(5) Flow sheet for water-soluble magnesia: The flow sheet for water-soluble magnesia in
fertilizers is shown below:

277

Testing Methods for Fertilizers(2021)

4.6.4.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D for solid
fertilizers and Type B for fluid fertilizers. Its symbol is 4.6.4.b-2019 or W-Mg.b-2.
Add water to an analytical sample to extract, introduce it to an ICP Optical Emission Spectrometer(ICP-OES) and measure the magnesium at a wavelength of 279.553 nm, etc. to obtain water-soluble
magnesia (W-MgO) in an analytical sample. In addition, the performance of this testing method isshown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Magnesium standard solution (MgO 1 mg/mL) (1): Weigh 0.603 g of magnesium (powder)specified in JIS K 8876 into a weighing dish. Transfer to a 1000-mL volumetric flask with asmall amount of water, add about 10 mL of hydrochloric acid to dissolve, and add water up to
the marked line.
d) Magnesium standard solution (MgO 0.1 mg/mL): Put 10 mL of magnesium standard solution(MgO 1 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to themarked line.
e) Magnesium standard solution (MgO 2 µg/mL - 16 µg/mL) for the calibration curve
preparation (1): Put 2 mL-16 mL of magnesium standard solution (MgO 0.1 mg/mL) in 100mL volumetric flasks step-by-step, and add hydrochloric acid (1+23) up to the marked line.
f) Magnesium standard solution (MgO 0.2 µg/mL - 2 µg/mL) for the calibration curve
preparation (1): Put 2 mL - 20 mL of magnesium standard solution (MgO 10 µg/mL) for thecalibration curve preparation in 100-mL volumetric flasks step-by-step, and add hydrochloric
acid (1+23) up to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the magnesium standard solution in (2), a magnesium standard solution forthe calibration curve preparation can be prepared by using a magnesium standard
solution (Mg 1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate water-soluble magnesia (W-MgO) in the analytical sample bymultiplying the concentration (Mg) of a magnesium standard solution for calibration
curve preparation or a measurement value (Mg) obtained in (4.2) by a conversion
factor (1.6583).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity
278

Testing Methods for Fertilizers(2021)b) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 400-mL tall beaker.
b) Add 400 mL of water, and cover with a watch glass to heat on a hot plate and boil for about 30
minutes (2).
c) After immediate cooling is complete, transfer it to a 500- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (2) Be aware that an analytical sample should not solidify in the bottom of a beaker.
Comment 3 The procedure in (4.1.1) is the same as the procedure in (4.1.1) in 4.6.4.a.
Comment 4 In the procedure in a), a 500-mL volumetric flask can be used instead of a 500-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. Additionally, “cover with a watch
glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 500-mL volumetricflask with water” in the procedure in c).
(4.1.2) Fluid test samplea) Weigh 1 mg of an analytical sample (3) to the order of 1 g, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (3) The sampling amount of the analytical sample is 10 g when there is less magnesia
content in the fertilizers such as a home garden-use fertilizer.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 279.553 nm or 280.270 nm (4)b) Calibration curve preparation
1) Spray the magnesium standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at an analytical line wavelength.
2) Prepare a curve for the relationship between the magnesium concentration and the indicatedvalue of the magnesium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.02 mg - 1.6 mg as
MgO) in a 100-mL volumetric flask.
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Testing Methods for Fertilizers(2021)

2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the magnesium content from the calibration curve, and calculate the water-soluble
magnesia (W-MgO) in the analytical sample.
Note (4) 280.270 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 279.553 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 6 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 7 The comparison of the measurement value (yi：0.361 % (mass fraction) - 14.51 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of flame atomic absorbance spectrometry was conducted to evaluate trueness using
solid fertilizers (28 samples). As a result, a regression equation was y=−0.0263+1.004x, and its correlation coefficient (r) was 1.000. Similarly the comparison of themeasurement value (yi：0.160 % (mass fraction) - 9.36 % (mass fraction )) and themeasurement value (xi) was conducted using fluid fertilizers (12 samples). As a result,a regression equation was y＝−0.006+0.985x, and its correlation coefficient (r) was
0.999. In addition, additive recovery testing was conducted using preparation
fertilizers (5 samples). As a result, the mean recovery rate at the additive level of
0.846 % (mass fraction) - 18.79 % (mass fraction) was 97.7 % - 103.0 %. Additive
recovery testing was conducted using a fluid compound fertilizer (1 brand), a homegarden-use compound fertilizer (1 brand) and a liquid microelement compound
fertilizer (1 sample). As a result, the mean recovery rates at the additive level of 1 %(mass fraction) and 0.15 % (mass fraction) were 98.7 % - 102.8 % and 102.3 %respectively.
The results of the repeatability tests on different days using a mixed microelement
fertilizer, a blended fertilizer, a fluid compound fertilizer and a home garden-use
compound fertilize (fluid) were analyzed by the one-way analysis of variance toevaluate precision. Table 1-1 and 1-2 show the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study
implemented for testing method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.06 % (mass fraction) for solid fertilizers and about 0.002 % (mass fraction)
for fluid fertilizers.

280

Testing Methods for Fertilizers(2021)

281

Testing Methods for Fertilizers(2021)

References
1)
Keisuke AOYAMA: Simultaneous Determination of Water-Soluble Principal
Ingredients (W-P2O5, W-K2O, W-MgO, W-MnO and W-B2O3) in Liquid Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research
Report of Fertilizer, Vol. 8, p. 1 - 9 (2015)
2)
Norio FUNAKI: Simultaneous Determination of Water-soluble Principal Ingredients in
Fertilizer using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES),
Research Report of Fertilizer, Vol. 12, p. 28 – 51 (2019)
3)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)(5)

Flow sheet: The flow sheet for water-soluble magnesia in fluid fertilizers is shown below:282

Testing Methods for Fertilizers(2021)

4.7 Manganese
4.7.1 Acid-soluble manganese
4.7.1.a Flame atomic absorption spectrometry(1) Summary
This test method is applicable to fertilizers containing manganese carbonate fertilizers. This testing
method is classified as Type D and its symbol is 4.7.1.a-2017 or S-Mn.a-1.
Add hydrochloric acid (1+23) to an analytical sample, boil to extract and add an interference
suppressor solution, and then spray into an acetylene−air flame, and measure the atomic absorption
with manganese at a wavelength of 279.5 nm to obtain the hydrochloric acid (1+23) soluble
manganese (acid-soluble manganese (S-MnO)) in an analytical sample. In addition, the performanceof this testing method is shown in Comment 4.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Manganese standard solution (MnO 1 mg/mL) (1): Weigh 0.775 g of manganese powder(purity no less than 99 % (mass fraction)) into a weighing dish. Transfer to a 1000-mL
volumetric flask with a small amount of water, add about 10 mL of hydrochloric acid to dissolve,
and add water up to the marked line.
d) Manganese standard solution (MnO 0.1 mg/mL) (1): Put 10 mL of manganese standard
solution (MnO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
e) Manganese standard solution (MnO 1 µg/mL-10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of manganese standard solution (MnO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
f) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution used in the procedure e) in a 250-mL volumetric flask (3), and add water up
to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the manganese standard solution in (2), a manganese standard solution forthe calibration curve preparation can be prepared by using a manganese standard
solution (Mn 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate acid-soluble manganese (S-MnO) in the analytical sample bymultiplying the concentration (Mn) of a manganese standard solution for calibration
curve preparation or a measurement value (Mn) obtained in (4.2) by a conversion
factor (1.2912).
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
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Testing Methods for Fertilizers(2021)

1) Light source: A manganese hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2 g of an analytical sample to the order of 1 mg, and put it in a 500-mL tall beaker.
b) Add about 200mL of hydrochloric acid (1+23), cover with a watch glass, and boil on a hot plate
for about 5 minutes (4).
c) After immediate cooling is complete, transfer it to a 250-mL- 500-mL volumetric flask withwater.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (4) Be aware that an analytical sample should not solidify in the bottom of a beaker.
Comment 2 In the procedure in a), a 500-mL volumetric flask can be used instead of a 500-mL tallbeaker. However, the volumetric flask used should be distinguished as an extraction
flask and should not be used for the other purposes. In addition, “cover with a watch
glass” in b) is replaced by “place a funnel”, and “transfer it to a 250-mL - 500 mL
volumetric flask with water” in the procedure in c) is skipped.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 279.5 nmb) Calibration curve preparation
1) Spray the manganese standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 279.5 nm.
2) Prepare a curve for the relationship between the manganese concentration and the indicatedvalue of the manganese standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MnO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the manganese content from the calibration curve, and calculate the acid-soluble
manganese (S-MnO) in the analytical sample.

284

Testing Methods for Fertilizers(2021)

Comment 4 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 5 % (mass fraction) and 0.1 %(mass fraction) were 100.5 % and 101.3 % as acid-soluble manganese (S-MnO)
respectively.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.006 % (mass fraction).
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.176- 177, Yokendo, Tokyo (1988)
2)
Keiji YAGI, Natuki TOYODOME, Tokiya SUZUKI and Hideo SOETA: Verification of
Performance Characteristics of Testing Methods for Manganese Content in Fertilizer by
Atomic Absorption Spectrometry, Research Report of Fertilizer Vol. 6, p. 203 - 212(2013)(5)

Flow sheet for acid-soluble manganese: The flow sheet for acid-soluble manganese infertilizers is shown below:

2 g analytical sample
Weigh to the order of 1 mg into a 500-mL tall beaker.
← About 200 mL of hydrochloric acid (1+23)
Heating
Cover with a watch glass, and boil for about 5 minutes.
Cooling

Immediately

Transfer
Water, 250-mL - 500-mL volumetric flask
Water
(up
to
the marked line)←
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for acid-soluble manganese in fertilizers (Extraction procedure)

Sample solution
Aliquot
100-mL volumetric flask(predetermined amount)← About 10 mL of interference suppressor solution← Water (up to the marked line)
Measurement
Atomic absorption spectrometer (279.5 nm)
Figure 2 Flow sheet for acid-soluble manganese in fertilizers (Mrasurement procedure)

285

Testing Methods for Fertilizers(2021)

4.7.2 Citric acid-soluble manganese
4.7.2.a Flame atomic absorption spectrometry(1) Summary
This test method is applicable to fertilizers containing manganese carbonate fertilizers. This testing
method is classified as Type B and its symbol is 4.7.2.a-2021 or C-Mn.a-3.
Extract by adding a citric acid solution to an analytical sample and add an interference suppressor
solution, and then spray into an acetylene−air flame, and measure the atomic absorption withmanganese at a wavelength of 279.5 nm to obtain citric acid-soluble manganese (citric acid-soluble
manganese(C-MnO)) in an analytical sample. In addition, the performance of this testing method isshown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
c) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
d) Manganese standard solution (MnO 1 mg/mL) (1): Weigh 0.775 g of manganese powder(purity no less than 99 % (mass fraction)) into a weighing dish. Transfer to a 1000-mL
volumetric flask with a small amount of water, add about 10 mL of hydrochloric acid to dissolve,
and add water up to the marked line.
e) Manganese standard solution (MnO 0.1 mg/mL): Put 10 mL of manganese standard solution(MnO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
f) Manganese standard solution (MnO 1 µg/mL - 10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of manganese standard solution (MnO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
g) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution used in the procedure f) in a 250-mL volumetric flask (3), and add water up
to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the manganese standard solution in (2), a manganese standard solution forthe calibration curve preparation can be prepared by using a manganese standard
solution (Mn 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate citric acid-soluble manganese (C-MnO) in the analytical sample bya multiplying the concentration (Mn) of manganese standard solution for calibration
curve preparation or a measurement value (Mn) obtained in (4.2) by a conversion
factor (1.2912).
(3) Instruments: Instruments are as shown below:a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water286

Testing Methods for Fertilizers(2021)

bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A manganese hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (4), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (4) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(5).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (4), and shake to mix by reciprocating
horizontally at amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) at 160 times/min for 1 hour.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Note (5) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 3 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 4 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
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Testing Methods for Fertilizers(2021)

a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 279.5 nmb) Calibration curve preparation
1) Spray the manganese standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 279.5 nm.
2) Prepare a curve for the relationship between the manganese concentration and the indicatedvalue of the manganese standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MnO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the manganese content from the calibration curve, and citric acid-soluble manganese(C-MnO) in the analytical sample.
Comment 5 The analytical line wavelength may be set to 403.1 nm with lower sensitivity. An
example preparation of standard solutions for calibration curve preparation for awavelength of 403.1 nm is 0.3 µg/mL - 19 µg/mL as MnO, and the minimum limit ofquantification was estimated to be about 0.3 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 5 % (mass fraction) and 0.1 %(mass fraction) were 101.9 % and 100.5 % as citric acid-soluble manganese (C-MnO)
respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and their analysis are shown in Table 1.
Additionally, the results of the collaborative study to determine a certified referencematerial fertilizer were analyzed by using a three-level nesting analysis of variance.
Table 2 shows the calculation results of reproducibility, intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.006 % (mass fraction).

288

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.176- 177, Yokendo, Tokyo (1988)
2)
Keiji YAGI, Natuki TOYODOME, Tokiya SUZUKI and Hideo SOETA: Verification of
Performance Characteristics of Testing Methods for Manganese Content in Fertilizer by
Atomic Absorption Spectrometry, Research Report of Fertilizer Vol. 6, p. 203 - 212(2013)
3)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)4)
Toshio HIRABARA, Masahiro ECHI, Ryouto KOBAYASHI: Performance Evaluation of
Determination Method for Manganese in Fertilizer: Harmonized Collaborative Validation,
Research Report of Fertilizer, Vol. 13, p. 102 – 111 (2020)
289

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble manganese: The flow sheet for citric acid-soluble
manganese in fertilizers is shown below:
1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker.

← About 150 mL of citrate-solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble manganese in fertilizers(Extraction procedure (4.1.1))

1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker.

← About 150 mL of citrate solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30 ºC ± 1ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble manganese in fertilizers(Extraction procedure (4.1.2))
Sample solution
Aliquot(predetermined amount)

100-mL volumetric flask← About 10 mL of interference suppressor solution← Water (up to the marked line)
Measurement
Atomic absorption spectrometer (279.5 nm)
Figure 2 Flow sheet for citric acid-soluble manganese in fertilizers(Measurement procedure)290

Testing Methods for Fertilizers(2021)

4.7.2.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 4.7.2.b-2018 or C-Mn.b-1.
Extract by adding a citric acid solution to an analytical sample, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the manganese at a wavelength of 257.610 nm toobtain citric acid-soluble manganese (citric acid-soluble manganese (C-MnO)) in an analyticalsample. In addition, the performance of this testing method is shown in Comment 7.
(2) Reagent: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
d) Manganese standard solution (MnO 1 mg/mL) (1): Weigh 0.775 g of manganese powder(purity no less than 99 % (mass fraction)) into a weighing dish. Transfer to a 1000-mL
volumetric flask with a small amount of water, add about 10 mL of hydrochloric acid to dissolve,
and further add hydrochloric acid (1+23) up to the marked line.
e) Manganese standard solution (MnO 0.1 mg/mL): Put 10 mL of manganese standard solution(MnO 1 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to themarked line.
f) Manganese standard solution (MnO 2 µg/mL - 8 µg/mL) for the calibration curve
preparation (1): Put 2 mL - 8 mL of manganese standard solution (MnO 0.1 mg/mL) in 100mL volumetric flasks step-by-step and add hydrochloric acid (1+23) up to the marked line.
g) Manganese standard solution (MnO 0.1 µg/mL - 2 µg/mL) for the calibration curve
preparation (1): Put 1 mL - 20 mL of manganese standard solution (MnO 10 µg/mL) in 100-mL
volumetric flasks step-by-step and add hydrochloric acid (1+23) up to the marked line.
h) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) and g).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the manganese standard solution in (2), a manganese standard solution forthe calibration curve preparation can be prepared by using a manganese standard
solution (Mn 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case,calculate citric acid-soluble manganese (C-MnO) in the analytical sample by amultiplying the concentration (Mn) of manganese standard solution for calibration
curve preparation or a measurement value (Mn) obtained in (4.2) by a conversion
factor (1.2912).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116
291

Testing Methods for Fertilizers(2021)

1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
ba) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
bb) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note(2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.

Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(3).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix by reciprocating
horizontally at amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) at 160 times/min for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note(3) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.

Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 257.610 nm292

Testing Methods for Fertilizers(2021)b) Calibration curve preparation
1) Spray the manganese standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 257.610 nm.
2) Prepare a curve for the relationship between the manganese concentration and the indicatedvalue of the manganese standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 0.8 mg as
MnO) in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the manganese content from the calibration curve, and calculate the citric acid-soluble
manganese (C-MnO) in the analytical sample.
Comment 6 The simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 7 The comparison of the measurement value (yi：0.089 % (mass fraction) - 1.88 % (massfraction )) of ICP Optical Emission Spectrometry and the measurement value (xi) of
Flame atomic absorption spectrometry analysis was conducted to evaluate truenessusing compound fertilizers (7 samples), mixed phosphorus fertilizers (2 samples),solid compound fertilizers (2 samples), blended fertilizers (4 samples) and organic
blended fertilizer (1 sample). As a result, a regression equation was y=0.0015+0.9988x,
and its correlation coefficient (r) was 0.999. In addition, additive recovery testing was
conducted using a preparation sample. As a result, the mean recovery rate at theadditive level of 0.595 % (mass fraction) - 28.94 % (mass fraction) was 98.5 % 105.5 %.
The results of the repeatability tests on different days using compound fertilizers andblended fertilizers to evaluate precision were analyzed by one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 % (mass fraction).

293

Testing Methods for Fertilizers(2021)

References
1)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)2)
Shingo MATSUO:
Simultaneous Determination of Citrate-Soluble Principal
Ingredients (C-P2O5, C-K2O, C-MgO, C-MnO and C-B2O3) in Fertilizer using Inductively
Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research Report of
Fertilizer, Vol. 11, p. 14 – 28 (2018)(5)

Flow sheet for citric acid-soluble manganese: The flow sheet for citric acid-soluble
manganese in fertilizers is shown below:
1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker.

← About 150 mL of citrate-solution [about 30 ºC]
Constant-temperature vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble manganese in fertilizers (Extraction procedure (4.1.1))

1 g analytical sample

Weigh to the order of 1 mg into a 250-mL tall beaker.

← About 150 mL of citrate solution [about 30 ºC]
Shaking to mix

Horizontal reciprocating water bath shaker (160 reciprocations/min,
amplitude of 25 mm - 40 mm), at 30 ºC ± 1 ºC, for 1 hour

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble manganese in fertilizers (Extraction procedure (4.1.2))

Sample solution
Aliquot
100-mL volumetric flask(predetermined amount)← About 25 mL of hydrochloric acid (1+5)← Water (up to the marked line)
Measurement
ICP Optical Emission Spectrometer (257.610 nm)
Figure 2 Flow sheet for citric acid-soluble manganese in fertilizers (Measurement procedure)294

Testing Methods for Fertilizers(2021)

4.7.3 Water-soluble manganese
4.7.3.a Flame atomic absorption spectrometry(1) Summary
This test method is applicable to fertilizers containing manganese sulfate fertilizers. This testing
method is classified as Type B and its symbol is 4.7.3.a-2021 or W-Mn.a-2.
Extract by adding water to an analytical sample and add an interference suppressor solution, and thenspray in an acetylene−air flame, and measure the atomic absorption with manganese at a wavelengthof 279.5 nm to obtain water-soluble manganese (W-MnO) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 7.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Interference suppressor solution (1): Weigh 60.9 g - 152.1 g of strontium chloride hexahydrate(2)
specified in JIS K 8132 into a 2000-mL beaker, add a small amount of water, add gradually
420 mL of hydrochloric acid to dissolve, and further add water to make 1000 mL.
c) Manganese standard solution (MnO 1 mg/mL) (1): Weigh 0.775 g of manganese powder(purity no less than 99 % (mass fraction)) into a weighing dish. Transfer to a 1000-mL
volumetric flask with a small amount of water, add about 10 mL of hydrochloric acid to dissolve,
and add water up to the marked line.
d) Manganese standard solution (MnO 0.1 mg/mL) (1): Put 10 mL of manganese standard
solution (MnO 1 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
e) Manganese standard solution (MnO 1 µg/mL - 10 µg/mL) for the calibration curve
preparation (1): Put 2.5 mL-25 mL of manganese standard solution (MnO 0.1 mg/mL) in 250mL volumetric flasks step-by-step, add about 25 mL of interference suppressor solution (3), andadd water up to the marked line.
f) Blank test solution for the calibration curve preparation (1): Put about 25 mL of interference
suppressor solution used in the procedure e) in a 250-mL volumetric flask (3), and add water up
to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) 29 g of lanthanum oxide (atomic absorption analysis grade or equivalents) can also beused.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the manganese standard solution in (2), a manganese standard solution forthe calibration curve preparation can be prepared by using a manganese standard
solution (Mn 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology. In
this case, calculate water-soluble manganese (W-MnO) in the analytical sample by amultiplying the concentration (Mn) of manganese standard solution for calibration
curve preparation or a measurement value (Mn) obtained in (4.2) by a conversion
factor (1.2912).
(3) Instruments: Instruments are as shown below.
a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
295

Testing Methods for Fertilizers(2021)

volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A manganese hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample(4.1.1.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 2 In the procedure of (4.1.1.1) a), it is also allowed to weigh 2.5 g of an analytical sample
to the order of 1 mg, and put it in a 250-mL volumetric flask. In that case, add about
200 mL of water in the procedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.1.2) Vertical reciprocating shakera) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 200 mL of water, and shake to mix by reciprocating vertically at 300 times/min(amplitude of 40 mm) for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.1.2) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement296

Testing Methods for Fertilizers(2021)

conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 279.5 nmb) Calibration curve preparation
1) Spray the manganese standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 279.5 nm.
2) Prepare a curve for the relationship between the manganese concentration and the indicatedvalue of the manganese standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as MnO)
in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the manganese content from the calibration curve, and water-soluble manganese (WMnO) in the analytical sample.
Comment 6 The analytical line wavelength may be set to 403.1 nm with lower sensitivity. An
example preparation of standard solutions for calibration curve preparation for awavelength of 403.1 nm is 0.3 µg/mL - 19 µg/mL as MnO, and the minimum limit ofquantification was estimated to be about 0.3 µg/mL in a measurement solution.
However, it is necessary to understand in advance the concentration range ofcalibration curve suitable for the instrument and prepare standard solutions forcalibration curve preparation.
Comment 7 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 6 % (mass fraction) and 0.1 %(mass fraction) were 101.2 % and 101.1 % as water-soluble manganese (W-MnO)
respectively.
The comparison of the measurement value (yi: 0.0330 % (mass fraction) - 6.18 % (massfraction)) of extraction by a vertical reciprocating shaker and the measurement value(xi) of extraction by a vertical rotating mixer was conducted to evaluate trueness of theextraction of solid fertilizers using fertilizers (12 samples). As a result, a regression
equation was y = −0.009 + 1.011x, and its correlation coefficient (r) was 1.000. The
comparison of the measurement value (yi: 0.0590 % (mass fraction) - 1.27 % (massfraction)) of simple extraction and the measurement value (xi) of extraction by avertical rotating mixer was conducted to evaluate trueness of the extraction of fluid
fertilizers using fluid fertilizers (12 samples). As a result, a regression equation was y= −0.001 + 1.006x, and its correlation coefficient (r) was 1.000. The results of therepeatability tests on different days using compound fertilizers and mixed
microelement fertilizers to evaluate precision were analyzed by one-way analysis ofvariance. Table 1-1 shows the calculation results of intermediate precision andrepeatability. The results of the repeatability tests on different days using a fluid
compound fertilizer and a liquid microelement compound fertilizer to evaluate theextract precision of fluid fertilizers were analyzed by the one-way analysis of variance.
Table 1-2 shows the calculation results of intermediate precision and repeatability.
Additionally, results from a collaborative study for testing method validation and its
analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.004 % (mass fraction).
297

Testing Methods for Fertilizers(2021)

Table 1-1 Analysis results of the repeatability tests on different daysof water-soluble manganese(Solid fertilizers)
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability T
(%)
(%)
(%)
(%)
(%)
Mixed microelement fertilizer
7
3.57
0.03
0.7
0.05
1.5
Compound fertilizer
70.226 0.002
1.0
0.004
1.7
1) The number of test days conducting a duplicate test
6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

Table 2 Analysis results of the collaborative study
for the test method validation of water-soluble manganese4)6)5)
Number of Mean2)
sr
sR
RSD r
Sample name
1)
3)
3)
3)
laboratories
(%)
(%)
(%)
(%)

7)

RSD R
(%)

Manganese sulfate fertilizer

12

11.07

0.17

1.5

0.44

3.9

Mixed microelement fertilizer

12

5.11

0.05

1.0

0.12

2.4

Designated blended fertilizer
Compound fertilizer

12
11

0.47
0.43

0.00
0.00

1.0
0.8

0.01
0.01

2.2
2.1

Magnesia sulfate fertilzer
11
0.11
0.00
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

1.4

0.10

3.4

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.176- 177, Yokendo, Tokyo (1988)
298

Testing Methods for Fertilizers(2021)

2)

3)
4)
5)

(5)

Keiji YAGI, Natuki TOYODOME, Tokiya SUZUKI and Hideo SOETA: Verification of
Performance Characteristics of Testing Methods for Manganese Content in Fertilizer by
Atomic Absorption Spectrometry, Research Report of Fertilizer Vol. 6, p. 203 - 212(2013)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components in
Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20 (2016)
Shinji KAWAGUCHI: Extraction Method for the Water-soluble Principal Ingredientsin the Solid Fertilizer using a General-purpose Equipment , Research Report of Fertilizer,
Vol. 10, p. 1 - 8 (2017)
Toshio HIRABARA, Masahiro ECHI, Ryouto KOBAYASHI: Performance Evaluation of
Determination Method for Manganese in Fertilizer: Harmonized Collaborative Validation,
Research Report of Fertilizer, Vol. 13, p. 102 – 111 (2020)

Flow sheet for water-soluble manganese: The flow sheet for water-soluble manganese infertilizers is shown below:

5 g analytical sample
Weigh to the order of 1 mg into a 500-mL volumetric flask.
(Powdery)← About 400 mL of water
Vertical rotating mixer (30 - 40
Shaking to mix
revolutions/min), for 30 minutes
Filtration

Type 3 filter paper

Sample solution
Figure 1-1 Flow sheet for water-soluble manganese in fertilizers(Extraction procedure (4.1.1.1))
2.5 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask.
(Powdery)← About 200 mL of water
Vertical reciprocating shaker(300 times/min,Shaking to mix
with amplitude of 40 mm), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for water-soluble manganese in fertilizers(Extraction procedure (4.1.1.2))

299

Testing Methods for Fertilizers(2021)

1 g analytical sample(Fluid)Weigh to the order of 1 mg into a 100-mL volumetric flask.

← About 50 mL of water
Shaking to mix← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-3 Flow sheet for water-soluble manganese in fertilizers(Extraction procedure (4.1.2))

Sample solution
Aliquot
100-mL volumetric flask(predetermined amount)← About 10 mL of interference suppressor solution← Water (up to the marked line)
Measurement
Atomic absorption spectrometer (279.5 nm)
Figure 2 Flow sheet for water-soluble manganese in fertilizers(Measurement procedure)300

Testing Methods for Fertilizers(2021)

4.7.3.b ICP Optical Emission Spectrometry(1) Summary
The test method is applicable to fertilizers. This testing method is classified as Type D for solid
fertilizers and Type B for fluid fertilizers. Its symbol is 4.7.3.b-2019 or W-Mn.b-2.
Add water to an analytical sample to extract, introduce it to an ICP Optical Emission Spectrometer(ICP-OES) and measure the manganese at a wavelength of 257.610 nm, etc. to obtain water-soluble
manganese (W-MnO) in an analytical sample. In addition, the performance of this testing method isshown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Manganese standard solution (MnO 1 mg/mL) (1): Weigh 0.775 g of manganese powder(purity no less than 99 % (mass fraction)) into a weighing dish. Transfer to a 1000-mL
volumetric flask with a small amount of water, add about 10 mL of hydrochloric acid to dissolve,
and further add hydrochloric acid (1+23) up to the marked line.
d) Manganese standard solution (MnO 0.1 mg/mL) (1): Put 10 mL of manganese standard
solution (MnO 1 mg/mL) to a 100-mL volumetric flask and add hydrochloric acid (1+23) up in
the marked line.
e) Manganese standard solution (MnO 2 µg/mL - 8 µg/mL) for the calibration curve
preparation (1): Put 2 mL - 8 mL of manganese standard solution (MnO 0.1 mg/mL) in 100mL volumetric flasks step-by-step and add hydrochloric acid (1+23) up to the marked line.
f) Manganese standard solution (MnO 0.1 µg/mL - 2 µg/mL) for the calibration curve
preparation (1): Put 1 mL - 20 mL of manganese standard solution (MnO 10 µg/mL) in 100mL volumetric flasks step-by-step and add hydrochloric acid (1+23) up to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the manganese standard solution in (2), a manganese standard solution forthe calibration curve preparation can be prepared by using a manganese standard
solution (Mn 1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case,calculate water-soluble manganese (W-MnO) in the analytical sample by a multiplying
the concentration (Mn) of manganese standard solution for calibration curve
preparation or a measurement value (Mn) obtained in (4.2) by a conversion factor(1.2912).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A vertical rotating mixer or vertical reciprocating shaker as described below.
aa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
301

Testing Methods for Fertilizers(2021)

volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
b) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test sample(4.1.1.1) Vertical rotating mixera) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 3 In the procedure of (4.1.1.1) a), it is also allowed to weigh 2.5 g of an analyticalsample to the order of 1 mg, and put it in a 250-mL volumetric flask. In that case,
add about 200 mL of water in the procedure in b).
Comment 4 A sample solution obtained in the procedure in (4.1.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.1.2) Vertical reciprocating shakera) Weigh 2.5 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetricflask.
b) Add about 200 mL of water, and shake to mix by reciprocating vertically at 300 times/min(amplitude of 40 mm) for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 5 A sample solution obtained in the procedure in (4.1.1.2) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 mg of an analytical sample (2) to the order of 1 mg, and put it in in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c)
Filter with Type 3 filter paper to make a sample solution.
Note (2) The sampling amount of the analytical sample is 10 g when there is less manganesecontent in the fertilizers such as a home garden-use fertilizer.
Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:302

Testing Methods for Fertilizers(2021)

Analytical line wavelength: 257.610 nm or 260.569 nm (3)b) Calibration curve preparation
1) Spray the manganese standard solution for the calibration curve preparation and blank test
solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 257.610 nm.
2) Prepare a curve for the relationship between the manganese concentration and the indicatedvalue of the manganese standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 0.8 mg as
MnO) in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the manganese content from the calibration curve, and water-soluble manganese (WMnO) in the analytical sample.
Note (3) 260.569 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 257.610 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 7 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement valuesof the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 The comparison of the measurement value (yi：0.0145 % (mass fraction) - 0.260 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of Flame atomic absorption spectrometry was conducted to evaluate truenessusing powdery test fertilizers (14 samples). As a result, a regression equation was
y=−0.0035+0.972x, and its correlation coefficient (r) was 0.997. The comparison of
the measurement value (yi：0.027 % (mass fraction) - 1.49 % (mass fraction )) andthe measurement value (xi) was conducted using fluid fertilizers (12 samples). As aresult, a regression equation was y＝−0.0013+1.025x, and its correlation coefficient(r) was 0.999. In addition, additive recovery testing was conducted using preparation
fertilizers (6 samples). As a result, the mean recovery rate at the additive level of
0.0907 % (mass fraction) - 41.97 % (mass fraction) was 96.9 % - 101.0 %. Additive
recovery testing was conducted using a fluid compound fertilizer (1 brand) and ahome garden-use compound fertilizer (1 brand) and a liquid microelement compound
fertilizer (1 bland). As a result, the mean recovery rates at the additive level of 0.15 %(mass fraction) - 0.2 % and 0.005 % (mass fraction) were 96.3 % - 96.5 % and107.0 % respectively.
The results of the repeatability tests on different days using a home garden-use
compound fertilize (solid), a blended fertilizer, a fluid compound fertilizer and ahome garden-use compound fertilize (fluid) to evaluate precision were analyzed by
the one-way analysis of variance. Table 1-1 and 1-2 show the calculation results ofintermediate precision and repeatability. Additionally, results from a collaborative
study implemented for testing method validation and its analysis are shown in Table
2
303

Testing Methods for Fertilizers(2021)

Note that the minimum limit of quantification of this testing method was estimatedto be about 0.005 % (mass fraction) for solid fertilizers and about 0.0002 % (massfraction) for fluid fertilizers.

304Testing Methods for Fertilizers(2021)
Table 2 Analysis results of the collaborative study
for the test method validation of water-soluble manganese

Analytical line
wavelength (nm)257.610260.569

1)
2)
3)
4)
5)
6)
7)

Number of

Mean

2)

sr

3)

4)

laboratories

(%)

(%)

RSD r
(%)

Preparation sample (Liquid) 1

10

0.518

0.004

Preparation sample (Liquid) 2

10

1.06

Preparation sample (Liquid) 3

10Preparation sample (Liquid) 4

5)

sR

6)

7)

(%)

RSD R
(%)

0.8

0.013

2.5

0.01

0.8

0.02

2.3

2.11

0.02

0.9

0.08

3.8

10

0.05180.00061.2

0.0027

5.2

Preparation sample (Liquid) 5110.01080.00011.0

0.0002

2.3

Preparation sample (Liquid) 1

11

0.518

0.004

0.8

0.015

2.9

Preparation sample (Liquid) 2

10

1.06

0.01

0.9

0.02

2.2

Preparation sample (Liquid) 3

11

2.13

0.03

1.2

0.08

3.8

Preparation sample (Liquid) 4100.05120.00061.2

0.00142.6

0.01080.00010.7

0.0003

2.5

Sample name1)

Preparation sample (Liquid) 5
11
Number of laboratories used in analysis
Mean (n = number of laboratories × number of samples (2))
Mass fraction
Repeatability standard deviation
Repeatability relative standard deviation
Reproducibility standard deviation
Reproducibility relative standard deviation

3)

3)

References
1)
Keisuke AOYAMA:
Simultaneous Determination of Water-Soluble Principal
Ingredients (W-P2O5, W-K2O, W-MgO, W-MnO and W-B2O3) in Liquid Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research
Report of Fertilizer, Vol. 8, p. 1 - 9 (2015)
2)
Norio FUNAKI: Simultaneous Determination of Water-soluble Principal Ingredients in
Fertilizer using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES),
Research Report of Fertilizer, Vol. 12, p. 28 – 51 (2019)
3)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)305

Testing Methods for Fertilizers(2021)(5)

Flow sheet: The flow sheet for water-soluble manganese in fertilizers is shown below:

5 g analytical sample
Weigh to the order of 1 mg to a 500-mL volumetric flask(Powdery)← Water, about 400 mL
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble manganese in fertilizers(Extraction procedure (4.1.1.1))
2.5 g analytical sample
Weigh to the order of 1 mg to a 250-mL volumetric flask(Powdery)← Water, about 200 mL
Vertical reciprocating shaker (300 times/ min,Shaking to mix
amplitude of 40 mm), 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for water-soluble manganese in fertilizers(Extraction procedure (4.1.1.2))

1 g analytical sample
Weigh to the order of 1 mg to a 100-mL volumetric flask(Fluid)← Water, about 50 mL
Shaking to mix← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-3 Flow sheet for water-soluble manganese in fertilizers(Extraction procedure (4.1.2))

306

Testing Methods for Fertilizers(2021)

Sample solution
Aliquot
100-mL volmetric flask(predetermined volume)← 25 mL of hydrochloric acid (1+5)← Water (up to the marked line)
Measurement

ICP Optical Emission Spectrometer (257.610 nm)

Figure 2 Flow sheet for water-soluble manganese in fertilizers(Measurement procedure)307

Testing Methods for Fertilizers(2021)

4.8 Boron
4.8.1 Citric acid-soluble boron
4.8.1.a Azomethine-H method(1) Summary
The test method is applicable to fertilizers. This testing method is classified as Type B and its symbol
is 4.8.1.a-2019 or C-B.a-3. Extract by adding a citric acid solution to an analytical sample, mask coexisting copper, iron and other salts with ethylenediamine tetraacetate and measure the absorbancewith azomethine-H borate formed by the reaction with azomethine-H and correct the absorbanceoriginated in coloring of a sample solution to obtain citric acid-soluble boron (C-B2O3) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 7.
(2) Reagent: Reagents are as shown below.
a) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
b) Ethylenediamine tetraacetate solution (1): Dissolve 37.2 g of ethylenediaminetetraacetic aciddihydrogen disodium dihydrate specified in JIS K 8107 in water to make 1000 mL.
c) Ammonium acetate solution (1): Dissolve 250 g of ammonium acetate specified in JIS K 8359
in water to make 500 mL and adjust pH with sulfuric acid (1+4) to pH 5.2 ± 0.1.
d) Azomethine-H solution: Add water to 0.6 g of azomethine-H and 2 g of L (+) – ascorbic acidspecified in JIS K 9502, and heat up to 35 ºC - 40 ºC to dissolve and add water after cooling to
make 100 mL.
e) Boron standard solution (B2O3 2.5 mg/mL) (1): After leaving boric acid specified in JIS K
8863 at rest in a desiccator for about 24 hours to dry, weigh 4.441 g to a weighing dish. Dissolve
in a small amount of water, transfer to a 1000-mL volumetric flask, and add water up to themarked line.
f) Boron standard solution (B2O3 0.1 mg/mL): Dilute the predetermined volume of boron
standard solution (B2O3 2.5 mg/mL) with water exactly by a factor of 25.
g) Boron standard solution (B2O3 0.01 mg/mL): Dilute the predetermined volume of boron
standard solution (B2O3 0.1 mg/mL) with water exactly by a factor of 10.
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the boron standard solution in (2), a boron standard solution for thecalibration curve preparation can be prepared by using a boron standard solution (B 1
mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate citricacid-soluble boron (C-B2O3) in the analytical sample by multiplying the concentration(B) of a boron standard solution for calibration curve preparation or a measurement
value (B) obtained in (4.3) by a conversion factor (3.2199).
(3) Instruments: Instruments are as shown below:a) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
aa) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
ab) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
b) Spectrophotometer: A spectrophotometer specified in JIS K 0115
308

Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (2) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 2 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(3).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (2), and shake to mix by reciprocating
horizontally at amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) at 160 times/min for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (3) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 3 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 4 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg – 0.8 mg as
P2O5 and no more than the equivalents of 15 mL of citric acid solution) in a 100-mL volumetricflask.
b) Add the solution to make citric acid solution equivalent to 15 mL.
c) Add 25 mL of ethylenediamine tetraacetate solution, and then add 10 mL of ammonium acetate
solution.
d) Add 10 mL of azomethine-H solution.
e) After adding water up to the marked line, leave at rest for about 2 hours (4) to make a sample
solution for measurement.
f) Conduct the same procedures as a) – c) and e) using another 100-mL volumetric flask to makea sample solution for correction.
Note (4) When the solution is muddled, conduct centrifugation with about 1700 × g centrifugal
force (5) for about five minutes after the procedure in e) or filtrate with Type 3 filter
paper.
(5) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
309

Testing Methods for Fertilizers(2021)

Comment 5 If formaldehyde processed urea, a large quantity of aluminum, copper, iron zinc,organic matters, etc. coexists to affect quantification, put a predetermined amount of
the sample solution (the equivalents of 0.1 mg - 0.8 mg as B2O3, no more than 10 mLof the solution) in a 100-mL separatory funnel, add 10 mL of hydrochloric acid (1+3),
add water to about 20 mL and add 20 mL of 2-ethyl-1,3-hexanediol – 4-methyl-2pentanone (1+9) to shake to mix with a shaking apparatus for about 1 minute. Afterallowing to stand still, remove the lower layer (aqueous phase) and add 20 mL of
sodium hydroxide (20 g/L) to shake to mix with a shaking apparatus for about 1
minute. After allowing to stand still, transfer the lower layer (aqueous phase) to a
100-mL volumetric flask, add a few drops of phenolphthalein solution (1 g/100mL)
to neutralize with hydrochloric acid (1+3) until the color of the solution becomes
achromatic, and conduct the procedure in (4.2) b).
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of spectrophotometer: Set up the measurement conditions ofspectrophotometer considering the following.
Detection wavelength: 415 nmb) Calibration curve preparation
1) Put 1 mL - 8 mL of boron standard solution (B2O3 0.1 mg/mL) in 100-mL volumetric flasks
step-by-step.
2) Put 1 mL - 10 mL of boron standard solution (B2O3 0.01 mg/mL) in 100-mL volumetric flasks
step-by-step.
3) Add 15 mL of citric acid solution and conduct the same procedure as (4.2) c) - e) to make theB2O3 0.01 mg/100 mL - 0.8 mg/100 mL boron standard solution for the calibration curve
preparation.
4) Conduct the same procedures as 3) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
5) Further, put 15 mL of citric acid solution in another 100-mL volumetric flask and conduct thesame procedures as 4.2) c) and e) to make a test solution for control.
6) Measure absorbance at a wavelength of 415 nm of the blank test solution for the calibration
curve preparation and the boron standard solutions for the calibration curve preparation using
the test solution for control as the control.
7) Prepare a curve for the relationship between the boron concentration and the absorbance of theboron standard solution for the calibration curve preparation and the blank test solution for thecalibration curve preparation.
c) Sample measurement
1) Regarding the sample solution for measurement in (4.2) e) and the sample solution forcorrection in (4.2) f), measure absorbance by the same procedure as b) 6).
2) Obtain the boron (B2O3) content from the calibration curve using the absorbance obtained bysubtracting the absorbance of a sample solution for correction from the absorbance of a sample
solution for measurement and calculate citric acid-soluble boron (C-B2O3) in the analyticalsample.
Comment 6 If it is known in advance, according to the results of quality control analysis, thatcoloring of a sample solution does not affect the analysis of citric acid-soluble boron
in an analytical sample, there is no need to prepare the sample solution for correction((4.2) f)).
310

Testing Methods for Fertilizers(2021)

In that case, read 4.3) c) 2) as “Obtain the boron (B2O3) content from the calibration
curve using the absorbance of a sample solution for measurement and calculate citricacid-soluble boron (C-B2O3) in the analytical sample”.
Comment 7 Recovery testing was conducted using preparation sample to evaluate trueness. As aresult, the mean recovery rates at the content level of 1.02 % (mass fraction) - 5.11 %(mass fraction) and 0.20 % (mass fraction) as citric acid-soluble boron (C-B2O3) were
99 %, 97 % - 99 % and 106 %.
The results of the repeatability tests on different days using a borate fertilizer and acompound fertilizer (1 brand for each) to evaluate precision were analyzed by oneway analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study for testing
method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 % (mass fraction).

311

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.184- 187, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)3)
Akira SHIMIZU: Verification of Performance Characteristics of Testing Methods for
Boron Content by Azomethine H Absorption Photometry, Research Report of Fertilizer
Vol. 6, p. 174 -182 (2013)4)
Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)
5)
Masayuki YAMANISHI: Improved Determination Method of Boron (B2O3) in Fertilizer,
Research Report of Fertilizer Vol. 22, p. 10 - 27 (2019)6)
Keisuke AOYAMA: Performance Evaluation of Determination Method for Boron in
Fertilizer: Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13,
p. 112 – 122 (2020)

312

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble boron: The flow sheet for citric acid-soluble boron in
fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Shaking to mix

Constant-temperature vertical rotating mixer (30 - 40
revolutions/min), at 30 ºC ± 1 ºC, for 1 hour

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble boron in fertilizers(Extraction procedure (4.1.1))

1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160
Shaking to mix
reciprocations/min, amplitude of 25 mm - 40 mm), at 30 º
C ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble boron in fertilizers(Extraction procedure (4.1.2))

313

Testing Methods for Fertilizers(2021)

Boronstandard solution
Aliquot
100-mL volumetric flask(predetermined amount)← 15 mLof citric acid solution← 25 mL of ethylenediamine tetraacetate← 10 mL of ammonium acetate← 10 mL of azomethine-H solution← Water (up to the marked line)
Leaving at rest

For about 2 hours

Measurement

Spectrophotometer (415 nm)

Figure 2-2 Flow sheet for citric acid-soluble boron in fertilizers(Preparation and measurement procedures of boron standard solution
for the calibration curve preparation)

314

Testing Methods for Fertilizers(2021)

100-mLvolumetric flask← 15 mL of citric acid solution← 25 mL of ethylenediamine tetraacetate(Sample solution
for control)← 10 mL of ammonium acetate(Blank test solution for the calibration curve preparation)← 10 mL of azomethine-H solution← Water (up to the marked line)

Leaving at rest

For about 2 hours

Measurement

Spectrophotometer (415 nm)

Figure 2-3 Flow sheet for citric acid-soluble boron in fertilizers(Preparation and measurement procedures of test solution for control
and blank test solution for the calibration curve preparation)

Reference:

A calculation example of citric acid-soluble boron content in an analytical sample isshown below.

a) Reference table 1-1 shows the absorbance (example) of a standard solution for the calibration
curve preparation and a blank test solution for the calibration curve preparation using a test
solution for control as the control.
In addition, calibration curves are shown in Reference diagram 1 and regression coefficientsof the regression equations are in Reference table 1-2.
b) Reference table 2 shows the sampling amount of an analytical sample, the constant volume ofextract, the transferred amount of extract and the constant volume of the sample solution formeasurement as well as the absorbance (example) of the sample solution for measurement andthe sample solution for correction using a test solution for control as the control.
c) Obtain the boron (B2O3) content in the sample solution for measurement by formula (1)(Refer to Reference diagram 1) and calculate citric acid-soluble boron (C-B2O3) in theanalytical sample by formula (2)”.

315

Testing Methods for Fertilizers(2021)

Boron (B2O3) content in a sample solution for measurement (C1)＝((As－Ab)－a)/b＝(Ac－a)/b
・・・・・
Citric acid-soluble boron (C-B2O3) in an analytical sample (C2)
＝C1×(V1/V2)×(1/W)×(100/1000)
・・・・・ (2)(1)

C1： Boron (B2O3) content in 100 mL of a sample solution for measurement (mg)
As： Absorbance of a sample solution for measurement in (4.2) e) using a test solution
for control ((4.3 b) 5)) as the control
Ab： Absorbance of a sample solution for correction in (4.2) f) using a test solution forcontrol ((4. 3) b) 5)) as the control
Ac： Corrected absorbancea： Intercept of a regression equation of a calibration curveb： Inclination of a regression equation of a calibration curve
C2： Citric acid-soluble boron (C-B2O3) in an analytical sample (% (mass fraction))
V1： Constant volume (mL) of the sample solution in (4.1.1) c) or (4.1.2) c)
V2： Aliquot volume (mL) of the sample solution in (4.2) a)
W： Mass (g) of the analytical sample
Reference Table 1-1 Calibration curve (example ) of citric acid-soluble boron
Calibration curve for low concentration Calibration curve for moderate or high concentration
Sample name
Boron （B2 O3 ）concentration
Absorbance
Boron （B2 O3 ）concentration Absorbance
(ABS)
(ABS)
（mg/100 mL）（mg/100 mL）
Blank test solution
0
0.025
0.0
0.025
for calibration curveStandard solution
0.01
0.034
0.1
0.115
for calibration curveStandard solution
0.02
0.043
0.2
0.205
for calibration curveStandard solution
0.04
0.061
0.4
0.385
for calibration curveStandard solution
0.06
0.079
0.6
0.565
for calibration curveStandard solution
0.08
0.097
0.8
0.745
for calibration curveStandard solution
0.1
0.115
for calibration curve316

Testing Methods for Fertilizers(2021)
0.800

0.120

y = 0.025+0.900x

y = 0.025+0.900x
0.600

Ac(1)=As(1)-Ab(1)0.080

Absorbance （ABS）

Absorbance （ABS）

0.100

0.060
0.040
C1(1)

0.020

Ac(2)=As(2)-Ab(2)
0.400

0.200

C1(2)

0.000

0.000
0.00

0.05

0.00

0.10

0.40

0.60

0.80

Boron concentration （B2O3 mg/100 mL ）Boron concentration (B2O3mg/100mL)

1) Low concentration range(B2O3 0 mg/100 mL - 0.10 mg/100 mL)
Reference diagram 1

0.20

(B2O3

2) High concentration range
0 mg/100 mL - 0.80 mg/100 mL)

Calibration curve (example) of citric acid-soluble boron (C-B2O3)
1)

Reference table 1-2 Regression equationof a calibration curve (example) of citric acid-soluble boron
Regression coefficient （y =a +bx ）ab
Low concentration range
0.025
0.900
High concentration range
0.025
0.900
1） Regression equation calculated by the least squares method

Reference table 2

Measurement (example) of sample solution and calculation of citric acid-soluble boron
Unit
Blended fertilizer (1) Compound fertilizer (2) Borate fertilizer
Sampling amount of analytical sample (W)g111Predetermined volume of extract (V 1 )
mL
250
250
250
1)
mL
25
10
0.25
Transferred amount of extract (V 2 )Predetermined volume of sampling solution,
mL
100
100
100
1)
etc. for measurement（V 3 ）Absorbance of sampling solution
ABS
0.055
0.170
0.400
for measurement (A s )Absorbance of sampling solution
ABS
0.005
0.020
0.000
for correction（A b）
Corrected absorbance （A c=A s -A b）
ABS
0.050
0.150
0.400
Boron concentration in sampling solution
for measurement (C 1 )2)

mg/100 mL

0.028

Citrate-soluble boron content

0.139

0.417

%
0.03
0.35
41.7
3)
in analytical sample (C 2 )1） 2 steps dilutionis is applied to borate fertilizers. Ex： （5 mL→50 mL） （2.5 mL→100 mL）
2） Calculate C 1 by substituting the regression coefficient (interception (a ) and gradient (b )) in Table 1-2 for formula (1).
3） Calculate C 2 by substituting C 1 , W, V 1 and V 2 for formula 2.

317

Testing Methods for Fertilizers(2021)

4.8.1.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 4.8.1.b-2018 or C-B.b-1.
Extract by adding a citric acid solution to an analytical sample, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the boron at a wavelength of 249.773 nm to obtaincitric acid-soluble boron (citric acid-soluble boron acid (C-B2O3)) in an analytical sample. In addition,
the performance of this testing method is shown in Comment 8.
(2) Reagent: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Citric acid solution (1): Dissolve 20 g of citric acid monohydrate specified in JIS K 8283 inwater to make 1000 mL.
d) Boron standard solution (B2O3 2.5 mg/mL) (1): After leaving boric acid specified in JIS K
8863 at rest in a desiccator for about 24 hours to dry, weigh 4.441 g to a weighing dish. Dissolve
in a small amount of water, transfer to a 1000-mL volumetric flask, and add water up to themarked line.
e) Boron standard solution (B2O3 0.1 mg/mL) (1): Put 4 mL of boron standard solution (B2O3
2.5 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to the marked
line (2).
f) Boron standard solution (B2O3 2 µg/mL - 16 µg/mL) for the calibration curve preparation(1): Put 2 mL - 16 mL of boron standard solution (B2O3 0.1 mg/mL) in a 100-mL volumetricflask step by step and add hydrochloric acid (1+23) up to the marked line (2).
g) Boron standard solution (B2O3 0.2 µg/mL - 2 µg/mL) for the calibration curve preparation(1): Put 2 mL - 20 mL of boron standard solution (B2O3 10 µg/mL) in a 100-mL volumetricflask step by step and add hydrochloric acid (1+23) up to the marked line (2).
h) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) - g).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) When preserving, use a container, which can be sealed tightly, made of material such as
PTFE that boron hardly elutes
Comment 1 Instead of the boron standard solution in (2), a boron standard solution for thecalibration curve preparation can be prepared by using a boron standard solution (B 1
mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate citricacid-soluble boron (C-B2O3) in the analytical sample by multiplying the concentration(B) of a boron standard solution for calibration curve preparation or a measurement
value (B) obtained in (4.2) by a conversion factor (3.2199).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An Optical Emission Spectrometer specified in JIS K
318

Testing Methods for Fertilizers(2021)

0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Extractor: A constant-temperature vertical rotating mixer or horizontal reciprocating water
bath shaker as described below.
ba) Constant-temperature vertical rotating mixer: A constant-temperature vertical rotating
mixer that can vertically rotate a 250-mL volumetric flask, set up in a thermostat adjustable to
30 ºC ± 1 ºC, at a rate of 30 - 40 revolutions/min.
bb) Horizontal reciprocating water bath shaker: A reciprocating water bath shaker that can be
adjusted to 30 °C ± 1 °C and horizontally reciprocate a 250-mL volumetric flask, set up verticalto the water surface using a shaking rack, at a rate of 160 reciprocations/min with an amplitudeof 25 mm - 40 mm.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Constant-temperature vertical rotating mixera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask.
b) Add 150 mL of citric acid solution heated up to about 30 ºC (3), and shake to mix at 30 - 40
revolutions/min (30 ºC ± 1 ºC) for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (3) Shake to mix the volumetric flask gently and disperse an analytical sample into the citricacid solution.
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Horizontal reciprocating water bath shakera) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 250-mL volumetric flask(4).
b) Add 150 mL of citric acid solution heated up to about 30 ºC (3), and shake to mix by reciprocating
horizontally at amplitude of 25 mm - 40 mm (30 ºC ± 1 ºC) at 160 times/min for 1 hour.
c) After immediate cooling is complete, add water up to the marked lined) Filter with Type 3 filter paper to make a sample solution.
Note (4) Use a 250-mL flat-bottom volumetric flask to stabilize the shaking.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
Comment 5 The determination may be affected if an analytical sample cakes on the bottom of a
250-mL volumetric flask. Therefore, confirm the status of the non-dissolved mattersafter the procedures of (4.1.1) b) and (4.1.2) b).
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 249.773 nmb) Calibration curve preparation
319

Testing Methods for Fertilizers(2021)

1) Spray the boron standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at a wavelength of 249.773 nm.
2) Prepare a curve for the relationship between the boron concentration and the indicated value ofthe boron standard solution for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.02 mg - 1.6 mg as
B2O3) in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the boron (B2O3) content from the calibration curve, and calculate citric acid-solubleboron (C-B2O3) in the analytical sample.
Comment 6 Wash the sample injector of an ICP-OES sufficiently with water because boron easily
causes the memory effect.
Comment 7 The simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 The comparison of the measurement value (yi：0.073 % (mass fraction) - 0.51 % (massfraction )) of ICP Optical Emission Spectrometry and the measurement value (xi) of
Flame atomic absorption spectrometry analysis was conducted to evaluate truenessusing compound fertilizers (7 samples), mixed phosphorus fertilizers (1 sample), solid
compound fertilizers (2 samples), blended fertilizers (3 samples) and organic
compound fertilizer (1 sample). As a result, a regression equation was
y=−0.0408+1.0456x, and its correlation coefficient (r) was 0.992. In addition, additive
recovery testing was conducted using a preparation sample. As a result, the mean
recovery rate at the additive level of 0.601 % (mass fraction) - 35.51 % (mass fraction)
was 97.0 % - 102.0 %.
The results of the repeatability tests on different days using compound fertilizers andblended fertilizers to evaluate precision were analyzed by one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 % (mass fraction).

320

Testing Methods for Fertilizers(2021)

References
1) Yasushi SUGIMURA: Extraction Method for the Citrate-Soluble Principal Ingredients in
the Fertilizer using a General-Purpose Equipment, Research Report of Fertilizer, Vol. 11,
p. 1 – 13 (2018)2) Shingo MATSUO: Simultaneous Determination of Citrate-Soluble Principal Ingredients(C-P2O5, C-K2O, C-MgO, C-MnO and C-B2O3) in Fertilizer using Inductively Coupled
Plasma-Optical Emission Spectrometry (ICP-OES), Research Report of Fertilizer, Vol.
11, p. 14 – 28 (2018)321

Testing Methods for Fertilizers(2021)(5)

Flow sheet for citric acid-soluble boron: The flow sheet for citric acid-soluble boron in
fertilizers is shown below:

1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Shaking to mix

Constant-temperature vertical rotating mixer (30 - 40 revolutions/min), at 30ºC ± 1 ºC, for 1 hour

Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for citric acid-soluble boron in fertilizers (Extraction procedure (4.1.1))

1 g analytical sample
Weigh to the order of 1 mg into a 250-mL volumetric flask← 150 mL of citric acid solution [about 30 ºC]
Horizontal reciprocating water bath shaker (160 reciprocations/min,Shaking to mix
amplitude of 25 mm - 40 mm), at 30 ºC ± 1 ºC, for 1 hour
Cooling
Immediately← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-2 Flow sheet for citric acid-soluble boron in fertilizers (Extraction procedure (4.1.2))

322

Testing Methods for Fertilizers(2021)

4.8.2 Water-soluble boron
4.8.2.a Azomethine-H method(1) Summary
This test method is applicable to fertilizers containing borate fertilizers, etc. This testing method isclassified as Type B and its symbol is 4.8.2.a-2019 or W-B.a-2.
Extract by adding water to an analytical sample and boiling, mask co-existing copper, iron and othersalts with ethylenediamine tetraacetate and measure the absorbance with azomethine-H borate formedby the reaction with azomethine-H and correct the absorbance originated in coloring of a sample
solution to obtain water-soluble boron (W-B2O3) in an analytical sample. In addition, the performanceof this testing method is shown in Comment 9.
(2) Reagent: Reagents are as shown below.
a) Ethylenediamine tetraacetate solution (1): Dissolve 37.2 g of ethylenediaminetetraacetic aciddihydrogen disodium dihydrate specified in JIS K 8107 in water to make 1000 mL.
b) Ammonium acetate solution (1): Dissolve 250 g of ammonium acetate specified in JIS K 8359
in water to make 500 mL and adjust pH with sulfuric acid (1+4) to pH 5.2 ± 0.1.
c) Azomethine-H solution (1): Add water to 0.6 g of azomethine-H and 2 g of L (+) – ascorbic
acid specified in JIS K 9502, and heat up to 35 ºC - 40 ºC to dissolve and add water after coolingto make 100 mL.
d) Boron standard solution (B2O3 2.5 mg/mL) (1): After leaving boric acid specified in JIS K
8863 at rest in a desiccator for about 24 hours to dry, weigh 4.441 g to a weighing dish. Dissolve
in a small amount of water, transfer to a 1000-mL volumetric flask, and add water up to themarked line.
e) Boron standard solution (B2O3 0.1 mg/mL): Dilute the predetermined volume of boron
standard solution (B2O3 2.5 mg/mL) with water exactly by a factor of 25.
f) Boron standard solution (B2O3 0.01 mg/mL): Dilute the predetermined volume of boron
standard solution (B2O3 0.1 mg/mL) with water exactly by a factor of 10.
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the boron standard solution in (2), a boron standard solution for thecalibration curve preparation can be prepared by using a boron standard solution (B
1 mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate watersoluble boron (W-B2O3) in the analytical sample by multiplying the concentration(B) of a boron standard solution for calibration curve preparation or a measurement
value (B) obtained in (4.3) by a conversion factor (3.2199).
(3) Instruments: Instruments are as shown below:a) Spectrophotometer: A spectrophotometer specified in JIS K 0115b) Hot plate : A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 2.5 g (2) of an analytical sample to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add about 200 mL of water, and cover with a watch glass and heat on a hot plate to boil forabout 15 minutes.
c) After immediate cooling is complete, transfer it to a 250- mL volumetric flask with water.
d) Add water up to the marked linee) Filter with Type 3 filter paper to make a sample solution.
323

Testing Methods for Fertilizers(2021)

Note (2) The sampling amount of the analytical sample is 1 g when there is a high amount ofboric acid content in the fertilizers such as a borate fertilizer and boric acid fertilizer.
Comment 2 In the procedure in (4.1.1) a) and (4.1.1) b), a 250-mL volumetric flask can be usedinstead of a 300-mL tall beaker. However, the volumetric flask used should be
distinguished as an extraction flask and should not be used for the other purposes.
Additionally, “cover with a watch glass” in b) is replaced by “place a funnel”. Skip
“transfer it to a 250-mL volumetric flask with water” in the procedure in c).
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample to the order of 1 mg, and put it in a 100-mL tall beaker.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 0.8 mg as
B2O3) in a 100-mL volumetric flask.
b) Add 25 mL of ethylenediamine tetraacetate solution, and then add 10 mL of ammonium acetate
solution.
c) Add 10 mL of azomethine-H solutiond) After adding water up to the marked line, leave at rest for 2 hours (4) to make a sample solution
for measurement.
e) Conduct the same procedures as a) - b) and d) using another 100-mL volumetric flask to makea sample solution for correction.
Note (4) When the solution is muddled, conduct centrifugation with about 1700 × g centrifugal
force (5) for about five minutes after the procedure in d) or filtrate with Type 3 filter
paper.
(5) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
Comment 5 If formaldehyde processed urea, a large quantity of aluminum, copper, iron zinc,organic matters, etc. coexists to affect quantification, put a predetermined amount of
the sample solution (the equivalents of 0.01 mg - 0.8 mg as B2O3, no more than 10
mL of the solution) in a 100-mL separatory funnel, add 10 mL of hydrochloric acid(1+3), add water to about 20 mL and add 20 mL of 2-ethyl-1,3-hexanediol–4-methyl2-pentanone (1+9) to shake to mix with a shaking apparatus for about 1 minute. Afterallowing to stand still, remove the lower layer (aqueous phase) and add 20 mL of a
sodium hydroxide solution (20 g/L) to shake to mix with a shaking apparatus forabout 1 minute. After allowing to stand still, transfer the lower layer (aqueous phase)to a 100-mL volumetric flask, add a few drops of phenolphthalein solution (1g/100mL) to neutralize with hydrochloric acid (1+3) until the color of the solution
324

Testing Methods for Fertilizers(2021)

becomes achromatic, and conduct the procedure in (4.2) b).
Comment 6 Water-soluble boron can be measured simultaneously with citric acid-soluble boron
by adding 15 mL of citric acid solution before the procedure in (4.2) b).
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 415 nmb) Calibration curve preparation
1) Put 1 mL - 8 mL of boron standard solution (B2O3 0.1 mg/mL) in 100-mL volumetric flasks
step-by-step.
2) Put 1 mL - 10 mL of boron standard solution (B2O3 0.01 mg/mL) in 100-mL volumetric flasks
step-by-step.
3) Conduct the same procedures as (4.2) b) - d) to make B2O3 0.01 mg/100 mL - 0.8 mg/100 mLof the boron standard solutions for the calibration curve preparation.
4) Conduct the same procedures as 3) for another 100-mL volumetric flask to make the blank test
solution for the calibration curve preparation.
5) Further, conduct the same procedures as 4.2 b) and d) for another 100-mL volumetric flask tomake the test solution for control.
6) Measure absorbance at a wavelength of 415 nm of the blank test solution for the calibration
curve preparation and the boron standard solutions for the calibration curve preparation using
the test solution for control as the control.
7) Prepare a curve for the relationship between the boron concentration and absorbance of theboron standard solutions for the calibration curve preparation and the blank test solution for thecalibration curve preparation.
c) Sample measurement
1) Regarding the sample solution for measurement in (4.2) d) and the sample solution forcorrection in (4.2) e), measure absorbance by the same procedure as b) 6).
2) Obtain the boron (B2O3) content from the calibration curve using the absorbance obtained bysubtracting the absorbance of a sample solution for correction from the absorbance of a sample
solution for measurement and calculate water-soluble boron (W-B2O3) in the analytical sample.
Comment 7 Water-soluble boron can be measured simultaneously with citric acid-soluble boron
by adding 15 mL of citric acid solution before the procedure in (4.2) b), (4.3) b) 3),(4.3) b) 4) and (4.3) b) 5).
Comment 8 If it is known in advance, according to the results of quality control analysis, thatcoloring of a sample solution does not affect the analysis of citric acid-soluble boron
in an analytical sample, there is no need to prepare the sample solution for correction((4.2) e)). In that case, read 4.3) c) 2) as “Obtain the boron (B2O3) content from thecalibration curve using the absorbance of a sample solution for measurement andcalculate water-soluble boron (W-B2O3) in the analytical sample”.
Comment 9 Recovery testing was conducted using a powdery preparation sample to evaluate
trueness. As a result, the mean recovery rates at the content level of 10.22 % (massfraction) - 5.11 % (mass fraction) and 0.20 % (mass fraction) as water-soluble boron(W-B2O3) were 99 %, 101 % - 103 %, and 102 %.
Recovery testing was conducted using a fluid preparation sample to evaluate trueness.
As a result, the mean recovery rates at the content level of 5 % (mass fraction), 0.1 %(mass fraction) and 0.01 % (mass fraction) as water-soluble boron (W-B2O3) were325

Testing Methods for Fertilizers(2021)

102 %, 99 %, and 93 %.
The results of the repeatability tests on different days using a borate fertilizer, acompound fertilizer and a home garden-use compound fertilizer and a fluid
compound fertilizer (one brand for each) to evaluate precision were analyzed by oneway analysis of variance. Table 1-1 and 1-2 show the calculation results ofintermediate precision and repeatability. Additionally, results from a collaborative
study for testing method validation and its analysis are shown in Table 2
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.01 % (mass fraction) for solid fertilizers and about 0.003 % (massfraction) for fluid fertilizers.

326

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.184- 187, Yokendo, Tokyo (1988)
2)
Kimie KATO, Sakiko TAKAHASHI and Yuji SHIRAI: Validation of a Color metric
Method for Determination of Nitrogen, Phosphorus and Boron: Evaluation of Calibration
curve, Research Report of Fertilizer Vol. 2, p. 137 - 144 (2009)3)
Akira SHIMIZU: Verification of Performance Characteristics of Testing Methods for
Boron Content by Azomethine H Absorption Photometry, Research Report of Fertilizer
Vol. 6, p. 174 -182 (2013)
4)
Masayuki YAMANISHI: Improved Determination Method of Boron(B2O3) in Fertilizer,
Research Report of Fertilizer Vol. 22, p. 10 - 27 (2019)5)
Keisuke AOYAMA: Performance Evaluation of Determination Method for Boron in
Fertilizer: Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13,
p. 112 – 122 (2020)

327

Testing Methods for Fertilizers(2021)(5)

Flow sheet for water-soluble boron: The flow sheet for water-soluble boron in fertilizers isshown below:

328

Testing Methods for Fertilizers(2021)

329

Testing Methods for Fertilizers(2021)

Reference:

A calculation example of water-soluble boron content in an analytical sample isshown below.

a) Reference table 1-1 shows the absorbance (example) of a standard solution for the calibration
curve preparation and a blank test solution for the calibration curve preparation using a test
solution for control as the control.
In addition, calibration curves are shown in Reference diagram 1 and regression coefficients of
the regression equations are in Reference table 1-2.
b) Reference table 2 shows the sampling amount of an analytical sample, the constant volume ofextract, the transferred amount of extract and the constant volume of the sample solution formeasurement as well as the absorbance (example) of the sample solution for measurement andthe sample solution for correction using a test solution for control as the control.
c) Obtain the boron (B2O3) content in the sample solution for measurement by formula (1)(Refer to Reference diagram 1) and calculate water-soluble boron (W-B2O3) in the analyticalsample by formula (2).

330

Testing Methods for Fertilizers(2021)

Boron (B2O3) content in a sample solution for measurement (C1)＝((As－Ab)－a)/b＝(Ac－a)/b
・・・・・ (1)
Water-soluble boron (W-B2O3) in an analytical sample (C2)
＝C1×(V1/V2)×(1/W)×(100/1000)
・・・・・ (2)C1： Boron (B2O3) content in 100 mL of a sample solution for measurement (mg)
As： Absorbance of a sample solution for measurement in (4.2) d) using a test solution forcontrol ((4.3 b) 5)) as the control
Ab： Absorbance of a sample solution for correction in (4.2) e) using a test solution forcontrol ((4. 3) b) 5)) as the control
Ac： Corrected absorbancea： Intercept of a regression equation of a calibration curveb： Inclination of a regression equation of a calibration curve
C2： Water-soluble boron (W-B2O3) in an analytical sample (% (mass fraction))
V1： Constant volume (mL) of the sample solution in (4.1.1) d) or (4.1.2) c)
V2： Aliquot (mL) of the sample solution in (4.2) a)
W： Mass (g) of the analytical sample

331

Testing Methods for Fertilizers(2021)
0.150

1.000

y = 0.025+1.050x

0.800
Ac(1)=As(1)-Ab(1)Absorbance（ABS）

Absorbance (ABS)

0.120
0.090
0.060
0.030

C1(1)

0.000

0.600

y = 0.025+1.050x

Ac(2)=As(2)-Ab(2)

0.400
0.200

C1(2)

0.000
0.00 0.02 0.04 0.06 0.08 0.10
Boron concentration（B2O3 mg/100 mL ）

0.00
0.20
0.40
0.60
0.80
Boron concentration （B2O3 mg/100 mL ）1) Low concentration range(B2O3 0 mg/100 mL - 0.10 mg/100 mL)
Reference diagram 1

2) High concentration range(B2O3 0 mg/100 mL - 0.80 mg/100 mL)

Calibration curve (example) of water-soluble boron (W-B2O3)

332

Testing Methods for Fertilizers(2021)

4.8.2.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D for solid
fertilizers and Type B for fluid fertilizers. Its symbol is 4.8.2.b-2019 or W-B.b-2.
Extract by adding water to an analytical sample, further dilute the filtered solution, introduce it toan ICP Optical Emission Spectrometer (“ICP-OES”) and measure the boron at a wavelength of
249.773 nm, etc. to obtain water-soluble boron (W-B2O3) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Boron standard solution (B2O3 2.5 mg/mL) (1): After leaving boric acid specified in JIS K
8863 at rest in a desiccator for about 24 hours to dry, weigh 4.441 g to a weighing dish. Dissolve
in a small amount of water, transfer to a 1000-mL volumetric flask, and add water up to themarked line.
d) Boron standard solution (B2O3 0.1 mg/mL) (1): Put 4 mL of boron standard solution (B2O3 2.5
mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to the marked line(2).
e) Boron standard solution (B2O3 2 µg/mL - 16 µg/mL) for the calibration curve preparation(1): Put 2 mL - 16 mL of boron standard solution (B2O3 0.1 mg/mL) in a 100-mL volumetricflask step by step and add hydrochloric acid (1+23) up to the marked line (2).
f) Boron standard solution (B2O3 0.2 µg/mL - 2 µg/mL) for the calibration curve preparation(1): Put 2 mL - 20 mL of boron standard solution (B2O3 10 µg/mL) in a 100-mL volumetric flask
step by step and add hydrochloric acid (1+23) up to the marked line (2).
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f) (2).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) When preserving, use a container, which can be sealed tightly, made of material such as
PTFE that boron hardly elutes
Comment 1 Instead of the boron standard solution in (2), a boron standard solution for thecalibration curve preparation can be prepared by using a boron standard solution (B 1
mg/mL or 10 mg/mL) traceable to National Metrology. In this case, calculate watersoluble boron (W-B2O3) in the analytical sample by multiplying the concentration (B)of a boron standard solution for calibration curve preparation or a measurement value(B) obtained in (4.2) by a conversion factor (3.2199).
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5% (volume fraction) in purity
333Testing Methods for Fertilizers(2021)b) Hot plate:
A hot plate whose surface temperature can be adjusted up to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 2.5 g of an analytical sample (3) to the order of 1 mg, and put it in a 300-mL tall beaker.
b) Add about 200 mL of water, and cover with a watch glass and heat on a hot plate to boil forabout 15 minutes.
c) After immediate cooling is complete, transfer it to a 250- mL volumetric flask with water.
d) Add water up to the marked line.
e) Filter with Type 3 filter paper to make a sample solution.
Note (3) The sampling amount of the analytical sample is 1 g when there is a high amount ofboric acid content in the fertilizers such as a borate fertilizer and boric acid fertilizer.
Comment 3 In the procedure in (4.1.1) a), 250-mL volumetric flask can be used instead of a 300mL tall beaker. However, the volumetric flask used should be distinguished as an
extraction flask and should not be used for the other purposes. Additionally, “coverwith a watch glass” in b) is replaced by “place a funnel”. Skip “transfer it to a 250-mL
volumetric flask with water” in the procedure in c).
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1 g of an analytical sample (4) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (4) The sampling amount of the analytical sample is 10 g when there is less boron content
in the fertilizers such as a home garden-use fertilizer.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 249.773 nm or 249.678 nm (5)b) Calibration curve preparation
1) Spray the boron standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at an analytical line wavelength.
2) Prepare a curve for the relationship between the boron concentration and the indicated value ofthe boron standard solution for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
334

Testing Methods for Fertilizers(2021)c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.02 mg - 1.6 mg as
B2O3) in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the boron content from the calibration curve, and calculate water-soluble boron (WB2O3) in the analytical sample.
Note (5) 249.678 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 249.773 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 6 Wash the sample injector of an ICP-OES sufficiently with water because boron easily
causes the memory effect.
Comment 7 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 8 The comparison of the measurement value (yi：0.0165 % (mass fraction) - 0.590 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of Azomethine-H method was conducted to evaluate trueness using solid fertilizers(21 samples). As a result, a regression equation was y=0.0002+0.993x, and its
correlation coefficient (r) was 0.998. The comparison of the measurement value (yi：0.013 % (mass fraction) - 0.530 % (mass fraction )) of ICP Optical Emission
Spectrometry and the measurement value (xi) of Azomethine-H method was conducted
to evaluate trueness using fluid fertilizers (12 samples). As a result, a regression
equation was y=−0.0041+0.986x, and its correlation coefficient (r) was 0.999. In
addition, additive recovery testing was conducted using preparation fertilizers (6samples). As a result, the mean recovery rate at the additive level of 0.0912 % (massfraction) - 56.30 % (mass fraction) was 97.4 % - 101.2 %. Additive recovery testing
was conducted using a fluid compound fertilizer (1 brand) and a home garden-use
compound fertilizer (1 brand) and a liquid microelement compound fertilizer (1 bland).
As a result, the mean recovery rates at the additive level of 0.15 % (mass fraction) 0.2 % and 0.01 % (mass fraction) were 95.5 % - 99.4 % and 96.5 % respectively.
The results of the repeatability tests on different days using a compound fertilizer, ablended fertilizer, a fluid compound fertilizer and a home garden-use compound
fertilizer to evaluate precision were analyzed by the one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Additionally, results from a collaborative study implemented for testing method
validation and its analysis are shown in Table 2
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005% (mass fraction) for solid fertilizers and about 0.0005% (mass fraction)
for fluid fertilizers.

335

Testing Methods for Fertilizers(2021)

References
1)
Keisuke AOYAMA:

Simultaneous Determination
336

ofWater-Soluble

Principal

Testing Methods for Fertilizers(2021)

2)
3)

Ingredients (W-P2O5, W-K2O, W-MgO, W-MnO and W-B2O3) in Liquid Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Research
Report of Fertilizer, Vol. 8, p. 1 - 9 (2015)
Norio FUNAKI: Simultaneous Determination of Water-soluble Principal Ingredients in
Fertilizer using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES),
Research Report of Fertilizer, Vol. 12, p. 28 – 51 (2019)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)

337

Testing Methods for Fertilizers(2021)(5)

Flow sheet: The flow sheet for water-soluble boron in fluid fertilizers is shown below:

338

Testing Methods for Fertilizers(2021)

4.9 Zinc4.9.1 Total zinc
4.9.1.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type C and its
symbol is 4.9.1.a-2017 or T-Zn.a-1.
Pretreat an analytical sample with incineration and nitric acid-hydrochloric acid (1+3), and thenspray in an acetylene−air flame, and measure the atomic absorption with zinc at a wavelength of
213.9 nm to quantify the total zinc (T-Zn). In addition, the performance of this testing method isshown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
d) Zinc standard solution (Zn 0.1 mg/mL): A zinc standard solution (Zn 0.1 mg/mL) traceable
to National Metrology.
e) Zinc standard solutions (Zn 0.5 µg - 5 µg/mL) for the calibration curve preparation (1): Put
2.5 mL - 25 mL of zinc standard solution (Zn 0.1 mg/mL) in 500-mL volumetric flasks step-bystep, and add hydrochloric acid (1+23) to the marked line.
f) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the zinc standard solution in (2), a zinc standard solution for the calibration
curve preparation can be prepared by using a zinc standard solution (Zn 1 mg/mL or
10 mg/mL) traceable to National Metrology.
Comment 2 When using a sample solution obtained in the procedure in (4.1.2) h) for themeasurement of cadmium, nickel, chromium or lead, sulfuric acid and hydrochloric
acid in (2) should be a reagent of harmful metal analysis grade, microanalysis grade orequivalents.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (2) function.
1) Light source: A zinc hollow cathode lamp (when the continuous source method as the
background correction method is used, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can be adjusted to 450 °C±5 °C or 550 ºC ± 5 °C.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
Note (2) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
339

Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Incineration-hydrochloric acid boilinga) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (3).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (3).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After cooling is complete, transfer to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (3) Example of charring and incineration procedure: After raising from room temperature
to about 250 °C in 30 minutes to 1 hour, continue heating for about 1 hour and further
raise to 550 °C in 1 to 2 hours.
Comment 3 Do not conduct the procedures in (4.1.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Incineration-aqua regia digestiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 450 ºC ± 4 ºC for 8 - 16 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (5), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (6) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water
up to the marked line, and filter with Type 3 filter paper to make a sample solution.
Note (4) Example of charring and incineration procedure: After raising from room temperature
to about 250 °C in 30 minutes to 1 hour, continue heating for about 1 hour and further
raise to 450 °C in 1 to 2 hours.
(5) The watch glass can be removed.
(6) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 5 Do not conduct the procedures in (4.1.2) b) - c) in the case of fertilizers not containing
organic matters.
340

Testing Methods for Fertilizers(2021)

Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 213.9 nmb) Calibration curve preparation
1) Spray the zinc standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation into a flame, and read the indicated value at a wavelengthof 213.9 nm.
2) Prepare a curve for the relationship between the zinc concentration and the indicated value ofthe zinc standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Subject the sample solution (7) to the same procedure as in b) 1) to read the indicated value.
2) Obtain the zinc content from the calibration curve, and calculate the total zinc (T-Zn) in theanalytical sample.
Note (7) If there is a possibility that the zinc concentration in the sample solution will exceed the
maximum limit of the calibration curve, dilute a predetermined amount withhydrochloric acid (1+23).
Comment 7 The zinc concentration in the analytical sample can also be corrected by subjecting theblank test solution to the same procedures as in c) 1) to obtain the zinc content in theblank test solution.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 1.2 % (mass fraction) and 90
mg/kg were 99.5 % and 97.8 % as the total zinc (T-Zn) respectively.
The results of the collaborative study to determine a certified reference material
fertilizer were analyzed by using a three-level nesting analysis of variance. Table 1
shows the calculation results of reproducibility, intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 5 mg/kg for solid fertilizers.

341

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.193- 194, Yokendo, Tokyo (1988)
2)
Kimie KATO, Masayuki YOSHIMOTO and Yuji SHIRAI: Systematization of
Determination Methods of Major Components in Sludge Fertilizer, Compost and Organic
Fertilizer, Research Report of Fertilizer, Vol. 3 p. 107 - 116 (2010)3)
Shin ABE and Yoshiyuki SUNAGA: Verification of Performance Characteristics ofTesting Methods for Zinc in Fertilizer by Atomic Absorption Spectrometry, Research
Report of Fertilizer Vol. 6, p. 156 -164 (2013)(5)

Flow sheet for total zinc: The flow sheet for total zinc in fertilizers is shown below:342

Testing Methods for Fertilizers(2021)

343

Testing Methods for Fertilizers(2021)

4.9.1.b ICP Optical Emission Spectrometry(1) Summary
The testing method is applicable to sludge fertilizers, etc. This testing method is classified as TypeD and its symbol is 4.9.1.b-2017 or T-Zn.b-1.
Pretreat an analytical sample with incineration, nitric acid−hydrochloric acid (1+3), introduce it toan ICP Optical Emission Spectrometer (“ICP-OES”) and measure the emission with zinc at awavelength of 206.191 nm to obtain the total zinc (T-Zn) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Zinc standard solution (Zn 0.1 mg/mL): A zinc standard solution (Zn 0.1 mg/mL) traceable
to National Metrology.
e) Zinc standard solution (Zn 25 µg/mL) (1): Dilute a predetermined amount of zinc standard
solution (Zn 0.1 mg/mL) with hydrochloric acid (1+23) to prepare a zinc standard solution (Zn25 µg/mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the zinc standard solution in (2), a zinc standard solution for the calibration
curve preparation can be prepared by using a zinc standard solution (Zn 1 mg/mL or
10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (2).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (2).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (3), and continue heating on the hot plate or sand bath to344

Testing Methods for Fertilizers(2021)

concentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (4) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water up
to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (2) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(3) The watch glass can be removed.
(4) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 3 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Standard Addition Method) according to JIS K 0116 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Optical Emission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 206.191 nmb) Calibration curve preparation and sample measurement
1) Put 5mL of sample solution in three 10-mL volumetric flasks respectively.
2) Add 2mL and 4 mL of zinc standard solution (25 μg/mL) to volumetric flasks of 1) above, then
add hydrochloric acid (1+23) up to the marked line to make a sample solution of Standard
Addition Method.
3) Add hydrochloric acid (1+23) to the marked line of the remaining volumetric flask of 1) above
to make a sample solution without a standard solution.
4) Spray the sample solution of Standard Addition Method and the sample solution without astandard solution into the induction plasma, and read the indicated value at a wavelength of
206.191 nm.
5) Transfer 5 mL of blank test solution to a 10-mL volumetric flask, conduct the same proceduresas in 3) - 4) to read the indicated value, and correct the indicated value obtained from therespective sample solutions.
6) Prepare a curve for the relationship between the added zinc concentration and the correctedindicated value of the sample solution for Standard Addition Method and the sample solution
without a standard solution.
7) Obtain the zinc content from the intercept of the calibration curve to calculate the total zinc (TZn) in the analytical sample.
Comment 5 The total zinc (T-Zn) in the analytical sample can also be corrected by subjecting theblank test solution to the same procedures as in b) 1) - b) 4) and b) 6) - b) 7) to obtainthe zinc content in the blank test solution.
345

Testing Methods for Fertilizers(2021)

Comment 6 The simultaneous measurement of multiple elements is possible with the ICP‐OES. In
this case, put a pre-determined amount of copper standard solution (Cu 0.1 mg/mL, 1
mg/mL or 10 mg/mL), zinc standard solution (Zn 0.1 mg/mL, 1 mg/mL or 10 mg/mL),
cadmium standard solution (Cd 0.1 mg/mL, 1 mg/mL or 10 mg/mL), nickel standard
solution (Ni 0.1 mg/mL, 1 mg/mL or 10 mg/mL), chromium standard solution (Cr 0.1
mg/mL, 1 mg/mL or 10 mg/mL) and lead standard solution (Pb 0.1 mg/mL, 1 mg/mL
or 10 mg/mL) in a volumetric flask to mix, add hydrochloric acid (1+5) to make acidconcentration 0.5 mol/L and further add water up to the marked line to prepare a
primary mixed standard solution. Transfer a pre-determined amount of primary mixed
standard solution to a volumetric flask, add hydrochloric acid (1+23) up to the marked
line to prepare a mixed standard solution for addition within the concentration rangein Table 1. The measurement wavelengths of respective elements are according toTable 1.
In addition, the additive amount of mixed standard solution for addition and the
additive concentrations of respective elements in a sample solution are shown in the
Table below.

Comment 7 The comparison of the measurement value (xi：65.0 mg/kg - 3310 mg/kg) of ICP
Optical Emission Spectrometry and the measurement value (yi) of Flame Atomic
Absorption Spectrometry was conducted to evaluate trueness using sludge fertilizers(49 samples). As a result, a regression equation was y=−47.6+1.080x and its correlation
coefficient (r) was 0.995. Triplicates measurement for each one sample of sewage
sludge fertilizer, human waste sludge fertilizer, industrial sludge fertilizer, mixed
sludge fertilizer, calcined sludge fertilizers and composted sludge fertilizer was
conducted. As a result, a repeatability obtained was 0.1 % - 2.3 % as a relative standard
deviation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 8 mg/kg.
References
1)
Masahiro ECHI, Tomoe INOUE, Megumi TABUCHI and Tetuya NOMURA:
Simultaneous Determination of Cadmium, Lead, Nickel, Chromium, Copper and Zinc in
Sludge Fertilizer using Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES), Research Report of Fertilizer, Vol. 4, p. 30 - 35 (2011)346

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total zinc: The flow sheet for total zinc in fertilizers is shown below:

347

Testing Methods for Fertilizers(2021)

4.9.2 Water-soluble zinc
4.9.2.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers that indicate zinc content as a response modifier. This
testing method is classified as Type D and its symbol is 4.9.2.a-2017 or W-Zn.a-1.
Extract by adding water to an analytical sample, spray in an acetylene−air flame and measure theatomic absorption with zinc at a wavelength of 213.9 nm to obtain water-soluble zinc (W-Zn) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Zinc standard solution (Zn 0.1 mg/mL): A zinc standard solution (Zn 0.1 mg/mL) traceable
to National Metrology.
d) Zinc standard solutions (Zn 0.5 µg - 5 µg/mL) for the calibration curve preparation (1): Put
2.5 mL - 25 mL of zinc standard solution (Zn 0.1 mg/mL) in 500-mL volumetric flasks step-bystep, and add hydrochloric acid (1+23) to the marked line.
e) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the zinc standard solution in (2), a zinc standard solution for the calibration
curve preparation can be prepared by using a zinc standard solution (Zn 1 mg/mL or
10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (2) function.
1) Light source: A zinc hollow cathode lamp (when the continuous source method as the
background correction method is used, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
Note (2) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 5.00 g of an analytical sample, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.

348

Testing Methods for Fertilizers(2021)

Comment 2 In the procedure in (4.1.1) a), it is also allowed to weigh 2.50 g of the analytical sample
and put it in a 250-mL volumetric flask. In that case, add about 200 mL of water in theprocedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 213.9 nmb) Calibration curve preparation
1) Spray the zinc standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation into a flame, and read the indicated value at a wavelengthof 213.9 nm.
2) Prepare a curve for the relationship between the zinc concentration and the indicated value ofthe zinc standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.05 mg - 0.5 mg as Zn)
in a 100-mL volumetric flask.
2) Add about 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the zinc content from the calibration curve, and calculate the water-soluble zinc (W-Zn)
in the analytical sample.
Comment 5 Recovery testing was conducted to evaluate trueness using a preparation sample (solid).
As a result, the mean recovery rates at the content level of 10 % (mass fraction), 2 %(mass fraction) and 0.01 % (mass fraction) were 101.6 %, 101.9 % and 98.9 % aswater-soluble zinc (W-Zn) respectively. In addition, recovery testing was conductedusing a preparation sample (fluid). As a result, the mean recovery rates at the content
level of 1 % (mass fraction), 0.05 % (mass fraction) and 20 mg/kg were 99.6 %,100.4 % and 100.6 % as water-soluble zinc respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a liquid microelement compound fertilizer to evaluate the extract precision of fluid
fertilizers were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 10 mg/kg for solid fertilizers and about 0.9 mg/kg for fluid fertilizers.
349

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.192- 194, Yokendo, Tokyo (1988)
2)
Shin ABE and Yoshiyuki SUNAGA: Verification of Performance Characteristics ofTesting Methods for Zinc in Fertilizer by Atomic Absorption Spectrometry, Research
Report of Fertilizer Vol. 6, p. 156 -164 (2013)3)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components in
Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20 (2016)(5)

Flow sheet for water-soluble zinc: The flow sheet for water-soluble zinc in fertilizers is shown
below:
5.00 g analytical sample(powdery)

500-mL volumetric flask.

← Water, About 400 mL
Vertical rotating mixer (30 - 40 revolutions/min), for
Shaking to mix
30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble zinc in fertilizers(Extraction procedure(4.1.1))

350

Testing Methods for Fertilizers(2021)

351

Testing Methods for Fertilizers(2021)

4.9.2.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type B and its symbol is 4.9.2.b-2017 or W-Zn.b-1.
Extract by adding water to an analytical sample, introduce it to an ICP Optical Emission
Spectrometer (ICP-OES) and measure the zinc at a wavelength of 213.856 nm, etc. to obtain watersoluble zinc (W-Zn) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Zinc standard solution (Zn 1 mg/mL): A zinc standard solution (Zn 1 mg/mL) traceable to
National Metrology.
d) Zinc standard solution (Zn 0.1 mg/mL) (1): Put 10 mL of zinc standard solution (Zn 1 mg/mL)
in a 100-mL flask and add hydrochloric acid (1+23) up to the marked line.
e) Zinc standard solutions (Zn 1 µg - 20 µg/mL) for the calibration curve preparation (1): Put
1 mL - 20 mL of zinc standard solution (Zn 0.1 mg/mL) in 100-mL volumetric flasks step-bystep, and add hydrochloric acid (1+23) to the marked line.
f) Zinc standard solutions (Zn 0.1 µg - 1 µg/mL) for the calibration curve preparation (1): Put
1 mL - 10 mL of zinc standard solution (Zn 10 µg/mL) in 100-mL volumetric flasks step-bystep, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the zinc standard solution in (2), a zinc standard solution for the calibration
curve preparation can be prepared by using a zinc standard solution (Zn 10 mg/mL)
traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and a spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g (2) of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
352

Testing Methods for Fertilizers(2021)

Note (2) The sampling amount of the analytical sample is 10 g when the content in the sample isless than 0.01 % (mass fraction) as water-soluble zinc.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 213.856 nm or 206.200 nm (3)b) Calibration curve preparation
1) Spray the zinc standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation into a flame, and read the indicated value at an analyticalline wavelength.
2) Prepare a curve for the relationship between the zinc concentration and the indicated value ofthe zinc standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Zn)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the zinc content from the calibration curve, and calculate the water-soluble zinc (W-Zn)
in the analytical sample.
Note (3) 206.200 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 213.856 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 4 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 5 The comparison of the measurement value (yi：0.0109 % (mass fraction) - 0.0827 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of flame atomic absorbance spectrometry was conducted to evaluate trueness using
fluid fertilizers (12 samples). As a result, a regression equation was y= −0.0007+0.984x,
and its correlation coefficient (r) was 0.998. Additionally, additive recovery testing
was conducted using a fluid compound fertilizer (1 brand) and a home garden-use
compound fertilizer (1 brand). As a result, the mean recovery rates at the additive levelof 0.01 % (mass fraction) and 0.1 % (mass fraction) were 91.6 % and 95.9 %respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a home garden-use compound fertilizer to evaluate precision were analyzed by the353

Testing Methods for Fertilizers(2021)

one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study
implemented for 3333testing method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0005 % (mass fraction).

References
1)
Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development
Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research
Report of Fertilizer, Vol. 9, p. 1 - 9 (2016)
2)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)
354

Testing Methods for Fertilizers(2021)(5)

Flow sheet for water-soluble zinc: The flow sheet for water-soluble zinc in fluid fertilizers isshown below:

355

Testing Methods for Fertilizers(2021)

4.10 Copper
4.10.1 Total copper
4.10.1.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type C and its
symbol is 4.10.1.a-2017 or T-Cu.a-1.
Pretreat an analytical sample with incineration and nitric acid−hydrochloric acid (1+3), and thenspray in an acetylene−air flame, and measure the atomic absorption with copper at a wavelength of
324.8 nm to obtain the total copper (T-Cu) in an analytical sample. In addition, the performance of
this testing method is shown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Nitric acid: A JIS Guaranteed Reagent specified in JIS K 8541 (HNO3 60 % (mass fraction))or a reagent of equivalent quality.
d) Copper standard solution (Cu 0.1 mg/mL): A copper standard solution (Cu 0.1 mg/mL)
traceable to National Metrology.
e) Copper standard solutions (Cu 0.5 µg - 5 µg/mL) for the calibration curve preparation (1):
Put 2.5 mL - 25 mL of copper standard solution (Cu 0.1 mg/mL) in 500-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) to the marked line.
f) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the copper standard solution in (2), a copper standard solution for thecalibration curve preparation can be prepared by using a copper standard solution (Cu
1 mg/mL or 10 mg/mL) traceable to National Metrology.
Comment 2 When using a sample solution obtained in the procedure in (4.1.2) h) for themeasurement of cadmium, nickel, chromium or lead, sulfuric acid and hydrochloric
acid in (2) should be a reagent of harmful metal analysis grade, microanalysis grade orequivalents.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (2) function.
1) Light source: A copper hollow cathode lamp (In case of background correction system using
continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C or
550 ºC ± 5 ºC.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
Note (2) There are the continuous source method, the Zeeman method, the non-resonance356

Testing Methods for Fertilizers(2021)

spectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Incineration-hydrochloric acid boilinga) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (3).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (3).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After cooling is complete, transfer to a 250-mL - 500-mL volumetric flask with water.
g) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (3) Example of charring and incineration procedure: After raising from room temperature
to about 250 °C in 30 minutes to 1 hour, continue heating for about 1 hour and further
raise to 550 °C in 1 to 2 hours.
Comment 3 Do not conduct the procedures in (4.1.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Incineration-aqua regia digestiona) Weigh 5 g of an analytical sample to the order of 1 mg, and put it in a 200-mL - 300-mL tallbeaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (5), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (6) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water
up to the marked line, and filter with Type 3 filter paper to make a sample solution.
Note (4) Example of charring and incineration procedure: After raising from room temperature
to about 250 °C in 30 minutes to 1 hour, continue heating for about 1 hour and further
raise to 450 °C in 1 to 2 hours.
(5) The watch glass can be removed.
(6) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 5 Do not conduct the procedures in (4.1.2) b) - c) in the case of fertilizers not containing
357

Testing Methods for Fertilizers(2021)

organic matters.
Comment 6 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 324.8 nmb) Calibration curve preparation
1) Spray the copper standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 324.8 nm.
2) Prepare a curve for the relationship between the copper concentration and the indicated valueof the copper standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Subject the sample solution (7) to the same procedure as in b) 1) to read the indicated value.
2) Obtain the copper content from the calibration curve, and calculate the total copper (T-Cu) in
the analytical sample.
Note (7) If there is a possibility that the copper concentration in the sample solution will exceed
the maximum limit of the calibration curve, dilute a predetermined amount withhydrochloric acid (1+23).
Comment 7 The copper concentration in the analytical sample can also be corrected by subjecting
the blank test solution to the same procedures as in c) 1) to obtain the copper content
in the blank test solution.
Comment 8 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 0.15 % (mass fraction) and
0.03 % (mass fraction) were 100.4 % and 99.6 % as total copper (T-Cu) respectively.
The results of the collaborative study to determine a certified reference material
fertilizer were analyzed by using a three-level nesting analysis of variance. Table 1
shows the calculation results of reproducibility, intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 4 mg/kg.

358

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.254- 255, Yokendo, Tokyo (1988)
2)
Kimie KATO, Masayuki YOSHIMOTO and Yuji SHIRAI: Systematization of
Determination Methods of Major Components in Sludge Fertilizer, Compost and Organic
Fertilizer, Research Report of Fertilizer, Vol. 3 p. 107 - 116 (2010)3)
Shin ABE and Yoshiyuki SUNAGA: Verification of Performance Characteristics ofTesting Methods for Copper in Fertilizer by Atomic Absorption Spectrometry, Research
Report of Fertilizer, Vol. 6, p. 165 - 173 (2013)(5)

Flow sheet for total copper: The flow sheet for total copper in fertilizers is shown below:359

Testing Methods for Fertilizers(2021)

360

Testing Methods for Fertilizers(2021)

4.10.1.b ICP Optical Emission Spectrometry(1) Summary
The test method is applicable to sludge fertilizers, etc. This testing method is classified as Type D
and its symbol is 4.10.1.b-2017 or T-Cu.b-1.
Pretreat an analytical sample with incineration, nitric acid−hydrochloric acid (1+3), introduce it to
ICP Optical Emission Spectrometry (ICP-OES) and measure the emission with copper at awavelength of 324.754 nm to quantify the total copper (T-Cu) in an analytical sample. In addition,
the performance of this testing method is shown in Comment 7.
(2)
a)
b)
c)
d)
e)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Hydrochloric acid:
Copper standard solution (Cu 0.1 mg/mL): A copper standard solution (Cu 0.1 mg/mL)
traceable to National Metrology.
Copper standard solutions (Cu 25 µg/mL) (1): Dilute a predetermined amount of copper
standard solution (Cu 0.1 mg/mL) with hydrochloric acid (1+23) to prepare a copper standard
solution (Cu 25 µg/mL).

Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the copper standard solution in (2), a copper standard solution for thecalibration curve preparation can be prepared by using a copper standard solution (Cu
1 mg/mL or 10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (2).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (2).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (3), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
361

Testing Methods for Fertilizers(2021)g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (4) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water up
to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (2) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(3) The watch glass can be removed.
(4) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 3 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 324.754 nmb) Calibration curve preparation and sample measurement
1) Put 5mL of sample solution in three 10-mL volumetric flasks respectively.
2) Add 2mL and 4 mL of copper standard solution (25 μg/mL) to volumetric flasks of 1) above,
then add hydrochloric acid (1+23) to the marked line to make a sample solution of Standard
Addition Method.
3) Add hydrochloric acid (1+23) to the marked line of the remaining volumetric flask of 1) above
to make a sample solution without a standard solution.
4) Spray the sample solution of Standard Addition Method and the sample solution without astandard solution into the induction plasma, and read the indicated value at a wavelength of
324.754 nm.
5) Transfer 5 mL of blank test solution to a 10-mL volumetric flask, conduct the same proceduresas in 3) - 4) to read the indicated value, and correct the indicated value obtained from therespective sample solutions.
6) Prepare a curve for the relationship between the added copper concentration and the correctedindicated value of the sample solution for Standard Addition Method and the sample solution
without a standard solution.
7) Obtain the copper content from the intercept of the calibration curve to calculate the total copper(T-Cu) in the analytical sample.
Comment 5 The copper concentration in the analytical sample can also be corrected by subjecting
the blank test solution to the same procedures as in b) 1) - b) 4) and b) 6) - b) 7) toobtain the copper content in the blank test solution.
Comment 6 The simultaneous measurement of multiple elements is possible with the ICP-OES. In
362

Testing Methods for Fertilizers(2021)

that case, see 4.9.1.b Comment 6.
Comment 7 The comparison of the measurement value (xi：12.0 mg/kg - 1400 mg/kg) of ICP
Optical Emission Spectrometry and the measurement value (yi) of Flame Atomic
Absorption Spectrometry was conducted to evaluate trueness using sludge fertilizers(49 samples). As a result, a regression equation was y=−5.5+1.062x and its correlation
coefficient (r) was 0.997. Triplicates measurement for each one sample of sewage
sludge fertilizer, human waste sludge fertilizer, industrial sludge fertilizer, mixed
sludge fertilizer, calcined sludge fertilizers and composted sludge fertilizer was
conducted. As a result, a repeatability obtained was 0.6 % - 1.8 % as a relative standard
deviation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 3 mg/kg.
References
1)
Masahiro ECHI, Tomoe INOUE, Megumi TABUCHI and Tetuya NOMURA:
Simultaneous Determination of Cadmium, Lead, Nickel, Chromium, Copper and Zinc in
Sludge Fertilizer using Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES), Research Report of Fertilizer, Vol. 4, p. 30 - 35 (2011)363

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total copper: The flow sheet for total copper in fertilizers is shown below:
5.00 ganalytical sample
Charring
Incineration

200-mL - 300-mL tall beaker.
Heat gently
Ignite at 450 ºC ± 5 ºC, 8 - 16 hours

Standing to coolRoom temperature← A small amount of water← About 10 mL of nitric acid
← About 30 mL of hydrochloric acid
Heating
Cover with a watch glass, and digest
Heating

Slightly move a watch glass to remove acid

Standing to coolRoom temperature← 25 mL - 50 mL of hydrochloric acid (1+5)
Heating
Cover with a watch glass, and dissolve
Standing to coolRoom temperature

Transfer
100-mL - 200-mL volumetric flask, water← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for total copper in fertilizers (Extraction procedure)

Sample solution
Aliquot 5 mL
10-mL volumetric flask, 3 flasks← 0, 2 and 4 mL of copper standard solution (25 μg / mL)← Hydrochloric acid (1+23) ( up to the marked line)
Measurement
ICP Optical Emission Spectrometer (324.754 nm)
Figure 2 Flow sheet for total copper in fertilizers (Measurement procedure)364

Testing Methods for Fertilizers(2021)

4.10.2 Water-soluble copper
4.10.2.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers that indicate copper content as a response modifier.
This testing method is classified as Type D and its symbol is 4.10.2.a-2017 or W-Cu.a-1.
Extract by adding water to an analytical sample, spray in an acetylene−air flame and measure theatomic absorption with copper at a wavelength of 324.8 nm to obtain water-soluble copper (W-Cu)
in an analytical sample. In addition, the performance of this testing method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
c) Copper standard solution (Cu 0.1 mg/mL): A copper standard solution (Cu 0.1 mg/mL)
traceable to National Metrology.
d) Copper standard solutions (Cu 0.5 µg - 5 µg/mL) for the calibration curve preparation (1):
Put 2.5 mL - 25 mL of copper standard solution (Cu 0.1 mg/mL) in 500-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) to the marked line.
e) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the copper standard solution in (2), a copper standard solution for thecalibration curve preparation can be prepared by using a copper standard solution (Cu
1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (2) function.
1) Light source: A copper hollow cathode lamp (In case of background correction system using
continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
Note (2) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 5.00 g of an analytical sample, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.

365

Testing Methods for Fertilizers(2021)

Comment 2 In the procedure in (4.1.1) a), it is also allowed to weigh 2.50 g of the analytical sample
and put it in a 250-mL volumetric flask. In that case, add about 200 mL of water in theprocedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 324.8 nmb) Calibration curve preparation
1) Spray the copper standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 324.8 nm.
2) Prepare a curve for the relationship between the copper concentration and the indicated valueof the copper standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.05 mg - 0.5 mg as Cu)
in a 100-mL volumetric flask.
2) Add about 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the copper content from the calibration curve, and calculate the water-soluble copper(W-Cu).
Comment 5 Recovery testing was conducted to evaluate trueness using a preparation sample (solid).
As a result, the mean recovery rates at the content level of 10 % (mass fraction), 1 %(mass fraction) and 0.03 % (mass fraction) were 100.7 %, 99.4 % and 102.6 % aswater-soluble copper (W-Cu) respectively. In addition, recovery testing was conductedusing a preparation sample (fluid). As a result, the mean recovery rates at the content
level of 1 % (mass fraction), 0.05 % (mass fraction) and 20 mg/kg were 98.8 %, 99.3 %and 101.4 % as water-soluble copper respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a liquid microelement compound fertilizer to evaluate the extract precision of fluid
fertilizers were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 10 mg/kg for solid fertilizers and about 3 mg/kg for fluid fertilizers.
366Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.254- 255, Yokendo, Tokyo (1988)
2)
Shin ABE and Yoshiyuki SUNAGA: Verification of Performance Characteristics ofTesting Methods for Copper in Fertilizer by Atomic Absorption Spectrometry, Research
Report of Fertilizer, Vol. 6, p. 165 - 173 (2013)3)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components in
Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20 (2016)(5)

Flow sheet for water-soluble copper: The flow sheet for water-soluble copper in fertilizers isshown below:
5.00 g analytical sample
500-mL volumetric flask.
(powdery)← Water, About 400 mL
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes
Water
(up
to
the marked line)←
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble copper in fertilizers (Extraction procedure (4.1.1))

367

Testing Methods for Fertilizers(2021)

368

Testing Methods for Fertilizers(2021)

4.10.2.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type B and its symbol is 4.10.2.b-2017 or W-Cu.b-1.
Extract by adding water to an analytical sample, introduce it to an ICP Optical Emission
Spectrometer (ICP-OES) and measure the copper at a wavelength of 327.396 nm, etc. to obtain watersoluble copper (W-Cu) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Copper standard solution (Cu 1 mg/mL): A copper standard solution (Cu 1 mg/mL) traceable
to National Metrology.
d) Copper standard solutions (Cu 0.1 mg/mL) for the calibration curve preparation (1): Put
10 mL of copper standard solution (Cu 1 mg/mL) in 100-mL volumetric flask, and addhydrochloric acid (1+23) to the marked line.
e) Copper standard solutions (Cu 1 µg - 20 µg/mL) for the calibration curve preparation (1):
Put 1 mL - 20 mL of copper standard solution (Cu 0.1 mg/mL) in 100-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) to the marked line.
f) Copper standard solutions (Cu 0.1 µg - 1 µg/mL) for the calibration curve preparation (1):
Put 1 mL - 10 mL of copper standard solution (Cu 10 µg/mL) in 100-mL volumetric flasks stepby-step, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the copper standard solution in (2), a copper standard solution for thecalibration curve preparation can be prepared by using a copper standard solution (Cu
10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
369

Testing Methods for Fertilizers(2021)c)

Filter with Type 3 filter paper to make a sample solution.

Note (2) The sampling amount of the analytical sample is 10 g when the content in the sample isless than 0.01 % (mass fraction) as water-soluble copper.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 327.396 nm, 224.700 nm or 324.754 nm (3)b) Calibration curve preparation
1) Spray the copper standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at an analytical line wavelength.
2) Prepare a curve for the relationship between the copper concentration and the indicated valueof the copper standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Cu)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the copper content from the calibration curve, and calculate the water-soluble copper(W-Cu).
Note (3) 224.700 nm or 324.754 nm can also be used. However, since the intensity of emission
obtained is different from the one of 327.396 nm, it is necessary to understand thesuitable concentration range of the calibration curve and prepare a standard solution forthe calibration curve in advance.
Comment 4 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 5 The comparison of the measurement value (yi：0.00982 % (mass fraction) - 0.0819 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of flame atomic absorbance spectrometry was conducted to evaluate trueness using
fluid fertilizers (12 samples). As a result, a regression equation was y=−0.0006+0.966x,
and its correlation coefficient (r) was 0.999. Additionally, additive recovery testing
was conducted using a fluid compound fertilizer (1 brand) and a home garden-use
compound fertilizer (1 brand). As a result, the mean recovery rates at the additive levelof 0.01 % (mass fraction) and 0.1 % (mass fraction) were 93.5 % and 95.3 %respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
370

Testing Methods for Fertilizers(2021)

and a home garden-use compound fertilizer to evaluate precision were analyzed by the
one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study
implemented for testing method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0005 % (mass fraction).

371

Testing Methods for Fertilizers(2021)

References
1) Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development
Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research
Report of Fertilizer, Vol. 9, p. 1 – 9 (2016)
2) Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 –
145 (2020)(5)

Flow sheet for water-soluble copper: The flow sheet for water-soluble copper in fluid
fertilizers is shown below:372

Testing Methods for Fertilizers(2021)

4.11 Organic carbon and carbon-nitrogen ratio
4.11.1 Organic carbon
4.11.1.a Dichromate oxidation(1) Summary
This test method is applicable to sludge fertilizers and compost, etc. This testing method isclassified as Type C and its symbol is 4.11.1.a-2017 or O-C.a-1.
Add a potassium dichromate-sulfuric acid solution to an analytical sample and heat to oxidizeorganic carbon with potassium dichromate. Quantify unconsumed potassium dichromate byoxidation-reduction titration to obtain organic carbon (O-C). This test method is also referred to as
Tyurin’s method. In addition, the performance of this testing method is shown in Comment 2.
(2) Reagent: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) 0.2 mol/L ammonium iron (II) sulfate solution (1): Weigh 80 g of ammonium iron (II) sulfate
hexahydrate specified in JIS K 8979 into a 2000-mL beaker, and add 1000 mL of sulfuric acid
(1+50) to dissolve.
Standardization: Grind potassium dichromate reference material for volumetric analysis
specified in JIS K 8005 in an agate mortar to powder, heat at 150 ºC ± 2 ºC for 1 hour, let it
stand to cool in a desiccator, and then transfer about 1 g to a weighing dish, and weigh themass to the order of 0.1 mg. Dissolve in a small amount of water, transfer to a 100-mL
volumetric flask, and add water up to the marked line to make the potassium dichromate
standard solution (1) (2). On each day to use a 0.2 mol/L ammonium iron (II) sulfate solution,
put 10 mL of the potassium dichromate standard solution in a 100-mL Erlenmeyer flask, add
about 5 mL of sulfuric acid (1+2), and then conduct the procedures in (4.2) b) - c), andcalculate the factor of a 0.2 mol/L ammonium iron (II) sulfate solution by the following
formula:Factor (f) of 0.2 mol/L ammonium iron (II) sulfate solution= W1 × (A/100) × (6/294.18) × (V1/V2) × (1000/V3)/C= (W1×A/V3) × (30/294.18)
W1： Mass (g) of potassium dichromate weighed
A： Purity (% (mass fraction)) of potassium dichromate
V1： Aliquot volume (10 mL) of potassium dichromate solution
V2： Constant volume (100 mL) of potassium dichromate solution
V3： Volume (mL) of 0.2 mol/L ammonium iron (II) sulfate solution needed for titration
C： Set concentration (0.2 mol/L) of 0.2 mol/L ammonium iron (II) sulfate solutiond) Potassium dichromate-sulfuric acid solution (1): Weigh 40 g of potassium dichromate
specified in JIS K 8517 to a 3000-mL beaker. Add 1000 mL of water to dissolve, and further
add gradually 1000 mL of sulfuric acid while cooling and mixing.
e) N-Phenylanthranilic acid solution: Dissolve 0.2 g of N-phenylanthranilic acid of no lessthan 98 % (mass fraction) in purity and 0.2 g of sodium carbonate specified in JIS K 8625 in asmall amount of water, and add water to make 100 mL.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard potassium dichromate solution (0.2 M (1/6 K2Cr2O7)
solution) in 7.1 B 1) in the Official Methods of Analysis of Fertilizers (1992).
373

Testing Methods for Fertilizers(2021)(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
b) Sample digestion flask (3): A 100-mL borosilicate glass volumetric flask 100 mL (180 mm totalheight, 13 mm mouth diameter)
Note (3) Distinguish the volumetric flask used in digestion as a sample digestion flask and do notuse it for any other purposes.
(4) Test procedure(4.1) Dichromate oxidation: Conduct oxidation as follows:a) Weigh 0.05 g of an analytical sample to the order of 0.1 mg (4), and put it in a sample digestion
flask.
b) Add 25 mL of potassium dichromate-sulfuric acid solution.
c) Heat on a hot plate at 200 ºC until organic matters are completely digested (5).
d) After immediate cooling is complete, precisely adjust to 100 mL with water to make a sample
solution.
e) As a blank test, conduct the procedures in b) and d) using another sample digestion flask to
prepare a blank test solution.
Note (4) Up to about 28 mg as organic carbon (O-C).
(5) Heat for no less than 1 hour after boiling
Comment 1 Sample an analytical sample from a test sample prepared in 2.3.3 Grinding (3.1) bygrinding with a mill until it completely passes through a sieve of 500 µm aperture orfrom a test sample prepared in 2.3.3 Grinding Comment 1.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
a) Put 20 mL of the sample solution in a 100-mL Erlenmeyer flask.
b) Add a 0.2 mol/L ammonium iron (II) sulfate solution drop-by-drop until the brown color ofdichromate ion almost disappears from the sample solution.
c) Add about a 0.25 mL of N-phenylanthranilic acid solution (6), and titrate with a 0.2 mol/Lammonium iron (II) sulfate solution until the color of the solution changes from dark red-purple
to blue-green.
d) Put 20 mL of the blank test solution in a 100-mL Erlenmeyer flask, and conduct the proceduresin b) - c) to titrate.
e) Calculate the organic carbon (O-C) in the analytical sample by the following formula:
Organic carbon (% (mass fraction)) in the analytical sample= (V4－V5) × C × f × (12.011/4)/W2× (100/1000) × (V6/ V7)= (V4－V5) × f × (12.011/40)/W2
V4： Volume (mL) of 0.2 mol/L ammonium iron (II) sulfate solution needed for thetitration of the blank test solution
V5： Volume (mL) of 0.2 mol/L ammonium iron (II) sulfate solution needed for thetitration of the sample solution
C： Set concentration (0.2 mol/L) of 0.2 mol/L ammonium iron (II) sulfate solution
f： Factor of 0.2 mol/L ammonium iron (II) sulfate solution
V6： Constant volume (100 mL) of the sample solution and the blank test solutionin (4.1) d)374

Testing Methods for Fertilizers(2021)

V7： Aliquot volume (20 mL) of the sample solution and the blank test solution
subjected to titration in (4.2) a) and (4.2) d)
W2： Mass (g) of the analytical sample
Note (6) About 5 drops with a 1-mL - 2-mL Komagome pipette. Add the same volume to thesample solution and the blank test solution.
Comment 2 The results of the collaborative study to determine a certified reference material
fertilizer were analyzed using a three-level nesting analysis of variance. Table 1 shows
the calculation results of reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 1.5 % (mass fraction).

References
1) Yuji SHIRAI, Yuko SEKINE, and Toshiaki HIROI: Validation of Determination Method for
Organic Form Carbon in Sludge Fertilizer and Compost, Research Report of Fertilizer, Vol.
3, p. 117 - 122 (2010)375

Testing Methods for Fertilizers(2021)(5)

Flow sheet for organic carbon: The flow sheet for organic carbon in sludge fertilizers andcompost, etc. is shown below:376

Testing Methods for Fertilizers(2021)

4.11.1.b Combustion method(1) Summary
This testing method is applicable to compost and sludge fertilizers. This testing method is classified
as Type B and its symbol is 4.11.1.b-2017 or O-C.b-1.
Add hydrochloric acid (1+3) drop by drop to an analytical sample and evaporate inorganic carbon as
carbon dioxide, then thermally decompose carbon compounds using a total nitrogen-total carbon
analyzer by the combustion method to measure carbon dioxide gas with a thermal conductivity
detector and obtain organic carbon (O-C) in an analytical sample. In addition, the performance of thistesting method is shown in Comment 4.
(2) Reagent: Reagents are as shown below.
a) Sea sand: Particle diameter 425 µm - 850 µmb) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
Comment 1 Sea sand (particle diameter 425 µm - 850 µm) is commercially sold by FUJIFILM
Wako Pure Chemical Co., Ltd. and YONEYAMA YAKUHIN KOGYO Co., Ltd.
(3) Instruments: Instruments are as shown below:a) Total nitrogen-total carbon analyzer by the combustion method: A total nitrogen-total
carbon analyzer configured on the basis of the principle of the combustion method (modified
Dumas’ method).
1) Turn on the total nitrogen-total carbon analyzer by the combustion method (1), and adjust so thatstable indicated values can be obtained.
(i) Combustion gas: Oxygen having purity no less than 99.99 % (volume percentage)(ii) Carrier gas: Helium having purity no less than 99.99 % (volume percentage)b) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
c) Drying apparatus: A drying apparatus that can be adjusted to 105 ºC ± 2 ºC.
Note (1) The setup of the program and the parameters of the analyzer are according to thespecification and the operation method of the total nitrogen-total carbon analyzer by the
combustion method used.
(4)

Test procedures: Conduct measurement as shown below. However, confirm that there is nodifference from the measured value of organic carbon obtained in advance according to 4.11.1.a
by using an analytical sample.

(4.1) Hydrochloric acid treatmenta) Weigh 0.05 g of an analytical sample to the order of 0.1 mg, and put it in a container for
combustion.
b) Cover the analytical sample with about 0.2 g of sea sand and add a few drops of water drop bydrop to moisten the analytical sample.
c) After adding 0.5 mL - 0.7 mL of hydrochloric acid (1+3) little by little (2), add about 0.3 mL ofwater drop by drop (3) (4).
d) Heat a container for combustion on a hot plate at 100 ºC for 90 minutes to exsiccate it.
e) Put the container for combustion at 105 °C ± 2 °C into a drying apparatus and heat for 30
minutes (5).
f) After heating, let it stand to cool to make a sample for measurement.
Note (2) The additive amount of hydrochloric acid (1+3) is merely a target. It is enough to makethe whole analytical sample come into contact with hydrochloric acid. Let it stand for a377

Testing Methods for Fertilizers(2021)

short time in the case of producing bubbles.
(3) In some cases, it is not necessary to add water due to the capacity of a container.
(4) Shake calmly the container for combustion to make the analytical sample come into
complete contact with hydrochloric acid.
(5) Remove hydrochloric acid completely
Comment 2 Sample an analytical sample from a test sample prepared in 2.3.3 Grinding (3.1) bygrinding with a mill until it completely passes through a sieve of 500 µm aperture orfrom a test sample prepared in 2.3.3 Grinding Comment 1.
Comment 3 When it is confirmed that, for example, the volatilization of hydrogen chloride is notdetected by using a test paper, etc. and hydrochloric is completely removed in theprocedure d), the procedure e) can be skipped.
(4.2) Measurement: Specific measurement procedures are according to the operation method of a
total nitrogen-total carbon analyzer by the combustion method.
a) Measurement conditions for the total nitrogen-total carbon analyzer by the combustion
method: Set up the measurement conditions for the total nitrogen-total carbon analyzer
considering the following:
Combustion temperature: No less than 870 ºCb) Calibration curve preparation
1) Turn on the total nitrogen-total carbon analyzer by the combustion method (1), and adjust so thatstable indicated values can be obtained.
2) Weigh a predetermined amount of the standard for calibration curves (6) to the order of 0.1 mg
into a combustion vessel.
3) Insert the combustion vessel into the total nitrogen-total carbon analyzer by the combustion
method, and read the indicated value.
4) Conduct the procedure in 3) for another combustion vessel for a blank test, and read theindicated value.
5) Prepare a curve for the relationship between the carbon content and the indicated value of thestandard for calibration curves and the blank test for calibration curves.
c) Sample measurement
1) Insert the combustion vessel containing the sample for measurement to the total nitrogen-total
carbon analyzer by the combustion method, and read the indicated value.
2) Obtain the carbon content from the calibration curve, and calculate organic carbon in theanalytical sample.
Note (6) Standard for calibration curves: DL-Aspartic acid (purity no less than 99 % (massfraction)), EDTA (purity no less than 99 % (mass fraction)), hippuric acid (purity no lessthan 98 % (mass fraction)) or other reagents having equivalent purity recommended by
the total nitrogen-total carbon analyzer by the combustion method used.
Comment 4 The comparison of the measurement value (yi：0.21 % (mass fraction) - 45.40 % (massfraction)) of Combustion method and the measurement value (xi) of Dichromate
oxidation was conducted to evaluate trueness using sludge fertilizers and compost(total 25 samples). As a result, a regression equation was y=0.004+1.009x and its
correlation coefficient (r) were 0.999.
Results from a collaborative study for test method validation and its analysis are shownin Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.05 % (mass fraction).
378

Testing Methods for Fertilizers(2021)

References
1)
Aiko YANO, Satono AKIMOTO, and Yuji SHIRAI: Determination of Organic Carbon in
Sludge Fertilizer and Compost by Hydrochloric Acid-Treated Combustion Method,
Research Report of Fertilizer, Vol. 6, p. 9 - 19 (2013)
2)
Aiko YANO and Yuji SHIRAI: Determination of Organic Carbon in Sludge Fertilizer andCompost by Hydrochloric Acid-Treated Combustion Method: A Collaborative Study,
Research Report of Fertilizer, Vol. 7, p. 22 - 27 (2014)(4)

Flow sheet for organic carbon: The flow sheet for organic carbon in sludge fertilizers andcompos is shown below:379

Testing Methods for Fertilizers(2021)

Reference: Chromatograms of the standard for calibration curves and an analytical sample areshown below:

1) Total carbon in a standard for calibration curve (DL-Aspartic acid)2) Total carbon in an analytical sample (sludge fertilizer)
Reference figures:

Chromatograms of organic carbon.

Measurement conditions for total nitrogen-total carbon analyzer by the combustion
methodCombustion gas: Highly pure oxygen, purity no less than 99.99995 % (volume
fraction), flow rate 200 mL/min
Carrier gas: Highly pure helium, purity no less than 99.9999 % (volume fraction),flow rate 80 mL/min
Separation column: A silica gel stainless column (length 1m)
Detector: Thermal conductivity detector (TCD)
Measurement cycle: Purge time = 60 seconds, circulation combustion time = 300
seconds, measurement time = 270 seconds
Current value of Detector: 160 mA
Temperature conditions: Reaction furnace temperature: 870 ºC
Reaction furnace temperature: 600 °C
Column oven temperature: 70 °C
Detector temperature: 100 °C
380

Testing Methods for Fertilizers(2021)

4.11.2 Carbon-nitrogen ratio
4.11.2.a Calculation with organic carbon and total nitrogen(1) Summary
This test method is applicable to compost and sludge fertilizers. This testing method is classified as
Type A (Def-C) and its symbol is 4.11.2.a-2017 or C/N.a-1.
Calculate carbon-nitrogen ratio (CN ratio) by dividing the organic carbon obtained in 4.11.1 by the
total nitrogen obtained in 4.1.1.
(2) The calculation of carbon-nitrogen ratioa) Calculate the carbon-nitrogen ratio (CN ratio) in an analytical sample by the following formula:
Carbon-nitrogen ratio in an analytical sample= O-C/T-N
Organic carbon (% (mass fraction)) (1) in the analytical sample obtained in
4.11.1
T-N： Total nitrogen (% (mass fraction)) (1) in the analytical sample obtained in
4.1.1
O-C：

Note (1) O-C and T-N use raw data without rounding numerical value381

Testing Methods for Fertilizers(2021)

4.12 Sulfur
4.12.1 Total sulfur content
4.12.1.a Potassium permanganate analysis(1) Summary
This testing method is applicable to fertilizers mainly containing ferrous sulfate (iron (II) sulfate)(FeSO4)) among sulfur and its compound. This testing method is classified as Type D and its symbol
is 4.12.1.a-2017 or T-S.a-1.
Dissolve an analytical sample in water and diluted sulfuric acid, add phosphoric acid and then titrate
ferrous sulfate (iron (II) sulfate) (FeSO4)) by oxidation-reduction with a potassium permanganate
solution to obtain the total sulfate (T-SO3). In addition, the performance of this testing method isshown in Comment 1.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
c) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
d) 0.02 mol/L potassium permanganate solution: Dissolve 3.16 g of potassium permanganate
specified in JIS K 8247 in about 800 mL of water to boil and add water to make 1000 mL andleave at rest 1 - 2 day(s). Further filter with a funnel type glass filter (G4) and store in a coloredbottle. Or, a reagent of equivalent quality (volumetric analysis grade) that is commerciallyavailable.
Standardization: Dry sodium oxalate of reference materials for volumetric analysis specified in
JIS K 8005 at 200 ºC for 1 hour and let it stand to cool in a desiccator, and then put about 0.3
g into a weighing dish to measure the mass to the order of 0.1 mg. Add about 250 mL of
sulfuric acid (1+20) cooled down to 25 ºC - 30 ºC after boiling and dissolve. Add about 40
mL of 0.02 mol/L potassium permanganate solution while gently shaking for about 1 minute.
Heat up to 55 ºC - 60 ºC after the red color of a potassium permanganate solution disappears.
Titrate with a 0.02 mol/L potassium permanganate solution while keeping the temperature andcontinue titrating until the color of the solution becomes light red (1). Calculate the factor of a0.02 potassium permanganate solution by the following formula.
Factor (f) of 0.02 mol/L potassium permanganate solution= W1 × (A/100) × ((2/5)/133.999) × ((1000/V1)/C)= W1 × (A/V1) × 1.4925
W1： Mass (g) of sodium oxalate sampled
A： Purity (% (mass fraction)) of sodium oxalate sampled
V1： Volume (mL) of 0.02 mol/L potassium permanganate needed for titration
C： 0.02 mol/L potassium permanganate solution
Note (1) The endpoint is reached when the color of solution keeps as it is for 30 seconds aftercoloring(3) Instruments: Instruments are as shown below:a) Magnetic stirrer(4) Test procedure(4.1) Measurement: Conduct measurement as shown below.
382

Testing Methods for Fertilizers(2021)a) Weigh 0.5 g - 1 g of an analytical sample to the order of 0.1 mg, and put it in a 200-mL tallbeaker.
b) Add about 50 mL of water and about 15 mL of sulfuric acid (1+5) and shake with a magnetic
stirrer to dissolve.
c) Immediately add about 1 mL of phosphate, and then titrate with a 0.02 mol/L potassium
permanganate solution until the color of the solution becomes light red (2).
d) As a blank test, conduct the procedures in b) - c) using another 200-mL tall beaker to titrate (2).
e) Calculate the total sulfur content (T-SO3) in an analytical sample by the following formula.
Total sulfur content (% (mass fraction)) = (5 × 0.02 × f × (V2−V3)/1000×80.064)/W2×100= (f × (V2−V3))/W2 × 0.80064
W2： Mass (g) of the sampled analytical sample
V2： Volume (mL) of 0.02 mol/L potassium permanganate needed for titration
V3： Volume (mL) of 0.02 mol/L potassium permanganate needed for titration
f ： Factor of 0.02 mol/L potassium permanganate solution
Note (2) Titrate using a brown burette.
Comment 1 Recovery testing was conducted using a reagent (ferrous sulfate heptahydrate); as aresult, the mean recovery rate was 29.1 % (mass fraction) as total sulfate content (TSO3). The recovery rate to a theoretical value was 101.0 %.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.04 % (mass fraction).
References
1)
Yasushi SUGIMURA and Shinjiro IZUKA: Method validation of Redox Titration for
Determination of Sulfur content (as sulfur trioxide) in Fertilizers of Ferrous sulfate andits mixture materials, Research Report of Fertilizer, Vol. 3, 25 - 29 (2010).
2) JIS K 8978： Iron (II) sulfate heptahydrate (Reagent) (2008)(5)

Flow sheet for total sulfur content: The flow sheet for total sulfur content in fertilizers mainlycontaining ferrous sulfate is shown below.

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Testing Methods for Fertilizers(2021)

4.12.1.b Barium chloride gravimetric analysis(1) Summary
This test method is applicable to fertilizers mainly containing sulfur or sulfuric acid among sulfur andits compound. This testing method is classified as Type B and its symbol is 4.12.1.b-2017 or T-S.b-1.
Dissolve an analytical sample in a potassium hydroxide-ethanol solution and add hydrogen peroxide
to oxidize, and measure the mass of barium sulfate (BaSO4) formed by reaction with barium chloride
to obtain the total sulfate content (T-SO3). In addition, the performance of this testing method is shownin Comment 1.
(2) Reagent: Reagents are as shown below.
a) Potassium hydroxide/ethanol solution: Dissolve 10 g of potassium hydroxide specified in JIS
K 8574 in 50 mL of ethanol (95) specified in JIS K 8102, further add 50 mL of water.
b) Hydrogen peroxide: A JIS Guaranteed Reagent (30 % (mass fraction)) specified in JIS K 8230
or a reagent of equivalent quality.
c) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
d) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K 8541
or a reagent of equivalent quality.
e) Barium chloride solution (1): Dissolve 100 g of barium chloride dihydrate specified in JIS K
8155 in water to make 1000 mL.
f) Silver nitrate solution (2 g/100mL): Dissolve 2 g of silver nitrate specified in JIS K 8550 inwater to make 100 mL.
g) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
b) Water bath: Water bath that can be adjusted to 80 ºC - 90 ºC.
c) Crucible: After heating porcelain crucible or platinum crucible in an electric furnace at 800 ºC
in advance, let it stand to cool in a desiccator and measure the mass to the order of 0.1 mg.
d) Drying apparatus: Drying apparatus that can be adjusted to 110 ºC - 120 ºC.
e) Electric furnace: An electric furnace that can be kept at 800 ºC ± 5 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as follows (2):a) Weigh 1 g - 5 g of an analytical sample to the order of 0.1 mg, and put it in a 200-mL tall beaker.
b) Add about 50 mL of potassium hydroxide/ethanol solution, cover with a watch glass and heaton a hot plate to boil (3).
c) After standing to cool, transfer to a 250-mL volumetric flask with water and add water up to themarked line.
d) Filter with Type 3 filter paper (4) to make a sample solution.
Note (2) Omit extraction if fluid fertilizers are made from only sulfuric acid and all materials are
dissolved(3) Until sulfur content is dissolved. About 5 minutes when raw materials, etc. are notdissolved.
(4) Omit the procedures in d) when all materials are dissolved.
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Testing Methods for Fertilizers(2021)(4.2) Measurement: Conduct measurement as shown below.
a) Put a predetermined volume (the equivalents of 30 mg - 170 mg as SO3) of sample solution in
a 300-mL tall beaker. (5)b) Add about 50 mL of water and about 5 mL of hydrogen peroxide and heat in a water bath at 80ºC - 90 ºC for about 1 hour while sometimes shaking (6).
c) After standing cool, add 1 - 2 drop(s) of phenolphthalein solution (1 g/100 mL) (7), and addhydrochloric acid (2+1) until the color of the solution disappears (8).
d) Further add hydrochloric acid (2+1), add water to make about 100 mL and boil on a hotplate
for about 5 minutes.
e) Immediately add about 6 mL of thermal barium chloride solution (9) while sometimes shaking
in a water bath at 80 ºC - 90 ºC (10).
f) After leaving at rest for a few minutes (11), add a few drops of thermal barium chloride solution
and check that new precipitate of barium sulfate is no longer formed.
g) Further add about 2 mL of thermal barium chloride solution (100 g/L) while shaking to mix (12).
h) After heating in a water bath at 80 ºC - 90 ºC for about 2 hours, stop the heat source of water
bath and let it stand to cool for no less than 4 hours. (6)i) Filter with filter paper (Type 5 - C), wash a container with water and transfer the whole
precipitate to a filter paper.
j) Wash the precipitate and the filter paper (Type 5 - C) with water several times (13).
k) Put the precipitate together with the filter paper into the crucible.
l) Put the crucible into a drying apparatus and dry at about 110 ºC - 120 ºC for 1 hour.
m) After standing to cool, put the crucible into an electric funnel and heat gently to char (14).
n) Ignite at about 800 ºC ± 5 ºC for 2 hours (14).
o) After ignition (15), move the crucible to a desiccator and let it stand to cool (16).
p) Measure the mass of crucible to the order of 0.1 mg.
q) Calculate the total sulfur content (T-SO3) in an analytical sample by the following formula.
Total sulfur content (% (mass fraction)) = (A × 0.343)/ (W × V2/V1) × 100= 34.3 × A × V1/(W×V2)
A：
W：
V1：
V2：

Mass (g) of the precipitate in p)
Mass (g) of the analytical sample
Constant volume (mL) of sample solution
Volume (mL) of sample solution transferred

Note (5)Weigh 1g - 5g of an analytical sample to the order of 0.1 mg if the fluid fertilizers of theanalytical sample are made from only sulfuric acid and all materials are dissolved.
(6) It can be suspended after the procedures end.
(7) A pH meter can be used for neutralization.
(8) Omit the procedures in c) if fluid fertilizers are made from only sulfuric acid and allmaterials are dissolved.
(9) Heated up to 70 ºC - 80 ºC in a water bath in advance.
(10) Add drop-by-drop.
(11) Until precipitate settles.
(12) Add a barium chloride solution slightly excessively to reduce the solubility of barium
sulfate.
(13) Wash the precipitate until a white turbidity is no longer formed when about 5 mL ofnitric acid (1+2) and about 1 mL of silver nitrate solution (2 g/100 mL) are added toabout 20 mL of washing.
(14) Example of charring and incineration procedure: After raising the temperature from385

Testing Methods for Fertilizers(2021)

room temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 800 °C in 1 to 2 hours.
(15) To prevent a crucible from chipping, it is recommended to let it stand to cool gently inan electric furnace until the temperature of an electric furnace falls to no more than 200ºC.
(16) Time to let it stand to cool in a desiccator should be constant. In the case of a porcelain
crucible, it is about 45 - 60 minutes.
Comment 1 Testing was conducted using sulfur simple substance fertilizers containing no materials(2 samples); as a result, the quantitative value of the total sulfur content (T-SO3) was
99.9 % - 100.1 % to a theoretical value.
Results from a collaborative study for test method validation and its analysis are shownin Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.4 % (mass fraction).

References
1) JIS K 8088： Sulfur (Regent) (2010)
2) JIS K 8217： Iron ores - Methods for determination of sulfur content (1994)
3) Edited by KANTO CHEMICAL CO., INC.: Technique on Chemical Analysis of Regent- Practical Basic Technique and Knowledge, p. 112 - 120 (2009)4) Yasushi SUGIMURA Validation of Gravimetric Analysis for Determination of Sulfur
Content (as Sulfur Trioxide) in Sulfur and its Compounds as Fertilizers, Research Reportof Fertilizer, Vol. 4, P. 9 - 15 (2011)5) Shin ABE, Chika SUZUKI and Yuji SHIRAI: Testing Method of the Total Amount of
Sulfur Content (as Sulfur Trioxide): A Collaborative Study, Research Report of Fertilizer,
Vol. 7, p. 28 - 35 (2014)386

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total sulfur content: The flow sheet for total sulfur content in fertilizers mainlycontaining sulfur and sulfuric acid is shown below.

387

Testing Methods for Fertilizers(2021)

388

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4.12.1.c Transmitted light analysis(1) Summary
This test method is applicable to fertilizers mainly containing sulfur or sulfuric acid among sulfur andits compound. This testing method is classified as Type D and its symbol is 4.12.1.c-2017 or T-S.c-1.
Dissolve an analytical sample in a potassium hydroxide-ethanol solution and add hydrogen peroxide
to oxidize, and then measure the intensity of transmitted light of suspension of barium sulfate (BaSO4)
formed by the reaction with barium chloride as the absorbance to obtain total sulfur content (T-SO3)
in an analytical sample. In addition, the performance of this testing method is shown in Comment 2.
(2) Reagent, etc.: Reagents are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Potassium hydroxide/ethanol solution: Dissolve 10 g of potassium hydroxide specified in JIS
K 8574 in 50 mL of ethanol (95) specified in JIS K 8102, further add 50 mL of water.
c) Hydrogen peroxide: A JIS Guaranteed Reagent (H2O2 30 % (mass fraction)) specified in JIS
K 8230 or a reagent of equivalent quality.
d) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
e) Glycerin – ethanol solution (1+1): Add 250 mL of ethanol (95) specified in JIS K 8102 to 250
mL of glycerin specified in JIS K 8295.
f) Sodium chloride solution (1): Dilute 240 g of sodium chloride specified on JIS K 8150 in watercontaining 20 mL of hydrochloric acid specified in JIS K 8180, further add water to make 1000mL.
g) Barium chloride solution: Sieve barium chloride dihydrate specified in JIS K 8155 to makebarium chloride whose particle size is between 500 μm - 710 μm.
h) Sulfate standard solution (SO3 2 mg/mL) (1): Heat potassium sulfate specified in JIS K 8962
until it becomes constant weight value at 800 ºC in advance, stand to cool it in a desiccator, andthen transfer 4.3531 g to a weighing dish. Dissolve in a small amount of water, transfer to a
1000-mL volumetric flask, and add water up to the marked line.
i) Sulfate standard solution (SO3 0.02 mg/mL - 0.1 mg/mL): Put 2mL - 10 mL of sulfate
standard solution (SO3 2 mg/mL) in 200-mL volumetric flasks step by step and add water up to
the marked line.
j) Phenolphthalein solution (1 g/100 mL): Dissolve 1 g of phenolphthalein specified in JIS K
8799 in 100 mL of ethanol (95) specified in JIS K 8102.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3)
a)
b)
c)
d)

Apparatus and instruments: Apparatus and instruments are shown below.
Hot plate: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Water bath: Water bath that can be adjusted to 30 ºC ± 2 °C and 80 ºC - 90 ºC.
Magnetic stirrer
Spectrophotometer: A spectrophotometer specified in JIS K 0115

(4) Test procedure(4.1) Extraction: Conduct extraction as follows (2):a) Weigh 1 g - 2 g of an analytical sample to the order of 0.1 mg, and put it in a 200-mL tall beaker.
b) Add about 50 mL of potassium hydroxide/ethanol solution, cover with a watch glass and heaton a hot plate to boil (3).
c) After standing to cool, transfer to a 250-mL volumetric flask with water and add water up to
the marked line.
d) Filter with Type 3 filter paper (4) to make an extract.
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Testing Methods for Fertilizers(2021)

Note (2) Omit extraction if fluid fertilizers are made from only sulfuric acid and all materials are
dissolved(3) Until sulfur content is dissolved. About 5 minutes when raw materials, etc. are notdissolved.
(4) Omit the procedures in d) when all materials are dissolved.
(4.2) Oxidation: Conduct oxidation as follows:a) Put a predetermined volume (the equivalents of 5 mg - 200 mg as SO3) of sample solution in a
300-mL tall beaker (5).
b) Add about 50 mL of water and about 5 mL of hydrogen peroxide and heat in a water bath at 80ºC - 90 ºC for about 1 hour while sometimes shaking (6).
c) After standing cool, add 1 - 2 drop(s) of phenolphthalein solution (1 g/100 mL) (7), and addhydrochloric acid (2+1) until the color of the solution disappears (8).
d) After standing to cool, transfer to a 200-mL volumetric flask with water and add water up to
the marked line.
e) Filter with 0.3μm glass filter paper.
Note (5) Weigh 1g - 5g of an analytical sample to the order of 0.1 mg if the fluid fertilizers of theanalytical sample are made from only sulfuric acid and all materials are dissolved.
(6) It can be suspended after the procedures end.
(7) A pH meter can be used for neutralization.
(8) Omit the procedures in c) if fluid fertilizers are made from only sulfuric acid and allmaterials are dissolved.
(4.3)
Precipitate formation: Form precipitate as shown below.
a) Put 50 mL of filtrate in a 100-mL Erlenmeyer flask with screw cap.
b) Add about 10 mL of glycerin – ethanol solution (1+1) and about 5 mL of sodium chloride
solution in the Erlenmeyer flask with screw cap.
c) Warm up on a water bath at 30ºC ± 2 ºC.
d) After warming, add 0.30 g of barium chloride and stir with a magnetic stirrer for about 2
minutes.
e) Warm up on a water bath at 30ºC ± 2 ºC for about 4 minutes.
f) After warming, stir with a magnetic stirrer for about 3 minutes to make a sample solution.
g) As a blank test, conduct the procedures in a) - c) and f) using another 100-mL Erlenmeyer flaskwith screw cap to prepare a blank test solution.
(4.4) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 450 nmb) Calibration curve preparation
1) Put 50 mL of sulfate standard solution (SO3 0.02 mg/mL - 0.1 mg/mL) in a 100-mL Erlenmeyer
flask with screw cap and conduct the procedure (4.3) b) - f) to make an SO3 1 mg/65 mL - 5
mg/65 mL sulfate standard solution for the calibration curve preparation.
2) Put 50 mL of water in another 100-mL Erlenmeyer flask with screw cap and conduct the sameprocedures as 1) to make a blank test solution for the calibration curve preparation.
3) Measure absorbance at a wavelength of 450 nm of the sulfuric acid standard solutions for the390

Testing Methods for Fertilizers(2021)

calibration curve preparation using the blank test solution for the calibration curve preparation
as the control (8) (9).
4) Prepare the calibration curve of the sulfuric acid concentration and absorbance of the sulfuric
acid standard solutions for the calibration curve preparation.
c) Sample measurement
1) For the sample solution, conduct procedures similarly as in b) 3) to measure absorbance.
2) For the blank test solution, conduct procedures similarly as in 1) to measure absorbance, andcorrect the absorbance obtained for the sample solution.
3) Obtain the sulfate (SO3) content from the calibration curve, and calculate the total sulfur content(T-SO3) in the analytical sample.
Note (8) Measure right after stirring because barium sulfate easily precipitates.
(9) A spectrophotometer with automatic sample introducing device is preferable.
Comment 1 The range of calibration curve with linearity is SO3 1 mg/65 mL - 5 mg/65 mL and thecurve does not pass through the origin.
Comment 2 Testing was conducted using sulfur simple substance fertilizers containing no materials(2 samples); as a result, the quantitative value of the total sulfur content (T-SO3) was
98.4 % - 99.4 % to a theoretical value.
Note that the minimum limit of quantification of this testing method was estimated to
be about 1 % (mass fraction).
References
1) JIS K 8001： General rule for test methods of reagents (2009)
2) JIS K 8088： Sulfur (Regent) (2010)
3) JAPAN Sewage Works Association: Sewage Sludge Analysis -2007-, p. 132 - 134 Tokyo(2007)
4) Edited by KANTO CHEMICAL CO., INC.: Technique on Chemical Analysis of Regent Practical Basic Technique and Knowledge, p. 131 - 135 (2009)5) Yasushi SUGIMURA: Method Validation of Turbidimetry for Determination of Sulfur
Content (as Sulfur Trioxide) in Fertilizers of Sulfur, Sulfuric acid and Its Mixture, Research
Report of Fertilizer Vol. 6, p. 20 - 26 (2013)

391

Testing Methods for Fertilizers(2021)(5)

Flow sheet for total sulfur content: The flow sheet for total sulfur content in fertilizers mainlycontaining sulfur and sulfuric acid is shown below.

392

Testing Methods for Fertilizers(2021)

393

Testing Methods for Fertilizers(2021)

4.12.2 Acid-soluble sulfur
4.12.2.a Ion Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 4.12.2.a-2021 or S-S.a-2.
Add hydrochloric acid (1+23) to an analytical sample to extract sulfate ions, introduce them to an
Ion Chromatograph (IC) to isolate it with an ion exchange column, and then measure with an electric
conductivity detector to obtain the sulfate ion (SO42-) content in an analytical sample and calculate
acid-soluble sulfur (S-S). Note that the performance of this testing method is shown in Comment 6.
Examples of columns to be used, measurement conditions, and IC chromatograms are shown inAnnex D.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Sodium carbonate: A JIS Guaranteed Reagent specified in JIS K 8625 or a reagent ofequivalent quality.
c) Sodium hydrogencarbonate: A JIS Guaranteed Reagent specified in JIS K 8622 or a reagentof equivalent quality.
d) Eluent (1): Prepare an eluent with a composition suitable for the column to be used. If it is used
for the eluent of ion chromatograph, filter with a membrane filter (pore size: no more than 0.5µm) made of hydrophilic PTFE.
e) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
f) Sulfate ion standard solution (SO42- 1000 mg/L): A sulfate ion standard solution (SO42- 1000mg/L) traceable to National Metrology.
g) Sulfate ion standard solution (SO42- 50 µg/mL) (1): Put a predetermined amount of sulfate ion
standard solution (SO42- 1000 mg/mL) in a volumetric flask and add water up to the markedline.
h) Sulfate ion standard solution (SO42- 2 µg/mL - 5 µg/mL) for the calibration curve
preparation (1): Put 4 mL – 10 mL of sulfate ion standard solution (SO42- 50 µg/mL) in 100mL volumetric flasks step-by-step and add water up to the marked line.
i) Sulfate ion standard solution (SO42- 0.2 µg/mL - 1 µg/mL) for the calibration curve
preparation (1): Put 4 mL – 20 mL of sulfate ion standard solution for the calibration curve
preparation (SO42- 5 µg/mL) in 100-mL volumetric flasks step-by-step and add water up to themarked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Carbonate buffer solution and hydroxide solution are available as an eluent. A
carbonate buffer solution prepared by dissolving 0.191 g of sodium carbonate and
0.143 g of sodium hydrogencarbonate in water in a 1000-mL volumetric flask andadding water to the marked line has pH of approximately 10. One thousand mL of thiscarbonate buffer solution contains 1.8 mmol of sodium carbonate and 1.7 mmol of
sodium hydrogencarbonate.
It is also possible to make an eluent using an automated eluent generation system.
Stock solutions used for such systems are sold under the production name EGC-KOH,
etc.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 200-mL
ground-in stopper Erlenmeyer flask to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
394

Testing Methods for Fertilizers(2021)b) Centrifugal separator: A centrifugal separator that can work at 1700 × g.
c) Ion Chromatograph: An ion chromatograph specified in JIS K 0127 that satisfies thefollowing requirements.
1) Column: A no less than 4.0-mm inner diameter 7.5-mm long 3.5-μm particle diametercolumn tube filled with polymer particles, to which quaternary ammonium groups, quaternary
alkylamines or quaternary alkanolamines bond (3).
2) Column bath3) Suppressor: Cation exchange membrane or resin should be used.
4) Detection unit: An electric conductivity detector.
d) Membrane filters: Pore size is no more than 0.45 μm, made of hydrophilic PTFE
Comment 2 A column for which a carbonate buffer solution is used as the eluent is sold under the
production name Shodex IC SI-90 4E, TSKgel SuperIC-Anion HS, PCI-205, IonPac
AS22, Shim-pack IC-SA2, etc., and a column for which a hydroxide solution is usedas the eluent is sold under the production name IonPac AS20, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200-mL ground-in stopper Erlenmeyer
flask.
b) Add about 100 mL of hydrochloric acid (1+23) and shake to mix by using a vertical
reciprocating shaker at a rate of about 300 reciprocations/min (amplitude of 40 mm) for about
10 minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube (2).
d) Centrifuge it at about 1700 × g centrifugal force for about 10 minutes (3), and use the supernatant
as an extract.
e) Get a predetermined amount of the extract, and dilute by a factor of 100 with the eluent or water(4) (5).
f) Filter with a membrane filter (pore size: no more than 0.45 μm) to make a sample solution.
Note (2) The vessel should be made of polypropylene, etc. to not affect the measurement.
(3) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4) In case of exceeding the calibration curve, dilute by a factor of more than 100.
(5) Confirm in advance that the sample solution is within the pH range applicable to thecolumn.
Comment 3 An applicable pH range is limited for columns for which a carbonate buffer solution
is used as the eluent, and it is desirable to dilute using the eluent in the procedure in(4.1) e).
Comment 4 Instead of the procedures in (4.1) f), it is allowed to put the diluted solution in a 1.5mL ground-in stopper centrifugal precipitate tube (4), and centrifuge at 8000 × g 10000 × g for about 5 minutes to make the supernatant as a sample solution.
(4.2) Measurement: Conduct the measurement by using suppressor method as indicated in JIS K
0127 and as shown below. Specific measurement procedures are according to the operation
method of the ion chromatograph used in measurement.
a) Measurement conditions for Ion Chromatograph: Example measurement conditions areshown in Table 1 of Annex D. Set the actual measurement conditions suitable for the
instruments, column, etc. to be used for the items below referencing Annex D.
1) Column: An ion exchange column filled with polymer particles to which quaternary395

Testing Methods for Fertilizers(2021)

ammonium groups, quaternary alkylamines or quaternary alkanolamines bond.
2) Column bath temperature: 25 °C～40 °C
3) Eluent: Carbonate buffer solution or hydroxide solution4) Flow rate: 0.8～1.5 mL/min
5) Detection unit: An electric conductivity detector
Comment 5 Set the column bath temperature, eluent, flow rate, injection volume, etc. according to
the performance of the column to be used.
b) Calibration curve preparation
1) Inject 20 μL (6) of respective standard solutions for the calibration curve preparation to the ion
chromatograph, and record the chromatogram of electric conductivity to obtain a peak area or
peak height.
2) Prepare a curve for the relationship between the concentration and the peak area or peak heightof electric conductivity of respective standard solutions for the calibration curve preparation (7).
Prepare a calibration curve when the sample is measured.
Note(6) Change the injection volume according to the performance of the column to be used.

c) Sample measurement
1) Subject 20 μL of the sample solution to the same procedure as in b) 1).
2) Obtain a sulfate ion concentration from the calibration curve by the peak area or peak height tocalculate the sulfate ion (SO42-) in the analytical sample (7).
3) Calculate acid-soluble sulfur (S-S) by the following formula.
Acid-soluble sulfur (S-S) (% (mass fraction)) in an analytical sample＝A×(MW1/MW2)＝A×0.3338
A： Sulfate ion (SO42-) (% (mass fraction)) in the analytical sample
MW1： Atomic weight of sulfur (32.066)
MW2： Molecular weight of sulfate ion (96.063)
Note (7) As for potassium humic acid fertilizers and fertilizers containing potassium humic acid,their peak form sometimes changes depending on the measurement conditions.
Therefore, it should be calculated by a peak height.
Comment 6 The comparison of the analysis value (yi: 3.90 % (mass fraction) - 73.09% (massfraction)) of this method (6.10.1.a-2021) where extraction is performed usinghydrochloric acid (1+23) and the analysis value (xi) of 6.10.1.a Ion Chromatographyof the Testing Methods for Fertilizers (2020) was conducted to evaluate trueness using
ammonium sulfate (1 sample), guanylurea sulfate (1 sample), superphosphate of lime
(1 sample), double superphosphate of lime (1 sample), potassium sulfate (1 sample),compound fertilizer (1 sample), magnesia sulfate fertilizer (2 samples), humic acidmagnesia fertilizer (1 sample), mixed magnesia fertilizer (1 sample), manganese
sulfate fertilizer (1 sample), designated blended fertilizer (1 sample), gypsum (1sample), and 10 % preparation sample (1 sample). As a result, a regression equation
was y = 1.001x + 0.423, and its correlation coefficient (r) was 0.999.
The results of repeated experiments using potassium sulfate and double
superphosphate of lime were analyzed by the one-way analysis of variance. Table 1
shows the estimation results of intermediate precision and repeatability. Additionally,
results of statistical analysis using analysis values obtained by conducting aninternationally-standardized collaborative study to estimate reproducibility are shown396

Testing Methods for Fertilizers(2021)

in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 % (mass fraction).
The validity of this testing method was evaluated for sulfate iron (SO42-).

References
1) Satoko SAKAIDA, Kenji KOZUKA and Yuji SHIRAI: Determination of Sulfate ion by
Ion Chromatography, Research Report of Fertilizers, Vol. 13, p. 50 – 64 (2020)(5)

Flow sheet for testing method: The flow sheet for acid-soluble sulfur in fertilizers is shown
below:

397

Testing Methods for Fertilizers(2021)

4.13 Iron
4.13.1 Water-soluble iron4.13.1.a Flame atomic absorption spectrometry(1) Summary
This test method is applicable to fertilizers that indicate iron content as a response modifier. This
testing method is classified as Type D and its symbol is 4.13.1.a-2017 or W-Fe.a-1.
Extract by adding water to an analytical sample, spray in an acetylene−air flame and measure theatomic absorption with iron at a wavelength of 248.3 nm to obtain water-soluble iron (W-Fe) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Iron standard solution (Fe 0.1 mg/mL): An iron standard solution (Fe 0.1 mg/mL) traceable
to National Metrology.
d) Iron standard solutions (Fe 0.5 µg/ mL - 5 µg/ mL) for the calibration curve preparation(1): Put 2.5 mL - 25 mL of iron standard solution (Fe 0.1 mg/mL) in 500-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) up to the marked line.
e) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the iron standard solution in (2), an iron standard solution for the calibration
curve preparation can be prepared by using an iron standard solution (Fe 1 mg/mL or
10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (2) function.
1) Light source: An iron hollow cathode lamp (In case of background correction system using
continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
Note (2) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 5.00 g of an analytical sample, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30 - 40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
398

Testing Methods for Fertilizers(2021)

Comment 2 In the procedure in (4.1.1) a), it is also allowed to weigh 2.50 g of the analytical sample
and put it in a 250-mL volumetric flask. In that case, add about 200 mL of water in theprocedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 4 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 248.3 nmb) Calibration curve preparation
1) Spray the iron standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation into a flame, and read the indicated value at a wavelengthof 248.3 nm.
2) Prepare a curve for the relationship between the iron concentration and the indicated value ofthe iron standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.05 mg - 0.5 mg as Fe)
in a 100-mL volumetric flask.
2) Add about 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the iron content from the calibration curve, and calculate the water-soluble iron (W-Fe)in the analytical sample.
Comment 5

Recovery testing was conducted to evaluate trueness using a preparation sample(solid). As a result, the mean recovery rates at the content level of 10 % (mass fraction),
5 % (mass fraction) and 0.05 % (mass fraction) were 101.1 %, 102.8 % and 107.0 %as water-soluble iron (W-Fe) respectively. In addition, recovery testing was conductedusing a preparation sample (fluid). As a result, the mean recovery rates at the content
level of 1 % (mass fraction), 0.1 % (mass fraction) and 0.01 % (mass fraction) were103.6 %, 105.7 % and 105.1 % as a water-soluble iron (W-Fe) respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a liquid microelement compound fertilizer to evaluate the extract precision of fluid
fertilizers were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to399

Testing Methods for Fertilizers(2021)

be about 40 mg/kg for solid fertilizers and about 4 mg/kg for fluid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.252, Yokendo, Tokyo (1988)
2)
Shinei TAKAHASHI, Chika SUZUKI and Noriyuki SASAKI: Verification of
Performance Characteristics of Testing Method for Iron in Fertilizer by Atomic
Absorption Spectrometry, Research Report of Fertilizer, Vol. 7, p. 131 - 137 (2014)
3)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components in
Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20 (2016)(5)

Flow sheet for water-soluble iron: The flow sheet for water-soluble iron in fertilizers is shown
below:
5.00 g analytical sample
500-mL volumetric flask.
(powdery)← Water, About 400 mL
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble iron in fertilizers(Extraction procedure (4.1.1))

400

Testing Methods for Fertilizers(2021)

401

Testing Methods for Fertilizers(2021)

4.13.1.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type B and its symbol is 4.13.1.b-2017 or W-Fe.b-1.
Extract by adding water to an analytical sample, introduce it to an ICP Optical Emission
Spectrometer (ICP-OES) and measure the iron at a wavelength of 259.940 nm, etc. to obtain watersoluble iron(W-Fe) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Iron standard solution (Fe 1 mg/mL): An iron standard solution (Fe 1 mg/mL) traceable to
National Metrology.
d) Iron standard solution (Fe 0.1 mg/mL) (1): Put 10 mL of iron standard solution (Fe 1 mg/mL)
in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to the marked line.
e) Iron standard solutions (Fe 1 µg - 20 µg/mL) for the calibration curve preparation (1): Put
1 mL - 20 mL of iron standard solution (Fe 0.1 mg/mL) in 100-mL volumetric flasks step-bystep, and add hydrochloric acid (1+23) to the marked line.
f) Iron standard solutions (Fe 0.1 µg - 1 µg/mL) for the calibration curve preparation (1): Put
1 mL - 10 mL of iron standard solution (Fe 10 µg/mL) in 100-mL volumetric flasks step-bystep, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the iron standard solution in (2), an iron standard solution for the calibration
curve preparation can be prepared by using an iron standard solution (Fe 10 mg/mL)
traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
402

Testing Methods for Fertilizers(2021)

Note (2) The sampling amount of the analytical sample is 10 g when the content in the sample isless than 0.01 % (mass fraction) as water-soluble iron.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 259.940 nm or 238.204 nm (3)b) Calibration curve preparation
1) Spray the iron standard solution for the calibration curve preparation and blank test solution forthe calibration curve preparation into inductively coupled plasma, and read the indicated value
at an analytical line wavelength.
2) Prepare a curve for the relationship between the iron concentration and the indicated value ofthe iron standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Fe)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the iron content from the calibration curve, and calculate the water-soluble iron (W-Fe)in the analytical sample.
Note (3) 238.204 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 259.940 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 4 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 5 The comparison of the measurement value (yi：0.0191 % (mass fraction) - 0.517 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of flame atomic absorbance spectrometry was conducted to evaluate trueness using
fluid fertilizers (12 samples). As a result, a regression equation was y=0.001+0.968x,
and its correlation coefficient (r) was 0.999. Additionally, additive recovery testing
was conducted using a fluid compound fertilizer (1 brand) and a home garden-use
compound fertilizer (1 brand). As a result, the mean recovery rates at the additive levelof 0.01 % (mass fraction) and 0.1 % (mass fraction) were 96.5 % and 93.9 %respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
403

Testing Methods for Fertilizers(2021)

and a home garden-use compound fertilizer to evaluate precision were analyzed by the
one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study
implemented for testing method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0005 % (mass fraction).

References
1)
Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development
Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research404

Testing Methods for Fertilizers(2021)

2)

(5)

Report of Fertilizer, Vol. 9, p. 1 - 9 (2016)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)

Flow sheet: The flow sheet for water-soluble iron in fluid fertilizers is shown below:405

Testing Methods for Fertilizers(2021)

4.14 Molybdenum
4.14.1 Water-soluble molybdenum
4.14.1.a Sodium thiocyanate absorptiometric analysis(1) Summary
This test method is applicable to fertilizers that indicate molybdenum content as a response
modifier. This testing method is classified as Type D and its symbol is 4.14.1.a-2017 or W-Mo.a-1.
Extract by adding water to an analytical sample, add sulfuric acid (1+1) and perchloric acid, further
add a sodium thiocyanate solution and a tin (II) chloride solution, and measure the absorbance with
thiocyanate complex formed by the reaction of reduced molybdenum (V) with thiocyanate ion to
obtain water-soluble molybdenum (W-Mo) in an analytical sample. In addition, the performance of
this testing method is shown in Comment 6.
(2) Reagent: Reagents are as shown below.
a) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
b) Perchloric acid: A JIS Guaranteed Reagent specified in JIS K 8223 or a reagent of equivalentquality.
c) Iron (III) sulfate solution (1): Dissolve 5 g of iron (III) sulfate specified in JIS K 8981 in about
10 mL of sulfuric acid (1+1) and a proper amount of water, and further add water to make 100mL.
d) Sodium thiocyanate solution (1): Dissolve 50 g of sodium thiocyanate specified in JIS K 9002
in water to make 500 mL.
e) Tin (II) chloride solution (1): Dissolve 20 g of tin (II) chloride dihydrate specified in JIS K
8136 in 80 mL of hydrochloric acid (1+1) while heating, then add water to make 200 mL.
f) Molybdenum standard solution (Mo 1 mg/mL) (1): After leaving at rest molybdenum (VI)oxide (2) in a desiccator for about 24 hours to dry, put it to a 1,500 g weighing dish. Dissolve ina small amount of water, transfer to a 1000 mL volumetric flask and add about 5 g of sodiumhydroxide specified in JIS K 8576 to dissolve and add water up to the marked line.
g) Molybdenum standard solution (Mo 0.01 mg/mL): Dilute a predetermined amount ofmolybdenum standard solution (Mo 1 mg/mL) precisely by a factor of 100 with water.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 99.5 % (mass fraction) in purity is commercially sold as
molybdenum (VI) oxide.
Comment 1 Instead of the molybdenum standard solution in (2), a molybdenum standard solution
for the calibration curve preparation can be prepared by using a molybdenum standard
solution (Mo 0.1 mg/mL, 1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Spectrophotometer: A spectrophotometer specified in JIS K 0115
(4) Test procedure406

Testing Methods for Fertilizers(2021)(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 5.00 g of an analytical sample, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30-40 revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 2 In the procedure in (4.1.1) a), it is also allowed to weigh 2.50 g of the analytical sample
and put it in a 250-mL volumetric flask. In that case, add about 200 mL of water in theprocedure in b).
Comment 3 A sample solution obtained in the procedure in (4.1.1) is also applicable to thecomponents shown in Annex B.
Comment 4 When the sample solution in d) contains organic matters that affect the determination,
put a predetermined amount of the sample solution to a 100-mL tall beaker, add a small
amount of sulfuric acid and nitric acid to heat and digest the organic matters until whitesmoke of sulfuric acid evolves. After standing to cool, transfer the solution to a 100mL volumetric flask with water and add water up to the marked line to filter. The
filtrate is prepared as the sample solution of (4.2) a).
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make a sample solution.
Comment 5 A sample solution obtained in the procedure in (4.1.2) is also applicable to thecomponents shown in Annex B.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 0.3 mg as Mo)
in a 100-mL volumetric flask.
b) Add about 5 mL of sulfuric acid (1+1), about 5 mL of perchloric acid and about 2 mL of iron(III) sulfate solution.
c) Add about 16 mL of sodium thiocyanate solution and about 10 mL of tin (II) chloride solution
successively while shaking to mix and further add water up to the marked line (3).
Note (3) When the solution becomes muddy, centrifuge after the procedure in c). However, if itis presumed that copper (I) thiocyanate caused the muddying, centrifuge after leaving at
rest for 1 hour.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 460 nmb) Calibration curve preparation
1) Put 1 mL - 30 mL of molybdenum standard solution (Mo 0.01 mg/mL) in 100-mL volumetric407

Testing Methods for Fertilizers(2021)

flasks step-by-step.
2) Conduct the same procedure as (4.2) b) - c) to make a 0.01 mg/100 mL - 0.3 mg/100 mL
molybdenum standard solution for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 100-mL volumetric flask to make a blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength 460 nm of the molybdenum standard solution for thecalibration curve preparation using the blank test solution for the calibration curve preparation
as the control.
5) Prepare a curve for the relationship between the molybdenum concentration and the absorbanceof the molybdenum standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) c), measure absorbance by the same procedure as b) 4).
2) Obtain the molybdenum content from the calibration curve, and calculate the water-soluble
molybdenum (W- Mo).
Comment 6 Recovery testing was conducted to evaluate trueness using a preparation sample. As aresult, the mean recovery rates at the content level of 2.5 % (mass fraction) and 0.1 %(mass fraction) were 100.2 % and 100.8 % as water-soluble molybdenum (W-Mo)
respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a liquid microelement compound fertilizer to evaluate the extract precision of fluid
fertilizers were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 60 mg/kg for solid fertilizers and about 6 mg/kg for fluid fertilizers.

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.281- 283, Yokendo, Tokyo (1988)
2)
Keiji YAGI, Natuki TOYODOME, Tokiya SUZUKI and Hideo SOETA: Verification of
Performance Characteristics of Testing Method for Water-soluble Molybdenum Content
in Fertilizer by Sodium Thiocyanate Absorptiometric Analysis, Research Report of
Fertilizer Vol. 7, p. 138 - 144 (2014)
3)
Shinji KAWAGUCHI: Simple Extraction Method for Water-Soluble Components in408

Testing Methods for Fertilizers(2021)

Liquid Compound Fertilizers, Research Report of Fertilizer, Vol. 9, p. 10 - 20 (2016)(5)

Flow sheet for water-soluble molybdenum: The flow sheet for water-soluble molybdenum in
fertilizers is shown below:
5.00 g analytical sample
500-mL volumetric flask.
(powdery)← About 400 mL of water
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1-1 Flow sheet for water-soluble molybdenum in fertilizers (Extraction procedure (4.1.1))

409

Testing Methods for Fertilizers(2021)

4.14.1.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type B and its symbol is 4.14.1.b-2017 or W-Mo.b-1.
Extract by adding water to an analytical sample, introduce it to an ICP Optical Emission Spectrometer(ICP-OES) and measure the molybdenum at a wavelength of 202.030 nm, etc. to obtain water-soluble
molybdenum (W-Mo) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Molybdenum standard solution (Mo 1 mg/mL): A molybdenum standard solution (Mo 1
mg/mL) traceable to National Metrology.
d) Molybdenum standard solution (Mo 0.1 mg/mL) (1): Put 10 mL of molybdenum standard
solution (Mo 1 mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to
the marked line.
e) Molybdenum standard solutions (Mo 1 µg - 20 µg/mL) for the calibration curve
preparation (1): Put 1 mL - 20 mL of molybdenum standard solution (Mo 0.1 mg/mL) in 100mL volumetric flasks step-by-step, and add hydrochloric acid (1+23) to the marked line.
f) Molybdenum standard solutions (Mo 0.1 µg - 1 µg/mL) for the calibration curve
preparation (1): Put 1 mL - 10 mL of molybdenum standard solution (Mo 0.1 mg/mL) in 100mL volumetric flasks step-by-step, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the molybdenum standard solution in (2), a molybdenum standard solution
for the calibration curve preparation can be prepared by using a molybdenum standard
solution (Mo 10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
410

Testing Methods for Fertilizers(2021)b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (2) The sampling amount of the analytical sample is 10 g when the content in the sample isless than 0.01 % (mass fraction) as water-soluble molybdenum.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 202.030 nm or 277.540 nm (3)b) Calibration curve preparation
1) Spray the molybdenum standard solution for the calibration curve preparation and the blanktest solution for the calibration curve preparation into inductively coupled plasma, and read theindicated value at a wavelength of 202.030 nm.
2) Prepare a curve for the relationship between the molybdenum concentration and the indicatedvalue of the molybdenum standard solution for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Mo)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the molybdenum content from the calibration curve, and calculate the water-soluble
molybdenum (W- Mo).
Note (3) 277.540 nm can also be used. However, since the intensity of emission obtained isdifferent from the one of 202.030 nm, it is necessary to understand the suitableconcentration range of the calibration curve and prepare a standard solution for thecalibration curve in advance.
Comment 4 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 5 The comparison of the measurement value (yi：0.00342 % (mass fraction) - 0.20374 %(mass fraction)) of ICP Optical Emission Spectrometry and the measurement value (xi)of the Sodium thiocyanate absorptiometric analysis was conducted to evaluate truenessusing fluid fertilizers (12 samples). As a result, a regression equation was
y=0.0004+0.982x and its correlation coefficient (r) was 0.999. Additionally, additive
recovery testing was conducted using a fluid compound fertilizer (1 brand) and a homegarden-use compound fertilizer (1 brand). As a result, the mean recovery rates at theadditive level of 0.01 % (mass fraction) and 0.1 % (mass fraction) were 95.4 % and411

Testing Methods for Fertilizers(2021)

97.6 % respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a home garden-use compound fertilizer to evaluate precision were analyzed by the
one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study
implemented for testing method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0005 % (mass fraction).

References
1)
Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development412

Testing Methods for Fertilizers(2021)

2)

(5)

Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research
Report of Fertilizer, Vol. 9, p. 1 - 9 (2016)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)

Flow sheet: The flow sheet for water-soluble molybdenum in fluid fertilizers is shown below:

413

Testing Methods for Fertilizers(2021)

4.15
Cobalt
4.15.1 Water-soluble cobalt
4.15.1.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type E and its symbol is 4.15.1.a-2017 or W-Co.a-1.
Extract by adding water to an analytical sample, spray in an acetylene−air flame and measure theatomic absorption with cobalt at a wavelength of 240.7 nm to obtain water-soluble cobalt (W-Co) inan analytical sample.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Cobalt standard solution (Co 0.1 mg/mL): A cobalt standard solution (Co 0.1 mg/mL)
traceable to National Metrology.
d) Cobalt standard solutions (Co 0.5 µg - 5 µg/mL) for the calibration curve preparation (1):
Put 2.5 mL - 25 mL of cobalt standard solution (Co 0.1 mg/mL) in 500-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) to the marked line.
e) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the cobalt standard solution in (2), a cobalt standard solution for thecalibration curve preparation can be prepared by using a cobalt standard solution (Co
1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (2) function.
1) Light source: An cobalt hollow cathode lamp (In case of background correction system using
continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
Note (2) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample (3) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
c) Filter with Type 3 filter paper to make a sample solution.
Note (3) The sampling amount of the analytical sample is 10 g when the content in the sample is414

Testing Methods for Fertilizers(2021)

less than 0.01 % (mass fraction) as water-soluble cobalt.
Comment 2 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 240.7 nmb) Calibration curve preparation
1) Spray the cobalt standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 240.7 nm.
2) Prepare a curve for the relationship between the cobalt concentration and the indicated value ofthe cobalt standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Co)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the cobalt content from the calibration curve, and calculate the water-soluble cobalt (WCo) in the analytical sample.
(5)

Flow sheet: The flow sheet for water-soluble cobalt in fluid fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1mg into a 100-mL volumetric flask← Water, about 50 mL
Shaking to mix← Water (up to the marked line)
Filtration
Sample solution
Figure 1 The flow sheet for water-soluble cobalt in fluid fertilizers(Extraction procedure)

Sample solution
Aliquot
100-mL volmetric flask(predetermined volume)← 25 mL of hydrochloric acid (1+5)← Water (up to the marked line)
Measurement
Atomic absorption spectrometer (240.7 nm)
Figure 2 The flow sheet for water-soluble cobalt in fluid fertilizers(Measurement procedure)
415

Testing Methods for Fertilizers(2021)

4.15.1.b ICP Optical Emission Spectrometry(1) Summary
This testing method is applicable to fluid compound fertilizers, liquid microelement compound
fertilizers and the fluid fertilizers of home garden-use compound fertilizers. This testing method isclassified as Type B and its symbol is 4.15.1.b-2017 or W-Co.b-1.
Extract by adding water to an analytical sample, introduce it to an ICP Optical Emission
Spectrometer (ICP-OES) and measure the cobalt at a wavelength of 228.616 nm to obtain watersoluble cobalt (W-Co) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
c) Cobalt standard solution (Co 1 mg/mL): A cobalt standard solution (Co 1 mg/mL) traceable
to National Metrology.
d) Cobalt standard solution (Co 0.1 mg/mL) (1): Put 10 mL of cobalt standard solution (Co 1
mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to the marked line.
e) Cobalt standard solutions (Co 1 µg - 20 µg/mL) for the calibration curve preparation (1):
Put 1 mL - 20 mL of cobalt standard solution (Co 0.1 mg/mL) in 100-mL volumetric flasks stepby-step, and add hydrochloric acid (1+23) to the marked line.
f) Copper standard solutions (Cu 0.1 µg - 1 µg/mL) for the calibration curve preparation (1):
Put 1 mL - 10 mL of copper standard solution (Cu 10 µg/mL) in 100-mL volumetric flasks stepby-step, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in d), e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Instead of the cobalt standard solution in (2), a cobalt standard solution for thecalibration curve preparation can be prepared by using a cobalt standard solution (Co
10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample (2) to the order of 1 mg, and put it in a 100-mL volumetricflask.
b) Add about 50 mL of water, shake to mix and add water up to the marked line.
416

Testing Methods for Fertilizers(2021)c)

Filter with Type 3 filter paper to make a sample solution.

Note (2) The sampling amount of the analytical sample is 10 g when the content in the sample isless than 0.01 % (mass fraction) as water-soluble cobalt.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 228.616 nmb) Calibration curve preparation
1) Spray the cobalt standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at a wavelength of 228.616 nm.
2) Prepare a curve for the relationship between the cobalt concentration and the indicated value ofthe cobalt standard solution for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as Co)
in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+5), and add water up to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the cobalt content from the calibration curve, and calculate the water-soluble cobalt (WCo) in the analytical sample.
Comment 4 Simultaneous measurement of multiple elements is possible with the ICP OpticalEmission Spectrometry. In that case, prepare standard solutions for calibration curve
preparation referencing the measurement conditions in Table 1 of Annex C1, conduct
procedures similarly as (4.2) b) - c), and multiply the obtained measurement values of
the respective element concentrations by conversion factors to calculate respective
main components in an analytical sample.
Comment 5 The comparison of the measurement value (yi：0.00105 % (mass fraction) - 0.0213 %(mass fraction )) of ICP Optical Emission Spectrometry and the measurement value(xi) of flame atomic absorbance spectrometry was conducted to evaluate trueness using
fluid fertilizers (12 samples). As a result, a regression equation was y=0.0001+0.927x,
and its correlation coefficient (r) was 0.996. Additionally, additive recovery testing
was conducted using a fluid compound fertilizer (1 brand) and a home garden-use
compound fertilizer (1 brand). As a result, the mean recovery rates at the additive levelof 0.01 % (mass fraction) and 0.1 % (mass fraction) were 94.6 % and 98.4 %respectively.
The results of the repeatability tests on different days using a fluid compound fertilizer
and a home garden-use compound fertilizer to evaluate precision were analyzed by the
one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability. Additionally, results from a collaborative study
implemented for testing method validation and its analysis are shown in Table 2.
417

Testing Methods for Fertilizers(2021)

Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0005 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different days of water-soluble cobalt(Fluid fertilizer)
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Fluid compound fertilizer
70.05540.00101.7
0.00244.4
Home garden-use compound fertilizer
70.0105 0.0003
3.3
0.0005
4.8(fluid)1) The number of test days conducting a duplicate test
6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

References
1)
Keisuke AOYAMA: Simultaneous Determination Method for Effect-Development
Promoting Agent (Ca, Fe, Co, Cu, Zn and Mo) in Liquid Compound Fertilizer using
Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), Research
Report of Fertilizer, Vol. 9, p. 1 - 9 (2016)
2)
Masayuki YAMANISHI, Madoka KATOU and Yuji SHIRAI: Performance Evaluationof Determination Method for Effective Ingredients by ICP-OES in Liquid Fertilizer:
Harmonized Collaborative Validation, Research Report of Fertilizer, Vol. 13, p. 123 – 145(2020)

418

Testing Methods for Fertilizers(2021)(5)

Flow sheet: The flow sheet for water-soluble cobalt in fluid fertilizers is shown below:
1 g analytical sample
Weigh to the order of 1mg into a 100-mL volumetric flask
Water,
about
50 mL
←
Shaking to mix← Water (up to the marked line)
Filtration
Sample solution
Figure 1 The flow sheet for water-soluble cobalt in fluid fertilizers(Extraction procedure)

Sample solution
Aliquot
100-mL volmetric flask(predetermined volume)← 25 mL of hydrochloric acid (1+5)← Water (up to the marked line)
Measurement
ICP Optical Emission Spectrometer (228.616 nm)
Figure 2 The flow sheet for water-soluble cobalt in fluid fertilizers(Measurement procedure)

419

Testing Methods for Fertilizers(2021)

5. Harmful components
5.1 Mercury
5.1.a Cold vapor atomic absorption spectrometry(1) Summary
The test method is applicable to fertilizers excluding fluid sludge fertilizers. This testing method
is classified as Type B and its symbol is 5.1.a-2017 or Hg.a-1.
Pretreat an analytical sample with nitric acid- perchloric acid, and then reduce mercury (II) in thesolution with tin (II) chloride. Aerate this solution, and measure the atomic absorption for generated
mercury vapor at a wavelength of 253.7 nm to obtain mercury (Hg) in an analytical sample. In
addition, the performance of this testing method is shown in Comment 3.
(2)
a)
b)
c)
d)
e)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Perchloric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Tin (II) chloride solution: To 10 g of tin (II) chloride dihydrate (1) specified in JIS K 8136, add
60 mL of sulfuric acid (1+20), and stir while heating to dissolve. After cooling is complete, add
water to make 100 mL.
f) L-cysteine solution: To 10 mg of L-cysteine (HSCH2CH(NH2)COOH) of no less than 98.0 %in purity, add 100 mL of water and 2 mL of nitric acid to dissolve, and further add water to make1000 mL. Store in a refrigerator, and do not use after 6 months after preparation.
g) Tri-n-butyl phosphate (2): A reagent of no less than 98 % in purity.
h) Mercury standard solution (Hg 0.1 mg/mL): A mercury standard solution (Hg 0.1 mg/mL)
traceable to National Metrology.
i) Mercury standard solution (Hg 10 µg/mL) (3) (4): Put 10 mL of mercury standard solution (Hg
0.1 mg/mL) in a 100 mL of volumetric flask and add an L-cysteine solution up to the markedline.
j) Mercury standard solution (Hg 0.1 µg/mL) (3) (5): Dilute a predetermined amount of mercury
standard solution (Hg 10 µg/mL) with an L-cysteine solution to prepare a mercury standard
solution (Hg 0.1 µg/mL).
Note (1) Use a reagent with low mercury content, such as for mercury analysis or for harmful
metal analysis.
(2) Use as an anti-forming agent.
(3) This is an example of preparation; prepare an amount as appropriate.
(4) Store in a refrigerator, and do not use after 4 months after preparation.
(5) Store in a refrigerator, and do not use after 1 months after preparation.
Comment 1 Instead of the mercury standard solution in (2), a mercury standard solution for thecalibration curve preparation can be prepared by using a mercury standard solution(Hg 1 mg/mL or 10 mg/mL) traceable to National Metrology.

(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Mercury atomic absorption spectrometer: Mercury atomic absorption spectrometer using
a method for producing the atomic vapor by reduction specified in JIS K 0121.
1) Light source: Low-pressure mercury lampb) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature can420

Testing Methods for Fertilizers(2021)c)

be set to 180 °C - 200 °C.
Sample digestion flask (6): A 100-mL borosilicate glass volumetric flask 100 mL (180 mm totalheight, 13 mm mouth diameter)

Note (6) Distinguish the volumetric flask used in digestion as a sample digestion flask and do notuse it for any other purposes.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it in a sample digestion flask.
b) Add about 10 mL of nitric acid, and heat on a hot plate or sand bath for a short time (7).
c) After standing to cool, add about 10 mL of perchloric acid, and digest by heating on a hot plateor sand bath at 180 ºC - 200 ºC for about 30 minutes - 1 hour (8).
d) After standing to cool, precisely adjust with water to 100 mL to make a sample solution.
e) As a blank test, conduct the procedures in b) - d) using another sample digestion flask to preparea blank test solution.
Note (7) If it foams vigorously, leave at rest overnight.
(8) The sample solution and the blank test solution should be stored when they are cooled
after the procedure in (4.1) c). After precisely adjust the volume of the sample solution
and the blank test solution with water, immediately conduct the procedure in (4.2).
(4.2) Measurement: Conduct measurement by cold vapor atomic absorption spectrometry specified
in JIS K 0121. Specific measurement procedures are according to the operation method of theatomic absorption spectrometer used. An example of measurement using a mercury atomic
absorption spectrometer is shown below:a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 253.7 nmb) Calibration curve preparation
1) Put 1 mL - 20 mL of mercury standard solution (Hg 0.1 µg/mL) in 100-mL volumetric flasks
step-by-step, and add water up to the marked line. Put 5 mL of these solutions in respective
reduction vessels, add 1 drop of tri-n-butyl phosphate (9), to make mercury standard solutions
for the calibration curve preparation.
2) Put 5 mL of water in another reduction vessel, and add 1 drop of tri-n-butyl phosphate (9), tomake the blank test solution for the calibration curve preparation.
3) Connect the reduction vessel to the mercury atomic absorption spectrometer, and introduce
sulfuric acid (1+1) and a tin (II) chloride solution, and circulate air.
4) Read the indicated value at a wavelength of 253.7 nm.
5) Prepare a curve for the relationship between the mercury content (µg) and the indicated valueof the mercury standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation.
c) Sample measurement
1) Put 5 mL of a sample solution in respective reduction vessels, add 1 drop of tri-n-butyl
phosphate (9), and conduct similarly as in b) 3) - 4) to read the indicated value.
2) Put 5 mL of the blank test solution in a reduction vessel, add 1 drop of tri-n-butyl phosphate (9),and conduct similarly as in b) 3) - 4) to read the indicated value, and correct the indicated value
obtained for the sample solution.
421

Testing Methods for Fertilizers(2021)

3) Obtain the mercury content (µg) from the calibration curve, and calculate mercury (Hg) in theanalytical sample.
Note (9) It is not required to add tri-n-butyl phosphate if not needed.
Comment 2 Instead of the correction method in c) 2), mercury (Hg) can be corrected by obtaining
the mercury content in the blank test.
Comment 3 Recovery testing was conducted to evaluate trueness using an industrial sludge
fertilizer (1 sample), composted sludge (3 samples) and a human waste sludge
fertilizer (1 sample). As a result, the mean recovery rates at the concentration levelof 2 mg/kg and 0.2 mg/kg were 98.7 % - 101.6 % and 100.7 % - 105.4 % as mercury(Hg) respectively. In addition, recovery testing was conducted using soybean meal,rape seed meal, compound fertilizers (2 samples) and blended fertilizers. As a result,the mean recovery rates at the concentration level of 40 mg/kg and 0.5 mg/kg were
98.5 % - 101.5 % and 100.4 % - 103.3 % as mercury (Hg) respectively.
In order to evaluate precision, results from a collaborative study for test method
validation and its analysis are shown in Table 1. In addition, the results of thecollaborative study to determine a certified reference material fertilizer wereanalyzed by using a three-level nesting analysis of variance. Table 2 shows thecalculation results of reproducibility, intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.01 mg/kg.
Table 1 Analysis results of the collaborative study
for mercury test method validation
3)
2)
Number of
RSD r
Mean
Sample name1)
(mg/kg)(%)
laboratories
Human waste sludge fertilizer A
11
0.651
5.3
Human waste sludge fertilizer B
11
1.10
6.3
Composted sludge fertilizer A
11
0.489
6.8
Composted sludge fertilizer B
11
0.822
8.1
Composted sludge fertilizer C
9
0.182
10.6
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Repeatability relative standard deviation
4) Reproducibility relative standard deviation

422

4)

RSD R
(%)
11.6
10.2
10.2
13.1
10.6

Testing Methods for Fertilizers(2021)

References1)
Fumihiro ABE, Takeshi HASHIMOTO and Yasushi SUGIMURA: Determination of
mercury in sludge fertilizer - Improved decomposition method -, Research Report of
Fertilizer Vol. 1, p. 60 - 66 (2008)
2)
Fumihiro ABE, Takeshi HASHIMOTO and Norio HIKICHI: Determination of mercury
in sludge fertilizer - Collaborative Test Results -, Research Report of Fertilizer Vol. 1, p.
67 - 73 (2008)
3)
Akira SHIMIZU, Kaori OKADA, Takeshi HASHIMOTO, Yasuto IDE and Toshiaki
HIROI: Determination of Mercury in Fertilizer- Expanding the scope of application of
improved method -, Research Report of Fertilizer Vol. 2, p. 12 - 17 (2009)(5)

Flow sheet for mercury: The flow sheet for mercury in fertilizers is shown below:423

Testing Methods for Fertilizers(2021)

5.1.b Cold vapor atomic absorption spectrometry (Fluid sludge fertilizers)(1) Summary
The test method is applicable to fluid sludge fertilizers. This testing method is classified as Type D
and its symbol is 5.1.b-2017 or Hg.b-1.
Pretreat an analytical sample with nitric acid- perchloric acid, and then reduce mercury (II) in thesolution with tin (II) chloride. Aerate this solution, and measure the atomic absorption for generated
mercury vapor at a wavelength of 253.7 nm to obtain mercury (Hg) in an analytical sample. In
addition, the performance of this testing method is shown in Comment 3.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrogen peroxide: A JIS Guaranteed Reagent specified in JIS K 8230 or a reagent ofequivalent quality.
d) Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
e) Tin (II) chloride solution: To 10 g of tin (II) chloride dihydrate (1) specified in JIS K 8136,
add 60 mL of sulfuric acid (1+20), and stir while heating to dissolve. After cooling is complete,
add water to make 100 mL.
f) L-cysteine solution: To 10 mg of L-cysteine (HSCH2CH(NH2)COOH) of no less than 98.0 %in purity, add 100 mL of water and 2 mL of nitric acid to dissolve, and further add water to make1000 mL. Store in a refrigerator, and do not use after 6 months after preparation.
g) Mercury standard solution (Hg 0.1 mg/mL): A mercury standard solution (Hg 0.1 mg/mL)
traceable to National Metrology.
h) Mercury standard solution (Hg 10 µg/mL) (2) (3): Put 10 mL of mercury standard solution (Hg
0.1 mg/mL) in a 100 mL of volumetric flask and add an L-cysteine solution up to the marked
line.
i) Mercury standard solution (Hg 0.1 µg/mL) (2) (4): Dilute a predetermined amount of mercury
standard solution (Hg 10 µg/mL) with an L-cysteine solution to prepare a mercury standard
solution (Hg 0.1 µg/mL).
Note (1) Use a reagent with low mercury content, such as for mercury analysis or for harmful
metal analysis.
(2) This is an example of preparation; prepare an amount as appropriate.
(3) Store in a refrigerator, and do not use after 4 months after preparation.
(4) Store in a refrigerator, and do not use after 1 month after preparation.
Comment 1 Instead of the mercury standard solution in (2), a mercury standard solution for thecalibration curve preparation can be prepared by using a mercury standard solution(Hg 1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Mercury atomic absorption spectrometer : A mercury atomic absorption spectrometerusing a method for producing the atomic vapor by reduction specified in JIS K 0121.
1) Light source: Low-pressure mercury lampb) Pressure vessel decomposing device: A device which pressurizes the inside of a vessel by
putting acid, etc. to heat in the decomposing vessel, and decomposes a sample by the interactionof heating, pressurizing and acid. The following requirements should be met.
1) The main part of a decomposing device:
In the case of the microwave heating method, adevice should be able to produce a high-frequency wave using a frequency which is permitted424

Testing Methods for Fertilizers(2021)

at an industrial frequency facility. It is desirable to be able to monitor pressure and temperature,etc. in the decomposing vessel with a sensor inside the device. The interior of a device shouldbe acid-resistant treated and should have a high temperature durability and a high level of safety.
2) Exhaust system: A system which has an exhaust fan of acid-resistant specification, and has
an air-cool function inside the device to allow constant airflow, keeping operating temperature
below a certain temperature level.
3) Decomposing vessel: A vessel which is heat-resistance and pressure-tight and has the
durability required to decompose particles, and has resistance to internal contamination. Itshould have safety functions such as causing overheat prevention valve to work and internalpressure to drop by emitting gas, and preventing gas bumping in the case of exceeding apressure limitation.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 20.0 g (5) of an analytical sample, and put it in an airtight vessel.
b) Gradually add 2.5 mL of nitric acid and 2 mL of hydrogen peroxide.
c) Put the airtight vessel into the main part of a decomposing device and heat using a microwave(6).
d) Ignite at 240 ºC ±5 ºC for no less than 10 minutes (6) to decompose (7).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (8) with water.
f) Add water up to the marked line and transfer it to a 50-mL ground-in stopper centrifugal
precipitate tube (8).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (9) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another airtight vessel to prepare a blanktest solution.
Note (5) The maximum limit of solid content, which is converted from moisture content, in thesampling volume 20.0 g of an analytical sample is about 0.5 g. If solid content is likely
to exceed the limit, reduce sampling volume as necessary.
(6) Condition examples for a microwave decomposing device: 0 min (room temperature)→ 10min (240 ºC) → 20 min (240 ºC) → 40 min (room temperature), initial output
1400 W(7) When organic matters still remain, for example the digestion solution is colored, repeat
the procedures in (4.1) b) - c).
(8) The vessel should be made of polypropylene, etc. to not affect the measurement.
(9) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal force.
(4.2) Measurement: Conduct measurement by cold vapor atomic absorption spectrometry specified
in JIS K 0121. Specific measurement procedures are according to the operation method of theatomic absorption spectrometer used. An example of the measurement using the mercury
atomic absorption spectrometer is shown below:a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 253.7 nmb) Calibration curve preparation
1) Put 0.4 mL - 10 mL of mercury standard solution (Hg 0.1 µg/mL) in 100-mL volumetric flasks
step-by-step, and add water up to the marked line. Put 5 mL of these solutions in respective
425

Testing Methods for Fertilizers(2021)

reduction vessels to make mercury standard solutions for the calibration curve preparation.
2) Put 5 mL of water in another reduction vessel to make the blank test solution for the calibration
curve preparation.
3) Connect the reduction vessel to the mercury atomic absorption spectrometer, and introduce
sulfuric acid (1+1) and a tin (II) chloride solution, and circulate air.
4) Read the indicated value at a wavelength of 253.7 nm.
5) Prepare a curve for the relationship between the mercury content (µg) and the indicated valueof the mercury standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation.
c) Sample measurement
1) Put 5 mL of a sample solution in respective reduction vessels, and conduct similarly as in b) 3)- 4) to read the indicated value.
2) Put 5 mL of the blank test solution in a reduction vessel and conduct similarly as in b) 3) - 4)
to read the indicated value, and correct the indicated value obtained for the sample solution.
3) Obtain the mercury content (µg) from the calibration curve, and calculate mercury (Hg) in theanalytical sample.
Comment 2 Instead of the correction method in c) 2), mercury (Hg) can be corrected by obtaining
the mercury content in the blank test.
Comment 3 Triplicates additive recovery testing was conducted to evaluate trueness using fluid
industrial sludge fertilizers (2 samples), and composted sludge fertilizers (6 samples).
As a result, the mean recovery rates at the concentration level of 0.2 mg/kg - 0.4 mg/kg,
0.01 mg/kg - 0.09 mg/kg and 0.7µg /kg - 7µg /kg were 100.0 % - 109.1 %, 99.0 % 114.6 % and 100.4 % - 113.4 % as mercury (Hg) in an actual article respectively.
The results of the repeatability tests on different days using two kinds of fluid sludge
fertilizers to evaluate precision were analyzed by the one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 µg/kg.
Table 1 Analysis results of the repeatability tests on different days of mercury(Fluid fertilizer)
2)
3)
4)
5)
Test days of
Mean
sr
RSD r
s I(T)Name of sample
1)
repeatability (T)(mg/kg) (mg/kg) (%)(mg/kg)Composted sludge fertilizer 1
50.05770.00091.50.0014Composted sludge fertilizer 2
50.01420.00021.7
0.0003
1) The number of test days conducting a duplicate test
2) Mean (the number of test days(T )×the number of duplicate testing(2))3) Repeatability standard deviation
4) Repeatability relative standard deviation

RSD I(T)
(%)
2.5
2.2

6)

5) Intermediate standard deviation
6) Intermediate relative standard deviation

References1)
Toshiharu YAGI: Determination of Heavy Metals in Fluid Sludge Fertilizers by ICP-MSand CV-AAS, Research Report of Fertilizer Vol. 8, p. 26 - 37 (2015)

426

Testing Methods for Fertilizers(2021)(5)

Flow sheet for mercury: The flow sheet for mercury in fluid sludge fertilizers is shown below:

427

Testing Methods for Fertilizers(2021)

5.2 Arsenic
5.2.a Hydride generation atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.2.a-2017 or As.a-1.
Pretreat an analytical sample with nitric acid-sulfuric acid-perchloric acid, and then generatearsenic hydride by the addition of sodium tetrahydroborate in the acidic condition with hydrochloric
acid, introduce it with argon gas to a heated absorption cell, and measure the atomic absorption witharsenic at a wavelength of 193.7 nm to obtain arsenic (As) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 7.
(2)
a)
b)
c)
d)
e)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Perchloric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Hydrochloric acid: Hydrochloric acid for arsenic analysis specified in JIS K 8180, or of
harmful metal analysis grade, microanalysis grade or equivalents.
f) Potassium iodide solution (1): Dissolve 20 g of potassium iodide specified in JIS K 8913 inwater to make 100 mL.
g) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
h) Sodium tetrahydroborate solution (1): Dissolve 10 g of sodium tetrahydroborate (NaBH4) for
atomic absorption spectrometry in a sodium hydroxide solution (4 g/L) to make 1000 mL.
i) Arsenic standard solution (As 0.1 mg/mL): An arsenic standard solution (As 0.1 mg/mL)
traceable to National Metrology.
j) Arsenic standard solution (As 1 µg/mL) (2) (3): Dilute a predetermined amount of arsenic
standard stock solution (As 0.1 mg/mL) accurately with hydrochloric acid (1+100) to prepare
an arsenic standard solution (As 1 µg/mL).
k) Arsenic standard solution (As 0.1 µg/mL) (2) (4): Dilute a predetermined amount of arsenic
standard solution (As 0.1 µg/mL) with hydrochloric acid (1+100) to prepare an arsenic standard
solution (As 0.1 µg/mL).
Note (1) The concentrations of a potassium iodide solution and a sodium tetrahydroborate
solution vary depending on the instrument used.
(2) This is an example of preparation; prepare an amount as appropriate.
(3) Store in a refrigerator, and do not use after 6 months after preparation.
(4) Store in a refrigerator, and do not use after 1 month after preparation.
Comment 1 Instead of the arsenic standard solution in (2), an arsenic standard solution for thecalibration curve preparation can be prepared by using an arsenic standard solution(As 1 mg/mL or 10 mg/mL) traceable to National Metrology.

(3) Instruments: Instruments are as shown below:a) Atomic absorption spectrometer : To an atomic absorption spectrometer specified in JIS K
0121, connect a hydride generator and parts shown below. Also, an atomic absorption
spectrometer with a built-in hydride generator can be used.
1) Light source: An arsenic hollow cathode lamp or an arsenic high-intensity discharge lamp.
2) Atomizer: Heated absorption cell (5)3) Gas: Gases for heating the heated absorption cell.
428

Testing Methods for Fertilizers(2021)(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hydride generator: A batch-type or continuous-type hydride generator specified in JIS K
0121. For continuous hydride generators, there is a method to introduce a potassium iodide
solution on-line in addition to a sample solution, hydrochloric acid, and a sodium
tetrahydroborate solution.
1) Argon: Argon of grade 2 specified in JIS K 1105 or equivalents.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 350 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to no less than 300 °C.
Note (5) For cell heating, there are a method of electric heating and a method of flame heating.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g - 2.00 g of an analytical sample, and put it in a 200-mL - 300-mL tall beaker.
b) Add about 10 mL of nitric acid and about 5 mL of sulfuric acid, cover the tall beaker with awatch glass, and leave at rest overnight.
c) Heat mildly on a hot plate or sand bath at 170 ºC - 220 ºC for no less than 30 minutes. Afterbubbles cease to form, set the temperature of the hot plate or sand bath to no less than 300 ºC,
and heat until nitroxide (yellow-brown smoke) is no longer generated (6) (7).
d) After standing to cool, add about 5 mL of perchloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or sand bath at no less than 300ºC for 2 - 3 hours to digest (8).
f) Slightly move the watch glass (9), and keep on heating on the hot plate or sand bath toconcentrate until the liquid volume becomes no more than 2 mL (10).
g) After standing to cool, add about 5 mL of hydrochloric acid (1+10) and about 20 mL of water,
cover the tall beaker with a watch glass and heat mildly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200-mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (6) Carbonization (degradation) of organic matters by sulfuric acid begins by heating when
nitric acid no longer remains. In this state, As5+ may be reduced to As3+ and evaporate;
therefore, stop heating immediately after the end of the generation of nitroxide (yellowbrown smoke).
(7) Oxidation of organic matters by perchloric acid progresses extremely rapidly andexplosively. For that reason, add perchloric acid after fully degrading organic matterswith nitric acid to avoid danger.
(8) When the white smoke of perchloric acid is generated, if the solution is colored such as
black-brown or brown, stop heating immediately, and after standing to cool, add nitricacid, and heat again to degrade remaining organic matters.
(9) The watch glass can be removed.
(10) The generation of arsenic hydride is inhibited by the presence of nitric acid; therefore,
remove nitric acid by sufficiently generating the white smoke of sulfuric acid.
Comment 2 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B. However, the sampling amount of the analytical429

Testing Methods for Fertilizers(2021)

sample in (4.1) a) in 5.5.c is 1.00 g.
Comment 3 When the analytical sample solidifies in the procedure in (4.1) b), moisten theanalytical sample with a small amount of water as necessary in advance.
Comment 4 It is not necessary to conduct the procedure in (4.1) b) “leave at rest overnight” in thecase of fertilizers not containing organic matters.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used. Two examples of measurement procedures with a continuous
hydride generator are shown below.
(4.2.1) Measurement (A): Leaving at rest after adding a potassium iodide solution.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 193.7 nmb) Calibration curve preparation
1) Put 2.5 mL - 10 mL of arsenic standard solution (As 0.1 µg/mL) in 50-mL volumetric flasks
step-by-step.
2) Add 5 mL of hydrochloric acid and 5 mL of potassium iodide solution, leave at rest for about
15 minutes, and then add water up to the marked line, to make 5 ng/mL -20 ng/mL arsenic
standard solutions for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 50-mL volumetric flask to make a blank test
solution for the calibration curve preparation.
4) While letting argon flow, introduce the arsenic standard solution for the calibration curve
preparation for each step and the blank test solution for the calibration curve preparation
respectively, further introduce hydrochloric acid (1+1) and a sodium tetrahydroborate solution
to the hydride generator to generate arsenic hydride.
5) Separate arsenic hydride and liquid waste, and then introduce the gas containing arsenic hydride
to a heated absorption cell, and read the indicated value at a wavelength of 193.7 nm.
6) Prepare a curve for the relationship between the arsenic concentration and the indicated valueof the arsenic standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution in a 50-mL volumetric flask, and conduct
procedures similarly as in b) 2) and b) 4) - 5) to read the indicated value.
2) Put a predetermined amount of the blank test solution in a 50-mL volumetric flask, and conduct
procedures similarly as in b) 2) and b) 4) - 5) to read the indicated value, and correct theindicated value obtained for the sample solution.
3) Obtain the arsenic content from the calibration curve, and calculate arsenic (As) in the analyticalsample.
(4.2.2) Measurement (B): On-line introduction of a potassium iodide solution.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 193.7 nmb) Calibration curve preparation
1) Put 5 mL - 25 mL of arsenic standard solution (As 0.1 µg/mL) in 50-mL volumetric flasks stepby-step, add water up to the marked line, to make the 10 ng/mL - 50 ng/mL arsenic standard
solution for the calibration curve preparation. Use water as the blank test solution for thecalibration curve preparation.
2) While letting argon flow, introduce arsenic standard solutions for the calibration curve430

Testing Methods for Fertilizers(2021)

preparation and the blank test solution for the calibration curve preparation, respectively, andfurther introduce a potassium iodide solution, hydrochloric acid (1+1) and a sodium
tetrahydroborate solution to the hydride generator to generate arsenic hydride.
3) Separate arsenic hydride and liquid waste, and then introduce the gas containing arsenic hydride
to a heated absorption cell, and read the indicated value at a wavelength of 193.7 nm.
4) Prepare a curve for the relationship between the arsenic concentration and the indicated valueof the arsenic standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution in a 50-mL volumetric flask, and conduct
procedures similarly as in b) 2) - 3) to read the indicated value.
2) Put a predetermined amount of the blank test solution in a 50-mL volumetric flask, add water
up to the marked line, and conduct similarly as in b) 2) - 3) to read the indicated value, andcorrect the indicated value obtained for the sample solution.
3) Obtain the arsenic content from the calibration curve, and calculate arsenic (As) in the analyticalsample.
Comment 5 The coexistence of iron, nickel, and cobalt at over 5, 10, 80 folds amount of arsenic,
respectively, inhibits the generation of arsenic hydride. However, the inhibition ofarsenic hydride generation even in the coexistence of iron at 1000 folds amount can beremoved by adding or introducing a potassium iodide solution.
Comment 6 Instead of the correction method in c) 2), the arsenic (As) in the analytical sample canalso be corrected by obtaining the arsenic content in the blank test solution.
Comment 7 Recovery testing was conducted using industrial sludge fertilizer, composted sludge
fertilizer (3 samples) and human waste sludge fertilizer; as a result, the recovery rates
at the concentration level of 50 mg/kg and 5 mg/kg were 94.6 % - 100.6 % and 99.9 %- 103.3 % as arsenic (As), respectively. Also, recovery testing was conducted using
processed slug phosphorus fertilizer, soybean meal, rape seed meal, compound
fertilizer and magnesia-potassium-sulfate fertilizer; as a result, the recovery rates atthe concentration level of 50 mg/kg and 5 mg/kg were 98.5 % - 109.8 % and 103.5 %- 108.6 %, respectively.
Results from a collaborative study for test method validation and its analysis are shownin Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.1 mg/kg.

431

Testing Methods for Fertilizers(2021)

Table 1 Analysis results of the collaborative study
for arsenic test method validation
2)
3)
4)
Number of
Mean
RSD r
RSD R
Sample name1)laboratories(mg/kg)
(%)
(%)
11
6.42
3.5
10.7
Sewage sludge fertilizer
10
4.62
4.9
7.0
Human waste sludge fertilizer
12
0.632
5.7
19.7
Industrial sludge fertilizer
12
5.08
4.1
9.5
Calcined sludge fertilizer
10
1.23
6.1
11.4
Composted sludge fertilizer
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Repeatability relative standard deviation
4) Reproducibility relative standard deviation

References
1)
Naoki ASAO, Yukie ISHIDA, Shinjiro IZUKA and Masakazu SAIKI: Determination of
Arsenic in Sludge Fertilizer - Improved Decomposition Method - Research Report of
Fertilizer Vol. 1, p. 74 - 81 (2008)
2)
Naoki ASAO, Shinjiro IZUKA and Norio HIKICHI: Determination of Arsenic in Sludge
Fertilizer - Collaborative Test Results - Research Report of Fertilizer Vol. 1, p. 82 - 89
(2008)
3)
Yasushi SUGIMURA, Naoki ASAO and Shinjiro IZUKA: Determination of Arsenic in
Fertilizer- Expanding the scope of application of improved method -, Research Report of
Fertilizer Vol. 2, p. 18 - 24 (2009)432

Testing Methods for Fertilizers(2021)(5)

Flow sheet for arsenic: The flow sheet for arsenic in fertilizers is shown below:
1.00 g - 2.00 g
200-mL - 300-mL tall beaker
analytical sample← A small amount of water to moisten analytical sample(if needed).
← About 10 mL nitric acid
← About 5 mL sulfuric acid
Leaving at rest
Cover with a watch glass
overnight
HeatingHeat mildly on a hot plate or sand bathat 170 ºC - 220 ºC for no less than 30 minutes.

HeatingHeat on a hot plate or sand bath at no less than 300 ºC
until yellow-brown smoke is no longer generated

Standing to coolRoom temperature← About 5 mL of perchloric acid
Cover with a watch glass, and heat on a hot plate or
Heatingsand bath at no less than 300 ºC for 2 - 3 hours
Heating

Slightly move the watch glass, and concentrate
until it becomes no more than 2 mL

Standing to coolRoom temperature← About 5 mL of hydrochloric acid (1+10)← About 20 mL of water
Heating
Cover with a watch glass, and dissolve
Standing to coolRoom temperature

Transfer
100-mL volumetric flask← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Measurement

Atomic absorption spectrometerwith a hydride generator (193.7 nm)

Figure Flow sheet for arsenic in fertilizers

433

Testing Methods for Fertilizers(2021)

5.2.b Silver diethyl dithiocarbamate absorptiometric analysis(1) Summary
This test method is applicable to fertilizers other than sulfur and its compound. This testing method
is classified as Type E and its symbol is 5.2.b-2017 or As.b-1.
Pretreat an analytical sample with nitric acid - sulfuric acid - perchloric acid, and then put thepredetermined volume into an arsenic hydride generation bottle, and generate arsenic hydride byadding a potassium iodide solution, a tin chloride solution and zinc successively in the acidic
condition with hydrochloric acid to react with silver diethyl dithiocarbamate in pyridine. Measure theabsorbance with the silver diethyl dithiocarbamate solution, the coloring liquid, at a wavelength of
510 nm or 519 nm to obtain arsenic (As) in an analytical sample.
(2)
a)
b)
c)
d)
e)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Perchloric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Hydrochloric acid: Hydrochloric acid for arsenic analysis specified in JIS K 8180, or of
harmful metal analysis grade, microanalysis grade or equivalents.
f) Potassium iodide solution: Dissolve 20 g of potassium iodide specified in JIS K 8913 in water
to make 100 mL.
g) Tin (II) chloride solution: Dissolve 15 g of tin (II) chloride dihydrate specified in JIS K 8136
in 100 mL of hydrochloric acid (1+1), add a small amount of granular tin specified in JIS K
8580 then store in a colored bottle.
h) Ascorbic acid: A JIS Guaranteed Reagent specified in JIS K 9502 or a reagent of equivalentquality.
i) Zinc: A reagent of arsenic analysis grade specified in JIS K 8012 or equivalents. (1 mm - 1.5
mm particle diameter)j) Lead acetate glass wool: Glass wool air-dried after moisturizing with 100 mL of the solution,
where 10 g of lead acetate (II) trihydrate specified in JIS K 8374 is dissolved in water.
k) Silver diethyldithiocarbamate solution:
Dissolve 0.5 g of silver N, N-diethyl
dithiocarbamate specified in JIS K 9512 in 100 ml of pyridine specified in JIS K 8777, thenstore in cool and dark placel)Arsenic standard solution (As 0.1 mg/mL): An arsenic standard solution (As 0.1 mg/mL)
traceable to National Metrology.
m) Arsenic standard solution (As 1 µg/mL) (1) (2): Dilute a predetermined amount of arsenic
standard stock solution (As 0.1 mg/mL) accurately with hydrochloric acid (1+100) to prepare
an arsenic standard solution (As 1 µg/mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in a refrigerator, and do not use after 6 months after preparation.
Comment 1 Instead of the arsenic standard solution in (2), an arsenic standard solution for thecalibration curve preparation can be prepared by using an arsenic standard solution(As 1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Arsenic hydride generator: An arsenic hydride generator specified in 61.1 in JIS K 0102 or
equivalents.
b) Spectrophotometer: A spectrophotometer specified in JIS K 0115
434

Testing Methods for Fertilizers(2021)c)

Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 350 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to no less than 300 °C.

(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g - 2.00 g of an analytical sample, and put it in a 200-mL - 300-mL tall beaker.
b) Add about 10 mL of nitric acid and about 5 mL of sulfuric acid, cover the tall beaker with awatch glass, and leave at rest overnight.
c) Heat mildly on a hot plate or sand bath at 170 ºC - 220 ºC for no less than 30 minutes. Afterbubbles cease to form, set the temperature of the hot plate or sand bath to no less than 300 ºC,
and heat until nitroxide (yellow-brown smoke) is no longer generated (3) (4).
d) After standing to cool, add about 5 mL of perchloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or sand bath at no less than 300ºC for 2 - 3 hours to digest (5).
f) Slightly move the watch glass (6), and keep on heating on the hot plate or sand bath toconcentrate until the liquid volume becomes no more than 2 mL (7).
g) After standing to cool, add about 5 mL of hydrochloric acid (1+10) and about 20 mL of water,
cover the tall beaker with a watch glass and heat mildly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL volumetric flask with water, add water
up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (3) Carbonization (degradation) of organic matters by sulfuric acid begins by heating when
nitric acid no longer remains. In this state, As+5 may be reduced to As+3 and evaporate;
therefore, stop heating immediately after the end of the generation of nitroxide (yellowbrown smoke).
(4) Oxidation of organic matters by perchloric acid progresses extremely rapidly andexplosively. For that reason, add perchloric acid after fully degrading organic matterswith nitric acid to avoid danger.
(5) When the white smoke of perchloric acid is generated, if the solution is colored such as
black-brown or brown, stop heating immediately, and after standing to cool, add nitricacid, and heat again to degrade remaining organic matters.
(6) The watch glass can be removed.
(7) The generation of arsenic hydride is inhibited by the presence of nitric acid; therefore,
remove nitric acid by sufficiently generating the white smoke of sulfuric acid.
Comment 2
Comment 3
Comment 4

A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
When the analytical sample solidifies in the procedure in (4.1) b), moisten theanalytical sample with a small amount of water as necessary in advance.
It is not necessary to conduct the procedure in (4.1) b) “leave at rest overnight” inthe case of fertilizers not containing organic matters.

(4.2) Reaction: Conduct reaction as shown below.
a) Put a predetermined amount (the equivalents of 1 μg - 20 μg of As and liquid volume is no morethan 40 mL) of the sample solution into an arsenic hydride generation bottle.
b) Add water to the solution to make about 40 mL.
c) Add about 10 mL of hydrochloric acid.
435

Testing Methods for Fertilizers(2021)d) Add about 2 mL of potassium iodide solution, shake and leave at rest for a few minutes.
e) Add about 1 mL of tin (II) chloride solution, shake and leave at rest for about 10 minutes (8).
f) Connect arsenic hydride generation bottle, glass tube lightly stuffed with lead acetate glass woolin advance and 5 mL of silver diethyl dithiocarbamate solution (9), and quickly put 2.5g of zinc
into an arsenic hydride generation bottle.
g) Leave at rest at room temperature (15ºC - 25ºC) for about 45 minutes, and allow generated
arsenic hydride to absorb into the silver diethyl dithiocarbamate solution and color.
h) Put a predetermined amount of blank test solution into the arsenic hydride generation bottle,
conduct procedures similarly as in b) - g) to allow generated arsenic hydride to absorb into thesilver diethyl dithiocarbamate solution and color.
Note (8) When a large amount of iron is contained, add 1 g of ascorbic acid and 2mL of tin (II)chloride solution and shake to mix to leave at rest for about 10 minutes instead of theprocedure in e).
(9) Apply a small amount of silicone grease, etc. to the connecting parts of an arsenic
hydride generation bottle, glass tube and arsenic hydride absorption tube to maintaintheir airtightness.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used.
a) Measurement conditions of the spectrophotometer: Set up the measurement conditions of
the spectrophotometer considering the following.
Detection wavelength: 510 nm or 519 nmb) Calibration curve preparation
1) Put 2.5 mL - 20 mL of arsenic standard solution (1 µg/mL) in arsenic hydride generation bottles
step-by-step.
2) Conduct procedures similarly as in (4.2) b) - g) and allow them to react.
3) For another arsenic hydride generation bottle, the silver diethyl dithiocarbamate solution
prepared similarly as in the procedure in 2) is used as the blank test solution for the calibration
curve preparation.
4) Measure the absorbance at a wavelength 510 nm of the silver diethyl dithiocarbamate solutionof the arsenic standard solution for the calibration curve preparation using the blank test solution
for the calibration curve preparation as the control.
5) Prepare a curve for the relationship between the arsenic concentration and the indicated valueof the arsenic standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) For the silver diethyl dithiocarbamate solution of (4.2) g), conduct procedures similarly as inb) 4) to measure absorbance.
2) For the silver diethyl dithiocarbamate solution of (4.2) h), conduct procedures similarly as inb) 4) to measure absorbance, and correct the absorbance obtained for the sample solution.
3) Obtain the arsenic content from the calibration curve, and calculate arsenic (As) in the analyticalsample.
Comment 5 Instead of the correction method in c) 2), the arsenic (As) in the analytical sample canalso be corrected by obtaining the arsenic content in the blank test solution.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers
436

Testing Methods for Fertilizers(2021)(Details), p.270- 273, Yokendo, Tokyo (1988)(5)

Flow sheet for arsenic: The flow sheet for arsenic in fertilizers is shown below:

437

Testing Methods for Fertilizers(2021)

Sample solution
Aliquot
Transfer into an arsenic hydride generation bottle(predetermined volume)← Water (until liquid volume becomes about 40 mL)← About 10 mL of hydrochloric acid
← About 2 mL of potassium iodide solution
Shaking to mix
Leaving at rest
For a few minutes←About 1 mL of tin (II) chloride solution
Shaking to mix
Leaving at rest
For about 10 minutes←2.5 g of zinc
Generation ofarsenic hydrideººRoom temperature (15 C - 25 C),
about 45 minutes

Absorption

5 mL of silver diethyldithiocarbamate solution

Measurement

Spectrophotometer (510 nm or 519 nm)

Figure 2 Flow sheet for arsenic in fertilizers(Reaction and measurement procedure)

438

Testing Methods for Fertilizers(2021)

5.2.c
ICP Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 5.2.c-2021 or As.c-2.
Add nitric acid – hydrogen peroxide to an analytical sample, and heat to decompose by microwave
irradiation. Introduce it to an ICP Mass Spectrometer (ICP-MS) and measure the respective indicatedvalues of arsenic and an internal standard element (tellurium) with mass/charge number (m/z) andobtain arsenic (As) in the analytical sample from the ratio of the indicated value for arsenic and theindicated value for the internal standard element. Note that the performance of this testing method isshown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Nitric acid: Nitric acid used to dilute a standard solution and a sample solution is a highly
pure reagent specified in JIS K 9901.
d) Hydrogen peroxide: A JIS Guaranteed Reagent specified in JIS K 8230 or a reagent ofequivalent quality.
e) Tellurium standard solution (Te 1000 mg/L): A tellurium standard solution (Te 1000 mg/L)
traceable to National Metrology.
f) Tellurium standard solution (Te 5 µg/mL) (1) (2) (3): Dilute a predetermined amount of tellurium
standard solution (Te 1000 mg/L) with nitric acid (1+19) to prepare a tellurium standard solution(Te 5 µg/mL).
g) Tellurium standard solution (Te 100 ng/mL) (1) (3): Dilute a predetermined amount of
tellurium standard solution (Te 5 µg/mL) with nitric acid (1+19) to prepare a tellurium standard
solution (Te 100 ng/mL).
h) Arsenic standard solution (As 1000 mg/L): An arsenic standard solution (As 1000 mg/L)
traceable to National Metrology.
i) Arsenic standard solution (As 200 ng/mL) (1) (2) (3): Dilute the arsenic standard solution (As1000 mg/L) with nitric acid (1+19) to prepare an arsenic standard solution (As 200 ng/mL).
j) Arsenic standard solutions (As 4 ng/mL - 20 ng/mL) for the calibration curve preparation(1) (3): Put 2 mL - 10 mL of arsenic standard solution (As 200 ng/mL) in 100-mL volumetricflasks step-by-step, and add nitric acid (1+19) to the marked line.
k) Arsenic standard solutions (As 0.2 ng/mL - 2 ng/mL) for the calibration curve preparation(1) (3): Put 1 mL - 10 mL of arsenic standard solution (As 20 ng/mL) in 100-mL volumetric flasks
step-by-step, and add nitric acid (1+19) to the marked line.
l) Blank test solution for the calibration curve preparation (1) (3): Nitric acid (1+19) used in theprocedures in f), g), i), j) and k).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in a cool, dark place, and do not use after 6 months after preparation.
(3) For preparation and storage, use sealable containers made of materials such as
polypropylene containing no arsenic.
Comment 1 Instead of the tellurium standard solution in (2), a tellurium standard solution can beprepared by using a tellurium standard solution (Te 100 mg/L or 10000 mg/L) traceable
to National Metrology.
Comment 2 Instead of the arsenic standard solution in (2), an arsenic standard solution for thecalibration curve preparation can be prepared by using an arsenic standard solution(As 100 mg/L or 10000 mg/L) traceable to National Metrology.
439

Testing Methods for Fertilizers(2021)

Comment 3 If a sample solution or a standard solution for the calibration curve preparation and aninternal standard solution are not simultaneously introduced in the measurement of
ICP-MS, when preparing respective solutions in the procedures in j), k) and l), add
tellurium standard solution (Te 100 ng/mL) 1/10 of the volume of the solution.
Comment 4 ICP-MS detection methods include a pulse detection method and an analog detection
method. There are detection method models that combine them, but when themeasurement value is affected by switching, the concentration of the standard solution
and the internal standard solution may be changed as appropriate so that measurement
can be performed with either detection method.
(3) Instruments: Instruments are as shown below:a) ICP Mass Spectrometer: A high-frequency plasma mass spectrometer specified in JIS K
0133, that is equipped with a collision/reaction cell.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.995 % in purityb) Pressure vessel decomposing device: A device which pressurizes the inside of a vessel by
putting acid, etc. to heat in the decomposing vessel, and decomposes a sample by the interactionof heating, pressurizing and acid. The following requirements should be met.
1) The main part of a decomposing device: In the case of the microwave heating method, adevice should be able to produce a high-frequency wave using a frequency which is permitted
at an industrial frequency facility. It is desirable to be able to monitor pressure and temperature,etc. in the decomposing vessel with a sensor inside the device. The interior of a device shouldbe acid-resistant treated and should have a high temperature durability and a high level of safety.
2) Exhaust system: A system which has an exhaust fan of acid-resistant specification, and has
an air-cool function inside the device to allow constant airflow, keeping operating temperature
below a certain temperature level.
3) Decomposing vessel: A vessel which is heat-resistance and pressure-tight and has the
durability required to decompose particles, and has resistance to internal contamination. Itshould have safety functions such as causing overheat prevention valve to work and internalpressure to drop by emitting gas, and preventing gas bumping in the case of exceeding apressure limitation.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Fluid sludge fertilizera) Weigh 20.0 g (4) of an analytical sample, and put it into a decomposing vessel.
b) Gradually add 2.5 mL of nitric acid and 2 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and put it in a 50-mL ground-in stopper centrifugal precipitate
tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
(4.1.2) Fertilizers except fluid sludge fertilizersa) Weigh 0.20 g of an analytical sample, and put it into a decomposing vessel.
440

Testing Methods for Fertilizers(2021)b) Gradually add 10 mL of nitric acid and 1 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and transfer it to a 50-mL ground-in stopper centrifugal
precipitate tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
Note (4) The maximum limit of solid content, which is converted from moisture content, in thesampling volume 20.0 g of an analytical sample is about 0.5 g. If solid content is likely
to exceed the limit, reduce sampling volume as necessary.
(5) Example setting conditions of a microwave decomposing device are as shown in Table
1.
Table 1 Example setting conditions of a microwave decomposing device
Time (min)Temperature (°C)

Output (kW)

0

-

0

20

200 (temperature rising)

1400

10

200

1400

40

Room temperature0(6) When organic matters, for example colored precipitate, etc., still remain, add 2 mL ofnitric acid and 1 mL of hydrogen peroxide and repeat the procedures in (4.1) c) – d).
(7) The vessel should be made of polypropylene, etc. to not affect the measurement.
(8) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal force.
Comment 5 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Internal Standard Method) according to JIS K 0113 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Mass Spectrometer used in measurement.
a) Measurement conditions for the ICP Mass Spectrometer: Set up the measurement conditions
for the ICP Mass Spectrometer considering the following:
Arsenic: mass/charge number (m/z): 75
Tellurium: mass/charge number (m/z): 125
Collision cell: He-KED (Kinetic Energy Discrimination) mode (9)b) Calibration curve preparation
1) Spray the arsenic standard solution for the calibration curve preparation and the blank test
solution for the calibration curve preparation together with tellurium standard solution (Te 100
ng/mL) into the inductively coupling plasma (10), and read the ratio of the indicated values forthe respective mass/charge number of an element subjected to measurement and an internal441

Testing Methods for Fertilizers(2021)

standard element.
2) Prepare a calibration curve for the relationship between the concentration and the ratio of theindicated value of an element subjected to measurement.
c) Sample measurement
1) Put no more than 2.5 mL of the sample solution in a 50-mL volumetric flask (7), add nitric acidto be nitric acid (1+19), and add water to the marked line (11).
2) Subject to the same procedure as in b) 1) to read the ratio of the indicated values.
3) For the blank test solution, conduct procedures similarly as in 1) - 2) to correct the ratio of theindicated value obtained for the measurement solution.
4) Obtain the cadmium content from the calibration curve, and calculate cadmium (Cd) in theanalytical sample.
Note (9) Note that, when He-H2 mixture gas is used, H2 may react with As and the indicated valueof As becomes lower, affecting the measurement.
(10) Simultaneously introduce an internal standard solution 1/9 of the volume of the standard
solution for the calibration curve preparation or the blank test solution for the calibration
curve preparation.
(11) If there is a possibility that the arsenic concentration in the sample solution will exceed
the maximum limit of the calibration curve, reduce the sampling amount for the sample
solution or dilute it with nitric acid (1+19).
Comment 6 Instead of the correction method in c) 3), the arsenic concentration in the analyticalsample can also be corrected by obtaining the arsenic concentration in the blank test
solution.
Comment 7 Divalent ions 150Sm and 150Nd cause spectrum interference to 75As. Spectrum
interference affects analysis values depending on the resolution of the instrument.
Therefore, ascertain in advance the resolution of the instrument and the Sm and Ndconcentrations that affect analysis values, and perform analysis using other methods
such as hydride generation atomic absorption spectrometry if the sample is known tohave Sm and Nd concentrations higher than the interfering concentrations.
Comment 8 Triplicates additive recovery testing was conducted to evaluate trueness using mixed
compost compound fertilizers and fluid composted sludge fertilizers. As a result, themean recovery rates at the concentration level of 1 mg/kg - 50 mg/kg were 102 % 112 % as arsenic (As).
The comparison of the analysis value (yi: 0.06 mg/kg - 40.2 mg/kg) of ICP-MS and theanalysis value (xi) of hydride generation flame atomic absorption spectrometer was
conducted using sewage sludge fertilizer (2 samples), human waste sludge fertilizer (5samples), industrial sludge fertilizer (1 sample), mixed sludge fertilizer (1 sample),
calcined sludge fertilizer (3 samples), composted sludge fertilizer (12 samples),composted seafood byproduct fertilizer (1 sample), superphosphate of lime (1 sample),double superphosphate of lime (1 sample), processed phosphorus fertilizer (2 samples),byproduct animal fertilizer (1 sample), compound fertilizer (13 samples), blended
fertilizer (3 samples), fluid compound fertilizer (1 sample), coating compound
fertilizer (2 samples), solid compound fertilizer (2 samples), byproduct compound
fertilizer (2 samples), mixed compost compound fertilizer (1 samples), silicate slag
fertilizer (1 sample), byproduct magnesia fertilizer (1 sample), mixed microelement
fertilizer (1 sample), and distribution fertilizer (58 samples). As a result, a regression
equation was y = −0.0982 + 0.9987x, and its correlation coefficient (r) was 0.993.
The results of repeated analyses on different days using a composted sludge fertilizer
442

Testing Methods for Fertilizers(2021)

and standard solution-added compound fertilizer were analyzed by the one-way
analysis of variance. Table 2 shows the estimation results of intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 mg/kg for fluid sludge fertilizers and about 1 mg/kg for other fertilizers.
Table 2 Estimation results of repeatability and intermediate precision
Days of
Repeatability
Intermediate precision
2)
4)
5)
6)
7)
repeatability
Sample name
Mean
sr
RSD r
s I(T)RSD I(T)1)

Composted sludge fertilizer

T5(mg/kg)3

3)Compound fertilizer(mg/kg)
0.1

3)

(%)
3.0

5
53
0.7
1.3
1) The number of days conducting duplicate analysis
2) Mean ([Number of days of repeatability (T )] × [Number of duplicates (2)])3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Intermediate standard deviation
7) Intermediate relative standard deviation(mg/kg)
0.2
0.7

3)

(%)
5.8
1.3

Comment 9 The simultaneous measurement of multiple elements is possible with the ICP-MS. In
that case, prepare standard solutions, etc. referencing Table 1 of Annex C2, conduct
procedures similarly as (4.2) b) - c), and calculate respective element concentrationsin an analytical sample.
Note that the concentration of a standard solution and an internal standard solution can
be changed as appropriate according to Comment 4.
References1)
Toshiharu YAGI: Determination of Heavy Metals in Fluid Sludge Fertilizers by ICP-MSand CV-AAS, Research Report of Fertilizer Vol. 8, p. 26 - 37 (2015)2)
Toshiharu YAGI, Kenta SAKUMA and Yoshimi HASHIMOTO: Determination of Heavy
Metals in Sludge Fertilizers using Inductively Coupled Plasma-Mass Spectrometer (ICPMS), Research Report of Fertilizer, Vol. 9, p. 21 – 32 (2016)
3)
Satoko SAKAIDA, Mayu OSHIMA, Keisuke AOYAMA and Yuji SHIRAI:
Determination of Harmful Components in Fertilizers using Inductively Coupled PlasmaMass Spectrometer (ICP-MS), Research Report of Fertilizer, Vol. 12, p. 52 – 68 (2019)(5)

Flow sheet for arsenic: The flow sheet for arsenic in fluid sludge fertilizers is shown below:443

Testing Methods for Fertilizers(2021)

20.0 g analytical sample

Decomposing vessel← Nitric acid, 2.5 mL← Hydrogen peroxide, 2 mL
Microwave decomposition

Transfer

50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube, 1700 × g , 5 minutes

Sample solution
Figure 1 Flow sheet for arsenic in fluid sludge fertilizers (Extraction procedure)

0.20 g analytical sample

Decomposing vessel← Nitric acid, 10 mL← Hydrogen peroxide, 1 mL
Microwave decomposition

Transfer

50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube, 1700 × g , 5 minutes

Sample solution
Figure 2 Flow sheet for arsenic in fertilizers except fluid sludge fertilizers (Extraction procedure)
Sample solution

Aliquot (no more than 2.5
mL)

50-mL Volumetric flask← Nitric acid, to be nitric acid (1+19)← Water (up to the marked line)
Measurement

ICP-MS (internal standard: Te, As: m/z 75 Te: m/z 125）

Figure 3 Flow sheet for arsenic in fertilizers (Measurement procedure)444

Testing Methods for Fertilizers(2021)

5.3 Cadmium
5.3.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.3.a-2017 or Cd.a-1.
Pretreat an analytical sample with incineration and nitric acid-hydrochloric acid (1+3), spray into
an acetylene-air flame, and measure the atomic absorption with cadmium at a wavelength of 228.8
nm to obtain cadmium (Cd) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Cadmium standard solution (Cd 0.1 mg/mL): A cadmium standard solution (Cd 0.1 mg/mL)
traceable to National Metrology.
e) Cadmium standard solution (Cd 10 µg/mL): Put 10 mL of cadmium standard solution (Cd0.1 mg/mL) in a 100-mL volumetric flask, and add hydrochloric acid (1+23) up to the markedline.
f) Cadmium standard solutions (Cd 0.05 µg - 0.5 µg/mL) for the calibration curve
preparation (1) (2): Put 2.5 mL - 25 mL of cadmium standard solution (Cd 0.1 mg/mL) in 500mL volumetric flasks step-by-step, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1) (2): Hydrochloric acid (1+23)
used in the procedures in e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the cadmium standard solution in (2), a cadmium standard solution for thecalibration curve preparation can be prepared by using a cadmium standard solution(Cd 1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (3) function.
1) Light source: A cadmium hollow cathode lamp (In case of background correction systemusing continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
Note (3) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.

445

Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and pit it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (5), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (6) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water up
to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (4) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(5) The watch glass can be removed.
(6) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 2 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 228.8 nmb) Calibration curve preparation
1) Spray the cadmium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 228.8 nm.
2) Prepare a curve for the relationship between the cadmium concentration and the indicated valueof the cadmium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation.
c) Sample measurement
1) Subject the sample solution (7) to the same procedure as in b) 1) to read the indicated value.
2) Subject the blank test solution to the same procedure as in b) 1) to read the indicated value, andcorrect the indicated value obtained for the sample solution.
3) Obtain the cadmium content from the calibration curve, and calculate cadmium (Cd) in the446

Testing Methods for Fertilizers(2021)

analytical sample.
Note (7) If there is a possibility that the cadmium concentration in the sample solution will exceed
the maximum limit of the calibration curve, dilute a predetermined amount withhydrochloric acid (1+23).
Comment 4 Instead of the correction method in c) 2), the cadmium (Cd) in the analytical sample
can also be corrected by obtaining the cadmium content in the blank test solution.
Comment 5 Recovery testing was conducted using industrial sludge fertilizer and composted
sludge fertilizer (5 samples); as a result, the recovery rates at the concentration levelof 5 mg/kg and 0.5 mg/kg were 97.5 % - 99.2 % and 96.7 % - 99.7 %, respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.1 mg/kg.
Table 1 Analysis results of the collaborative study
for cadmium test method validation
Number of Mean2) RSD r3)
Sample name1)(%)
laboratories (mg/kg)
Sewage sludge fertilizer a
10
1.50
5.5
Sewage sludge fertilizer b
10
3.35
1.2
Composted sludge fertilizer a
10
1.96
1.0
Composted sludge fertilizer b
11
3.81
1.9
Composted sludge fertilizer c
10
1.80
3.5
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Repeatability relative standard deviation
4) Reproducibility relative standard deviation

4)

RSD R
(%)
6.4
4.2
4.4
3.2
4.9

References
1)
Yoshinari SAKAKIBARA, Manabu MATSUZAKI and Tadao AMANO: Determinationof Cadmium, Lead, Nickel and Chromium in Sludge Fertilizer - Improved Decomposition
Method - Research Report of Fertilizer Vol. 1, p. 41 - 49 (2008)
2) Yoshinari SAKAKIBARA and Manabu MATSUZAKI: Determination of Cadmium, Lead,
Nickel and Chromium in Sludge Fertilizer - Collaborative Test Results - Research Reportof Fertilizer Vol. 1, p. 50 - 59 (2008)
3)
Hisanori ARAYA and Yoshimi TAKEBA: Validation of atomic absorption spectrometryfor determination of cadmium, lead, nickel and chromium in calcined sludge fertilizer Research Report of Fertilizer Vol. 3, p. 30 - 42 (2010)

447

Testing Methods for Fertilizers(2021)(5)

Flow sheet for cadmium: The flow sheet for cadmium in fertilizers is shown below:
5.00 ganalytical sample
Charring
Incineration

200-mL - 300-mL tall beaker.
Heat gently
Ignite at 450 ºC ± 5 ºC, 8 - 16 hours

Standing to coolRoom temperature← A small amount of water← About 10 mL of nitric acid
← About 30 mL of hydrochloric acid
Heating
Cover with a watch glass, and digest
Heating

Slightly move a watch glass to remove acid

Standing to coolRoom temperature← About 25 mL - 50 mL of hydrochloric acid (1+5)
Heating
Cover with a watch glass, and dissolve
Standing to coolRoom temperature

Transfer
100-mL - 200-mL volumetric flask, water← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Measurement

Atomic absorption spectrometer (228.8 nm)

Figure Flow sheet for nickel in fertilizers

448

Testing Methods for Fertilizers(2021)

5.3.b ICP Optical Emission Spectrometry(1) Summary
The test method is applicable to sludge fertilizers, etc. This testing method is classified as Type D and
its symbol is 5.3.b-2017 or Cd.b-1.
Pretreat an analytical sample with incineration, nitric acid - hydrochloric acid (1+3), introduce it toan ICP Optical Emission Spectrometer (ICP-OES) and measure the emission with cadmium at awavelength of 228.802 nm to quantify the cadmium (Cd) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 8.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Cadmium standard solution (Cd 0.1 mg/mL): A cadmium standard solution (Cd 0.1 mg/mL)
traceable to National Metrology.
e) Cadmium standard solution (Cd 0.25µg/mL) (1) (2): Dilute a predetermined amount of
cadmium standard solution (Cd 0.1 mg/mL) with hydrochloric acid (1+23) to prepare a
cadmium standard solution (Cd 0.25 µg/mL)
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the cadmium standard solution in (2), a cadmium standard solution for thecalibration curve preparation can be prepared by using a cadmium standard solution(Cd 1 mg/mL or 10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purity.
b) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (3).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (3).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
449

Testing Methods for Fertilizers(2021)

Slightly move the watch glass (4), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (5) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200 mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
f)Note (3) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(4) The watch glass can be removed.
(5) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 3 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Standard Addition Method) according to JIS K 0116 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Optical Emission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 228.802 nmb) Calibration curve preparation and sample measurement
1) Put 5mL of sample solution in three 10-mL volumetric flasks respectively.
2) Add 2mL and 4 mL of cadmium standard solution (0.25 μg/mL) to volumetric flasks of 1) above,and further add hydrochloric acid (1+23) to the marked line to make a sample solution ofStandard Addition Method.
3) Add hydrochloric acid (1+23) to the marked line of the remaining volumetric flask of 1) above
to make a sample solution without a standard solution.
4) Spray the sample solution of Standard Addition Method and the sample solution without astandard solution into the induction plasma, and read the indicated value at a wavelength of
228.802 nm.
5) Put 5 mL of blank test solution in a 10-mL volumetric flask, conduct the same procedures as in3) - 4) to read the indicated value, and correct the indicated value obtained from the respective
sample solutions.
6) Prepare a curve for the relationship between the added cadmium concentration and the correctedindicated value of the sample solution for Standard Addition Method and sample solution
without a standard solution.
7) Obtain the cadmium content from the intercept of the calibration curve to calculate cadmium(Cd) in the analytical sample
Comment 5 Instead of the correction method in b) 5), the cadmium (Cd) in the analytical sample
can also be corrected by obtaining the cadmium content in the blank test solution.
450

Testing Methods for Fertilizers(2021)

Comment 6 Coexistence of As in large quantities causes interference. Ascertain in advance the Asconcentration that causes interference for the instrument, and perform analysis using
other methods such as flame atomic absorption spectrometry if the sample is known
to have an As concentrations higher than the interfering concentration.
Comment 7. The simultaneous measurement of multiple elements is possible with the ICP-OES. In
that case, see 4.9.1.b Comment 6.
Comment 8 The comparison of the measurement value (xi：0.003 mg/kg - 3.32 mg/kg) of ICP
Optical Emission Spectrometry and the measurement value (yi) of Flame Atomic
Absorption Spectrometry was conducted to evaluate trueness using sludge fertilizers(49 samples). As a result, a regression equation was y=−0.03+1.009x and its
correlation coefficient (r) was 0.996. Triplicates measurement for each one sample ofsewage sludge fertilizer, human waste sludge fertilizer, industrial sludge fertilizer,
mixed sludge fertilizer, calcined sludge fertilizers and composted sludge fertilizer was
conducted. As a result, a repeatability obtained was 0.8 % - 4.1 % as a relative standard
deviation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.2 mg/kg.
References
1)
Masahiro ECHI, Tomoe INOUE, Megumi TABUCHI and Tetuya NOMURA:
Simultaneous Determination of Cadmium, Lead, Nickel, Chromium, Copper and Zinc in
Sludge Fertilizer using Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES), Research Report of Fertilizer, Vol. 4, p. 30 - 35 (2011)451

Testing Methods for Fertilizers(2021)(5)

Flow sheet for cadmium: The flow sheet for cadmium in fertilizers is shown below:452

Testing Methods for Fertilizers(2021)

5.3.c
ICP Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 5.3.c-2021 or Cd.c-2.
Add nitric acid–hydrogen peroxide to an analytical sample, and heat to decompose by microwave
irradiation. Introduce it to an ICP Mass Spectrometer (ICP-MS) and measure the respective indicatedvalues of cadmium and an internal standard element (rhodium) with mass/charge number (m/z) andobtain cadmium (Cd) in the analytical sample from the ratio of the indicated value for cadmium andthe indicated value for the internal standard element. Note that the performance of this testing method
is shown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Nitric acid: Nitric acid used to dilute a standard solution and a sample solution is a highly
pure reagent specified in JIS K 9901.
d) Hydrogen peroxide: A JIS Guaranteed Reagent specified in JIS K 8230 or a reagent ofequivalent quality.
e) Rhodium standard solution (Rh 1000 mg/L): A rhodium standard solution (Rh 1000 mg/L)
traceable to National Metrology.
f) Rhodium standard solution (Rh 5 µg/mL) (1) (2) (3): Dilute a predetermined amount of rhodium
standard solution (Rh 1000 mg/L) with nitric acid (1+19) to prepare a rhodium standard solution(Rh 5 µg/mL).
g) Rhodium standard solution (Rh 50 ng/mL) (1) (3): Dilute a predetermined amount of rhodium
standard solution (Rh 5 µg/mL) with nitric acid (1+19) to prepare a rhodium standard solution(Rh 50 ng/mL).
h) Cadmium standard solution (Cd 1000 mg/L): A cadmium standard solution (Cd 1000 mg/L)
traceable to National Metrology.
i) Cadmium standard solution (Cd 50 ng/mL) (1) (2) (3): Dilute a predetermined amount of
cadmium standard solution (Cd 1000 mg/L) with nitric acid (1+19) to prepare a cadmium
standard solution (Cd 50 ng/mL).
j) Cadmium standard solutions (Cd 1 ng/mL - 5 ng/mL) for the calibration curve
preparation (1) (2) (3): Put 2 mL - 10 mL of cadmium standard solution (Cd 50 ng/mL) in 100mL volumetric flasks step-by-step, and add nitric acid (1+19) up to the marked line.
k) Cadmium standard solutions (Cd 0.05 ng/mL - 0.5 ng/mL) for the calibration curve
preparation (1) (3): Put 1 mL - 10 mL of cadmium standard solution (Cd 5 ng/mL) in 100-mL
volumetric flasks step-by-step, and add nitric acid (1+19) up to the marked line.
l) Blank test solution for the calibration curve preparation (1) (3): Nitric acid (1+19) used in theprocedures in f), g), i), j) and k).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in cool and dark place, and do not use after 6 month after preparation.
(3) For preparation and storage, use sealable containers made of materials such as
polypropylene containing no cadmium.
Comment 1 Instead of the rhodium standard solution in (2), a rhodium standard solution for thecalibration curve preparation can be prepared by using a rhodium standard solution(Rh 100 mg/L or 10000 mg/L) traceable to National Metrology.
Comment 2 Instead of the cadmium standard solution in (2), a cadmium standard solution for the453

Testing Methods for Fertilizers(2021)

calibration curve preparation can be prepared by using a cadmium standard solution(Cd 100 mg/L or 1000 mg/L) traceable to National Metrology.
Comment 3 When a sample solution or a standard solution for the calibration curve preparation
and an internal standard solution are not simultaneously introduced in themeasurement of ICP-MS, add 1/10 volume of rhodium standard solution (Rh 50
ng/mL) to the volume of the solution when preparing respective solutions in theprocedures in j), k) and l).
Comment 4 ICP-MS detection methods include a pulse detection method and an analog detection
method. There are detection method models that combine them, but when themeasurement value is affected by switching, the concentration of the standard solution
and the internal standard solution may be changed as appropriate so that measurement
can be performed with either detection method.
(3) Instruments: Instruments are as shown below:a) ICP Mass Spectrometer: A high-frequency plasma mass spectrometer specified in JIS K
0133, that is equipped with a collision/reaction cell.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.995 % in purity.
b) Pressure vessel decomposing device: A device which pressurizes the inside of a vessel by
putting acid, etc. to heat in the decomposing vessel, and decomposes a sample by the interactionof heating, pressurizing and acid. The following requirements should be met.
1) The main part of a decomposing device: In the case of the microwave heating method, adevice should be able to produce a high-frequency wave using a frequency which is permitted
at an industrial frequency facility. It is desirable to be able to monitor pressure and temperature,etc. in the decomposing vessel with a sensor inside the device. The interior of a device shouldbe acid-resistant treated and should have a high temperature durability and a high level of safety.
2) Exhaust system:
A vessel which is heat-resistance and pressure-tight and has the durability
required to decompose particles, and has resistance to internal contamination. It should havesafety functions such as causing overheat prevention valve to work and internal pressure to dropby emitting gas, and preventing gas bumping in the case of exceeding a pressure limitation.
3) Decomposing vessel: A vessel which is heat-resistance and pressure-tight and has the
durability required to decompose particles, and has resistance to internal contamination. Itshould have safety functions such as causing overheat prevention valve to work and internalpressure to drop by emitting gas, and preventing gas bumping in the case of exceeding apressure limitation.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Fluid sludge fertilizera) Weigh 20.0 g (4) of an analytical sample, and put it into a decomposing vessel.
b) Gradually add 2.5 mL of nitric acid and 2 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and put it in a 50-mL ground-in stopper centrifugal precipitate
tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
454

Testing Methods for Fertilizers(2021)h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
(4.1.2) Fertilizers except fluid sludge fertilizersa) Weigh 0.20 g of an analytical sample, and put it into a decomposing vessel.
b) Gradually add 10 mL of nitric acid and 1 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and transfer it to a 50-mL ground-in stopper centrifugal
precipitate tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
Note (4) The maximum limit of solid content, which is converted from moisture content, in thesampling volume 20.0 g of an analytical sample is about 0.5 g. If solid content is likely
to exceed the limit, reduce sampling volume as necessary.
(5) Example setting conditions of a microwave decomposing device are as shown in Table
1.
Table 1 Example setting conditions of a microwave decomposing device
Time (min)Temperature (°C)

Output (kW)

0

-

0

20

200 (temperature rising)

1400

10

200

1400

40

Room temperature0(6) When organic matters, for example colored precipitate, etc., still remain, add 2 mL ofnitric acid and 1 mL of hydrogen peroxide and repeat the procedures in (4.1) c) – d).
(7) The vessel should be made of polypropylene, etc. to not affect the measurement.
(8) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal force.
Comment 5 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Internal Standard Method) according to JIS K 0113 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Mass Spectrometer used in measurement.
a) Measurement conditions for the ICP Mass Spectrometer: Set up the measurement conditions
for the ICP Mass Spectrometer considering the following:
Cadmium: mass/charge number (m/z): 111
Rhodium: mass/charge number (m/z): 103
Collision cell: He-KED (Kinetic Energy Discrimination) mode (9) (10)b) Calibration curve preparation
455

Testing Methods for Fertilizers(2021)

1) Spray the cadmium standard solution for the calibration curve preparation and the blank test
solution for the calibration curve preparation together with rhodium standard solution (Rh 50
ng/mL) into the inductively coupling plasma (11), and read the ratio of the indicated values forthe respective mass/charge number of an element subjected to measurement and an internal
standard element.
2) Prepare a curve for the relationship between the concentration and the ratio of the ion countnumber of an element subjected to measurement.
c) Sample measurement
1) Put no more than 2.5 mL of the sample solution in a 50-mL volumetric flask (7), add nitric acidto be nitric acid (1+19), and add water to the marked line (12).
2) Subject to the same procedure as in b) 1) to read the ratio of the indicated values (13).
3) For the blank test solution, conduct procedures similarly as in 1) - 2) to correct the ratio of theindicated value obtained for the measurement solution.
4) Obtain the cadmium content from the calibration curve, and calculate cadmium (Cd) in theanalytical sample.
Note (9) Note that, when He-H2 mixture gas is used, H2 may react with Rh and the indicatedvalue of Rh becomes lower, affecting the measurement.
(10) For MoO, etc. that causes spectrum interference to 111Cd, its generation can besuppressed by reducing the oxide ion generation ratio. Adjust the instrument conditions
to reducing the oxide ion generation ratio prior to the measurement. (Example: The
CeO/Ce ratio is less than 1%.)(11) Simultaneously introduce an internal standard solution 1/9 of the volume of the standard
solution for the calibration curve preparation or the blank test solution for the calibration
curve preparation.
(12) If there is a possibility that the cadmium concentration in the sample solution will exceed
the maximum limit of the calibration curve, reduce the sampling amount for the sample
solution or dilute it with nitric acid (1+19).
(13) In the case of a fertilizer in which raw materials or a fertilizer using Mo are usedsecondarily, correct the indicated value of 111Cd using the correction formula (a) below.
111

Cd = 1.000×111M－1.073(108M－0.712×106M) ・・・

(a)

111

Cd： Indicated value of 111Cd after correction
111
M: Indicated value of 111Cd before correction108
M： Indicated value of 108Cd
106
M: Certified indicated value of 106Cd
Comment 6 Instead of the correction method in c) 3), the cadmium concentration in the analyticalsample can also be corrected by obtaining the cadmium concentration in the blank test
solution.
Comment 7 Triplicates additive recovery testing was conducted to evaluate trueness using mixed
compost compound fertilizers and fluid composted sludge fertilizers. As a result, themean recovery rates at the concentration level of 0.1 mg/kg - 5 mg/kg were 98.9 % 111 % as cadmium (Cd).
The comparison of the analysis value (yi: 0.09 mg/kg – 5.52 mg/kg) of ICP Mass
Spectrometry and the analysis value (xi) of Flame Atomic Absorption Spectrometry
was conducted using sludge fertilizers (20 samples). As a result, a regression equation
was y = −0.0084 + 0.98x, and its correlation coefficient (r) was 0.999. Similarly, the456Testing Methods for Fertilizers(2021)

comparison of the analysis value (yi: 0.10 mg/kg - 5.55 mg/kg) of ICP Mass
Spectrometry and the analysis value (xi) of Flame Atomic Absorption Spectrometry
was conducted using superphosphate of lime (1 sample), double superphosphate oflime (1 sample), processed phosphorus fertilizer (2 samples), byproduct animal
fertilizer (1 sample), compound fertilizer (11 samples), blended fertilizer (1 sample),coating compound fertilizer (2 samples), solid compound fertilizer (2 samples),byproduct compound fertilizer (1 sample), mixed compost compound fertilizer (6samples), byproduct magnesia fertilizer (1 sample), and mixed microelement fertilizer(1 sample). As a result, a regression equation was y = 0.0199 + 1.0147x, and its
correlation coefficient (r) was 0.998.
The results of repeated analyses using two types of composted sludge fertilizer andcompound fertilizer were analyzed by the one-way analysis of variance. Table 2 showsthe estimation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.002 mg/kg for fluid sludge fertilizers and about 0.2 mg/kg for otherfertilizers.
Table 2 Estimation results of repeatability and intermediate precision
Sample nameDays ofrepeatability

Composted sludge fertilizer 1
Composted sludge fertilizer 2
Compound fertilizer 1
Compound fertilizer 2

T
5
5
5
5

1)

Repeatability
2)

Mean

(mg/kg)
0.1
4.6
0.6
5.6

3)

sr

4)

(mg/kg)
0.003
0.07
0.05
0.1

3)

RSD r
(%)
3.0
1.6
9.1
2.2

Intermediate precision5)s I(T)

6)(mg/kg)
0.004
0.1
0.06
0.1

3)

RSD I(T)
(%)

7)

3.5
2.7
9.9
2.6

1) The number of days conducting duplicate analysis

4) Repeatability standard deviation

2) Mean ([Number of days of repeatability (T )]× [Number of duplicates (2)])5) Repeatability relative standard deviation

3) Mass fraction7) Intermediate relative standard deviation

6) Intermediate standard deviation

Comment 8 The simultaneous measurement of multiple elements is possible with the ICP-MS. In
that case, prepare standard solutions, etc. referencing Table 1 of Annex C2, conduct
procedures similarly as (4.2) b) - c), and calculate respective element concentrationsin an analytical sample.
Note that the concentration of a standard solution and an internal standard solution can
be changed as appropriate according to Comment 4.
References1)
Toshiharu YAGI: Determination of Heavy Metals in Fluid Sludge Fertilizers by ICPMS and CV-AAS, Research Report of Fertilizer, Vol. 8, p. 26 - 37 (2015)
2)
Satoko SAKAIDA, Mayu OSHIMA, Keisuke AOYAMA and Yuji SHIRAI:
Determination of Harmful Components in Fertilizers using Inductively Coupled PlasmaMass Spectrometer (ICP-MS), Research Report of Fertilizer, Vol. 12, p. 52 – 68 (2019)(5)

Flow sheet for cadmium: The flow sheet for cadmium in fluid sludge fertilizers is shown
below:
457

Testing Methods for Fertilizers(2021)

0.20 g analytical sample

Decomposing vessel← Nitric acid, 10 mL← Hydrogen peroxide, 1 mL
Microwave decomposition

Transfer
50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube, 1700 × g , 5 minutes

Sample solution
Figure 2 Flow sheet for cadmium in fertilizers except fluid sludge fertilizers (Extraction procedure)

Sample solution
Aliquot (no more than 2.5 mL)

50-mL Volumetric flask← Nitric acid, to be nitric acid (1+19)← Water (up to the marked line)
Measurement

ICP-MS (internal standard: Rh, Cd: m/z 111 Rh: m/z 103）

Figure 3 Flow sheet for cadmium in fertilizers (Measurement procedure)

458

Testing Methods for Fertilizers(2021)

5.3.d

459

Testing Methods for Fertilizers(2021)

5.4 Nickel
5.4.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.4.a-2017 or Ni.a-1.
Pretreat an analytical sample with incineration and nitric acid−hydrochloric acid (1+3), spray into anacetylene−air flame, and measure the atomic absorption with nickel at a wavelength of 232.0 nm toobtain nickel (Ni) in an analytical sample. In addition, the performance of this testing method isshown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Nickel standard solution (Ni 0.1 mg/mL): A nickel standard solution (Ni 0.1 mg/mL) traceable
to National Metrology.
e) Nickel standard solutions (Ni 0.5 µg/mL - 5 µg/mL) for the calibration curve preparation(1) (2): Put 2.5 mL - 25 mL of nickel standard solution (Ni 0.1 mg/mL) in 500-mL volumetricflasks step-by-step, and add hydrochloric acid (1+23) to the marked line.
f) Blank test solution for the calibration curve preparation (1) (2): Hydrochloric acid (1+23)
used in the procedures in e).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the nickel standard solution in (2), a nickel standard solution for thecalibration curve preparation can be prepared by using a nickel standard solution (Ni1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (3) function.
1) Light source: A nickel hollow cathode lamp (In case of background correction system using
continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
Note (3) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
460

Testing Methods for Fertilizers(2021)c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (5), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (6) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200 mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (4) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(5) The watch glass can be removed.
(6) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 2 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 232.0 nmb) Calibration curve preparation
1) Spray the nickel standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 232.0 nm.
2) Prepare a curve for the relationship between the nickel concentration and the indicated value ofthe nickel standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Subject the sample solution (7) to the same procedure as in b) 1) to read the indicated value.
2) Subject the blank test solution to the same procedure as in b) 1) to read the indicated value, andcorrect the indicated value obtained for the sample solution.
3) Obtain the nickel content from the calibration curve, and calculate nickel (Ni) in the analyticalsample.
Note (7) If there is a possibility that the nickel concentration in the sample solution will exceed
the maximum limit of the calibration curve, dilute a predetermined amount withhydrochloric acid (1+23).
461

Testing Methods for Fertilizers(2021)

Comment 4 Instead of the correction method in c) 2), the nickel (Ni) in the analytical sample canalso be corrected by obtaining the nickel content in the blank test solution.
Comment 5 Recovery testing was conducted using industrial sludge fertilizer and composted
sludge fertilizer (5 samples); as a result, the recovery rates at the concentration levelof 300 mg/kg and 30 mg/kg were 98.5 % - 100.3 % and 97.1 % - 99.9 %, respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 1 mg/kg.

References
1)
Yoshinari SAKAKIBARA, Manabu MATSUZAKI and Tadao AMANO: Determinationof Cadmium, Lead, Nickel and Chromium in Sludge Fertilizer - Improved Decomposition
Method - Research Report of Fertilizer Vol. 1, p. 41 - 49 (2008)
2) Yoshinari SAKAKIBARA and Manabu MATSUZAKI: Determination of Cadmium, Lead,
Nickel and Chromium in Sludge Fertilizer - Collaborative Test Results - Research Reportof Fertilizer Vol. 1, p. 50 - 59 (2008)
3)
Hisanori ARAYA and Yoshimi TAKEBA: Validation of atomic absorption spectrometryfor determination of cadmium, lead, nickel and chromium in calcined sludge fertilizer Research Report of Fertilizer Vol. 3, p. 30 - 42 (2010)462

Testing Methods for Fertilizers(2021)(5)

Flow sheet for nickel: The flow sheet for nickel in fertilizers is shown below:463

Testing Methods for Fertilizers(2021)

5.4.b ICP Optical Emission Spectrometry(1) Summary
The test method is applicable to sludge fertilizers, etc. This testing method is classified as Type D
and its symbol is 5.4.b-2017 or Ni.b-1.
Pretreat an analytical sample with incineration and nitric acid−hydrochloric acid (1+3), and thenintroduce it to an ICP Optical Emission Spectrometer (ICP-OES) and measure the emission withnickel at a wavelength of 231.604 nm to obtain nickel (Ni) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Nickel standard solution (Ni 0.1 mg/mL): A nickel standard solution (Ni 0.1 mg/mL) traceable
to National Metrology.
e) Nickel standard solutions (Ni 2.5 µg/mL) (1) (2): Dilute a predetermined amount of nickel
standard solution (Ni 0.1 mg/mL) with hydrochloric acid (1+23) to prepare a nickel standard
solution (Ni 2.5 µg/mL)
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the nickel standard solution in (2), a nickel standard solution for thecalibration curve preparation can be prepared by using a nickel standard solution (Ni1 mg/mL or 10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (3).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (3).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
464

Testing Methods for Fertilizers(2021)

Slightly move the watch glass (4), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (5) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200 mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
f)Note (3) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(4) The watch glass can be removed.
(5) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 3 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Standard Addition Method) according to JIS K 0116 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Optical Emission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 231.604 nmb) Calibration curve preparation and sample measurement
1) Put 5mL of sample solution in three 10-mL volumetric flasks respectively.
2) Add 2 mL and 4 mL (2.5 μg/mL) of nickel standard solution to volumetric flasks of 1) above,
then add hydrochloric acid (1+23) to the marked line to make a sample solution of Standard
Addition Method.
3) Add hydrochloric acid (1+23) to the marked line of the remaining volumetric flask of 1) above
to make a sample solution without a standard solution.
4) Spray the sample solution of Standard Addition Method and the sample solution without astandard solution into the induction plasma, and read the indicated value at a wavelength of
231.604 nm.
5) Put 5 mL of blank test solution in a 10-mL volumetric flask, conduct the same procedures as in3) - 4) to read the indicated value, and correct the indicated value obtained from the respective
sample solutions.
6) Prepare a curve for the relationship between the added nickel concentration and the correctedindicated value of the sample solution for Standard Addition Method and the sample solution
without a standard solution.
7) Obtain the nickel content from the intercept of the calibration curve to calculate nickel (Ni)concentration in the analytical sample.
Comment 5 Instead of the correction method in b) 5), the nickel (Ni) in the analytical sample canalso be corrected by obtaining the nickel content in the blank test solution.
465

Testing Methods for Fertilizers(2021)

Comment 6 The simultaneous measurement of multiple elements is possible with the ICP‐OES. In
that case, see 4.9.1.b Comment 6.
Comment 7 The comparison of the measurement value (xi：8.4 mg/kg - 129 mg/kg) of ICP OpticalEmission Spectrometry and the measurement value (yi) of Flame Atomic Absorption
Spectrometry was conducted to evaluate trueness using sludge fertilizers (49 samples).
As a result, a regression equation was y=−0.96+1.010x and its correlation coefficient(r) was 0.995. Triplicates measurement for each one sample of sewage sludge fertilizer,
human waste sludge fertilizer, industrial sludge fertilizer, mixed sludge fertilizer,
calcined sludge fertilizers and composted sludge fertilizer was conducted. As a result,a repeatability obtained was1.0 % - 2.6 % as a relative standard deviation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 8 mg/kg.
References
1)
Masahiro ECHI, Tomoe INOUE, Megumi TABUCHI and Tetuya NOMURA:
Simultaneous Determination of Cadmium, Lead, Nickel, Chromium, Copper and Zinc in
Sludge Fertilizer using Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES), Research Report of Fertilizer, Vol. 4, p. 30 - 35 (2011)466

Testing Methods for Fertilizers(2021)(5)

Flow sheet for nickel: The flow sheet for nickel in fertilizers is shown below:

467

Testing Methods for Fertilizers(2021)

5.4.c ICP Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 5.4.c-2021 or Ni.c-2.
Add nitric acid – hydrogen peroxide to an analytical sample, and heat to decompose by microwave
irradiation. Introduce it to an ICP Mass Spectrometer (ICP-MS) and measure the respective indicatedvalues of nickel and an internal standard element (rhodium) with mass/charge number (m/z) andobtain nickel (Ni) in the analytical sample from the ratio of the indicated value for nickel and theindicated value for an internal standard element. Note that the performance of this testing method isshown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Nitric acid: Nitric acid used to dilute a standard solution and a sample solution is a highly
pure reagent specified in JIS K 9901.
d) Hydrogen peroxide: A JIS Guaranteed Reagent specified in JIS K 8230 or a reagent ofequivalent quality.
e) Rhodium standard solution (Rh 1000 mg/L): A rhodium standard solution (Rh 1000 mg/L)
traceable to National Metrology.
f) Rhodium standard solution (Rh 5 µg/mL) (1)(2)(3): Dilute a predetermined amount of rhodium
standard solution (Rh 1000 mg/L) with nitric acid (1+19) to prepare a rhodium standard solution(Rh 5 µg/mL).
g) Rhodium standard solution (Rh 50 ng/mL) (1) (3): Dilute a predetermined amount of rhodium
standard solution (Rh 5 µg/mL) with nitric acid (1+19) to prepare a rhodium standard solution(Rh 50 ng/mL).
h) Nickel standard solution (Ni 1000 mg/L): A nickel standard solution (Ni 1000 mg/L) traceable
to National Metrology.
i) Nickel standard solution (Ni 500 ng/mL) (1) (2) (3): Dilute a predetermined amount of nickel
standard solution (Ni 1000 mg/L) with nitric acid (1+19) to prepare a nickel standard solution(Ni 500 ng/mL).
j) Nickel standard solutions (Ni 10 ng/mL - 50 ng/mL) for the calibration curve preparation(1) (3): Put 2 mL - 10 mL of nickel standard solution (Ni 500 ng/mL) in 100-mL volumetric flasks
step-by-step, and add nitric acid (1+19) up to the marked line.
k) Nickel standard solutions (Ni 0.5 ng/mL - 5 ng/mL) for the calibration curve preparation(1) (3): Put 1 mL - 10 mL of nickel standard solution (Ni 50 ng/mL) in 100-mL volumetric flasks
step-by-step, and add nitric acid (1+19) up to the marked line.
l) Blank test solution for the calibration curve preparation (1) (3): Nitric acid (1+19) used in theprocedures in f), g), i), j) and k).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in cool and dark place, and do not use after 6 month after preparation.
(3) For preparation and storage, use sealable containers made of materials such as
polypropylene containing no nickel.
Comment 1 Instead of the rhodium standard solution in (2), a rhodium standard solution for thecalibration curve preparation can be prepared by using a rhodium standard solution(Rh 100 mg/L or 10000 mg/L) traceable to National Metrology.
Comment 2 Instead of the nickel standard solution in (2), a nickel standard solution for the468

Testing Methods for Fertilizers(2021)

calibration curve preparation can be prepared by using a nickel standard solution (Ni
100 mg/L or 10000 mg/L) traceable to National Metrology.
Comment 3 When a sample solution or a standard solution for the calibration curve preparation
and an internal standard solution are not simultaneously introduced in themeasurement of ICP-MS, add 1/10 volume of rhodium standard solution (Rh 50
ng/mL) to the volume of the solution when preparing respective solutions in theprocedures in j), k) and l).
Comment 4 ICP-MS detection methods include a pulse detection method and an analog detection
method. There are detection method models that combine them, but when themeasurement value is affected by switching, the concentration of the standard solution
and the internal standard solution may be changed as appropriate so that measurement
can be performed with either detection method.
(3) Instruments: Instruments are as shown below:a) ICP Mass Spectrometer: A high-frequency plasma mass spectrometer specified in JIS K
0133, that is equipped with a collision/reaction cell.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.995 % in purityb) Pressure vessel decomposing device: A device which pressurizes the inside of a vessel by
putting acid, etc. to heat in the decomposing vessel, and decomposes a sample by the interactionof heating, pressurizing and acid. The following requirements should be met.
1) The main part of a decomposing device: In the case of the microwave heating method, adevice should be able to produce a high-frequency wave using a frequency which is permitted
at an industrial frequency facility. It is desirable to be able to monitor pressure and temperature,etc. in the decomposing vessel with a sensor inside the device. The interior of a device shouldbe acid-resistant treated and should have a high temperature durability and a high level of safety.
2) Exhaust system: A system which has an exhaust fan of acid-resistant specification, and has
an air-cool function inside the device to allow constant airflow, keeping operating temperature
below a certain temperature level.
3) Decomposing vessel: A vessel which is heat-resistance and pressure-tight and has the
durability required to decompose particles, and has resistance to internal contamination. Itshould have safety functions such as causing overheat prevention valve to work and internalpressure to drop by emitting gas, and preventing gas bumping in the case of exceeding apressure limitation.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Fluid sludge fertilizera) Weigh 20.0 g (4) of an analytical sample, and put it into an airtight vessel.
b) Gradually add 2.5 mL of nitric acid and 2 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and put it in a 50-mL ground-in stopper centrifugal precipitate
tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to prepare469

Testing Methods for Fertilizers(2021)

a blank test solution.
(4.1.2) Fertilizers except fluid sludge fertilizersa) Weigh 0.20 g of an analytical sample, and put it into a decomposing vessel.
b) Gradually add 10 mL of nitric acid and 1 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and transfer it to a 50-mL ground-in stopper centrifugal
precipitate tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
Note (4) The maximum limit of solid content, which is converted from moisture content, in thesampling volume 20.0 g of an analytical sample is about 0.5 g. If solid content is likely
to exceed the limit, reduce sampling volume as necessary.
(5) Example setting conditions of a microwave decomposing device are as shown in Table
1.
Table 1 Example setting conditions of a microwave
decomposing device
Time (min)Temperature (°C)
Output (kW)0020200 (temperature rising)
1400
10
200
1400
40
Room temperature0(6) When organic matters, for example colored precipitate, etc., still remain, add 2 mL ofnitric acid and 1 mL of hydrogen peroxide and repeat the procedures in (4.1) c) – d).
(7) The vessel should be made of polypropylene, etc. to not affect the measurement.
(8) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal force.
Comment 5 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Internal Standard Method) according to JIS K 0113 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Mass Spectrometer used in measurement.
a) Measurement conditions for the ICP Mass Spectrometer: Set up the measurement conditions
for the ICP Mass Spectrometer considering the following:
Nickel: mass/charge number (m/z): 60
Rhodium: mass/charge number (m/z): 103
Collision cell: He-KED (Kinetic Energy Discrimination) mode (9)b) Calibration curve preparation
470

Testing Methods for Fertilizers(2021)

1) Spray the nickel standard solution for the calibration curve preparation and the blank test
solution for the calibration curve preparation together with rhodium standard solution (Rh 50
ng/mL) into the inductively coupling plasma (10), and read the ratio of the indicated values forthe respective mass/charge number of an element subjected to measurement and an internal
standard element.
2) Prepare a calibration curve for the relationship between the concentration and the ratio of theindicated value of an element subjected to measurement.
c) Sample measurement
1) Put no more than 2.5 mL of the sample solution in a 50-mL volumetric flask (7), add nitric acidto be nitric acid (1+19), and add water to the marked line (11).
2) Subject to the same procedure as in b) 1) to read the ratio of the indicated values.
3) For the blank test solution, conduct procedures similarly as in 1) - 3) to correct the ratio of theindicated value obtained for the measurement solution.
4) Obtain the nickel content from the calibration curve, and calculate nickel (Ni) in the analyticalsample.
Note (9) Note that, when He-H2 mixture gas is used, H2 may react with Rh and the indicatedvalue of Rh becomes lower, affecting the measurement.
(10) Simultaneously introduce an internal standard solution 1/9 of the volume of the standard
solution for the calibration curve preparation or the blank test solution for the calibration
curve preparation.
(11) If there is a possibility that the nickel concentration in the sample solution will exceed
the maximum limit of the calibration curve, reduce the sampling amount for the sample
solution or dilute it with nitric acid (1+19).
Comment 6 Instead of the correction method in c) 4), the nickel (Ni) in the analytical sample canalso be corrected by obtaining the nickel content in the blank test solution.
Comment 7 Triplicates additive recovery testing was conducted to evaluate trueness using mixed
compost compound fertilizers and fluid composted sludge fertilizers. As a result, themean recovery rates at the concentration level of 6 mg/kg - 300 mg/kg were 102 % 109 % as nickel (Ni).
The comparison of the measurement value (xi: 3.67 mg/kg – 305 mg/kg) of ICP-MSand the measurement value (yi) of Flame Atomic Absorption Spectrometry was
conducted using sludge fertilizers (16 samples). As a result, a regression equation was
y = 0.7617 + 0.97x, and its correlation coefficient (r) was 1.000. Similarly, thecomparison of the analysis value (yi: 1.88 mg/kg - 320 mg/kg) of ICP Mass
Spectrometry and the analysis value (xi) of Flame Atomic Absorption Spectrometry
was conducted using superphosphate of lime (1 sample), double superphosphate oflime (1 sample), processed phosphorus fertilizer (2 samples), mixed phosphorus
fertilizer (1 sample), compound fertilizer (13 samples), blended fertilizer (1 sample),coating compound fertilizer (2 samples), solid compound fertilizer (2 samples),byproduct compound fertilizer (2 samples), mixed compost compound fertilizer (6samples), byproduct magnesia fertilizer (1 sample), and mixed microelement fertilizer(1 sample). As a result, a regression equation was y = 0.873 + 1.0032x, and its
correlation coefficient (r) was 0.999.
The results of repeated analyses using two types of human waste sludge fertilizer andcompound fertilizer were analyzed by the one-way analysis of variance. Table 2 showsthe estimation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to471

Testing Methods for Fertilizers(2021)

be about 0.03 mg/kg for fluid sludge fertilizers and about 3 mg/kg for other fertilizers.
Table 2 Estimation results of repeatability and intermediate precision
Repeatability
Intermediate precision
Days of
2)
4)
5)
6)
7)
repeatability
Sample name
Mean
sr
RSD r
s I(T)RSD I(T)1)

T
5(mg/kg)13

3)(mg/kg)
0.3

3)

(%)

2.5
Human waste sludge fertilizer 1
5
236
5
2.2
Human waste sludge fertilizer 2
5
13
0.5
3.6
Compound fertilizer 1
5
336
4
1.1
Compound fertilizer 2
1) The number of days conducting duplicate analysis
2) Mean ([Number of days of repeatability (T )]× [Number of duplicates (2)])3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Intermediate standard deviation
7) Intermediate relative standard deviation(mg/kg)
0.5

3)

(%)
4.1

5

2.0

0.5

3.8

6

1.7

Comment 8 The simultaneous measurement of multiple elements is possible with the ICP-MS.
In that case, prepare standard solutions, etc. referencing Table 1 of Annex C2, conduct
procedures similarly as (4.2) b) - c), and calculate respective element concentrations in ananalytical sample.
Note that the concentration of a standard solution and an internal standard solution can bechanged as appropriate according to Comment 4.
References1)
Toshiharu YAGI: Determination of Heavy Metals in Fluid Sludge Fertilizers by ICP-MSand CV-AAS, Research Report of Fertilizer Vol. 8, p. 26 - 37 (2015)2)
Toshiharu YAGI, Kenta SAKUMA and Yoshimi HASHIMOTO: Determination of Heavy
Metals in Sludge Fertilizers using Inductively Coupled Plasma-Mass Spectrometer (ICPMS), Research Report of Fertilizer, Vol. 9, p. 21 – 32 (2016)
3)
Satoko SAKAIDA, Mayu OSHIMA, Keisuke AOYAMA and Yuji SHIRAI:
Determination of Harmful Components in Fertilizers using Inductively Coupled PlasmaMass Spectrometer (ICP-MS), Research Report of Fertilizer, Vol. 12, p. 52 – 68 (2019)(5)

Flow sheet for nickel: The flow sheet for nickel in fluid sludge fertilizers is shown below:472

Testing Methods for Fertilizers(2021)
20.0 g analytical sample

Decomposing vessel← Nitric acid, 2.5 mL← Hydrogen peroxide, 2 mL
Microwave
decomposition

Transfer
50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
1700 × g , 5 minutes

Sample solution
Figure 1 Flow sheet for nickel in fluid sludge fertilizers (Extraction procedure)

0.20 g analytical sample

Decomposing vessel← Nitric acid, 10 mL← Hydrogen peroxide, 1 mL
Microwave
decomposition

Transfer
50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
1700 × g , 5 minutes

Sample solution
Figure 2 Flow sheet for nickel in fertilizers except fluid sludge fertilizers(Extraction procedure)

Sample solution
Aliquot (no more than
2.5 mL)

50-mL Volumetric flask← Nitric acid, to be nitric acid (1+19)← Water (up to the marked line)
Measurement

ICP-MS (internal standard: Rh, Ni: m/z 60 Rh: m/z 103）

Figure 3 Flow sheet for nickel in fertilizers (Measurement procedure)473

Testing Methods for Fertilizers(2021)

5.4.d

474

Testing Methods for Fertilizers(2021)

5.5 Chromium
5.5.a Flame atomic absorption spectrometry (Fertilizers containing organic matters)(1) Summary
This testing method is applicable to fertilizers containing organic matters. This testing method isclassified as Type B and its symbol is 5.5.a-2017 or Cr.a-1.
Pretreat an analytical sample with incineration and nitric acid−hydrochloric acid (1+3), spray into anacetylene−air flame, and measure the atomic absorption with chromium at a wavelength of 357.9 nm
or 359.3 nm to obtain chromium (Cr) in an analytical sample. In addition, the performance of thistesting method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Interference suppressor solution (1): Dissolve 100 g of potassium disulfate specified in JIS K
8783 in water to make 1000 mL.
e) Chromium standard solution (Cr 0.1 mg/mL): A chromium standard solution (Cr 0.1 mg/mL)
traceable to National Metrologyf) Chromium standard solutions (Cr 0.5 µg/mL - 5 µg/mL) for the calibration curve
preparation (1) (2): Put 2.5 mL - 25 mL of chromium standard solution (Cr 0.1 mg/mL) in 500mL volumetric flasks step-by-step, add about 50 mL of interference suppressor solution (3), andfurther add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1) (2): Put about 50 mL ofinterference suppressor solution (3) in a 500-mL volumetric flask, and add hydrochloric acid
(1+23) used in the procedure in f) to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the chromium standard solution in (2), a chromium standard solution for thecalibration curve preparation can be prepared by using a chromium standard solution(Cr 1 mg/mL or 10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (4) function.
1) Light source: A chromium hollow cathode lamp (In case of background correction systemusing continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
Note (4) There are the continuous source method, the Zeeman method, the non-resonance475

Testing Methods for Fertilizers(2021)

spectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (5).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (5).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (6), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (7) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water up
to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (5) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(6) The watch glass can be removed.
(7) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 2 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 357.9 nm or 359.3 nm (8)b) Calibration curve preparation
1) Spray the chromium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame (9), and read the indicated value at awavelength of 357.9 nm or 359.3 nm (8).
2) Prepare a curve for the relationship between the chromium concentration and the indicatedvalue of the chromium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put 25 mL of the sample solution (10) in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add hydrochloric acid (1+23) tothe marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Subject the blank test solution to the same procedure as in 1) - 2) and b) 1) to read the indicated476

Testing Methods for Fertilizers(2021)

value, and correct the indicated value obtained for the sample solution.
5) Obtain the chromium content from the calibration curve, and calculate chromium (Cr) in theanalytical sample.
Note (8) When background correction is conducted by the Zeeman method, 359.3 nm is
recommended as the analytical line wavelength.
(9) Use low-fuel acetylene−air flame. Acetylene−nitrous oxide flame can also be used.
(10) If there is a possibility that the chromium concentration in the sample solution will
exceed the maximum limit of the calibration curve, decrease the amount to betransferred.
Comment 3 In an acetylene−air flame, sensitivity is enhanced in high-fuel flame, but interferenceby coexisting substances such as iron and nickel will also be enhanced.
In an acetylene−nitrous oxide flame, such interference hardly affects the result.
Comment 4 Instead of the correction method in c) 4), the chromium (Cr) in the analytical sample
can also be corrected by obtaining the chromium content in the blank test solution.
Comment 5 Recovery testing was conducted using industrial sludge fertilizer and composted sludge
fertilizer (5 samples); as a result, the recovery rates at the concentration level of 500
mg/kg and 50 mg/kg were 97.5 % - 100.0 % and 95.9 % - 101.9 %, respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 1 mg/kg.

References
1)
Yoshinari SAKAKIBARA, Manabu MATSUZAKI and Tadao AMANO: Determinationof Cadmium, Lead, Nickel and Chromium in Sludge Fertilizer - Improved Decomposition
Method - Research Report of Fertilizer Vol. 1, p. 41 - 49 (2008)
2) Yoshinari SAKAKIBARA and Manabu MATSUZAKI: Determination of Cadmium, Lead,
Nickel and Chromium in Sludge Fertilizer - Collaborative Test Results - Research Reportof Fertilizer Vol. 1, p. 50 - 59 (2008)
3)
Yoshinari SAKAKIBARA, Chie INOUE: Validation of determination methods forchromium in sludge fertilizer - Evaluation of measurement procedure, Research Reportof Fertilizer Vol. 2, p. 130 - 136 (2009)477

Testing Methods for Fertilizers(2021)(5)

Flow sheet for chromium: The flow sheet for chromium in fertilizers containing organic
matters is shown below:

478

Testing Methods for Fertilizers(2021)

5.5.b Flame atomic absorption spectrometry (Fertilizers mainly containing fused matters, slag,
etc.)(1) Summary
This testing method is applicable to fertilizers mainly containing fused matters, slag, etc. This
testing method is classified as Type B and its symbol is 5.5.b-2017 or Cr.b-1.
Add ammonium sulfate to prevent the bumping of an analytical sample, pretreat the analyticalsample with nitric acid−sulfuric acid−perchloric acid, and then spray into an acetylene−air flame.
Measure the atomic absorption with chromium at a wavelength of 357.9 nm or 359.3 nm to obtainchromium (Cr) in an analytical sample. The performance of this testing method is shown in Comment
4.
In addition, fertilizers containing no organic matters can also be measured by the method of 5.5.c.
However, this method should be used for fertilizers that bump when heating. (Fertilizers made of
fused matters, slag, etc. may bump in many cases).
(2)
a)
b)
c)
d)
e)
f)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Ammonium sulfate: A reagent of atomic absorption analysis grade or equivalents
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Perchloric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
g) Interference suppressor solution (1): Dissolve 100 g of potassium disulfate specified in JIS K
8783 in water to make 1000 mL.
h) Chromium standard solution (Cr 0.1 mg/mL): A chromium standard solution (Cr 0.1
mg/mL) traceable to National Metrologyi) Chromium standard solutions (Cr 0.01 mg/mL) for the calibration curve preparation (1):
Put 10 mL of chromium standard solution (Cr 0.1 mg/mL) in 100-mL volumetric flask, and addhydrochloric acid (1+23) to the marked line.
j) Chromium standard solutions (Cr 0.5 µg/mL - 5 µg/mL) for the calibration curve
preparation (1) (2): Put 2.5 mL - 25 mL of chromium standard solution (Cr 0.1 mg/mL) or
chromium standard solution (Cr 0.01 mg/mL) in 500-mL volumetric flasks step-by-step, add
about 50 mL of interference suppressor solution (3), and further add hydrochloric acid (1+23) tothe marked line.
k) Blank test solution for the calibration curve preparation (1) (2): Put about 50 mL ofinterference suppressor solution (3) in a 500-mL volumetric flask, and add hydrochloric acid
(1+23) used in the procedure in i) and j) to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the chromium standard solution in (2), a chromium standard solution for thecalibration curve preparation can be prepared by using a chromium standard solution(Cr 1 mg/mL or 10 mg/mL) traceable to National Metrology.

(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (4) function.
479

Testing Methods for Fertilizers(2021)

1) Light source: A chromium hollow cathode lamp (In case of background correction systemusing continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 350 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to no less than 300 °C.
Note (4) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample and put it in a 300-mL tall beaker.
b) Add 4 g of ammonium sulfate and moisten the analytical sample with a small amount of water.
c) Add about 10 mL of nitric acid, about 5 mL of sulfuric acid and about 5 mL of perchloric acid.
Cover the tall beaker with a watch glass, heat on a hot plate or sand bath gently at 170 °C 220 °C for no less than 1 hour, and then warm to raise temperature gradually to no less than
300 °C taking no less than 30 minutes (5) and further heat at no less than 300 °C for 2-3 hours.
d) Slightly move the watch glass (6), and keep on heating on the hot plate or sand bath toconcentrate until the liquid volume becomes about 3 mL (7).
e) After standing to cool, add about 5 mL of hydrochloric acid (1+10) and about 20 mL of water,
cover the tall beaker with a watch glass and heat mildly for about 10 minutes to dissolve (8).
f) After standing to cool, transfer the solution to a 100-mL volumetric flask with water, add water
up to the marked line, and filter with Type 3 filter paper to make a sample solution.
g) As a blank test, conduct the procedures in b) - f) using another tall beaker to prepare a blanktest solution. However, the heating procedure after adding acid in the procedures in c) should
be conducted as shown below. Cover the tall beaker with a watch glass, heat on a hot plate orsand bath at about 170 °C for a while (8), slightly move the watch glass (6) and then heat gently
for no less than 1 hour to vapor nitric acid. After concentrating to about 15 mL (9), heat and raise
the temperature gradually to no less than 300 °C in more than 30 minutes (5). When white smoke
starts evolving, cover the tall beaker with a watch glass and further heat at no less than 300 °C
for 2-3 hours.
Note (5) Sudden temperature rise may cause bumping. Therefore, increase the temperature
gradually.
(6) If there is no possibility of bumping, the watch glass can be removed.
(7) Exsiccating it may cause the chromium to become insoluble. Therefore, care should betaken not to concentrate too much.
(8) Heating at high temperature may cause bumping. Therefore, it is recommended toincrease the temperature gradually from about 170 °C to the temperature at which itboils slightly.
(9) If much nitric acid remains, care should be taken because bumping can occur easily
when heating temperature rises.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement480

Testing Methods for Fertilizers(2021)

conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 357.9 nm or 359.3 nm (10)b) Calibration curve preparation
1) Spray the chromium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a low-fuel acetylene-air flame (11), and readthe indicated value at a wavelength of 357.9 nm or 359.3 nm (10).
2) Prepare a curve for the relationship between the chromium concentration and the indicatedvalue of the chromium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put 25 mL of the sample solution (12) in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add hydrochloric acid (1+17) tothe marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Subject the blank test solution to the same procedure as in 1) - 2) and b) 1) to read the indicatedvalue, and correct the indicated value obtained for the sample solution.
5) Obtain the chromium content from the calibration curve, and calculate chromium (Cr) in theanalytical sample.
Note (10) When background correction is conducted by the Zeeman method, 359.3 nm is
recommended as the analytical line wavelength.
(11) Acetylene−nitrous oxide flame can also be used.
(12) If there is a possibility that the concentration of chromium in the sample solution
exceeds the maximum limit of the calibration curve, put no more than 10 mL of thesample solution in a 100-mL volumetric flask and add about 10 mL of interference
suppressor solution and about 67 mL of hydrochloric acid (1+17), and add water up to
the marked line.
Comment 2 In an acetylene−air flame, sensitivity is enhanced in high-fuel flame, but interferenceby coexisting substances such as iron and nickel will also be enhanced.
In an acetylene−nitrous oxide flame, such interference hardly affects the result.
Comment 3 Instead of the correction method in c) 4), the chromium (Cr) in the analytical sample
can also be corrected by obtaining the chromium content in the blank test solution.
Comment 4 The comparison of the measurement value (yi：54 mg/kg - 4649 mg/kg) of this testing
method and the measurement value (xi) of 5.8 Chromium 5.8.2 Atomic Absorption
Spectrometry in Official Methods of Analysis of Fertilizers (1992) was conducted toevaluate trueness using fertilizers (29 samples). As a result, a regression equation was
y=− 6.842 + 0.998x and its correlation coefficient (r) was 0.999.
The results of the repeatability tests on different days using fused silicic phosphate
fertilizer, silicate slag fertilizer and compound fertilizer (1 sample for each) to evaluate
precision were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability. Additionally, resultsfrom a collaborative study for test method validation and its analysis are shown in
Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 6 mg/kg.

481

Testing Methods for Fertilizers(2021)

References1)
Toshiaki HIROI, Fumika TAKATSU: Evaluation of Digest Method for Determination of
Chromium in Inorganic Fertilizer by Atomic Absorption Spectrometry, Research Reportof Fertilizer Vol. 10, p. 9 - 28 (2017)2)
Toshio HIRABARA, Toshiaki HIROI, Tomomi ISIKAWA: Evaluation of Digest Method
for Determination of Chromium in Inorganic Fertilizer by Atomic Absorption
Spectrometry: A Collaborative Study, Research Report of Fertilizer Vol. 11, p. 39 - 46
(2018)

482

Testing Methods for Fertilizers(2021)(5)

Flow sheet for chromium: The flow sheet for chromium in fertilizers mainly containing fusedmatters and slag is shown below:

1.00 g300-mL tall beaker.
analytical sample← 4 g of ammonium sulfate← A small amount of water, moisten the analytical sample← About 10 mL of nitric acid
← About 5 mL of sulfuric acid
← About 5 mL of perchloric acid
Cover with a watch glass, and heat mildly on a hot plate
Heatingor sand bath at 170 ºC - 220 ºC for no less than 1 hour
Heating

Raise temperature gradually to no less than 300 °C in more than 30
minutesHeating

Digest on a hot plate or sand bath at no less than 300 °C for 2 -3
hours

Heating

Slightly move a watch glass and concentrate
until the liquid volume becomes about 3 mL

Standing to coolRoom temperature← About 5 mL of hydrochloric acid (1+5)← About 20 mL of water
Heating
Cover with a watch glass, and dissolve (heat for about 10 minutes)
Standing to coolRoom temperature

Transfer
100-mL volumetric flask← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for chromium in fertilizers mainly containing fused matters and slag, etc.
(Extraction procedure)

Sample solution
Aliquot
100-mL volumetric flasks← About 10 mL of interference suppressor solution← Hydrochloric acid (1+17) ( up to the marked line)
Measurement
Atomic absorption spectrometer (357.9 nm or 359.3 nm)
Figure 2 Flow sheet for chromium in fertilizers
mainly containing fused matters and slag, etc. (Measurement procedure)483

Testing Methods for Fertilizers(2021)

5.5.c Flame atomic absorption spectrometry (Fertilizers not containing organic matters)(1) Summary
This testing method is applicable to fertilizers not containing organic matters (including calcinedsludge fertilizer). This testing method is classified as Type B and its symbol is 5.5.c-2017 or Cr.c-1.
In addition, for fertilizers mainly made of fused matters, slag, etc., care should be taken because
they may bump while heating. 5.5.b applies to fertilizers that may bump.
Pretreat an analytical sample with nitric acid−sulfuric acid−perchloric acid, and then spray into anacetylene−air flame, and measure the atomic absorption with chromium at a wavelength of 357.9 nm
or 359.3 nm to obtain chromium (Cr) in an analytical sample. In addition, the performance of thistesting method is shown in Comment 8.
(2)
a)
b)
c)
d)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Perchloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
e) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
f) Interference suppressor solution (1): Dissolve 100 g of potassium disulfate specified in JIS K
8783 in water to make 1000 mL.
g) Chromium standard solution (Cr 0.1 mg/mL): A chromium standard solution (Cr 0.1 mg/mL)
traceable to National Metrologyh) Chromium standard solutions (Cr 0.01 mg/mL) for the calibration curve preparation (1):
Put 10 mL of chromium standard solution (Cr 0.1 mg/mL) in 100-mL volumetric flask, and addhydrochloric acid (1+23) to the marked line.
i) Chromium standard solutions (Cr 0.5 µg/mL - 5 µg/mL) for the calibration curve
preparation (1) (2): Put 2.5 mL - 25 mL of chromium standard solution (Cr 0.1 mg/mL) or
chromium standard solution (Cr 0.01 mg/mL) in 500-mL volumetric flasks step-by-step, add
about 50 mL of interference suppressor solution (3), and further add hydrochloric acid (1+23) tothe marked line.
j) Blank test solution for the calibration curve preparation (1) (2): Put about 50 mL ofinterference suppressor solution (3) in a 500-mL volumetric flask, and add hydrochloric acid
(1+23) used in the procedure in h) and i) to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
(3) Add an interference suppressor solution that is 1/10 volume of the volume to beprepared.
Comment 1 Instead of the chromium standard solution in (2), a chromium standard solution for thecalibration curve preparation can be prepared by using a chromium standard solution(Cr 1 mg/mL or 10 mg/mL) traceable to National Metrology.

(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (4) function.
1) Light source: A chromium hollow cathode lamp (In case of background correction systemusing continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame484

Testing Methods for Fertilizers(2021)(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 350 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to no less than 300 °C.
Note (4) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Add about 10 mL of nitric acid and about 5 mL of sulfuric acid, cover the tall beaker with awatch glass, and leave at rest overnight.
c) Heat mildly on a hot plate or sand bath at 170 ºC - 220 ºC for no less than 30 minutes. Afterbubbles cease to form, set the temperature of the hot plate or sand bath to no less than 300 ºC(5), and heat until nitroxide (yellow-brown smoke) is no longer generated (6).
d) After standing to cool, add about 5 mL of perchloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or sand bath at no less than 300ºC for 2 - 3 hours to digest (7).
f) Slightly move the watch glass (8), and keep on heating on the hot plate or sand bath toconcentrate until the liquid volume becomes no more than 2 mL (9).
g) After standing to cool, add about 5 mL of hydrochloric acid (1+10) and about 20 mL of water,
cover the tall beaker with a watch glass and heat mildly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200-mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (5) If there is vigorous bumping, increase the temperature gradually.
(6) Oxidation of carbides by perchloric acid progresses extremely rapidly and explosively.
For that reason, add perchloric acid after fully degrading carbides with nitric acid to
avoid danger.
(7) When the white smoke of perchloric acid is generated, if the solution is colored such as
black-brown or brown, stop heating immediately, and after standing to cool, add nitricacid, and heat again to degrade remaining carbides.
(8) If there is no possibility of bumping, the watch glass can be removed.
(9) When exsiccating it, chromium may not dissolve completely in g) and the concentration
may become a low value.
Comment 2
Comment 3
Comment 4
Comment 5

A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
When the analytical sample solidifies in the procedure in (4.1) b), moisten theanalytical sample with a small amount of water as necessary in advance.
It is not necessary to conduct the procedures in (4.1) b) “leave at rest overnight”
because the range subjected to analysis does not contain organic matters.
In some cases, about 10 minutes heating in procedure in (4.1) g) is required.

(4.2) Measurement:

Conduct the measurement as indicated in JIS K 0121 and as shown below.
485

Testing Methods for Fertilizers(2021)

Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 357.9 nm or 359.3 nm (10)b) Calibration curve preparation
1) Spray the chromium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a low-fuel acetylene−air flame (11), and readthe indicated value at a wavelength of 357.9 nm or 359.3 nm (10).
2) Prepare a curve for the relationship between the chromium concentration and the indicatedvalue of the chromium standard solutions for the calibration curve preparation and the blanktest solution for the calibration curve preparation.
c) Sample measurement
1) Put 25 mL of the sample solution (12) in a 100-mL volumetric flask.
2) Add about 10 mL of interference suppressor solution (3), and add hydrochloric acid (1+17) tothe marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Subject the blank test solution to the same procedure as in 1) - 2) and b) 1) to read the indicatedvalue, and correct the indicated value obtained for the sample solution.
5) Obtain the chromium content from the calibration curve, and calculate chromium (Cr) in theanalytical sample.
Note (10) When background correction is conducted by the Zeeman method, 359.3 nm is
recommended as the analytical line wavelength.
(11) Acetylene−nitrous oxide flame can also be used.
(12) If there is a possibility that the concentration of chromium in the sample solution
exceeds the maximum limit of the calibration curve, put no more than 10 mL of thesample solution in a 100-mL volumetric flask and add about 10 mL of interference
suppressor solution and about 67 mL of hydrochloric acid (1+17), and add water up to
the marked line.
Comment 6 In an acetylene-air flame, sensitivity is enhanced in high-fuel flame, but interferenceby coexisting substances such as iron and nickel will also be enhanced.
In an acetylene−nitrous oxide flame, such interference hardly affects the result.
Comment 7 Instead of the correction method in c) 4), the chromium (Cr) in the analytical sample
can also be corrected by obtaining the chromium content in the blank test solution.
Comment 8 The comparison of the measurement value (yi：52 mg/kg - 4052 mg/kg) of this testing
method and the measurement value (xi) of 5.8 Chromium 5.8.2 Atomic Absorption
Spectrometry in Official Methods of Analysis of Fertilizers (1992) was conducted toevaluate trueness using fertilizers (27 samples). As a result, a regression equation was
y=− 0.405+0.994x and its correlation coefficient (r) was 0.999.
The results of the repeatability tests on different days using mixed phosphate fertilizer,
compound fertilizer and silicate slag fertilizer (1 sample for each) to evaluate precisionwere analyzed by the one-way analysis of variance. Table 1 shows the calculation
results of intermediate precision and repeatability.
Additionally, results from a collaborative study for testing method validation using
calcined sludge fertilizers and its analysis are shown in Table 2.
The minimum limit of quantification of this testing method was estimated to be about
6 mg/kg.
486

Testing Methods for Fertilizers(2021)

References1)
Hisanori ARAYA, Yoshimi TAKEBA and Toshiaki HIROI: Evaluation of Digest Method
for Determination of Chromium in Calcined Sludge Fertilizer by Atomic Absorption
Spectrometry - Research Report of Fertilizer Vol. 4, p. 23 - 29 (2011)
2)
Takeshi UCHIYAMA and Yuji SHIRAI: Evaluation of Digest Method for Determinationof Chromium in Calcined Sludge Fertilizer by Atomic Absorption Spectrometry: A
Collaborative Study. Research Report of Fertilizer Vol. 5, p. 41 - 47 (2012)

487

Testing Methods for Fertilizers(2021)(5) Flow sheet for chromium: The flow sheet for chromium in calcined sludge fertilizer andfertilizers not containing organic matters is shown below: However, fertilizers that may bumpare excluded from the scope of application.
1.00 g200-mL - 300-mL tall beaker.
analytical sample← A small amount of water, moisten the analytical sample (as necessary)← About10 mL of nitric acid
← About 5 mL of sulfuric acid
Leaving at rest
Cover with a watch glass
HeatingHeat gently on a hot plate or a sand bath at 170 ºC - 220 ºC
for no less than 30 minutes

HeatingHeat on a hot plate or sand bath at no less than 300 ºC,
until yellow-brown smoke no longer evolves.

Standing to coolRoom temperature← About 5 mL of perchloric acid
Cover with a watch glass,
Heatingdigest on a hot plate or a sand bath at no less than 300 ºC for 2-3 hours
Heating

Slightly move the watch glass,concentrate until it becomes no more than 2mL

Standing to coolRoom temperature← About 5 mL of hydrochloric acid (1+10)← About 20 mL of water
Heating
Cover with watch glass, dissolve
Standing to coolRoom temperature

Transfer
100-mL volumetric flask, water← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for chromium in calcined sludge fertilizer and fertilizers not containing
organic matters (Extraction procedure)(Excluding fertilizers which may bump while heating)488

Testing Methods for Fertilizers(2021)

489

Testing Methods for Fertilizers(2021)

5.5.d ICP Optical Emission Spectrometry(1) Summary
The testing method is applicable to sludge fertilizers, etc. (except for calcined sludge fertilizer)
This testing method is classified as Type D and its symbol is 5.5.d-2017 or Cr.d-1.
Pretreat an analytical sample with incineration, nitric acid−hydrochloric acid (1+3), introduce it toan ICP Optical Emission Spectrometer (ICP-OES) and measure the emission with chromium at awavelength of 205.552 nm to quantify the chromium (Cr) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 6.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Chromium standard solution (Cr 0.1 mg/mL): A chromium standard solution (Cr 0.1 mg/mL)
traceable to National Metrologye) Chromium standard solutions (Cr 2.5 µg/mL) (1) (2): Dilute a predetermined amount ofchromium standard solution (Cr 0.1 mg/mL) with hydrochloric acid (1+23) to prepare achromium standard solution (Cr 2.5 µg/mL)
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the chromium standard solution in (2), a chromium standard solution for thecalibration curve preparation can be prepared by using a chromium standard solution(Cr 1 mg/mL or 10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (3).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (3).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
490

Testing Methods for Fertilizers(2021)

Slightly move the watch glass (4), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (5) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200 mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
f)Note (3) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(4) The watch glass can be removed.
(5) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Standard Addition Method) according to JIS K 0116 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Optical Emission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 205.552 nmb) Calibration curve preparation and sample measurement
1) Put 5mL of sample solution in three 10-mL volumetric flasks respectively.
2) Add 2mL and 4 mL of chromium standard solution (2.5 μg/mL) to volumetric flasks of 1) above,
then add hydrochloric acid (1+23) to the marked line to make a sample solution of Standard
Addition Method.
3) Add hydrochloric acid (1+23) to the marked line of the remaining volumetric flask of 1) above
to make a sample solution without a standard solution.
4) Spray the sample solution of Standard Addition Method and the sample solution without astandard solution into the induction plasma, and read the indicated value at a wavelength of
205.552 nm.
5) Put 5 mL of blank test solution in a 10-mL volumetric flask, conduct the same procedures as in3) - 4) to read the indicated value, and correct the indicated value obtained from the respective
sample solutions.
6) Prepare a curve for the relationship between the added chromium concentration and thecorrected indicated value of the sample solution for Standard Addition Method and the sample
solution without a standard solution.
7) Obtain the chromium content from the intercept of the calibration curve to calculate chromium(Cr) in the analytical sample.
Comment 4 Instead of the correction method in b) 5), the chromium (Cr) in the analytical sample
can also be corrected by obtaining the chromium content in the blank test solution.
Comment 5 The simultaneous measurement of multiple elements is possible with the ICP-OES. In
that case, see 4.9.1.b Comment 6.
491

Testing Methods for Fertilizers(2021)

Comment 6 The comparison of the measurement value (xi：12.9 mg/kg - 193 mg/kg) of ICP OpticalEmission Spectrometry and the measurement value (yi) of Flame Atomic Absorption
Spectrometry was conducted to evaluate trueness using sludge fertilizers (49 samples).
As a result, a regression equation was y=1.74+0.971x and its correlation coefficient (r)was 0.991. Triplicates measurement for each one sample of sewage sludge fertilizer,
human waste sludge fertilizer, industrial sludge fertilizer, mixed sludge fertilizer andcomposted sludge fertilizer was conducted. As a result, a repeatability obtained was
0.9 % - 2.5 % as a relative standard deviation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 4 mg/kg.
References
1)
Masahiro ECHI, Tomoe INOUE, Megumi TABUCHI and Tetuya NOMURA:
Simultaneous Determination of Cadmium, Lead, Nickel, Chromium, Copper and Zinc in
Sludge Fertilizer using Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES), Research Report of Fertilizer, Vol. 4, p. 30 - 35 (2011)(5)

Flow sheet for chromium: The flow sheet for chromium in fertilizers is shown below:492

Testing Methods for Fertilizers(2021)

493

Testing Methods for Fertilizers(2021)

5.5.e
ICP Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers containing organic matters. This testing method isclassified as Type D and its symbol is 5.5.e-2021 or Cr.e-2.
Add nitric acid – hydrogen peroxide to an analytical sample, and heat to decompose by microwave
irradiation. Introduce it to an ICP Mass Spectrometer (ICP-MS) and measure the respective indicatedvalues of chromium and an internal standard element (scandium) with mass/charge number (m/z) andobtain chromium (Cr) in the analytical sample from the ratio of the indicated value for chromium andthe indicated value for an internal standard element. Note that the performance of this testing method
is shown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Nitric acid: Nitric acid used to dilute a standard solution and a sample solution is a highly
pure reagent specified in JIS K 9901.
d) Hydrogen peroxide: A JIS Guaranteed Reagent specified in JIS K 8230 or a reagent ofequivalent quality.
e) Scandium standard solution (Sc 1000 mg/L): A scandium standard solution (Sc 1000 mg/L)
traceable to National Metrology.
f) Scandium standard solution (Sc 25 µg/mL) (1) (2) (3): Dilute a predetermined amount ofscandium standard solution (Sc 1000 mg/L) with nitric acid (1+19) to prepare a scandium
standard solution (Sc 25 µg/mL).
g) Scandium standard solution (Sc 500 ng/mL) (1) (3): Dilute a predetermined amount ofscandium standard solution (Sc 25 µg/mL) with nitric acid (1+19) to prepare a scandium
standard solution (Sc 500 ng/mL).
h) Chromium standard solution (Cr 1000 mg/L): A chromium standard solution (Cr 1000 mg/L)
traceable to National Metrology.
i) Chromium standard solution (Cr 1000 ng/mL) (1) (2) (3): Dilute a predetermined amount ofchromium standard solution (Cr 1000 mg/L) with nitric acid (1+19) to prepare a chromium
standard solution (Cr 1000 ng/mL).
j) Chromium standard solutions (Cr 20 ng/mL - 100 ng/mL) for the calibration curve
preparation (1) (3): Put 2 mL - 10 mL of chromium standard solution (Cr 1000 ng/mL) in 100mL volumetric flasks step-by-step, and add nitric acid (1+19) up to the marked line.
k) Chromium standard solutions (Cr 1 ng/mL - 10 ng/mL) for the calibration curve
preparation (1) (3): Put 1 mL - 10 mL of chromium standard solution (Cr 100 ng/mL) in 100-mL
volumetric flasks step-by-step, and add nitric acid (1+19) up to the marked line.
l) Blank test solution for the calibration curve preparation (1) (3): Nitric acid (1+19) used in theprocedures in f), g), i), j) and k).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in cool and dark place, and do not use after 6 month after preparation.
(3) For preparation and storage, use sealable containers made of materials such as
polypropylene containing no chromium.
Comment 1 Instead of the scandium standard solution in (2), a scandium standard solution can beprepared by using a scandium standard solution (Sc 100 mg/L or 10000 mg/L)
traceable to National Metrology.
Comment 2 Instead of the chromium standard solution in (2), a chromium standard solution for thecalibration curve preparation can be prepared by using a chromium standard solution(Cr 100 mg/L or 10000 mg/L) traceable to National Metrology.
Comment 3 When a sample solution or a standard solution for the calibration curve preparation
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Testing Methods for Fertilizers(2021)

and an internal standard solution are not simultaneously introduced in themeasurement of ICP-MS, add 1/10 volume of scandium standard solution (Sc 500
ng/mL) to the volume of the solution when preparing respective solutions in theprocedures in j), k) and l).
Comment 4 ICP-MS detection methods include a pulse detection method and an analog detection
method. There are detection method models that combine them, but when themeasurement value is affected by switching, the concentration of the standard solution
and the internal standard solution may be changed as appropriate so that measurement
can be performed with either detection method.
(3) Instruments: Instruments are as shown below:a) ICP Mass Spectrometer: A high-frequency plasma mass spectrometer specified in JIS K
0133, that is equipped with a collision/reaction cell.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.995 % in purityb) Pressure vessel decomposing device: A device which pressurizes the inside of a vessel by
putting acid, etc. to heat in the decomposing vessel, and decomposes a sample by the interactionof heating, pressurizing and acid. The following requirements should be met.
1) The main part of a decomposing device: In the case of the microwave heating method, adevice should be able to produce a high-frequency wave using a frequency which is permitted
at an industrial frequency facility. It is desirable to be able to monitor pressure and temperature,etc. in the decomposing vessel with a sensor inside the device. The interior of a device shouldbe acid-resistant treated and should have a high temperature durability and a high level of safety.
2) Exhaust system: A system which has an exhaust fan of acid-resistant specification, and has
an air-cool function inside the device to allow constant airflow, keeping operating temperature
below a certain temperature level.
3) Decomposing vessel: A vessel which is heat-resistance and pressure-tight and has the
durability required to decompose particles, and has resistance to internal contamination. Itshould have safety functions such as causing overheat prevention valve to work and internalpressure to drop by emitting gas, and preventing gas bumping in the case of exceeding apressure limitation.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Fluid sludge fertilizera) Weigh 20.0 g (4) of an analytical sample, and put it into an airtight vessel.
b) Gradually add 2.5 mL of nitric acid and 2 mL of hydrogen peroxide.
c) Put the decomposing vessel into the main part of a decomposing device and heat using a
microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and put it in a 50-mL ground-in stopper centrifugal precipitate
tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
(4.1.2) Fertilizers containing organic matters except fluid sludge fertilizersa) Weigh 0.20 g of an analytical sample, and put it into a decomposing vessel.
b) Gradually add 10 mL of nitric acid and 1 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
495

Testing Methods for Fertilizers(2021)

a microwave.
d) Ignite and pressurize at about 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and transfer it to a 50-mL ground-in stopper centrifugal
precipitate tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another airtight vessel to prepare a blanktest solution.
Note (4) The maximum limit of solid content, which is converted from moisture content, in thesampling volume 20.0 g of an analytical sample is about 0.5 g. If solid content is likely
to exceed the limit, reduce sampling volume as necessary.
(5) Example setting conditions of a microwave decomposing device are as shown in Table 1.
Table 1 Example setting conditions of a microwave
decomposing device
Time (min)Temperature (°C)

Output (kW)

0

-

0

20

200 (temperature rising)

1400

10

200

1400

40

Room temperature0(6) When organic matters, for example colored precipitate, etc., still remain, add 2 mL ofnitric acid and 1 mL of hydrogen peroxide and repeat the procedures in (4.1) c) – d).
(7) The vessel should be made of polypropylene, etc. to not affect the measurement.
(8) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal force.
Comment 5 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Internal Standard Method) according to JIS K 0113 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Mass Spectrometer used in measurement.
a) Measurement conditions for ICP Mass Spectrometer: Set up the measurement conditions for
the ICP Mass Spectrometer considering the following:
Chromium: mass/charge number (m/z): 52
Scandium: mass/charge number (m/z): 45
Collision cell: He-KED (Kinetic Energy Discrimination) modeb) Calibration curve preparation
1) Spray the chromium standard solution for the calibration curve preparation and the blank test
solution for the calibration curve preparation together with scandium standard solution (Sc 500
ng/mL) into the inductively coupling plasma (9), and read the ratio of the indicated values forthe respective mass/charge number of an element subjected to measurement and an internal
standard element.
2) Prepare a calibration curve for the relationship between the concentration and the ratio of theindicated value of an element subjected to measurement.
c) Sample measurement
1) Put no more than 2.5 mL of the sample solution in a 50-mL volumetric flask (7), add nitric acidto be nitric acid (1+19), and add water to the marked line (10).
2) Subject to the same procedure as in b) 1) to read the ratio of the indicated values.
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Testing Methods for Fertilizers(2021)

3) For the blank test solution, conduct procedures similarly as in 1) - 2) to correct the ratio of theindicated value obtained for the measurement solution.
4) Obtain the chromium content from the calibration curve, and calculate chromium (Cr) in theanalytical sample.
Note (9) Simultaneously introduce an internal standard solution 1/10 of the volume of thestandard solution for the calibration curve preparation or the blank test solution for thecalibration curve preparation.
Note (10) If there is a possibility that the chromium concentration in the sample solution will
exceed the maximum limit of the calibration curve, reduce the sampling amount for the
sample solution or dilute it with nitric acid (1+19).
Comment 6 Instead of the correction method in c) 4), the chromium (Cr) in the analytical sample
can also be corrected by obtaining the chromium content in the blank test solution.
Comment 7 Triplicates additive recovery testing was conducted to evaluate trueness using mixed
compost compound fertilizers and fluid composted sludge fertilizers. As a result, themean recovery rates at the concentration level of 10 mg/kg - 500 mg/kg were 93.9 %- 103 % as chromium (Cr).
The comparison of the measurement value (xi: 4.43 mg/kg – 428 mg/kg) of ICP-MSand the measurement value (yi) of Flame Atomic Absorption Spectrometry was
conducted using sludge fertilizers (15 samples). As a result, a regression equation was
y = 5.1849 + 0.98x, and its correlation coefficient (r) was 0.999. Similarly, thecomparison of the measurement value (yi: 16.0 mg/kg – 499 mg/kg) of ICP Mass
Spectrometry and the measurement value (xi) of Flame Atomic Absorption
Spectrometry was conducted using compound fertilizer (5 samples), solid compound
fertilizer (2 samples), and mixed compost compound fertilizer (6 samples). As a result,a regression equation was y = 15.028 + 1.0014x, and its correlation coefficient (r) was
0.999.
The results of repeated analyses using two types of human waste sludge fertilizer andcompound fertilizer were analyzed by the one-way analysis of variance. Table 2 showsthe estimation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.04 mg/kg for fluid sludge fertilizers and about 4 mg/kg for other fertilizers.

Comment 8 The simultaneous measurement of multiple elements is possible with the ICP-MS. In
that case, prepare standard solutions, etc. referencing Table 1 of Annex C2, conduct
procedures similarly as (4.2) b) - c), and calculate respective element concentrations
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Testing Methods for Fertilizers(2021)

in an analytical sample.
Note that the concentration of a standard solution and an internal standard solution can
be changed as appropriate according to Comment 4.
References1)
Toshiharu YAGI: Determination of Heavy Metals in Fluid Sludge Fertilizers by ICP-MSand CV-AAS, Research Report of Fertilizer Vol. 8, p. 26 - 37 (2015)2)
Toshiharu YAGI, Kenta SAKUMA and Yoshimi HASHIMOTO: Determination of Heavy
Metals in Sludge Fertilizers using Inductively Coupled Plasma-Mass Spectrometer (ICPMS), Research Report of Fertilizer, Vol. 9, p. 21 – 32 (2016)
3)
Satoko SAKAIDA, Mayu OSHIMA, Keisuke AOYAMA and Yuji SHIRAI:
Determination of Harmful Components in Fertilizers using Inductively Coupled PlasmaMass Spectrometer (ICP-MS), Research Report of Fertilizer, Vol. 12, p. 52 – 68 (2019)(5)

Flow sheet for chromium: The flow sheet for chromium in fluid sludge fertilizers is shown
below:

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Testing Methods for Fertilizers(2021)
0.20 g analytical sample

Decomposing vessel← Nitric acid, 10 mL← Hydrogen peroxide, 1 mL
Microwave decomposition

Transfer

50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube, 1700 × g , 5 minutes

Sample solution
Figure 2 Flow sheet for chromium in fertilizers containing organic matters except fluidsludge fertilizers (Extraction procedure)

Sample solution
Aliquot (no more than 2.5
mL)

50-mL Volumetric flask← Nitric acid, to be nitric acid (1+19)← Water (up to the marked line)
Measurement

ICP-MS (internal standard: Sc, Cr: m/z 52 Sc: m/z 45）

Figure 3 Flow sheet for chromium in fertilizers containing organic matters (Measurement procedure)

499

Testing Methods for Fertilizers(2021)

5.5.f

500

Testing Methods for Fertilizers(2021)

5.6 Lead
5.6.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.6.a-2017 or Pb.a-1.
Pretreat an analytical sample with incineration and nitric acid−hydrochloric acid (1+3), spray into
an acetylene−air flame, and measure the atomic absorption with lead at a wavelength of 217.0 nm or
283.3 nm to obtain the lead (Pb) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Lead standard solution (Pb 0.1 mg/mL): A lead standard solution (Pb 0.1 mg/mL) traceable
to National Metrology.
e) Lead standard solutions (Pb 0.5 µg - 5 µg/mL) for the calibration curve preparation (1) (2):
Put 2.5 mL - 25 mL of lead standard solution (Pb 0.1 mg/mL) in 500-mL volumetric flasks stepby-step, and add hydrochloric acid (1+23) to the marked line.
f) Blank test solution for the calibration curve preparation (1) (2): Hydrochloric acid (1+23)
used in the procedures in e).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the lead standard solution in (2), a lead standard solution for the calibration
curve preparation can be prepared by using a lead standard solution (Pb 1 mg/mL or
10 mg/mL) traceable to National Metrology.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121 with the background correction (3) function.
1) Light source: A lead hollow cathode lamp (In case of background correction system using
continuous spectrum source, the light source is a deuterium lamp.)
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
Note (3) There are the continuous source method, the Zeeman method, the non-resonancespectrum method, and the self-reversal method, etc.

501

Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
f) Slightly move the watch glass (5), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (6) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer to a 100-mL - 200 mL volumetric flask with water, add water up
to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (4) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250°C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(5) The watch glass can be removed.
(6) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 2 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the atomic absorption spectrometer: Set up the measurement
conditions for the atomic absorption spectrometer considering the following:
Analytical line wavelength: 217.0 nm or 283.3 nmb) Calibration curve preparation
1) Spray the lead standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation into a flame, and read the indicated value at a wavelengthof 217.0 nm or 283.3 nm.
2) Prepare a curve for the relationship between the lead concentration and the indicated value ofthe lead standard solutions for the calibration curve preparation and the blank test solution forthe calibration curve preparation.
c) Sample measurement
1) Subject the sample solution (7) to the same procedure as in b) 1) to read the indicated value.
2) Subject the blank test solution to the same procedure as in b) 1) to read the indicated value, andcorrect the indicated value obtained for the sample solution.
3) Obtain the lead content from the calibration curve, and calculate lead (Pb) in the analyticalsample.
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Testing Methods for Fertilizers(2021)

Note (7) If there is a possibility that the lead concentration in the sample solution will exceed the
maximum limit of the calibration curve, dilute a predetermined amount withhydrochloric acid (1+23).
Comment 4 Instead of the correction method in c) 2), the lead (Pb) in the analytical sample canalso be corrected by obtaining the lead content in the blank test solution.
Comment 5 Recovery testing was conducted using industrial sludge fertilizer and composted
sludge fertilizer (5 samples); as a result, the recovery rates at the concentration levelof 100 mg/kg and 10 mg/kg were 99.1 % - 100.6 % and 97.5 % - 99.6 %, respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 1 mg/kg.

References
1)
Yoshinari SAKAKIBARA, Manabu MATSUZAKI and Tadao AMANO: Determinationof Cadmium, Lead, Nickel and Chromium in Sludge Fertilizer - Improved Decomposition
Method - Research Report of Fertilizer Vol. 1, p. 41 - 49 (2008)
2) Yoshinari SAKAKIBARA and Manabu MATSUZAKI: Determination of Cadmium, Lead,
Nickel and Chromium in Sludge Fertilizer - Collaborative Test Results - Research Reportof Fertilizer Vol. 1, p. 50 - 59 (2008)
3)
Hisanori ARAYA and Yoshimi TAKEBA: Validation of atomic absorption spectrometryfor determination of cadmium, lead, nickel and chromium in calcined sludge fertilizer Research Report of Fertilizer Vol. 3, p. 30 - 42 (2010)503

Testing Methods for Fertilizers(2021)(5)

Flow sheet for lead: The flow sheet for lead in fertilizers is shown below:504

Testing Methods for Fertilizers(2021)

5.6.b ICP Optical Emission Spectrometry(1) Summary
The test method is applicable to sludge fertilizers, etc. This testing method is classified as Type D
and its symbol is 5.6.b-2017 or Pb.b-1.
Pretreat an analytical sample with incineration, nitric acid−hydrochloric acid (1+3), introduce it toan ICP Optical Emission Spectrometer (ICP-OES) and measure the emission with lead at awavelength of 220.351 nm to obtain the lead (Pb) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Hydrochloric acid: A reagent of harmful metal analysis grade, microanalysis grade orequivalents.
d) Lead standard solution (Pb 0.1 mg/mL): A lead standard solution (Pb 0.1 mg/mL) traceable
to National Metrology.
e) Lead standard solutions (Pb 2.5 µg/mL) (1) (2): Dilute a predetermined amount of lead standard
solution (Pb 0.1 mg/mL) with hydrochloric acid (1+23) to prepare a lead standard solution (Pb
2.5 µg/mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store at room temperature, and do not use after 6 months after preparation.
Comment 1 Instead of the lead standard solution in (2), a lead standard solution for the calibration
curve preparation can be prepared by using a lead standard solution (Pb 1 mg/mL or
10 mg/mL) traceable to National Metrology.
Comment 2 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Electric furnace: An electric furnace that can keep the test temperature at 450 °C ± 5 °C .
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (3).
c) Ignite at 450 ºC ± 5 ºC for 8 - 16 hours to incinerate (3).
d) After standing to cool, moisten the residue with a small amount of water, and add about 10 mLof nitric acid and about 30 mL of hydrochloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to digest.
505

Testing Methods for Fertilizers(2021)

Slightly move the watch glass (4), and continue heating on the hot plate or sand bath toconcentrate until nearly exsiccated.
g) After standing to cool, add 25 mL - 50 mL of hydrochloric acid (1+5) (5) to the digest, cover thetall beaker with the watch glass, and heat quietly to dissolve.
h) After standing to cool, transfer the solution to a 100-mL - 200 mL volumetric flask with water,
add water up to the marked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
f)Note (3) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 450 °C in 1 to 2 hours.
(4) The watch glass can be removed.
(5) Add hydrochloric acid (1+5) so that the hydrochloric acid concentration of the sample
solution will be hydrochloric acid (1+23). For example, when a 100-mL volumetric flask
is used in the procedure in h), about 25 mL of hydrochloric acid (1+5) should be added.
Comment 3 Do not conduct the procedures in (4.1) b) - c) in the case of fertilizers not containing
organic matters.
Comment 4 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Standard Addition Method) according to JIS K 0116
and as shown below. Specific measurement procedures are according to the operation methodof the ICP Optical Emission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 220.351 nmb) Calibration curve preparation and sample measurement
1) Put 5mL of sample solution in three 10-mL volumetric flasks respectively.
2) Add 2 mL and 4 mL of lead standard solution (0.25 μg/mL) to volumetric flasks of 1) above,
then add hydrochloric acid (1+23) to the marked line to make a sample solution of Standard
Addition Method.
3) Add hydrochloric acid (1+23) to the marked line of the remaining volumetric flask of 1) above
to make a sample solution without a standard solution.
4) Spray the sample solution of Standard Addition Method and the sample solution without astandard solution into the induction plasma, and read the indicated value at a wavelength of
220.351 nm.
5) Put 5 mL of blank test solution in a 10-mL volumetric flask, conduct the same procedures as in3) - 4) to read the indicated value, and correct the indicated value obtained from the respective
sample solutions.
6) Prepare a curve for the relationship between the added lead concentration and the correctedindicated value of the sample solution for Standard Addition Method and the sample solution
without a standard solution.
7) Obtain the lead content from the intercept of the calibration curve, and calculate lead (Pb) in
the analytical sample.
Comment 5 Instead of the correction method in b) 5), the lead (Pb) in the analytical sample canalso be corrected by obtaining the lead content in the blank test solution.
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Testing Methods for Fertilizers(2021)

Comment 6 The simultaneous measurement of multiple elements is possible with the ICP-OES. In
that case, see 4.9.1.b Comment 6.
Comment 7 The comparison of the measurement value (xi：1.1 mg/kg - 69.0 mg/kg) of ICP OpticalEmission Spectrometry and the measurement value (yi) of Flame Atomic Absorption
Spectrometry was conducted to evaluate trueness using sludge fertilizers (49 samples).
As a result, a regression equation was y=−0.31+1.045x and its correlation coefficient(r) was 0.993. Triplicates measurement for each one sample of sewage sludge fertilizer,
human waste sludge fertilizer, industrial sludge fertilizer, mixed sludge fertilizer,
calcined sludge fertilizers and composted sludge fertilizer was conducted. As a result,a repeatability obtained was 0.9 % - 3.3 % as a relative standard deviation.
Note that the minimum limit of quantification of this testing method was estimated to
be about 5 mg/kg.
References
1)
Masahiro ECHI, Tomoe INOUE, Megumi TABUCHI and Tetuya NOMURA:
Simultaneous Determination of Cadmium, Lead, Nickel, Chromium, Copper and Zinc in
Sludge Fertilizer using Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES), Research Report of Fertilizer, Vol. 4, p. 30 - 35 (2011)507

Testing Methods for Fertilizers(2021)(5)

Flow sheet for lead: The flow sheet for lead in fertilizers is shown below:

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Testing Methods for Fertilizers(2021)

5.6.c
ICP Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 5.6.c-2021 or Pb.c-2.
Add nitric acid – hydrogen peroxide to an analytical sample, and heat to decompose by microwave
irradiation. Introduce it to an ICP Mass Spectrometer (ICP-MS) and measure the respective indicatedvalues of lead and an internal standard element (thallium) with mass/charge number (m/z) and obtainlead (Pb) in the analytical sample from the ratio of the indicated value for lead and the indicated value
for an internal standard element. Note that the performance of this testing method is shown inComment 7.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
c) Nitric acid: Nitric acid used to dilute a standard solution and a sample solution is a highly
pure reagent specified in JIS K 9901.
d) Hydrogen peroxide: A JIS Guaranteed Reagent specified in JIS K 8230 or a reagent ofequivalent quality.
e) Thallium standard solution (Tl 1000 mg/L): A thallium standard solution (Tl 1000 mg/L)
traceable to National Metrology.
f) Thallium standard solution (Tl 2.5 µg/mL) (1) (2) (3): Dilute a predetermined amount ofthallium standard solution (Tl 1000 mg/L) with nitric acid (1+19) to prepare a thallium standard
solution (Tl 2.5 µg/mL).
g) Thallium standard solution (Tl 50 ng/mL) (1) (3): Dilute a predetermined amount of thallium
standard solution (Tl 2.5 µg/mL) with nitric acid (1+19) to prepare a thallium standard solution(Tl 50 ng/mL).
h) Lead standard solution (Pb 1000 mg/L): A lead standard solution (Pb 1000 mg/L) traceable
to National Metrology.
i) Lead standard solution (Pb 100 ng/mL) (1) (2) (3): Dilute a predetermined amount of leadstandard solution (Pb 1000 mg/L) with nitric acid (1+19) to prepare a lead standard solution (Pb
100 ng/mL).
j) Lead standard solutions (Pb 2 ng/mL - 10 ng/mL) for the calibration curve preparation (1)(3): Put 2 mL - 10 mL of lead standard solution (Pb 100 ng/mL) in 100-mL volumetric flasks
step-by-step, and add nitric acid (1+19) to the marked line.
k) Lead standard solutions (Pb 0.1 ng/mL - 1 ng/mL) for the calibration curve preparation(1) (3): Put 1 mL - 10 mL of lead standard solution (Pb 10 ng/mL) in 100-mL volumetric flasks
step-by-step, and add nitric acid (1+19) to the marked line.
l) Blank test solution for the calibration curve preparation (1) (3): Nitric acid (1+19) used in theprocedures in f), g), i), j) and k).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in cool and dark place, and do not use after 6 month after preparation.
(3) For preparation and storage, use sealable containers made of materials such as
polypropylene containing no lead.
Comment 1 Instead of the thallium standard solution in (2), a thallium standard solution can beprepared by using a thallium standard solution (Tl 100 mg/L or 10000 mg/L) traceable
to National Metrology.
Comment 2 Instead of the lead standard solution in (2), a lead standard solution for the calibration
curve preparation can be prepared by using a lead standard solution (Pb 100 mg/L or
10000 mg/L) traceable to National Metrology.
509

Testing Methods for Fertilizers(2021)

Comment 3 When a sample solution or a standard solution for the calibration curve preparation
and an internal standard solution are not simultaneously introduced in themeasurement of ICP-MS, add 1/10 volume of thallium standard solution (Tl 50 ng/mL)
to the volume of the solution when preparing respective solutions in the procedures inj), k) and l).
Comment 4 ICP-MS detection methods include a pulse detection method and an analog detection
method. There are detection method models that combine them, but when themeasurement value is affected by switching, the concentration of the standard solution
and the internal standard solution may be changed as appropriate so that measurement
can be performed with either detection method.
(3) Instruments: Instruments are as shown below:a) ICP Mass Spectrometer: A high-frequency plasma mass spectrometer specified in JIS K
0133, that is equipped with a collision/reaction cell.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.995 % in purityb) Pressure vessel decomposing device: A device which pressurizes the inside of a vessel by
putting acid, etc. to heat in the decomposing vessel, and decomposes a sample by the interactionof heating, pressurizing and acid. The following requirements should be met.
1) The main part of a decomposing device: In the case of the microwave heating method, adevice should be able to produce a high-frequency wave using a frequency which is permitted
at an industrial frequency facility. It is desirable to be able to monitor pressure and temperature,etc. in the decomposing vessel with a sensor inside the device. The interior of a device shouldbe acid-resistant treated and should have a high temperature durability and a high level of safety.
2) Exhaust system: A system which has an exhaust fan of acid-resistant specification, and has
an air-cool function inside the device to allow constant airflow, keeping operating temperature
below a certain temperature level.
3) Decomposing vessel: A vessel which is heat-resistance and pressure-tight and has the
durability required to decompose particles, and has resistance to internal contamination. Itshould have safety functions such as causing overheat prevention valve to work and internalpressure to drop by emitting gas, and preventing gas bumping in the case of exceeding apressure limitation.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Fluid sludge fertilizera) Weigh 20.0 g (4) of an analytical sample, and put it into an airtight vessel.
b) Gradually add 2.5 mL of nitric acid and 2 mL of hydrogen peroxide.
c) Put the decomposing vessel into the main part of a decomposing device and heat using a
microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and put it in a 50-mL ground-in stopper centrifugal precipitate
tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8 ) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
(4.1.2) Fertilizers except fluid sludge fertilizers
510

Testing Methods for Fertilizers(2021)a) Weigh 0.20 g of an analytical sample, and put it into a decomposing vessel.
b) Gradually add 10 mL of nitric acid and 1 mL of hydrogen peroxide.
c) Seal the decomposing vessel, put it into the main part of a decomposing device and heat using
a microwave.
d) Ignite and pressurize at 180 ºC - 220 ºC for no less than 10 minutes (5) to decompose (6).
e) After standing to cool, transfer the solution to a 50-mL volumetric flask (7) with water.
f) Add water up to the marked line and transfer it to a 50-mL ground-in stopper centrifugal
precipitate tube (7).
g) Centrifuge it at 1700 × g centrifugal force for about five minutes (8) and use the supernatant asa sample solution.
h) As a blank test, conduct the procedures in b) - g) using another decomposing vessel to preparea blank test solution.
Note (4) The maximum limit of solid content, which is converted from moisture content, in thesampling volume 20.0 g of an analytical sample is about 0.5 g. If solid content is likely
to exceed the limit, reduce sampling volume as necessary.
(5) Example setting conditions of a microwave decomposing device are as shown in Table 1.
Table 1Example setting conditions of a microwave decomposing device
Time (min)Temperature (°C)

Output (kW)

0

-

0

20

200 (temperature rising)

1400

10

200

1400

40

Room temperature0(6) When organic matters, for example colored precipitate, etc., still remain, add 2 mL ofnitric acid and 1 mL of hydrogen peroxide and repeat the procedures in (4.1) c) – d).
(7) The vessel should be made of polypropylene, etc. to not affect the measurement.
(8) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal force.
Comment 5 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct measurement (Internal Standard Method) according to JIS K 0113 andas shown below. Specific measurement procedures are according to the operation method of the
ICP Mass Spectrometer used in measurement.
a) Measurement conditions for ICP Mass Spectrometer: Set up the measurement conditions for
the ICP Mass Spectrometer considering the following:
Lead: mass/charge number (m/z): 208, 206, 207
Thallium: mass/charge number (m/z): 205
Collision cell: He-KED (Kinetic Energy Discrimination) modeb) Calibration curve preparation
1) Spray the lead standard solution for the calibration curve preparation and the blank test solution
for the calibration curve preparation together with thallium standard solution (Tl 50 ng/mL)
into the inductively coupling plasma (9), and read the ratio of the indicated values for therespective mass/charge number of an element subjected to measurement and an internal
standard element (10).
2) Prepare a calibration curve for the relationship between the concentration and the ratio of theindicated value of an element subjected to measurement.
511

Testing Methods for Fertilizers(2021)c) Sample measurement
1) Put no more than 2.5 mL of the sample solution in a 50-mL volumetric flask (7), add nitric acidto be nitric acid (1+19), and add water to the marked line (11).
2) Subject to the same procedure as in b) 1) to read the ratio of the indicated values.
3) For the blank test solution, conduct procedures similarly as in 1) - 3) to correct the ratio of theindicated value obtained for the measurement solution.
4) Obtain the lead content from the calibration curve, and calculate lead (Pb) in the analyticalsample.
Note (9) Simultaneously introduce an internal standard solution 1/9 of the volume of the standard
solution for the calibration curve preparation or the blank test solution for the calibration
curve preparation.
(10) If there is a possibility that the lead concentration in the sample solution will exceed the
maximum limit of the calibration curve, reduce the sampling amount for the sample
solution or dilute it with nitric acid (1+19).
Comment 6 Instead of the correction method in c) 3), the lead (Pb) in the analytical sample canalso be corrected by obtaining the lead content in the blank test solution.
Comment 7 Triplicates additive recovery testing was conducted to evaluate trueness using mixed
compost compound fertilizers and fluid composted sludge fertilizers. As a result, themean recovery rates at the concentration level of 2 mg/kg - 100 mg/kg were 96.5 % 101 % as lead (Pb).
The comparison of the measurement value (xi: 2.00 mg/kg – 101 mg/kg) of ICP-MSand the measurement value (yi) of Flame Atomic Absorption Spectrometry was
conducted using sludge fertilizers (14 samples). As a result, a regression equation was
y = −0.4586 + 0.98x, and its correlation coefficient (r) was 0.999. Similarly, thecomparison of the analysis value (yi: 3.41 mg/kg - 108 mg/kg) of ICP Mass
Spectrometry and the analysis value (xi) of Flame Atomic Absorption Spectrometry
was conducted using superphosphate of lime (1 sample), double superphosphate oflime (1 sample), mixed phosphorus fertilizer (1 sample), compound fertilizer (3samples), solid compound fertilizer (2 samples), mixed compost compound fertilizer(5 samples), and byproduct magnesia fertilizer (1 sample). As a result, a regression
equation was y = −0.7161 + 0.9923x, and its correlation coefficient (r) was 0.999.
The results of repeated analyses using two types of human waste sludge fertilizer andcompound fertilizer were analyzed by the one-way analysis of variance. Table 2 showsthe estimation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 mg/kg for fluid sludge fertilizers and about 1 mg/kg for other fertilizers.
Table 2 Estimation results of repeatability and intermediate precision
Sample name

Human waste sludge fertilizer 1
Human waste sludge fertilizer 2
Compound fertilizer 1
Compound fertilizer 2

Repeatability

Days ofrepeatability

2)

Mean

3)

sr

4)

s I(T)

6)

7)

1)(mg/kg)12

6.1(mg/kg)
0.7

5

100

2

1.8

3

2.8

5

4

0.1

3.0

0.2

5.0

5

101

1

1.1

1

1.4

1) The number of days conducting duplicate analysis

3)

RSD I(T)(%)

T
5(mg/kg)
0.7

3)

RSD r
(%)

Intermediate precision
5)5.74) Repeatability standard deviation

2) Mean ([Number of days of repeatability (T )] × [Number of duplicates (2)]) 5) Repeatability relative standard deviation
3) Mass fraction6) Intermediate standard deviation
7) Intermediate relative standard deviation

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Testing Methods for Fertilizers(2021)

Comment 8 The simultaneous measurement of multiple elements is possible with the ICP-MS. In
that case, prepare standard solutions, etc. referencing Table 1 of Annex C2, conduct
procedures similarly as (4.2) b) - c), and calculate respective element concentrationsin an analytical sample.
Note that the concentration of a standard solution and an internal standard solution can
be changed as appropriate according to Comment 4.
References1)
Toshiharu YAGI: Determination of Heavy Metals in Fluid Sludge Fertilizers by ICP-MSand CV-AAS, Research Report of Fertilizer Vol. 8, p. 26 - 37 (2015)2)
Toshiharu YAGI, Kenta SAKUMA and Yoshimi HASHIMOTO: Determination of Heavy
Metals in Sludge Fertilizers using Inductively Coupled Plasma-Mass Spectrometer (ICPMS), Research Report of Fertilizer, Vol. 9, p. 21 – 32 (2016)
3)
Satoko SAKAIDA, Mayu OSHIMA, Keisuke AOYAMA and Yuji SHIRAI:
Determination of Harmful Components in Fertilizers using Inductively Coupled PlasmaMass Spectrometer (ICP-MS), Research Report of Fertilizer, Vol. 12, p. 52 – 68 (2019)(5)

Flow sheet for lead: The flow sheet for lead in fluid sludge fertilizers is shown below:

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Testing Methods for Fertilizers(2021)
0.20 g analytical sample

Decomposing vessel← Nitric acid, 10 mL← Hydrogen peroxide, 1 mL
M icrowave decomposition

Transfer

50-mL volumetric flask, water← Water (up to the marked line)
Centrifugal separation

Ground-in stopper centrifugal precipitate tube, 1700 × g , 5 minutes

Sample solution
Figure 2 Flow sheet for lead in fertilizers except fluid sludge fertilizers (Extraction procedure)

Sample solution

Aliquot (no more than 2.5 mL)

50-mL Volumetric flask← Nitric acid, to be nitric acid (1+19)← Water (up to the marked line)
Measurement

ICP-MS (internal standard: Tl, Pb: m/z 208、206、207 Tl: m/z 205）

Figure 3 Flow sheet for lead in fertilizers (Measurement procedure)

514

Testing Methods for Fertilizers(2021)

5.6.d

515

Testing Methods for Fertilizers(2021)

5.7 Sulfamic acid (amidosulfuric acid)5.7.a Ion Chromatography(1) Summary
The testing method is applicable to ammonium sulfate. This testing method is classified as Type D
and its symbol is 5.7.a-2017 or AS-acid.a-1.
Add water to an analytical sample to extract sulfamic acid, introduce it to an Ion Chromatograph(IC) or a High-Performance Liquid Chromatograph (HPLC) to isolate it with an ion exchange column,
then measure the sulfamic acid with an electric conductivity detector to obtain sulfamic acid(amidosulfuric acid) in an analytical sample. Note that the performance of this testing method isshown in Comment 5.
Sulfamic acid and sulfurized cyanide (ammonium thiocyanate) can be simultaneously quantified byusing this method. (Refer to Comment 4).
(2)
a)
b)
c)
d)
e)
f)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Phthalic acid:A reagent of no less than 98 % (mass fraction) in purity.
p-hydroxybenzoic acid: A reagent of no less than 95 % (mass fraction) in purity.
1-sodium octane sulfonate: A reagent of no less than 98 % (mass fraction) in purity.
1-sodium hexane sulfonate: A reagent of no less than 98 % (mass fraction) in purity.
Boric acid: A JIS Guaranteed Reagent specified in JIS K 8863 or a reagent of equivalentquality.
g) Eluent (1) (2): Weigh 0.083 g of phthalic acid, 0.552 g of p-hydroxybenzoic acid, 0.195 g of 1sodium octane sulfonate, 0.376 g of 1-sodium hexane sulfonate and 6.183 g of boric acid to a
1000-mL volumetric flask, add about 500 mL of water to dissolve and add water up to themarked line. Filter with a membrane filter (aperture diameter: no more than 0.5 µm) made ofhydrophilic PTFE.
h) Sulfamic acid standard solution (1000 mg/L) (1): Put 0.1 g of sulfamic acid, reference material
for volumetric analysis (HOSO2NH2: dried for 48 hours in a silica gel desiccator), in a weighing
dish and measure the mass to the order of 0.1 mg. Add a small amount of water to dissolve, thentransfer to a 100-mL volumetric flask and add water up to the marked line.
i) Sulfamic acid standard solution (10 mg/L) (1): At the time of usage, put 2.5 mL of sulfamicacid standard solution (1000 mg/L) in a 250-mL volumetric flask and add water up to themarked line.
j) Sulfamic acid standard solution for the calibration curve preparation (0.3 mg/L - 3 mg/L):
At the time of usage, put 3 mL - 30 mL of sulfamic acid standard solution (10 mg/L) in 100-mL
volumetric flasks step-by-step and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) The concentration of prepared solutions is phthalic acid 0.5 mmol/L, p-hydroxybenzoic
acid 4.0 mmol/L, 1-sodium octane sulfonate 0.9 mmol/L, 1-sodium hexane sulfonate
2.0 mmol/L and boric acid 100 mmol/L.

(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Ion Chromatograph or High-Performance Liquid Chromatograph: An ion chromatographspecified in JIS K 0127 or a high-performance liquid chromatograph specified in JIS K 0124
that satisfies the following requirements.
1) Column: A 4-mm inner diameter 100-mm long stainless-steel column tube filled withhydrophilic methacrylate-gel, to which 5-μm particle diameter class 4 ammonium groupchemically bonds (3).
2) Column bath: A column bath whose temperature can be adjusted to 55 ºC - 60 ºC.
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Testing Methods for Fertilizers(2021)

3) Detection unit: An electric conductivity detectorb) Membrane filters: Pore size is no more than 0.5 μm, made of hydrophilic PTFE
Note (3) A column is commercially sold under the name Shodex IC NI-424, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water and shake to dissolve, and then add water up to the marked line.
c) Put a predetermined amount of the solution, and dilute exactly by a factor of 12.5 with water.
d) Filter with a membrane filter (pore size: no more than 0.5 μm) to make a sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0127 or JIS K 0124 and as
shown below. Specific measurement procedures are according to the operation method of the
Ion Chromatograph or the High-Performance Liquid Chromatograph used in measurement.
a) Measurement conditions for the Ion Chromatograph or High-Performance Liquid
Chromatograph: An example of measurement conditions is shown below. Set up themeasurement conditions considering it:1) Column: A hydrophilic methacrylate-gel column (4-mm inner diameter, 100-mm long, 5-μm
particle diameter) to which quaternary ammonium group chemically bonds.
2) Column bath temperature: 58 °C
3) Eluent: Prepared by the procedures in (2) g)
4) Flow rate: 1 mL/min
5) Injection volume: 20 µL
6) Detection unit: An electric conductivity detectorb) Calibration curve preparation
1) Inject 20 μL of respective standard solutions for the calibration curve preparation to the Ion
Chromatograph or the High-Performance Liquid Chromatograph, and record the chromatogramof electric conductivity to obtain a peak area.
2) Prepare a curve for the relationship between the concentration and the peak area of electric
conductivity of respective standard solutions for the calibration curve preparation.
Prepare a calibration curve when the sample is measured.
Comment 1 In the measurement of a sample solution, there is a possibility that the recovery rate
becomes lower than actual due to the influence of matrix if the concentration is calculated withthe peak height. Therefore, prepare a calibration curve using the peak area.
c) Sample measurement
1) Subject 20 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the sulfamic acid content from the calibration curve by the peak area to calculate thesulfamic acid (amidosulfuric acid) in the analytical sample.
Comment 2 Calculate the concentration by the peak area similarly as the calibration curve
preparation to prevent the influence of matrix.
Comment 3 Note that it takes time to stabilize the baseline due to the usage of the ion-pairing
reagent in the elute. It is recommended to take about 120 minutes for stabilization time
before starting measurement.
Comment 4 It is possible for the simultaneous measurement of sulfamic acid and ammonium
thiocyanate in this testing method. In that case, mix a predetermined amount of517

Testing Methods for Fertilizers(2021)

sulfamic acid standard solution (1000 mg/L) and ammonium thiocyanate standard
solution (1000 mg/L), dilute with water to prepare a mixture standard solution (10mg/L) (1) and use it instead of a sulfamic acid standard solution (10 mg/L) in (2) i).
After that, conduct the same procedure in (4.2) b) to calculate the respective
concentrations of materials subjected to measurement in the analytical sample.
Comment 5 Recovery testing of ammonium sulfate (3 brands) was conducted. As a result, the mean
recovery rates at additive level of 0.25 % (mass fraction) and 0.075 % (mass fraction)
were 94.4 % - 103.5 % and 94.4 % - 100.8 %.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.04 % (mass fraction).
References1)
Toshiaki HIROI and Yuji SHIRAI: Simultaneous Determination of Sulfamic Acid andAmmonium Thiocyanate in Ammonium Sulfate by Non-suppressed Ion Chromatography,
Research Report of Fertilizer, Vol. 5, p. 1 - 23 (2012)(5)

Flow sheet for testing method: The flow sheet for sulfamic acid in ammonium sulfate is shown
below:

518

Testing Methods for Fertilizers(2021)

Reference: Examples of the IC chromatograms of sulfamic acid and thiocyanic acid of the standard
solution for the calibration curve preparation and sample solution (ammonium sulfate)
are shown below.

12(A) Mixture standard solution (the equivalents of 60 ng (3 mg/L, 20 μL) as sulfamic acidand ammonium thiocyanate, respectively)

Enlarged diagram of peak for sulfamic acid112(B) Sample solution (the equivalents of 0.25 % (mass fraction) (2500 μg/g) as sulfamicacid and ammonium thiocyanate added in ammonium sulfate, respectively)
Reference diagram: IC chromatogram of sulfamic acid and thiocyanic acid.
(Peak: 1. Sulfamic acid, 2. Ammonium thiocyanate)
IC measurement conditions
Column: Shodex IC NI-424 (4.6-mm inner diameter, 100-mm long, 5μm-particle
diameter)Other conditions are according to the example of measurement conditions in (4.2) a)519

Testing Methods for Fertilizers(2021)

5.7.b High-Performance Liquid Chromatograph Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.7.b-2017 or AS-acid.b-1.
Add water to an analytical sample to extract sulfamic acid, introduce it to a High-Performance
Liquid Chromatograph Mass Spectrometer (LC-MS) to isolate it with a silica gel column, to whichcrosslink-type diol chemically bonds, and measure with a Selected Ion Monitoring (SIM) method to
obtain sulfamic acid (amidosulfuric acid) in an analytical sample. In addition, the performance of thistesting method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557. Note that water of A4 or equivalent quality should
be used as the eluent which is introduced to LC-MS.
b) Acetonitrile: A reagent of LC-MS analysis grade or equivalents.
c) Formic acid: A reagent of LC-MS analysis grade or equivalents.
d) Ammonium formate buffer solution (pH 3.2): Dilute 3.153 g of ammonium formate (no lessthan 95 % (mass fraction) in purity) with water to make 500 mL and adjust to pH 3.2 withformic acid.
e) Sulfamic acid standard solution (1 mg/L): Put 0.1 g of sulfamic acid, reference material forvolumetric analysis specified in JIS K 8005, in a weighing dish and measure the mass to theorder of 0.1 mg. Add a small amount of water to dissolve, then transfer to a 100-mL volumetricflask and add water up to the marked line.
f) Sulfamic acid standard solution (10 μg/L) (1): At the time of usage, put 2.5 mL of standard
solution (1 mg/L) in a 250-mL volumetric flask and add water up to the marked line.
g) Sulfamic acid standard solution (200 ng/L) (1): At the time of usage, put 5 mL of standard
solution (10 µg/L) in a 250-mL volumetric flask and add water up to the marked line.
h) Sulfamic acid standard solution for the calibration curve preparation (10 ng/L - 600 ng/L):
At the time of usage, put 2.5 mL - 6 mL of sulfamic acid standard solution (10 µg/L) in 100mL volumetric flasks step-by-step and add water up to the marked line. Similarly put 5 mL - 50
mL of sulfamic acid standard solution (200 ng/L) in 100-mL volumetric flasks step-by-stepand add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph/ Mass Spectrometer: A high-performance liquid
chromatograph/mass spectrometer specified in JIS K 0136 that satisfies the following
requirements.
1) High-Performance Liquid Chromatograph(i) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
(ii) Column: A 2-mm - 3-mm inner diameter 100-mm - 150 mm long stainless-steel column
tube filled with silica gel to which 5-μm crosslink-type diol chemically bonds or
polyhydroxymethacrylate. This should comply with the specification of a Mass
Spectrometer.
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Ion detection method: Selected Ion Monitoring (SIM) methodb) Magnetic stirrerc) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000520

Testing Methods for Fertilizers(2021)

× g.
Comment 1 A High-Performance Liquid Chromatograph/Mass Spectrometer (LC-MS/MS) can beused instead of an LC-MS. In this case, set up the measurement conditions considering(4.3) a) The measurement conditions of High-Performance Liquid
Chromatograph/Mass spectrometer and confirm that a calibration curve can beprepared by the procedure in b) in advance.
Comment 2 A column is sold under the production name LUNA HILIC, Shodex ODP2 HP-2D, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200-mL ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about five minutes (2) and use the supernatant as
an extract.
Note (2) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
Comment 3 Instead of the procedures in (4.1.1) c) and d), it is allowed to filter with Type 3 filter
paper and the filtrate can be the extract.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water to the marked line to make an extract(4.2) Dilution: Conduct dilution of the extract as shown below.
a) Put 2 mL of the sample solution in a 200-mL Erlenmeyer flask.
b) Add water up to the marked line and put it in a 1.5-mL ground-in stopper centrifugal precipitate
tube (3).
c) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (4) and use thesupernatant as a sample solution.
Note (3) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(4) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 4 Instead of the procedures in (4.2) b) and c), it is allowed to filter with a membranefilter (aperture diameter: no more than 0.5 µm) made of hydrophilic PTFE and thefiltrate can be the sample solution.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0136 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph Mass Spectrometer used in measurement.
521

Testing Methods for Fertilizers(2021)

a) The measurement conditions of the High-Performance Liquid Chromatograph/Mass
spectrometer: An example of measurement conditions is shown below. Set up the measurement
conditions considering it:
1) High-Performance Liquid Chromatograph(i) Column: A silica gel column to which crosslink-type diol chemically bonds or
polyhydroxymethacrylate (2-mm - 3-mm inner diameter, 100-mm - 150-mm long, 5-µm
particle diameter).
(ii) Flow rate: 0.2 mL/min(iii) Eluent: Ammonium formate buffer solution - Acetonitrile (1+9)(iv) Temperature of column bath: 40 °C(v) Injection rate: 1 μL(vi) Measurement time: About 20 minutes
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Mode: Negative(iii) Monitor ion: m/z 95.9b) Calibration curve preparation
1) Inject 1 μL of respective standard solutions for the calibration curve preparation to a HighPerformance Liquid Chromatograph/Mass Spectrometer, and record the chromatogram ofmonitor ion (m/z) to obtain a peak area.
2) Prepare a curve for the relationship between the sulfamic acid concentration and the peak areaof monitor ion of respective standard solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 1 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the sulfamic acid content from the calibration curve to calculate the sulfamic acid(amidosulfuric acid) in the analytical sample.
Comment 5 Recovery testing was conducted using samples that sulfamic acid equivalent to 1/5 - 4times of permissible content are added to ammonium sulfate fertilizer (1 brand), byproduct nitrogen fertilizer (1 brand), by-product compound fertilizer (1 brand),compound fertilizer (1 brand) and fluid compound fertilizer (1 brand). As a result, themean recovery rates at the additive level of 0.1 % (mass fraction), 0.025 % (massfraction) and 0.005 % (mass fraction) were 97.6 % - 104.2 %, 95.2 % - 107.0 % and96.4 % - 111.2 % respectively.
The results of the repeatability tests on different days using ammonium sulfate
fertilizer, by-product nitrogen fertilizer and compound fertilizer to evaluate precisionwere analyzed by the one-way analysis of variance. Table 1 shows the calculation
results of intermediate precision and repeatability.
Table 2 shows results and analysis results from a collaborative study for testing method
validation. Note that sufficient reproducibility by sulfamic acid concentration
0.0116 % (mass fraction) was not obtainable. But sufficient reproducibility was
obtained in the scope of sulfamic acid concentration 0.0386 % (mass fraction) 0.401 % (mass fraction).

522

Testing Methods for Fertilizers(2021)

References
1)
Kohei ITO, Mariko FUJITA, Yoshimi HASHIMOTO and Yuji SHIRAI: Determinationof Sulfamic Acid in Fertilizer by Liquid Chromatography/Mass Spectrometry (LC-MS),
Research Report of Fertilizer Vol. 8, p. 38 - 49 (2015)
2)
Tomoharu NOZAKI Determination of Sulfamic Acid in Fertilizers using Liquid
Chromatography-Mass Spectrometer (LC-MS): A Collaborative Study, Research Reportof Fertilizer Vol. 9, p. 69 - 76 (2016)3)
Kenji KOZUKA, Kohei ITO, Nobuhito NAKAMURA and Yuji SHIRAI: Determinationof Sulfamic Acid in Fertilizer by Liquid Chromatography/Mass Spectrometry (LC-MS):
A Collaborative Study, Research Report of Fertilizer Vol. 11, p. 47 – 53 (2018)

523

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for sulfamic acid in fertilizers is shown below:524

Testing Methods for Fertilizers(2021)

Reference:

An example of the chromatogram of sulfamic acid for the calibration curve
preparation is shown below.

Sulfamic acidSulfamic acid

Retention time

Retention time(A) Standard solution(B)(The equivalent of 0.6 ng as sulfamic acid)

Sample solution(The equivalent of 0.1 % of mass fraction as
sulfamic acid is added to a compound fertilizer)

Reference diagram: Chromatogram of sulfamic acid

LC-MS measurement conditions
Column: LUNA HILIC (2.0-mm inner diameter, 100-mm long, 5-μm particle
diameter)
Capillary voltage: - 3.5 kv
Temperature of ion source: 300 °C
Nebulizer gas rate: 1.5 L/min
Desolvation temperature: 250 °C
Other conditions are according to the example of LC-MS measurement conditionsin (4.3) a)525

Testing Methods for Fertilizers(2021)

5.8 Ammonium thiocyanate (Sulfurized cyanide)
5.8.a Ion Chromatography(1) Summary
The testing method is applicable to ammonium sulfate. This testing method is classified as Type D
and its symbol is 5.8.a-2017 or SCN.a-1.
Add water to an analytical sample to extract ammonium thiocyanate (sulfurized cyanide), introduce
it to an Ion Chromatograph (IC) or a High-Performance Liquid Chromatograph (HPLC) to isolate itwith an ion exchange column, then measure the thiocyanic acid with an electric conductivity detector
to obtain ammonium thiocyanate (sulfurized cyanide) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 5.
Sulfamic acid and ammonium thiocyanate (sulfurized cyanide) can be simultaneously quantified byusing this method. (Refer to Comment 4).
(2)
a)
b)
c)
d)
e)
f)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Phthalic acid: A reagent of no less than 98 % (mass fraction) in purity.
p-hydroxybenzoic acid: A reagent of no less than 95 % (mass fraction) in purity.
1-sodium octane sulfonate: A reagent of no less than 98 % (mass fraction) in purity.
1-sodium hexane sulfonate: A reagent of no less than 98 % (mass fraction) in purity.
Boric acid: A JIS Guaranteed Reagent specified in JIS K 8863 or a reagent of equivalentquality.
g) Eluent (1) (2): Weigh 0.083 g of phthalic acid, 0.552 g of p-hydroxybenzoic acid, 0.195 g of 1sodium octane sulfonate, 0.376 g of 1-sodium hexane sulfonate and 6.183 g of boric acid to a
1000-mL volumetric flask, add about 500 mL of water to dissolve and add water up to themarked line. Filter with a membrane filter (aperture diameter: no more than 0.5 µm) made ofhydrophilic PTFE.
h) Ammonium thiocyanate standard solution (1000 mg/L) (1): Put 0.1 g of ammonium
thiocyanate (3), specified in JIS K 9000 in weighing dish, and measure the mass to the order of
0.1 mg. Add a small amount of water to dissolve, then transfer to a 100-mL volumetric flask
and add water up to the marked line.
i) Ammonium thiocyanate standard solution (10 mg/L) (1): At the time of usage, put 10 mL ofammonium thiocyanate standard solution (1000 mg/L) in a 100-mL volumetric flask and add
water up to the marked line.
j) Ammonium thiocyanate standard solution for the calibration curve preparation (0.3 mg/L
- 3 mg/L): At the time of usage, put 3 mL - 30 mL of ammonium thiocyanate solutions (10mg/L) in 100-mLvolumetric flasks step-by-step and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) The concentration of prepared solutions is phthalic acid 0.5 mmol/L, p-hydroxybenzoic
acid 4.0 mmol/L, 1-sodium octane sulfonate 0.9 mmol/L, 1-sodium hexane sulfonate
2.0 mmol/L and boric acid 100 mmol/L.
(3) It is recommended to store in a desiccator because of deliquescence.

(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Ion Chromatograph or High-Performance Liquid Chromatograph: An ion chromatographspecified in JIS K 0127 or a high-performance liquid chromatograph specified in JIS K 0124
that satisfies the following requirements.
1) Column: A 4-mm inner diameter 100-mm long stainless steel column tube filled withhydrophilic methacrylate-gel, to which 5-μm particle diameter class 4 ammonium groupchemically bonds (4).
526

Testing Methods for Fertilizers(2021)

2) Column bath: A column bath whose temperature can be adjusted to 55 ºC - 60 ºC.
3) Detection unit: An electric conductivity detectorb) Membrane filters: Pore size is no more than 0.5 μm, made of hydrophilic PTFE
Note (4) A column is commercially sold under the name Shodex IC NI-424, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water and shake to dissolve, and then add water up to the marked line.
c) Transfer a predetermined amount of the solution, and dilute exactly by a factor of 12.5 withwater.
d) Filter with a membrane filter (pore size: no more than 0.5 μm) to make a sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0127 and as shown below.
Specific measurement procedures are according to the operation method of the Ion
Chromatograph or the High-Performance Liquid Chromatograph used in measurement.
a) Measurement conditions for the Ion Chromatograph or the High-Performance Liquid
Chromatograph: An example of measurement conditions is shown below. Set up themeasurement conditions considering it:1) Column: A hydrophilic methacrylate-gel column (4-mm inner diameter, 100-mm long, 5-μm
particle diameter) to which quaternary ammonium group chemically bonds.
2) Column bath temperature: 58 °C
3) Eluent: Prepared by the procedures in (2) g)
4) Flow rate: 1 mL/min
5) Injection volume: 20 µL
6) Detection unit: An electric conductivity detectorb) Calibration curve preparation
1) Inject 20 μL of respective standard solutions for the calibration curve preparation to the Ion
Chromatograph or the High-Performance Liquid Chromatograph, and record the chromatogramof electric conductivity to obtain a peak area.
2) Prepare a curve for the relationship between the concentration and the peak area of electric
conductivity of respective standard solutions for the calibration curve preparation.
Prepare a calibration curve when the sample is measured.
Comment 1 In the measurement of a sample solution, there is a possibility that the recovery rate
becomes lower than actual due to the influence of matrix if the concentration is
calculated with a peak height. Therefore, prepare a calibration curve using a peak area.
c) Sample measurement
1) Subject 20 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the ammonium thiocyanate content from the calibration curve by the peak area tocalculate ammonium thiocyanate (sulfurized cyanide) in the analytical sample.
Comment 2 Calculate the concentration by the peak area similarly as the calibration curve
preparation to prevent the influence of matrix.
Comment 3 Note that it takes time to stabilize the baseline due to the usage of the ion-pairing
reagent in the elute. It is recommended to take about 120 minutes for stabilization time
before starting measurement.
527

Testing Methods for Fertilizers(2021)

Comment 4 It is possible for the simultaneous measurement of sulfamic acid and ammonium
thiocyanate (sulfurized cyanide) in this testing method. In that case, mix apredetermined amount of sulfamic acid standard solution (1000 mg/L) and ammonium
thiocyanate standard solution (1000 mg/L), dilute with water to prepare a mixture
standard solution (10 mg/L) (1) and use it instead of an ammonium thiocyanate standard
solution (10 mg/L) in (2) i). After that, conduct the same procedure in (4.2) b) to
calculate the concentration of ammonium thiocyanate in the analytical sample.
Comment 5 Recovery testing of ammonium sulfate (3 brands) was conducted. As a result, the mean
recovery rates at the additive level of 0.25 % (mass fraction) and 0.075 % (massfraction) were 101.8 % - 103.7 % and 93.9 % - 97.4 %.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.04 % (mass fraction).
References1)
Toshiaki HIROI and Yuji SHIRAI: Simultaneous Determination of Sulfamic Acid andAmmonium Thiocyanate in Ammonium Sulfate by Non-suppressed Ion Chromatography,
Research Report of Fertilizer, Vol. 5, p. 1 - 23 (2012)(5)

Flow sheet for testing method: The flow sheet for ammonium thiocyanate in ammonium
sulfate is shown below:

528

Testing Methods for Fertilizers(2021)

Reference: Examples of the IC chromatogram of sulfamic acid and thiocyanic acid of the standard
solution for the calibration curve preparation and sample solution (ammonium sulfate) are shown
below.

1
2(A) Mixture standard solution (the equivalents of 60 ng (3 mg/L, 20 μL) as sulfamic acidand ammonium thiocyanate, respectively)

Enlarged diagram of peak for sulfamic acid112(B) Sample solution (the equivalents of 0.25 % (mass fraction) (2500 μg/g) as sulfamicacid and ammonium thiocyanate added in ammonium sulfate, respectively)
Reference diagram: IC chromatogram of sulfamic acid and thiocyanic acid.
(Peak: 1. Sulfamic acid, 2. Thiocyanic acid)IC measurement conditions
Column: Shodex IC NI-424 (4.6-mm inner diameter, 100-mm long, 5-μm particle
diameter)Other conditions are according to the example of HPLC measurement conditions in(4.2) a)529

Testing Methods for Fertilizers(2021)

5.8.b High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.8.b-2017 or SCN.b-1.
Add water to an analytical sample, extract ammonium thiocyanate (sulfurized cyanide) and adjust
pH as necessary. Introduce it into a High-Performance Liquid Chromatograph (HPLC), isolate witha silica gel column to which amino group chemically bonds or a vinyl alcohol polymer column towhich amino group chemically bonds, and measure at a wavelength of 210 nm to obtain ammonium
thiocyanate (sulfurized cyanide) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 5.
Nitrous acid and ammonium thiocyanate (sulfurized cyanide) can be simultaneously quantified byusing this method. (Refer to Comment 4).
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
c) Disodium hydrogen phosphate dodecahydrate: A JIS Guaranteed Reagent specified in JIS K
9019 or a reagent of equivalent quality.
d) Sodium dihydrogen phosphate dihydrate: A JIS Guaranteed Reagent specified in JIS K 9009
or a reagent of equivalent quality.
e) Sodium perchlorate monohydrate: A JIS Guaranteed Reagent specified in JIS K 8227 or areagent of equivalent quality.
f) Ammonium thiocyanate standard solution (1 mg/L) (1): Put 0.1 g of ammonium thiocyanate
specified in JIS K 9000 in weighing dish, and measure the mass to the order of 0.1 mg. Add asmall amount of water to dissolve, then transfer to a 100-mL volumetric flask and add water up
to the marked line.
g) Ammonium thiocyanate standard solution (10 mg/L) (1): At the time of usage, put 10 mL ofammonium thiocyanate standard solution (1 mg/L) in a 100-mL volumetric flask and add water
up to the marked line.
h) Ammonium thiocyanate standard solution for the calibration curve preparation (1 μg/mL- 20 μg/mL): At the time of usage, put 1 mL - 20 mL of ammonium thiocyanate standard
solution (100 μg/mL) in 100-mL volumetric flasks step-by-step and add water up to the marked
line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm to 6-mm inner diameter 150-mm to 250-mm long stainless steel column
tube filled with poly vinyl alcohol or silica gel (2) , to which 5-μm particle diameter amino groupchemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 210
nm.
b) Magnetic stirrerc) Centrifugal separator:
A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
530

Testing Methods for Fertilizers(2021)e)

pH test paper: A pH test paper infilled with indicator and dried, which can measure the value
from pH 1 to pH 11 and a color change chart with the pH interval value 1 is attached.

Note (2) Remaining silanol group of silica gel affects the measurement of ion in some cases.
Therefore, use a column which does not affect the measurement of sodium thiocyanateby treating the silanol group. As an example of the treatment, silica gel is to be entirely
covered with the uniform membrane of silicone polymer.
Comment 1 A column is sold under the names Asahipak NH2P-50 4E, CAPCELL PAK NH2 UG80,
etc.
Comment 2 pH test paper is sold under the name UNIV Test Paper, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it in a 200-mL volumetric flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about five minutes (3) and use the supernatant as
an extract.
Note (3) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water to the marked line to make an extract(4.2) pH adjustment: Conduct pH adjustment of the extract as shown below.
a) Get a small amount of the extract to confirm pH value using a pH-test paper.
b) If the pH value in a) is pH 5 or more, put the extract in a 1.5-mL ground-in stopper centrifugal
precipitate tube (4) and conduct the procedure in f) to prepare a sample solution.
c) If the pH value in a) is pH 4 or less, put 40 mL of the extract in a 100-mL beaker.
d) Add a sodium hydroxide solution (5 mg/mL), adjust it to pH 5 to pH 7 with a pH meter andtransfer to a 50-mL volumetric flask with water.
e) Add water up to the marked line and put it in a 1.5-mL ground-in stopper centrifugal precipitate
tube (4).
f) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as an extract.
Note (4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 3 Instead of procedures in (4.2) b) and e) - f), it is allowed to filter with a membranefilter (aperture diameter: no more than 0.5-µm) made of hydrophilic PTFE and thefiltrate can be the sample solution.
531

Testing Methods for Fertilizers(2021)(4.3) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions is shown below. Set up the measurement conditions considering it:1) Column: A vinyl alcohol polymer column (4-mm - 6-mm inner diameter, 150-mm - 250-mm
long, 5-µm particle diameter) to which amino group chemically bonds or a silica gel column(4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm particle diameter) to which aminogroup chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent (1): Dissolve 1.79 g of disodium hydrogen phosphate dodecahydrate, 0.78 g of sodium
dihydrogen phosphate dihydrate and 14.04 g of sodium perchlorate monohydrate in water tomake 1000 mL. Filter with a membrane filter (aperture diameter: no more than 0.5-µm) madeof hydrophilic PTFE.
4) Flow rate: 0.9 mL/min - 1.0 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 210 nmb) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to the HighPerformance Liquid Chromatograph, record a chromatogram at a wavelength 210 nm andobtain a peak area.
2) Prepare a curve for the relationship between the concentration and the peak area at a wavelength
210 nm of the respective standard solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the ammonium thiocyanate content from the calibration curve by the peak area tocalculate ammonium thiocyanate (sulfurized cyanide) in the analytical sample.
Comment 4 This testing method enables the simultaneous measurement of nitrous acid andammonium thiocyanate (sulfurized cyanide). In this case, mix a predetermined amountof nitrous acid standard solution (1 mg/mL) and ammonium thiocyanate standard
solution (1 mg/mL), dilute with water to prepare a mixture standard solution (100μg/mL) (1) and use it instead of (2) g) ammonium thiocyanate standard solution (100μg/mL). After that, conduct the same procedure in (4.3) b) to calculate the respective
concentrations of materials subjected to measurement in the analytical sample.
Comment 5 Recovery testing was conducted using samples that ammonium thiocyanate equivalent
to 1/5 - 5 times of permissible content are added to an ammonium sulfate fertilizer (1brand), a coating nitrogen fertilizer (1 brand), a blended fertilizer (2 brands), a
compound fertilizer (1 brand) and a fluid compound fertilizer (1 brand). As a result,the mean recovery rates at the additive level of 0.025 % (mass fraction), 0.01 % (massfraction), 0.005 % (mass fraction) and 0.0025 % (mass fraction) were 95.4 % - 100.5 %,94.7 % - 103.8 %, 83.8 % - 109.0 % and 87.2 % - 103.3 % respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are in Table 1. Ammonium thiocyanate had sufficient reproducibility in therange from 0.00476 % (mass fraction) to 0.204 %. (mass fraction).
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.002 % (mass fraction).
532

Testing Methods for Fertilizers(2021)

References
1)
Kohei ITO, Yasuharu KIMURA, Masanori HASEGAWA and Yuji SHIRAI: Simultaneous
Determination of Nitrous Acid and Thiocyanate in Fertilizer by High-Performance Liquid
Chromatography (HPLC), Japanese Journal of Soil Science and Plant Nutrition, Vol. 87(2), p.120 - 124 (2016)
2)
Masanori HASEGAWA and Yasuharu KIMURA: Determination of Nitrous Acid andAmmonium Thiocyanate in Fertilizer by High-Performance Liquid Chromatography(HPLC): A Collaborative Study, Research Report of Fertilizer Vol. 8, p. 70 - 78 (2015)(5)

Flow sheet for testing method: The flow sheet for ammonium thiocyanate in fertilizers isshown below:

533

Testing Methods for Fertilizers(2021)

534

Testing Methods for Fertilizers(2021)

Reference: Examples of the HPLC chromatogram of nitrous acid and ammonium thiocyanate
are shown below.

←1

2
↓

Retention time(A)
Mixture standard solution(The equivalents of 100 ng (10 µg/mL, 10 μL) as nitrous acid and ammonium thiocyanate,respectively)

1→

2
↓

Retention time(B)
Sample solution(The equivalents of 0.1 % (mass fraction) as nitrous acid and ammonium thiocyanate added inblended fertilizer respectively)
Reference diagram: HPLC chromatogram of nitrous acid and ammonium thiocyanate(Peak: 1. Nitrous acid, 2. Thiocyanate)
Measurement conditions for HPLC
Column: CAPCELL PAK NH2 UG80 (4.6-mm inner diameter, 250-mm long, 5μm particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.3) a)535

Testing Methods for Fertilizers(2021)

5.9 Nitrous acid
5.9.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 5.9.a-2017 or NO2.a-1.
Add water to an analytical sample, extract nitrous acid and adjust pH as necessary. Introduce it intoa High-Performance Liquid Chromatograph (HPLC), isolate with a silica gel column to which aminogroup chemically bonds or a vinyl alcohol polymer column to which amino group chemically bonds,
and measure at a wavelength 210 nm to obtain nitrous acid in an analytical sample. In addition, theperformance of this testing method is shown in Comment 5.
Nitrous acid and ammonium thiocyanate (sulfurized cyanide) can be simultaneously quantified byusing this method. (Refer to Comment 4).
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
c) Disodium hydrogen phosphate dodecahydrate: A JIS Guaranteed Reagent specified in JIS K
9019 or a reagent of equivalent quality.
d) Sodium dihydrogen phosphate dihydrate: A JIS Guaranteed Reagent specified in JIS K 9009
or a reagent of equivalent quality.
e) Sodium perchlorate monohydrate: A JIS Guaranteed Reagent specified in JIS K 8227 or areagent of equivalent quality.
f) Nitrous Acid standard solution (1 mg/mL) (1): Put 0.147 g of sodium nitrite specified in JIS
K 8019 in a weighing dish and measure the mass to the order of 0.1 mg. Add a small amount ofwater to dissolve, then transfer to a 100-mL volumetric flask and add water up to the markedline.
g) Nitrous acid standard solution (100 μg/mL) (1): At the time of usage, put 10 mL of nitrousacid standard solution (1 mg/mL) in a 100-mL volumetric flask and add water up to the markedline.
h) Nitrous acid standard solution for the calibration curve preparation (1 μg/mL - 20 μg/mL):
At the time of usage, put 1 mL - 20 mL of nitrous acid standard solution (100 μg/mL) in 100mL volumetric flasks step-by-step and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: a high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
filled with poly vinyl alcohol or silica gel (2), to which 5-μm particle diameter amino groupchemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 210
nm.
b) Magnetic stirrerc) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
e) pH test paper: A pH test paper infilled with indicator and dried, which can measure the value536

Testing Methods for Fertilizers(2021)

from pH 1 - pH 11 and a color change chart with the pH interval value 1 is attached.
Note (2)Remaining silanol group of silica gel affects the measurement of ion in some cases.
Therefore, use a column which does not affect the measurement of nitrous acid bytreating the silanol group. As an example of the treatment, silica gel is to be entirely
covered with the uniform membrane of silicone polymer.

Comment 1 A column is sold under the names Asahipak NH2P-50 4E, CAPCELL PAK NH2 UG80,
etc.
Comment 2 pH test paper is sold under the name UNIV Test Paper, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200-mL ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about five minutes (3) and use the supernatant as
an extract.
Note (3) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water to the marked line to make an extract(4.2) pH adjustment: Conduct pH adjustment of the extract as shown below.
a) Get a small amount of the extract to confirm pH value using a pH-test paper.
b) If the pH value in a) is pH 5 or more, put the extract in a 1.5-mL ground-in stopper centrifugal
precipitate tube (4) and conduct the procedure in f) to prepare a sample solution.
c) If the pH value in a) is pH 4 or less, put 40 mL of the extract in a 100-mL beaker.
d) Add a sodium hydroxide solution (5 mg/mL), adjust it to pH 5 to pH 7 with a pH meter andtransfer to a 50-mL volumetric flask with water.
e) Add water up to the marked line and put it in a 1.5-mL ground-in stopper centrifugal precipitate
tube (4).
f) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 3 Instead of procedures in (4.2) b) and e) - f), it is allowed to filter with a membranefilter (aperture diameter: no more than 0.5-µm) made of hydrophilic PTFE and thefiltrate can be the sample solution.
537

Testing Methods for Fertilizers(2021)(4.3) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the High-Performance
Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions is shown below. Set up the measurement conditions considering it:1) Column: A vinyl alcohol polymer column (4-mm - 6-mm inner diameter, 150-mm - 250-mm
long, 5-µm particle diameter) to which amino group chemically bonds or a silica gel column(4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm particle diameter) to which aminogroup chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent (1): Dissolve 1.79 g of disodium hydrogen phosphate dodecahydrate, 0.78 g of sodium
dihydrogen phosphate dihydrate and 14.04 g of sodium perchlorate monohydrate in water tomake 1000 mL. Filter with a membrane filter (aperture diameter: no more than 0.5-µm) madeof hydrophilic PTFE.
4) Flow rate: 0.9 mL/min - 1.0 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 210 nmb) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to the HighPerformance Liquid Chromatograph, record a chromatogram at a wavelength 210 nm andobtain a peak area.
2) Prepare a curve for the relationship between the concentration and the peak area at a wavelength
210 nm of the respective standard solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the nitrous acid content by the peak area using the calibration curve to calculate theconcentration of nitrous acid in the analytical sample.
Comment 4 This testing method enables the simultaneous measurement of nitrous acid andammonium thiocyanate (sulfurized cyanide). In this case, mix a predetermined amountof nitrous acid standard solution (1 mg/mL) and ammonium thiocyanate standard
solution (1 mg/mL), dilute with water to prepare a mixture standard solution (100μg/mL) (1) and use it instead of (2) g) nitrous acid standard solution (100 μg/mL). After
that, conduct the same procedure in (4.3) b) to calculate the respective concentrationsof materials subjected to measurement in the analytical sample.
Comment 5 Recovery testing was conducted using samples that nitrous acid equivalent to 1/5 - 5times of permissible content are added to ammonium sulfate fertilizer (1 brand),coating nitrogen fertilizer (1 brand), blended fertilizer (2brands), compound fertilizer(1 brand) and fluid compound fertilizer (1 brand). As a result, the mean recovery rates
at the additive level of 0.1 % (mass fraction), 0.04 % (mass fraction), 0.02 % (massfraction) and 0.01 % (mass fraction) were 99.0 % - 100.8 %, 100.4 % - 102.0 %,103.1 % - 106.6 % and 101.2 % - 105.9 % respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 1. Nitrous acid had sufficient reproducibility in the range
from 0.0255 % (mass fraction) to 0.291 %. (mass fraction).
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0003 % (mass fraction).
538

Testing Methods for Fertilizers(2021)

References
1)
Kohei ITO, Yasuharu KIMURA, Masanori HASEGAWA and Yuji SHIRAI: Simultaneous
Determination of Nitrous Acid and Thiocyanate in Fertilizer by High-Performance Liquid
Chromatography (HPLC), Japanese Journal of Soil Science and Plant Nutrition, Vol. 87(2), p.120 - 124 (2016)
2)
Masanori HASEGAWA and Yasuharu KIMURA: Determination of Nitrous Acid andAmmonium Thiocyanate in Fertilizer by High-Performance Liquid Chromatography(HPLC): A Collaborative Study, Research Report of Fertilizer Vol. 8, p. 70 - 78 (2015)(5)

Flow sheet for testing method: The flow sheet for nitrous acid in fertilizers is shown below:539

Testing Methods for Fertilizers(2021)

540

Testing Methods for Fertilizers(2021)

Reference: Examples of the HPLC chromatogram of nitrous acid and ammonium thiocyanate
are shown below.

←1

2
↓

Retention time (min)(A)
Mixture standard solution(The equivalents of 100 ng (10 µg/mL, 10 μL) as nitrous acid and ammonium thiocyanate,respectively)

1→

2
↓

Retention time (min)(B)
Sample solution(The equivalents of 0.1 % (mass fraction) as nitrous acid and ammonium thiocyanate added inblended fertilizer respectively)
Reference diagram: HPLC chromatogram of nitrous acid and ammonium thiocyanate
Measurement conditions for HPLC
Column: CAPCELL PAK NH2 UG80 (4.6-mm inner diameter, 250-mm long, 5μm particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.3) a)541

Testing Methods for Fertilizers(2021)

5.10 Biuret nitrogen
5.10.a High-Performance Liquid Chromatography(1) Summary
The testing method is applicable to nitrolime and fertilizers containing no nitrolime. This testing
method is classified as Type B and its symbol is 5.10.a-2017 or B-N.a-1.
Add water to an analytical sample to extract biuret, introduce it to a High-Performance Liquid
Chromatograph (HPLC) to isolate it with a weak acid ion-exchange column, and then measure at awavelength 190 nm to obtain biuret nitrogen (B-N) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 6.
Dicyandiamide nitrogen (Dd-N), urea nitrogen (U-N), guanidine nitrogen (Gd-N) and guanylurea
nitrogen (GU-N) and can be simultaneously quantified by using this method. (Refer to Comment 5).
(2) Reagent: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Potassium dihydrogen phosphate: A JIS Guaranteed Reagent specified in JIS K 9007 or areagent of equivalent quality.
c) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
d) Biuret nitrogen standard solution (B-N 2 mg/mL) (1): Put 0.491 g of biuret [C2H5N3O2] (2) ina weighing dish and measure the mass to the order of 0.1 mg. Add a small amount of water,transfer to a 100-mLvolumetric flask and warm up to 50ºC to dissolve. After standing to cool(3)
, add water up to the marked line (3).
e) Biuret nitrogen standard solution (B-N 200 µg/mL): Put 10 mL of biuret nitrogen standard
solution (B-N 2 mg/mL) in a 100-mL volumetric flask and add water up to the marked line.
f) Biuret nitrogen standard solution (B-N 50 µg/mL - 100 µg/mL): Put 25 mL - 50 mL of biuret
nitrogen standard solution (B-N 200 µg/mL) in 100-mL volumetric flasks and add water up to
the marked line.
g) Biuret nitrogen standard solution for the calibration curve preparation (B-N 1 μg/mL - 50
μg/mL): At the time of usage, put 1 mL - 50 mL of biuret nitrogen standard solution (B-N 100
μg/mL) in 100-mL volumetric flasks step-by-step and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 97 % (mass fraction) in purity is commercially sold as biuret.
(3) If biuret nitrogen standard solution (B-N 2 mg/mL) is stored in a refrigerator,
precipitates may appear. Therefore, it is recommended to store it at room temperature.
In addition, sudden cooling should be avoided.
Comment 1 Biuret is sold by FUJIFILM Wako Pure Chemical Co., Ltd., Kanto Chemical Co., Inc.
and Tokyo Chemical Industry Co., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 7.5-mm inner diameter 100-mm long stainless steel column tube filled with weakacid ion-exchange resin.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 190
nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
542

Testing Methods for Fertilizers(2021)

× g.
Comment 2 A column is sold under the production name Asahipak ES-502C 7C, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200-mL ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution (4) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (5).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (6) and use thesupernatant as a sample solution.
Note (4) If there is a possibility that the biuret nitrogen (B-N) concentration in the sample solution
will exceed the maximum limit of the calibration curve, dilute a predetermined amountof supernatant with water.
(5) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(6) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line (7) and put it in a 1.5-mL ground-in stopper centrifugal
precipitate tube (5).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (6) and use thesupernatant as a sample solution.
Note (7) If there is a possibility that the biuret nitrogen (B-N) concentration in the sample solution
will exceed the maximum limit of the calibration curve, dilute a predetermined amountof precisely adjusted solution with water.
Comment 3 Instead of procedures in (4.1.1) c) - d) or (4.1.2) c) - d), it is allowed to filter with amembrane filter (aperture diameter: no more than 0.5-µm) made of hydrophilic PTFE
and the filtrate can be the sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions is shown below. Set up the measurement conditions considering it:1) Column: A weak acid ion-exchange resin column (4.00-mm - 7.5-mm inner diameter, 100mm - 150-mm long, 5-µm – 10-µm particle diameter)
2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 3.92 g of potassium dihydrogen phosphate and 0.12 g of phosphoric acidin water to make 1000 mL. Filter with a membrane filter (aperture diameter: no more than 0.5µm) made of hydrophilic PTFE.
543

Testing Methods for Fertilizers(2021)

4) Flow rate: 0.6 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 190 nm
Comment 4 Eluent can be prepared as follows. Dissolve 19.6 g of potassium dihydrogen phosphateand 0.584 g of phosphoric acid with water to make 500 mL and store in a refrigerator.
At the time of usage, dilute a predetermined volume of the solution by a factor of 10
and filter with a membrane filter (aperture diameter: no more than 0.5-µm) made ofhydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to the HighPerformance Liquid Chromatograph, record a chromatogram at a wavelength 190 nm andobtain a peak height.
2) Prepare a curve for the relationship between the biuret nitrogen (B-N) concentration and thepeak height at a wavelength 190 nm of the respective standard solutions for the calibration
curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the biuret nitrogen (B-N) content from the peak height using the calibration curve tocalculate the biuret nitrogen (B-N) in the analytical sample.
Comment 5 This testing method enables the simultaneous measurement of biuret nitrogen (B-N),
dicyandiamide nitrogen (Dd-N), urea nitrogen (U-N), guanidine nitrogen (Gd-N) anda guanylurea nitrogen standard solution (GU-N). In this case, mix a predeterminedamount of biuret nitrogen (B-N 1 mg/mL), a urea nitrogen standard solution (U-N 2
mg/mL), a dicyandiamide nitrogen standard solution (Dd-N 2 mg/mL), a guanidine
nitrogen standard solution (Gd-N 2 mg/mL) and a guanylurea nitrogen standard
solution (GU-N 2 mg/mL), dilute with water to prepare a mixture standard solution(200 μg/mL) (1) and use it instead of (2) e) a biuret nitrogen standard solution (B-N
200 μg/mL). After that, conduct the same procedure in (4.2) b) to calculate therespective concentrations of materials subjected to measurement in the analyticalsample.
Comment 6 Additive recovery testing was conducted using one brand of an acetaldehyde
condensed urea fertilizer, a compound fertilizer, a blended fertilizer, a fluid compound
fertilizer and a home garden-use compound fertilizer respectively. As a result, the mean
recovery rates at the additive level of 0.2 % (mass fraction) and 0.1 % (mass fraction)and 0.02 % (mass fraction) were 87.0 % - 95.1 %, 90.6 % - 101.1 % and 91.2 % - 105
5 % respectively.
The results of the repeatability tests on different days using a blended fertilizer, acompound fertilizer and a home garden-use compound fertilizer to evaluate precisionwere analyzed by the one-way analysis of variance. Table 1 shows the calculation
results of intermediate precision and repeatability. Additionally, results from acollaborative study for testing method validation and its analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005 % (mass fraction).
Comment 7 Note that nitrolime has ingredients which affect the measurement of biuret nitrogen(B-N).
544

Testing Methods for Fertilizers(2021)

References
1)
Masahiro ECHI, Yasuharu KIMURA and Yuji SHIRAI: Determination of Urea Nitrogen,
Biuret Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogenin Fertilizer by High-Performance Liquid Chromatography: A Single-Laboratory
Validation, Research Report of Fertilizer, Vol. 10, p. 72 - 85 (2017)2)
Norio FUNAKI and Yasuharu KIMURA: Determination of Urea Nitrogen, Biuret
Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogen in
Fertilizer by High-Performance Liquid Chromatography (HPLC): A Collaborative Study,
Research Report of Fertilizer, Vol. 10, p. 86 - 100 (2017)

545

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for biuret nitrogen in fertilizers is shown below:
1.00 g analytical sample
200-mL ground-in stopper Erlenmeyer flask(powdery)← 100 mL of water
Stirring

Magnetic stirrer, 10 minites

Standing still
Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
1700 ×g , 5 minutes

Sample solution

Supernartant

Measurement

Liquid Chromatograph

Figure 1

Flow sheet for biuret nitrogen in fertilizers(Extraction procedure (4.1.1) and measurement)546

Testing Methods for Fertilizers(2021)

Reference:

An example of the chromatogram of the standard solution of biuret nitrogen for thecalibration curve preparation is shown below.

Reference diagram:

HPLC chromatogram of the mixture standard solutions for the calibration
curve preparation (10 mg/L for each)Peak name(1) Urea nitrogen(2) Biuret nitrogen(3) Dicyandiamide nitrogen(4) Guanidine nitrogen(5) Guanylurea nitrogen
Measurement conditions for HPLC
Column: Asahipak ES-502C 7C (7.5-mm inner diameter, 100-mm long, 9-μm
particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)547

Testing Methods for Fertilizers(2021)

5.11 Titanium
5.11.a ICP Optical Emission Spectrometry (1)(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 5.11.a-2017 or Ti.a-1.
Pretreat an analytical sample with nitric acid - sulfuric acid - perchloric acid, introduce it to an ICP
Optical Emission Spectrometer (ICP-OES) and measure the emission with titanium at a wavelengthof 334.941 nm to obtain the titanium (Ti) in an analytical sample. In addition, the performance of thistesting method is shown in Comment 4.
(2)
a)
b)
c)
d)
e)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A3 specified in JIS K 0557.
Nitric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Sulfuric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Perchloric acid: A reagent of harmful metal analysis grade, microanalysis grade or equivalents.
Hydrochloric acid: A reagent of harmful metal analysis grade or microanalysis grade specified
in JIS K 8180, or equivalents.
f) Titanium standard solution (Ti 1 mg/mL): A titanium standard solution (Ti 1 mg/mL)
traceable to National Metrology.
g) Titanium standard solution (Ti 0.1 mg/mL) (1): Put 10 mL of titanium standard solution (Ti 1
mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to the marked line.
h) Titanium standard solutions (Ti 0.1 µg - 20 µg/mL) for the calibration curve preparation(1): Put 1 mL - 20 mL of titanium standard solution (Ti 0.1 mg/mL) in 100-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.

(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 350 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to no less than 300 °C.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Add about 10 mL of nitric acid and about 5 mL of sulfuric acid, cover the tall beaker with awatch glass, and leave at rest overnight.
c) Heat mildly on a hot plate or sand bath at 170 ºC - 220 ºC for no less than 30 minutes. Afterbubbles cease to form, set the temperature of the hot plate or sand bath to no less than 300 ºC,
and heat until nitroxide (yellow-brown smoke) is no longer generated (2).
548

Testing Methods for Fertilizers(2021)d) After standing to cool, add about 5 mL of perchloric acid.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or sand bath at no less than 300ºC for 2 - 3 hours to digest (3).
f) Slightly move the watch glass (4), and keep on heating on the hot plate or sand bath toconcentrate until the liquid volume becomes no more than 2 mL.
g) After standing to cool, add about 5 mL of hydrochloric acid (1+10) and about 20 mL of water,
cover the tall beaker with a watch glass and heat mildly to dissolve.
h) After standing to cool, transfer to a 100-mL volumetric flask with water, add water up to themarked line, and filter with Type 3 filter paper to make a sample solution.
i) As a blank test, conduct the procedures in b) - h) using another tall beaker to prepare a blanktest solution.
Note (2) Oxidation of organic matters by perchloric acid progresses extremely rapidly andexplosively. For that reason, add perchloric acid after fully degrading organic matterswith nitric acid to avoid danger.
(3) When the white smoke of perchloric acid is generated, if the solution is colored such as
black-brown or brown, stop heating immediately, and after standing to cool, add nitricacid, and heat again to degrade remaining organic matters.
(4) The watch glass can be removed.
Comment 2 When the analytical sample solidifies in the procedure in (4.1) b), moisten theanalytical sample with a small amount of water as necessary in advance.
Comment 3 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Atomic Emission Spectrometer: Set up themeasurement conditions for the ICP Atomic Emission Spectrometer considering the following:
Analytical line wavelength: 334.941 nmb) Calibration curve preparation
1) Spray the titanium standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at a wavelength of 334.941 nm.
2) Prepare a curve for the relationship between the titanium concentration and the indicated valueof the titanium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.01 mg - 2 mg as
titanium) in a 100-mL volumetric flask.
2) Add 25 mL of hydrochloric acid (1+23) to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the titanium content from the calibration curve, and calculate titanium (Ti) in theanalytical sample.
Comment 4 Additive recovery testing was conducted using an autoclaved lightweight concrete
powdery fertilizer, a mixed phosphorus fertilizer, a compound fertilizer, a slag
manganese fertilizer, a solid compound fertilizer, a fluid compound fertilizer, a mixed549

Testing Methods for Fertilizers(2021)

compost compound fertilizer and a blended fertilizer respectively. As a result, the mean
recovery rate at the additive level of 0.01 % (mass fraction) - 0.5 % (mass fraction)
was 92.9 % - 99.5 %.
The results of the repeatability tests on different days using a mixed phosphate
fertilizer and a compound fertilizer to evaluate precision were analyzed by the oneway analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.001 % (mass fraction).

References
1)
Keisuke AOYAMA: Determination of Titanium in Fertilizer using Inductively Coupled
Plasma Optical Emission Spectrometry (ICP-OES) , Research Report of Fertilizer, Vol.
10, p. 29 - 40 (2017)550

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for titanium in fertilizers is shown below:551

Testing Methods for Fertilizers(2021)

5.11.b ICP Optical Emission Spectrometry (2)(1) Summary
The testing method is applicable to silicate slag fertilizers. This testing method is classified as TypeD and its symbol is 5.11.b-2017 or Ti.b-1.
Melt an analytical sample with ammonium hydrogensulfate, introduce it to an ICP OpticalEmission Spectrometer (ICP-OES) and measure the emission with titanium at a wavelength of
334.941 nm to obtain the titanium (Ti) in an analytical sample. In addition, the performance of thistesting method is shown in Comment 2.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Ammonium hydrogensulfate: A reagent of no less than 98 % (mass fraction) in purity.
c) Hydrochloric acid: A reagent of harmful metal analysis grade or microanalysis grade specified
in JIS K 8180 or equivalents.
d) Titanium standard solution (Ti 1 mg/mL): A titanium standard solution (Ti 1 mg/mL)
traceable to National Metrology.
e) Titanium standard solution (Ti 0.1 mg/mL) (1): Put 10 mL of titanium standard solution (Ti 1
mg/mL) in a 100-mL volumetric flask and add hydrochloric acid (1+23) up to the marked line.
f) Titanium standard solutions (Ti 0.1 µg - 20 µg/mL) for the calibration curve preparation(1): Put 1 mL - 20 mL of titanium standard solution (Ti 1 mg/mL) in 100-mL volumetric flasks
step-by-step, and add hydrochloric acid (1+23) to the marked line.
g) Blank test solution for the calibration curve preparation (1): Hydrochloric acid (1+23) usedin the procedures in e) and f).
Note (1) This is an example of preparation; prepare an amount as appropriate.
Comment 1 Since the indicated value at an arbitrary wavelength of an ICP-OES varies dependingon the observation mode (horizontal and axial mode) of emission and the spectrometer
type, the concentration range of the calibration curve suitable for the equipment useddiffers. Therefore, it is recommended the concentration range of the calibration curve
suitable to the equipment used and a standard solution prepared for the calibration
curve should be understood in advance.
(3) Instruments: Instruments are as shown below:a) ICP Optical Emission Spectrometer: An optical emission spectrometer specified in JIS K
0116.
1) Gas: Argon gas specified in JIS K 1105 of no less than 99.5 % (volume fraction) in purityb) Hot plate : A hot plate whose surface temperature can be adjusted up to 400 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample and put it in a 200-mL tall beaker.
b) Add about 10 g of ammonium hydrogensulfate (2).
c) Heat on a hot plate at no less than 350 ºC and make the melted ammonium hydrogensulfate
come into complete contact with the analytical sample (3).
d) Cover with a watch glass, and heat at no less than 350 ºC for 1 hour.
e) After standing to cool, add about 25 mL of hydrochloric acid (1+5), cover the tall beaker witha watch glass and heat mildly to dissolve.
f) After standing to cool, transfer to a 100-mL volumetric flask with water, add water up to themarked line, and filter with Type 3 filter paper.
552

Testing Methods for Fertilizers(2021)

g) Put 10 mL of the filtrate in another 100-mL volumetric flask and add hydrochloric acid (1+23)
to the marked line to make a sample solution.
h) As a blank test, conduct the procedures in b) - f) using another tall beaker to prepare a blanktest solution.
Note (2) Ammonium hydrogensulfate is corrosive. Therefore, use a dispensing spoon made ofresin.
(3) After the ammonium hydrogensulfate melts, make it come into contact with theanalytical sample by tilting the tall beaker or conducting a similar procedure.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0116 and as shown below.
Specific measurement procedures are according to the operation method of the ICP OpticalEmission Spectrometer used in measurement.
a) Measurement conditions for the ICP Optical Emission Spectrometer: Set up themeasurement conditions for the ICP Optical Emission Spectrometer considering the following:
Analytical line wavelength: 334.941 nmb) Calibration curve preparation
1) Spray the titanium standard solution for the calibration curve preparation and blank test solution
for the calibration curve preparation into inductively coupled plasma, and read the indicatedvalue at a wavelength of 334.941 nm.
2) Prepare a curve for the relationship between the titanium concentration and the indicated valueof the titanium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation.
c) Sample measurement
1) Subject the sample solution to the same procedure as in b) 1) to read the indicated value.
2) Obtain the titanium content from the calibration curve, and calculate titanium (Ti) in theanalytical sample.
Comment 2 Additive recovery testing was conducted to evaluate trueness using silicate slag
fertilizers (2 samples). As a result, the mean recovery rate at the additive level of 0.1 %(mass fraction) - 0.2 % (mass fraction) was 95.1 % - 98.2 %.
The results of the repeatability tests on different days using silicate slag fertilizers (2samples) to evaluate precision were analyzed by the one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.02 % (mass fraction).

553

Testing Methods for Fertilizers(2021)

References
1)
Keisuke AOYAMA: Determination of Titanium in Fertilizer using Inductively Coupled
Plasma Optical Emission Spectrometry (ICP-OES) , Research Report of Fertilizer, Vol.
10, p. 29 - 40 (2017)(5)

Flow sheet for testing method: The flow sheet for titanium in fertilizers is shown below:554

Testing Methods for Fertilizers(2021)

5.12 Sulfurous Acid
5.12.a This method is according to 5.3 Sulfurous acid analysis in “The Official Methods of Analysis
of Fertilizers 1992”.
References
1)
National Institute for Agro-Environmental Sciences, the Ministry of Agriculture, Forestry
and Fisheries: The Official Methods of Analysis of Fertilizers 1992, p.78 - 79, Japan
Fertilizers Analysis Association, Tokyo (1992)
2)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p. 196 - 197, Yokendo, Tokyo (1988)

555

Testing Methods for Fertilizers(2021)

6. Testing relating to the other limitations
6.1 Dicyandiamide nitrogen
6.1.a High-Performance Liquid Chromatography (1)(1) Summary
The testing method is applicable to nitrolime and fertilizers containing nitrolime. This testing
method is classified as Type B and its symbol is 6.1.a-2017 or Dd-N.a-1.
Add methanol to an analytical sample to extract dicyandiamide (Dd), introduce it to a HighPerformance Liquid Chromatograph (HPLC), isolate with an amino propyl silica gel column andmeasure at a wavelength 215 nm to obtain dicyandiamide nitrogen (Dd-N) in an analytical sample.
In addition, the performance of this testing method is shown in Comment 4.
(2) Reagent: Reagents are as shown below.
a) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
b) Methanol:
Methanol used in the eluent of a High-Performance Liquid Chromatographis a regent of High Performance Liquid Chromatograph analysis grade or equivalents.
c) Acetonitrile: A reagent of High Performance Liquid Chromatograph analysis grade orequivalents.
d) Dicyandiamide standard solution (1 mg/mL) (1): Put 0.1 g of dicyandiamide [C2H4N4] (2)in a weighing dish and measure the mass to the order of 0.1 mg. Add a small amount ofmethanol to dissolve, transfer to a 100-mL volumetric flask and add the solvent up to themarked line. Store in a refrigerator, and do not use after 6 months after preparation.
e) Dicyandiamide standard solution (0.1 mg/mL): Put 10 mL of dicyandiamide standard
solution (1 mg/ mL) in a 100-mL volumetric flask and add methanol up to the marked line.
f) Dicyandiamide standard solution (10 µg/ mL - 50 µg/ mL) for the calibration curve
preparation: At the time of usage, put 5 mL - 25 mL of dicyandiamide standard solution(0.1 mg/ mL) in 50-mL volumetric flasks step-by-step and add methanol up to the markedline.
g) Dicyandiamide standard solution (1 µg/mL - 10 µg/mL) for the calibration curve
preparation: In the case of usage, put 2.5 mL - 25 mL of dicyandiamide standard solution
for the calibration curve preparation (20 µg/mL) in 50-mL volumetric flasks step-by-stepand add methanol up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity as dicyandiamide iscommercially sold.
Comment 1 Dicyandiamide is commercially sold as dicyanodiamide by FUJIFILM Wako Pure
Chemical Co., Ltd. and Kanto Chemical Co., Inc.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A column of 4 mm - 6 mm inner diameter and 150 mm - 250 mm long stainlesssteel column tube filled with silica gel, to which amino or amino propyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 215
nm.
b) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300
556

Testing Methods for Fertilizers(2021)

c)reciprocations/min (amplitude of 40 mm).
High speed centrifugal separator: A centrifugal separator that can work at 8000 × g 10000 × g.

Comment 2 A column is sold under production names such as Hibar LiChrosorb NH2, Inertsil
NH2, Unison UK-Amino, Mightysil NH2, Shim-pack CLC-NH2, Shodex NH-5A,
Unisil Q NH2, etc.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL - 200-mL ground-in stopper
Erlenmeyer flask.
b) Immediately add 100 mL of methanol (3) and shake to mix by reciprocating vertically at 300
times/min (amplitude of 40 mm) for about 10 minutes.
c) After allowing to stand still, put a supernatant solution in a 1.5-mL ground-in stopper
centrifugal precipitate tube (4).
d) Centrifuge at 8000 × g - 10000 × g for about five minutes (5).
e) 1 mL of the supernatant is used as a sample solution.
Note (3) Add methanol immediately as the determined value becomes higher than usual if it
is left in air.
(4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 ×g - 10000 × g centrifugal force.
Comment 3 Instead of the procedures in (4.1) c) - e), it is allowed to filter with a membranefilter (aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate canbe the sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An
example of measurement conditions for the High-Performance Liquid Chromatograph isshown below. Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5µm particle diameter) to which amino or amino propyl chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent: Acetonitrile - methanol (6+1)
4) Flow rate: 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 215 nmb) Calibration curve preparation
1) Inject 10 µL of respective dicyandiamide standard solutions for the calibration curve
preparation to the High-Performance Liquid Chromatograph, record a chromatogram at awavelength 215 nm, and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or heightat a wavelength 215 nm of the respective dicyandiamide standard solutions for thecalibration curve preparation.
c) Sample measurement557

Testing Methods for Fertilizers(2021)

1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain dicyandiamide (Dd) content from the calibration curve to calculate theconcentration of dicyandiamide (Dd) in the analytical sample.
3) Calculate the dicyandiamide nitrogen (Dd-N) by the following formula.
Dicyandiamide nitrogen (Dd-N) (% (mass fraction)) in an analytical sample= A × (MW1/MW2 )= A × 0.6664
A： Dicyandiamide (Dd) (% (mass fraction)) in an analytical sample
MW1： 4 atomic weight of nitrogen (56.027)
MW2： Molecular weight of dicyandiamide (84.080)
Comment 4 Recovery testing was conducted using nitrolime (3 samples) and a blended
fertilizer containing nitrolime (2 samples), as a result, the recovery rates of
dicyandiamide at the concentration level of 6 % (mass fraction) and 0.6 % (massfraction) were 94.9 % - 105.1 % and 95.6 % - 103.5 % respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.01 % (mass fraction).
Table 1 Analysis results of the collaborative study
for the test method validation of dicyandiamide nitrogen
4)
5)
6)
2)
Number of
sr
RSD r
sR
Mean
Sample name
1)
3)
3)
3)
(%)
laboratories
(%)
(%)
(%)
Nitrolime 1
90.03210.00103.2
0.0012
Nitrolime 2
10
0.159
0.002
1.3
0.006
Nitrolime 3
11
0.245
0.002
0.7
0.008
Blended fertilizer 1
11
0.124
0.001
0.7
0.002
Blebded fertilizer 2
11
0.410
0.007
1.6
0.008
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

7)

RSD R
(%)
3.8
3.8
3.3
2.0
1.9

References
1)
Masakazu SAIKI and Miyuki ASAO: Validation of High-Performance Liquid
Chromatography for Determination of Dicyandiamide in Nitrolime, Research Reportof Fertilizers, Vol. 2, p. 25 - 31 (2009)
2)
Masakazu SAIKI and Masayuki YOSHIMOTO: Determination of Dicyandiamide
in Nitrolime by High-Performance Liquid Chromatography: A Collaborative Study,
Research Report of Fertilizers, Vol. 2, p. 32 - 37 (2009)558

Testing Methods for Fertilizers(2021)(5) Flow sheet for dicyandiamide nitrogen: The flow sheet for dicyandiamide nitrogen innitrolime and fertilizers containing nitrolime is shown below:
1.00 g200-mL - 300-mL ground-in stopper Erlenmeyer flask
analytical sample← 100 mL of methanol
Vertical reciprocating shaker
Shaking to mix(300 times/ minute, amplitude of 40 mm), 10 minutes
Standing still
Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
8000 ×g - 10000 ×g , 5 minutes

Sample solution

Supernatant

Measurement

High-Performance Liquid Chromatograph

Figure Flow sheet for dicyandiamide nitrogen in nitrolime and fertilizers containing nitrolime

Reference: Examples of the HPLC chromatogram of dicyandiamide standard solution andsample solution (nitrolime) for the calibration curve preparation are shown below.

0.09

0.10
0.09
0.08

0.07

0.07

0.06

0.06

AU

0.08

0.05

0.05

0.04

0.04

0.03

0.03

0.02

0.02

0.01

0.01

0.00
0

Dd 8.458

0.10

AU

0.11

Dd 8.541

0.11

0.00
1

2

3

4

5 6
min

7

8

9

10 11

0

1) Standard solution

1

2

3

4

5 6
min

7

8

9

10 11

2) Sample solution

Reference diagram: HPLC chromatogram of dicyandiamide
1) Dicyandiamide standard solution (the equivalents of 100 ng (10 µg/ mL, 10 µL) of
dicyandiamide)2) Sample solution (nitrolime)
Measurement conditions for HPLC
Column: Hibar LiChrosorb NH2 (4.6-mm inner diameter, 25-cm long, 5-µm
particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)559

Testing Methods for Fertilizers(2021)

6.1.b High-Performance Liquid Chromatography (2)(1) Summary
This testing method is applicable to fertilizers. In addition, nitrolime is excluded from thescope of application. This testing method is classified as Type B and its symbol is 6.1.b-2017 or
Dd-N.b-1.
Add water to an analytical sample to extract dicyandiamide, introduce it to a HighPerformance Liquid Chromatograph (HPLC) to isolate it with a weak acid ion-exchange column,
and then measure at a wavelength 190 nm to obtain dicyandiamide nitrogen (Dd-N) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 6.
Biuret nitrogen (B-N), urea nitrogen (U-N), guanidine urea (Gd-N) and guanylurea nitrogen(GU-N) can be simultaneously quantified by using this method. (Refer to Comment 5).
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Potassium dihydrogen phosphate: A JIS Guaranteed Reagent specified in JIS K 9007
or a reagent of equivalent quality.
c) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
d) Dicyandiamide nitrogen standard solution (Dd-N 2 mg/mL) (1): Put 0.300 g ofdicyandiamide [C2H4N4] (2) in a weighing dish and measure the mass to the order of 0.1 mg.
Add a small amount of water to dissolve, then transfer to a 100-mL volumetric flask andadd water up to the marked line.
e) Dicyandiamide nitrogen standard solution for the calibration curve preparation (Dd-N
200 µg/mL) (1): Put 10 mL of dicyandiamide nitrogen standard solution (Dd-N 2 mg/mL) in a
100-mL volumetric flask and add water up to the marked line.
f) Dicyandiamide nitrogen standard solution (Dd-N 50 µg/mL - 100 µg /mL) (1): Put 25
mL - 50 mL of dicyandiamide nitrogen standard solution (Dd-N 200 µg/mL) in 100-mL
volumetric flasks and add water up to the marked line.
g) Dicyandiamide nitrogen standard solution for the calibration curve preparation (DdN 1 μg/mL - 50 μg/mL) (1): At the time of usage, put 1 mL - 50 mL of dicyandiamide
nitrogen standard solution (Dd-N 100 μg/mL) in 100-mL volumetric flasks step-by-step and
add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity as dicyandiamide iscommercially sold.
Comment 1 Dicyandiamide is sold by Tokyo Chemical Industry Co., Ltd. In addition,dicyandiamide is commercially sold as dicyanodiamide by FUJIFILM Wako Pure
Chemical Co., Ltd. and Kanto Chemical Co., Inc.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 7.5-mm inner diameter 100-mm long stainless steel column tube filled withweak acid ion-exchange resin.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around
190 nm.
b) Magnetic stirrer
560

Testing Methods for Fertilizers(2021)c)

High speed centrifugal separator: A centrifugal separator that can work at 8000 × g 10000 × g.

Comment 2 A column is sold under the production name Asahipak ES-502C 7C, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper
Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution (3) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (3) If there is a possibility that the dicyandiamide nitrogen (Dd-N) concentration in thesample solution will exceed the maximum limit of the calibration curve, dilute apredetermined amount of supernatant with water.
(4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 ×g - 10000 × g centrifugal force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line (6) and put it in a 1.5-mL ground-in stopper centrifugal
precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (6) If there is a possibility that the dicyandiamide nitrogen (Dd-N) concentration in thesample solution will exceed the maximum limit of the calibration curve, dilute apredetermined amount of precisely adjusted solution with water.
Comment 3 Instead of procedures in (4.1.1) c) - d) or (4.1.2) c) - d), it is allowed to filter witha membrane filter (aperture diameter: no more than 0.5-µm) made of hydrophilic
PTFE and the filtrate can be the sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An
example of measurement conditions is shown below. Set up the measurement conditions
considering it:1) Column: A weak acid ion-exchange resin column (4.0-mm - 7.5-mm inner diameter, 100mm - 150-mm long, 5-µm – 10-µm particle diameter)
2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 3.92 g of potassium dihydrogenphosphate and 0.12 g of phosphoric561

Testing Methods for Fertilizers(2021)

acid in water to make 1000 mL. Filter with a membrane filter (aperture diameter: no morethan 0.5-µm) made of hydrophilic PTFE.
4) Flow rate: 0.6 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 190 nm
Comment 4 Eluent can be prepared as follows. Dissolve 19.6 g of potassium
dihydrogenphosphate and 0.584 g of phosphoric acid with water to make 500 mL
and store in a refrigerator. At the time of usage, dilute a predetermined volume ofthe solution by a factor of 10 and filter with a membrane filter (aperture diameter:
no more than 0.5-µm) made of hydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to theHigh-Performance Liquid Chromatograph, record a chromatogram at a wavelength 190 nm
and obtain a peak height.
2) Prepare a curve for the relationship between the dicyandiamide nitrogen (Dd-N)
concentration and the peak height at a wavelength 190 nm of the respective standard
solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the dicyandiamide nitrogen (Dd-N) content from the peak height using thecalibration curve to calculate the dicyandiamide nitrogen (Dd-N) in the analytical sample.
Comment 5 This testing method enables the simultaneous measurement of biuret nitrogen (BN), urea nitrogen (U-N), dicyandiamide nitrogen (Dd-N), guanidine urea (Gd-N)
and guanylurea nitrogen (GU-N). In that case, see 5.10.a Comment 5.
Comment 6 Additive recovery testing was conducted using one brand of an acetaldehyde
condensed urea fertilizer, a compound fertilizer, a blended fertilizer, a fluid
compound fertilizer and a home garden-use compound fertilizer respectively. As aresult, the mean recovery rates at the additive level of 3 % (mass fraction) and
1.5 % (mass fraction) and 0.3 % (mass fraction) were 96.3 % - 96.3 %, 94.5 % 99.7 % and 88.9 % - 100.6 % respectively.
The results of the repeatability tests on different days using a blended fertilizer, acompound fertilizer and a home garden-use compound fertilizer to evaluate
precision were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability. Additionally, resultsfrom a collaborative study for testing method validation and its analysis are shownin Table 2.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.01 % (mass fraction).

562

Testing Methods for Fertilizers(2021)
Table 1 Analysis results of the repeatability tests on different days of dicyandiamide nitrogen
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Blended fertilizer
5
3.03
0.02
0.5
0.02
Compound fertilizer
5
1.45
0.01
0.9
0.02
Home garden-use compound fertilizer
5
0.145
0.001
0.9
0.003
1) The number of test days conducting a duplicate test 6) Intermediate standard deviation
2) Mean (the number of test days(T )×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

0.5
1.6
2.3

7) Intermediate relative standard deviation

Table 2 Analysis results of the collaborative study
for the test method validation of dicyandiamide nitrogen
4)5)
6)
Number of Mean2)
sr
RSD r
sR
Sample name
1)
3)
3)
3)
(%)
laboratories
(%)
(%)
(%)
10
0.04640.00235.0
0.0148Compound fertilizer 1
12
0.206
0.011
5.1
0.031
Compound fertilizer 2
12
1.69
0.05
2.8
0.12
Compound fertilizer 3
10
2.76
0.07
2.6
0.12
Compound fertilizer 4
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

7)

RSD R
(%)
31.9
15.2
7.0
4.4

References
1)
Masahiro ECHI, Yasuharu KIMURA and Yuji SHIRAI: Determination of Urea
Nitrogen, Biuret Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl
urea Nitrogen in Fertilizer by High-Performance Liquid Chromatography: A SingleLaboratory Validation, Research Report of Fertilizer, Vol. 10, p. 72 - 85 (2017)2)
Norio FUNAKI and Yasuharu KIMURA: Determination of Urea Nitrogen, Biuret
Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogen in
Fertilizer by High-Performance Liquid Chromatography (HPLC): A Collaborative
Study, Research Report of Fertilizer, Vol. 10, p. 86 - 100 (2017)

563

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for dicyandiamide nitrogen in fertilizers isshown below:564

Testing Methods for Fertilizers(2021)

Reference: An example of the chromatogram of the standard solution for calibration curve
preparation of dicyandiamide nitrogen is shown below.

Reference diagram HPLC chromatogram of the mixture standard solutions (10 mg/L foreach) for calibration curve preparation
Peak name(1) Urea nitrogen (2) Biuret nitrogen(3) Dicyandiamide nitrogen(4) Guanidine nitrogen(5) Guanylurea nitrogen
Measurement conditions for HPLC
Column: Asahipak ES-502C 7C (7.5-mm inner diameter, 100-mm long, 9-μm
particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)565

Testing Methods for Fertilizers(2021)

6.2 Chlorine
6.2.a Ion Chromatography(1) Summary
The testing method is applicable to potassium sulfate, potassium bicarbonate, magnesium
potassium sulfate, fish cakes powder, fish cakes and compost. This testing method is classified
as Type D and its symbol is 6.2.a-2017 or Cl.a-1.
Add water to an analytical sample to extract chloride ions, introduce them to an Ion
Chromatograph (IC) to isolate it with an ion exchange column, and then measure with an electric
conductivity detector to obtain chlorine (Cl) in an analytical sample. In addition, the performanceof this testing method is shown in Comment 3.
(2)
a)
b)
c)
d)
e)
f)

Reagent, etc.: Reagents and water are as shown below.
Water: Water of A4 specified in JIS K 0557.
1 mol/L sodium carbonate solution: Solution for ion chromatography.
Phthalic acid: A reagent of no less than 98 % (mass fraction) in purity.
6-aminohexanic acid (1): A reagent of no less than 97 % (mass fraction) in purity.
Phenylboronic acid: A reagent of no less than 97 % (mass fraction) in purity.
Chloride ion standard solution (Cl- 1 mg/mL): A chloride ion standard solution (Cl- 1000
mg/mL) traceable to National Metrology.
g) Chloride ion standard solution (Cl- 100 µg/mL) (2): Put a predetermined amount ofchloride ion standard solution (Cl- 1 mg/mL) in a volumetric flask and add water up to themarked line.
h) Chloride ion standard solution (Cl- 5 µg/ mL - 50 µg/ mL) for the calibration curve
preparation (2): Put 5 mL - 50 mL of Chloride ion standard solution (Cl- 100 µg/mL) in a
100-mL volumetric flask and add water up to the marked line.
i) Chloride ion standard solution (Cl- 1 µg/ mL - 2 µg/ mL) for the calibration curve
preparation (2): Put 5 mL - 10 mL of Chloride ion standard solution (Cl- 20 mg/mL) in a
100-mL volumetric flask and add water up to the marked line.
j) Eluent for suppressor method (2): Put 6.4 mL of 1 mol/L sodium carbonate solution in a
1000-mL volumetric flask and add water up to the marked line. Then filter with membrane
type filter (pore size: no more than 0.5 μm) made of hydrophilic PTFE (2).
k) Eluent for non-suppressor method (2): Put 0.349 g of phthalic acid, 0.380 g of 6aminohexanic acid and 0.732 g of phenylboronic acid in a 1000-mL volumetric flask andadd about 500 mL of water to dissolve. Add water up to the marked line and filter withmembrane type filter (pore size: no more than 0.5 μm) made of hydrophilic PTFE (3).
Note (1) It is also known as “6-amino-n-caprotic acid”.
(2) This is an example of preparation; prepare an amount as appropriate.
(3) A solution concentrated by a factor of 10 can be prepared in advance and the solution
can be diluted by a factor of 10 at each usage.
Comment 1 Instead of the chloride ion standard solution in (2), a chloride ion standard solution
for the calibration curve preparation can be prepared by using a chloride ion
standard solution (Cl- 0.1 mg/mL) traceable to National Metrology.

(3)
a)
b)
c)

Apparatus and instruments: Apparatus and instruments are shown below.
Magnetic stirrer
Centrifugal separator: A centrifugal separator that can work at 1700 × g.
Ion Chromatograph: An ion chromatograph specified in JIS K 0127 that satisfies thefollowing requirements.
566

Testing Methods for Fertilizers(2021)

1) Column: In case of a suppressor method, a 4-mm inner diameter 250-mm long 5-μm
particle diameter column tube filled with poly vinyl alcohol porous particles, to which
quaternary ammonium group chemically bonds (4).
In case of non-suppressor method, a 4.6-mm inner diameter 100-mm long column tube
filled with hydrophilic polymethacrylate-gel, to which quaternary ammonium groupchemically bonds (5).
2) Column bath: A column bath whose temperature can be adjusted to 40 ºC.
3) Suppressor: Cation exchange membrane or resin should be used.
4) Detection unit: An electric conductivity detectord) Membrane filters: Pore size is no more than 0.45 μm, made of hydrophilic PTFE
Note (4) A column is commercially sold under the name Shodex IC SI-52 4E, etc.
(5) A column is commercially sold under the name Shodex IC NI-424, etc.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper
Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper
centrifugal precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about five minutes (6) and use the supernatant
as an extract.
e) Transfer a predetermined amount of the solution, and dilute exactly by a factor of 20 withwater (7).
f) Filter with a membrane filter (pore size: no more than 0.45 μm) to make a sample solution.
Note (6) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g
centrifugal force.
(7) In case of exceeding the calibration curve, dilute by a factor of more than 20.
Comment 2 Instead of the procedures in (4. 1) c) and d), it is allowed to filter with Type 3 filter
paper and the filtrate can be the extract.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0127 and as shown below.
Specific measurement procedures are according to the operation method of the Ion
Chromatograph used in measurement.
a) Measurement conditions for the Ion Chromatograph: An example of measurement
conditions is shown below. Set up the measurement conditions considering it:aa) Suppressor method
1) Column: A polyvinyl alcohol porous particles column (4-mm inner diameter 250-mm
long 5-μm particle diameter) to which quaternary ammonium group chemically bonds.
2) Column bath temperature: 40 °C
3) Eluent: Prepared in the procedure in (2) j).
4) Flow rate: 0.8 mL/min
5) Injection volume: 20 µL
6) Detection unit: An electric conductivity detectorab) Non-suppressor method
567

Testing Methods for Fertilizers(2021)

1) Column: A hydrophilic polymethacrylate-gel column (4.6-mm inner diameter 100-mmlong) to which quaternary ammonium group chemically bonds.
2) Column bath temperature: 40 °C
3) Eluent: Prepared in the procedure in (2) k).
4) Flow rate: 1.0 mL/min
5) Injection volume: 20 µL
6) Detection unit: An electric conductivity detectorb) Calibration curve preparation
1) Inject 20 μL of respective standard solutions for the calibration curve preparation to the ion
chromatograph and record a chromatogram of electric conductivity to obtain a peak area.
2) Prepare a curve for the relationship between the concentration and the peak area of electric
conductivity of respective standard solutions for the calibration curve preparation.
Prepare a calibration curve when the sample is measured.
c) Sample measurement
1) Subject 20 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the chloride ion concentration from the calibration curve by the peak area tocalculate the chlorine (Cl) in the analytical sample.
Comment 3 Additive recovery testing was conducted with a suppressor method using samples
that 1.8 % (mass fraction) – 33.4 % (mass fraction) of sodium chloride as chlorine
is added to potassium sulfate, magnesia potassium sulfate, potassium bicarbonate,
cow dung compost and fish cakes powder. As a result, the mean recovery rates atthe chlorine additive level of 33.4 % (mass fraction), 10 % (mass fraction) - 13.4 %(mass fraction) and 1.8 % (mass fraction) - 9.1 % (mass fraction) were 100.8 %,98.6 % - 101.1 % and 96.2 % - 103.2 % respectively. With a non-suppressor method,they are 100.2 %, 96.4 % - 97.2 % and 93.3 % - 101.4 %.
The results of the repeatability tests on different days using potassium sulfate,magnesia potassium sulfate, potassium bicarbonate, cow dung compost and fishcakes powder to evaluate precision were analyzed by one-way analysis of variance.
Table 1 shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.1 % (mass fraction).

568

Testing Methods for Fertilizers(2021)

References
1)
Satoko SAKAIDA, Mariko FUJITA and Yuji SHIRAI: Determination of Chloride
in Fertilizers by Ion Chromatography (IC), Research Report of Fertilizers, Vol. 8, p.
50 - 60 (2015)(5)

Flow sheet for testing method: The flow sheet for chlorine in fertilizers is shown below:

569

Testing Methods for Fertilizers(2021)

Reference: Examples of the IC chromatograms of the sample solutions (magnesia potassium
sulfate and fish cakes powder) are shown below.
Cl-

Cl-

(A) Chromatogram of magnesia
potassium sulfate(Suppressor method)(B) Chromatogram of magnesia
potassium sulfate(Non-suppressor method)

Cl-

Cl-

(C) Chromatogram of fish cakes powder(Suppressor method)(D) Chromatogram of fish cakes powder(Non-suppressor method)

Reference diagram: IC chromatogram of chloride ion(Peak：1.chloride ion (Cl-))

570

Testing Methods for Fertilizers(2021)

6.2.b Silver nitrate method(1) Summary
The test method is applicable to potassium sulfate, potassium bicarbonate and magnesium
potassium sulfate. This testing method is classified as Type E and its symbol is 6.2.b-2017 or
Cl.b-1.
Add water to an analytical sample to extract chloride ions and titrate (precipitate) with a 0.1
mol/L silver nitrate standard solution to obtain chlorine (Cl) in an analytical sample.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Nitric acid: A JIS Guaranteed (HNO3 60 % (mass fraction)) Reagent specified in JIS K
8541 or a reagent of equivalent quality.
c) 0.1 mol/L silver nitrate solution (1): Weigh 17 g of silver nitrate specified in JIS K 8550
to a 2000-mL beaker, add 1000 mL of water to dissolve and store in a colored bottle.
Standardization: Heat a sodium chloride reference material for volumetric analysis
specified in JIS K 8005 at 600 ºC ± 25 °C for 1 hour, let it stand to cool in a desiccator,
and then put about 1.5 g in a weighing dish, and weigh the mass to the order of 0.1 mg.
Dissolve in a small amount of water, transfer to a 250-mL volumetric flask, and add water
up to the marked line to make the sodium chloride solution (1). On each day to use a 0.1
mol/L silver nitrate solution, put 10 mL of the sodium chloride solution in a 200-mL
Erlenmeyer flask, add a few drops of potassium chromate solution (5 g/100 mL) as anindicator, and titrate with a 0.1 mol/L silver nitrate solution until the color of the solution
becomes reddish brown. Calculate the factor of a 0.1 mol/L silver nitrate solution by thefollowing formula:
Factor (f) of 0.1 mol/L silver nitrate solution= W1× (A/100) × (1/58.44) × (V1/V2 × (1000/V3)) × (1/C)= (W1×A/V3) × (4/58.44)
W1 ： Mass (g) of sodium chloride weighed
A： Purity (% (mass fraction)) of sodium chloride
V1： Aliquot volume (10 mL) of sodium chloride solution
V2： Constant volume (250 mL) of sodium chloride solution
V3： Volume (mL) of 0.1 mol/L silver nitrate solution needed for titration
C： Set concentration (0.1 mol/L) of 0.1 mol/L silver nitrate solutiond) Potassium chromate (5 g/ 100 mL) (1): Dissolve 5 g of potassium chromate in 100 mL ofwater.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Magnetic stirrerb) pH test paper: A pH test paper infiltrated with indicator and dried, which can measure thevalue from pH 1 to pH 11 and a color change chart with the pH interval value 1 is attached.
Comment 1 pH test paper is sold under the name UNIV Test Paper, etc.

571

Testing Methods for Fertilizers(2021)(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper
Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) Filter with Type 3 filter paper to make a sample solution.
(4.2) Measurement:
Conduct measurement as shown below.
a) Put 25 mL of sample solution in a 200-mL tall beaker.
b) Confirm the pH of the solution with a pH-test paper. If the pH is basic, neutralize with nitricacid (1+10).
c) Add a few drops of potassium chromate solution (5 g/100 mL) to the sample solution as anindicator and titrate with a 0.1 mol/L silver nitrate solution until the color of the solution
becomes reddish brown.
d) Calculate chlorine (Cl) by the following formula.
Chlorine (% (mass fraction)) in the analytical sample= V4 × C × f × (35.45)/W2 × (100/1000) × (V5/ V6)= V4 × f × (35.45/25)/W2
V4： Volume (mL) of the 0.1 mol/L silver nitrate solution required for titration
C： Set concentration (0.1 mol/L) of 0.1 mol/L silver nitrate solution
f： Factor of 0.1 mol/L silver nitrate solution
V5： Liquid volume of water (100 mL) subjected to extraction in (4.1) b).
V6： Aliquot volume (25 mL) of the sample solution subjected to titration in(4.2) a).
W2 ： Mass (g) of the analytical sample
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.199- 201, Yokendo, Tokyo (1988)

572

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for chlorine in potassium sulfate, etc. isshown below:573

Testing Methods for Fertilizers(2021)

6.3 Urea nitrogen
6.3.a Urease method(1) Summary
The test method is applicable to fertilizers containing urea or urea compounds such asacetaldehyde condensed urea, etc. However, in some cases, it is not applicable to the fertilizers
that contain such compounds as nitrolime that digests by heating. This testing method is classified
as Type D and its symbol is 6.3.a-2017 or U-N.a-1.
Add water to an analytical sample to extract and add urease to a predetermined amount of theextract to hydrolyze urea into ammonium ion. Add sodium hydroxide to alkalize the solution andsubject it to steam distillation. Collect isolated ammonia with 0.25 mol/L sulfuric acid and titrate(neutralize) surplus sulfuric acid using 0.1 mol/L - 0.2 mol/L sodium hydroxide solution andcorrect separately the titers of urease blank test and urease undigested blank test to obtain urea
nitrogen (U-N) in the analytical sample. Or collect isolated ammonia with a boric acid solution
and titrate (neutralize) the ammonium ion using 0.25 mol/L sulfuric acid and similarly correct toobtain urea nitrogen (U-N) in the analytical sample. In addition, the performance of this testing
method is shown in Comment 11.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 byadding in small portions while cooling, seal tightly and leave at rest for 4 - 5 days. Put 5.5
mL -11 mL of the supernatant in a ground-in stoppered storage container, and add 1000 mLof water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified in
JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours,
then put about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg.
Dissolve in a small amount of water, transfer to a 250-mL volumetric flask, and add water
up to the marked line (1). Put a predetermined amount of the solution in a 200-mL - 300mL Erlenmeyer flask, add a few drops of bromothymol blue solution (0.1 g/100 mL) as
an indicator, and titrate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until thecolor of the solution becomes green. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution by the following formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1 ： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Magnesium oxide: A JIS Guaranteed Reagent specified in JIS K 8432 or a reagent ofequivalent quality.
c) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
d) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100
mL of water in advance, stir well, and add water to make 1000 mL.
574

Testing Methods for Fertilizers(2021)

Standardization: Transfer a predetermined amount (3) of 0.25 mol/L sulfuric acid to a 200mL - 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture
solution, and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following
formula (1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula(2):
Volume (B) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution equivalent to 1 mL of
0.25 mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4 ：

Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acide)

Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water
to make 1000 mL.
f) Urease: A reagent which completely digests 0.25 g of urea by 0.5 g of urease.
g) Sodium hydroxide solution (5 g/L) (1): Dissolve 5 g of sodium hydroxide specified in JIS
K 8576 in water to make 1000 mL.
h) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
i) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified
in JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
j) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896
in 100 mL of ethanol (95) specified in JIS K 8102.
k) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in
JIS K 8897 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
m) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green
specified in JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
n) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100mL), add equal volume of bromocresol green solution (0.5 g/100 mL).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid)solution in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced witha 0.1 mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
575

Testing Methods for Fertilizers(2021)

conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) d) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
Comment 3 Refined products of urease made from sword beans are commercially sold. The
degree of activation may degrade even if stored in a refrigerator. Therefore, it isrecommended to test similarly and confirm activation by using urea specified in
JIS K 8731 in advance.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Extractor: A vertical rotating mixer or magnetic stirrer as described belowaa) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 500-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
ab) Magnetic stirrerb) Steam distillation apparatusc) Distillation flask: A Kjeldahl flask or a round bottom flask that can be connected to asteam distillation apparatus.
d) Water bath: Water bath that can be adjusted to 40 ºC - 45 ºC.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Vertical rotating mixera) Weigh 5.00 g of an analytical sample, and put it in a 500-mL volumetric flask.
b) Add about 400 mL of water, and shake to mix at 30 - 40 revolutions/min for about 30
minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make an extract.
Comment 4 In the procedure in (4.1.1) a), it is also allowed to weigh 2.50 g of the analyticalsample and transfer to a 250-mL volumetric flask. In that case, add about 200 mLof water in the procedure in b).
Comment 5 The procedure in (4.1.1) is the same as the procedure in (4.1.1.1) in 4.2.4.a.
(4.1.2) Magnetic stirrera) Weigh 1.00 g of an analytical sample, and put it into a 200- mL ground-in stopper
Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) Filter with Type 3 filter paper to make an extract.
Comment 6 The procedure in (4.1.2) is the same as the procedure in (4.1) in 6.3.c.
(4.2) Hydrolysis by urease: Conduct hydrolysis as shown below.
a) Put a predetermined amount of the extract (the equivalents of 10 mg or more as U- N, theequivalents of 10 mg - 100 mg as N) in a 300-mL distillation flask.
b) Add water to the solution to make about 50 mL.
c) Add a few drops of methyl red solution (0.1 g/100 mL), and add a sodium hydroxide
solution (5 g/L) or hydrochloric acid (1+200) until the color of the solution becomes lightyellowish red (6).
d) Add a sufficient amount of urease to digest urea in the extract (7) (8), seal tightly and heat in
the water bath at 40 ºC - 45 ºC.
e) Let it stand to cool to make a sample solution.
576

Testing Methods for Fertilizers(2021)

As an extract blank test, conduct the procedures in a) (9) using another distillation flask to
prepare an undigested test solution.
g) As a urease blank test, conduct the procedures in b), d) and e) (8) (10) using anotherdistillation flask to prepare a blank test solution.
f)Note (6) pH 5.6 - pH 5.8(7) An example of the additive volume of urease is shown in Comment 10.
(8) Wash urease off with a small amount of water if it adheres to the surface of a vessel.
(9) Aliquot the same amount of the extract as the prepared sample solution.
(10) Add the same amount of urease as the preparation of the sample solution used.
(4.3) Distillation: Conduct distillation as shown below. Specific distillation procedures areaccording to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (11) of 0.25 mol/L sulfuric acid in an acceptor (12), add a few
drops of methyl red−methylene blue mixture solution, and connect this acceptor to a steam
distillation apparatus. Or, put a predetermined amount (11) of boric acid solution (40 g/L) inan acceptor (12), add a few drops of methyl red−bromocresol green mixture solution, andconnect this acceptor to a steam distillation apparatus.
b) Add 2 g - 3 g of magnesium oxide to a distillation flask containing the sample solution (13),and connect this distillation flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at
a distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in
the acceptor with a small amount of water, and pool the washing with the distillate.
f) Subject the undigested test solution to the same procedure as in a) - e) to obtain the distillate
from the undigested test solution.
g) Subject the blank test solution to the same procedure as in a) - e) to obtain the distillate
from the blank test solution.
Note (11) 5 mL - 20 mL(12) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL
beaker with which the distillate outlet of the steam distillation apparatus can be
immersed in 0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(13) Add a small amount of silicone oil as necessary.
Comment 7 Immediately conduct the procedure in (4.3) b) not to emit ammonia gas in a vessel.
(4.4) Measurement: Conduct measurement as shown below.
(4.4.1) When 0.25 mol/L sulfuric acid is used in (4.3):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4).
b) Subject the distillate from the undigested test solution to the same procedure as in a) totitrate.
c) Subject the distillate from the blank test solution to the same procedure as in a) to titrate.
d) Calculate the urea nitrogen (U-N) in an analytical sample by the following formula:
Urea nitrogen (U-N) (% (mass fraction)) in the analytical sample= ((B × V6－V7) －(B × V6－V8)－(B × V6－V9)) × C1 × f1 × (V10/V11) × (14.007/W2) ×(100/1000)
577

Testing Methods for Fertilizers(2021)= (－(B × V6) － (V7－V8－V9)) × C1 × f1 × (V10/V11) × (1.4007/W2)
B： Volume of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution equivalent to 1 mL
of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid transferred to the acceptor in (4.3) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration in (4.4.1) a)
V8： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration in (4.4.1) b)
V9： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration in (4.4.1) c)
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V10： Constant volume (mL) of the extract in (4.1.1) c) or additive volume (mL) of
water in (4.1.2) b)
V11： Aliquot volume (mL) of the extract subjected to hydrolysis in (4.2) a)
W2 ： Mass (g) of the analytical sample in (4.1.1) a) or (4.1.2) a)(4.4.2) When a boric acid solution (40 g/L) is used in (4.3):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomeslight red (14).
b) Subject the distillate from the undigested test solution to the same procedure as in a) totitrate.
c) Subject the distillate from the blank test solution to the same procedure as in a) to titrate.
d) Calculate the urea nitrogen (U-N) in an analytical sample by the following formula:
Urea nitrogen (U-N) (% (mass fraction)) in the analytical sample= (V12－V13－V14) × C2 × 2 × f2 × (V10/V11) × (14.007/W2) × (100/1000)= (V12－V13－V14) × C2 × f2 × (V10/V11) × (2.8014/W2)
V12： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration in (4.4.2) a)
V13： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration in (4.4.2) b)
V14： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration in (4.4.2) c)
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV10： Constant volume (mL) of the extract in (4.1.1) c) or additive volume (mL)of water in (4.1.2) b)
V11： Aliquot volume (mL) of the extract subjected to hydrolysis in (4.2) a)
W2 ： Mass (g) of the analytical sample in (4.1.1) a) or (4.1.2) a)
Note (14) The endpoint is reached when the color changes from green to light red.
Comment 8 If it is hard to confirm the endpoint due to the carbon dioxide resulting fromcarbonate in the extract when magnesium oxide is used, it is recommended to boil
the extract for 1-2 minute(s) after distilling and cool, and then titrate.
Comment 9 The titration procedures in (2) a) Standardization, (2) d) Standardization and(4.4) can be conducted by an automatic titrator. The setup of the titration program,the determination parameter for the endpoint and vessels such as acceptors areaccording to the specification and the operation method of the automatic titrator
used.
578

Testing Methods for Fertilizers(2021)

Comment 10 An example of the additive volume and titter of urease is shown below.
If the urea content can be estimated, calculate the volume of urea in the aliquot
volume of the extract in (4.2) a) by the following formula.
Estimated urea content (mg) in the transferred volume of the extract= (D1/100) × W2 × (V11/ V10)
D1： Estimated urea content (% ( mass fraction)) in the analytical sample
V10： Constant volume (mL) of the extract in (4.1.1) c) or (4.1.2) c)
V11： Aliquot volume (mL) of the extract subjected to hydrolysis in (4.2) a)
W2 ： Mass (g) of the analytical sample in (4.1.1) a) or (4.1.2) a)
If the urea content cannot be estimated, subtract ammoniacal nitrogen and nitrate
nitrogen from the total nitrogen of the permissible content or the display component
content of the urea nitrogen in a urea compound to obtain nitrogen content. The obtained
nitrogen content is calculated as around the maximum content of urea nitrogen (U-N).
In this case, calculate the volume of urea in the transferred volume of the extract in(4.1.1) or (4.2) a) after the procedures in (4.1.1) by the following formula.
Estimated urea content (mg) in the transferred volume of the extract= (D2/100) × (60.056/ (14.007 × 2)) × W2 × (V11/ V10)
= (D2/100) × 2.1438 × W2 × (V11/ V10)
D2： Estimated urea nitrogen (U-N) content (% (mass fraction)) in the analyticalsampleV10： Constant volume (mL) of the extract in (4.1.1) c) or (4.1.2) c)
V11： Aliquot volume (mL) of the extract subjected to hydrolysis in (4.2) a)
W2 ： Mass (g) of the analytical sample in (4.1.1) a) or (4.1.2) a)
The specification of urease shows that “No more than 0.5 g of urease completely
digests 0.25 g of urea”. Therefore about 2 mg of urease is required to digest 1 mg of
urea. Assuming that the estimated urea content or the calculated urea content in thetransferred volume of the extract is about 43 mg (about 20 mg as urea nitrogen), about
86 mg of urease is required. When adding 0.2 g of urease (potency 130 unit - 150 unit),
the extract containing the equivalents of 10 mg - 100 mg as urea nitrogen (U-N) can behydrolyzed.
In addition, when about 20 mg aliquot is taken as urea nitrogen, the differences
between the titer of the distillate from the sample solution ((4.4.1) a) or (4.4.2) a)) andthe titer of the distillate from the undigested test solution ((4.4.1) b) or (4.4.2) b)) are
estimated as follows: About 14 mL, when a 0.1 mol/L sodium hydroxide solution is used
as a titrant, about 7 mL, when 0.2 mol/L sodium hydroxide is used as a titrant and about
3 mL, when 0.25 mol/L sulfuric acid is used as a titrant.
Comment 11 Additive recovery testing was conducted to evaluate trueness using samples
prepared by adding urea to sulfur, a compound fertilizer, isobutyraldehyde
condensed urea, a compound fertilizer containing formaldehyde processed urea
(one sample for each). As a result, the mean recovery rate at the additive level of
1.58 % (mass fraction) - 39.96 % (mass fraction) was 98.7 % to 103.7 %The results of the repeatability tests on different days using urea and a compound
fertilizer containing UF (one sample for each), to evaluate precision were analyzed579

Testing Methods for Fertilizers(2021)

by one-way analysis of variance. Table 1 shows the calculation results ofintermediate precision and repeatability.
The minimum limit of quantification of this testing method was estimated to beabout 0.4 % (mass fraction).

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.56- 59, Yokendo, Tokyo (1988)
2)
Toshifumi FUJITA, Kimie KATO, Toyokazu NIIMI, Yasuharu KIMURA, Kohei ITO
and Yuji SHIRAI: Determination Method for Urea Nitrogen in Fertilizer by Urease,
Research Report of Fertilizer, Vol. 10, p. 195 - 207 (2017)(5)

Flow sheet for urea nitrogen testing method: The flow sheets for urea nitrogen test
method in fertilizers are shown below:
5.00 gWeigh into a 500-mL volumetric flask
Analytical sample← About 400 mL of water
Shaking to mix
Vertical rotating mixer (30 - 40 revolutions/min), for 30 minutes← Water (up to the marked line)
Filtration
Type 3 filter paper
Extract
Figure 1-1 Flow sheet for urea nitrogen(Extraction procedure (4.1.1))
1.00 gWeigh into a 200-mL ground-in stopper Erlenmeyer flask
Analytical sample← 100 mL of water
Shaking to mix
Magnetic stirrer, 10 minures
Filtration

Type 3 filter paper

Extract
Figure 1-2 Flow sheet for urea nitrogen(Extraction procedure (4.1.2))
580

Testing Methods for Fertilizers(2021)

581

Testing Methods for Fertilizers(2021)

6.3.b High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B andits symbol is 6.3.b-2017 or U-N.b-1.
Add water to an analytical sample to extract urea, introduce it to a High-Performance Liquid
Chromatograph (HPLC) to isolate it with a weak acid ion-exchange column, and then measure
at a wavelength 190 nm to obtain urea nitrogen (U-N) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 5.
Biuret nitrogen (B-N), dicyandiamide nitrogen (Dd-N), guanidine urea (Gd-N) and guanylurea
nitrogen (GU-N) can be simultaneously quantified by using this method. (Refer to Comment 4).
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Potassium dihydrogen phosphate: A JIS Guaranteed Reagent specified in JIS K 9007
or a reagent of equivalent quality.
c) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
d) Urea nitrogen standard solution (U-N 2 mg/mL) (1): Put 0.429 g of urea specified in JIS
K 8731 in a weighing dish and measure the mass to the order of 0.1 mg. Add a small amountof water to dissolve, then transfer to a 100-mL volumetric flask and add water up to themarked line.
e) Urea nitrogen standard solution for the calibration curve preparation (U-N 200µg/mL): Put 10 mL of urea nitrogen standard solution (U-N 2 mg/mL) in a 100-mL
volumetric flask and add water up to the marked line.
f) Urea nitrogen standard solution (U-N 50 µg/mL - 100 µg/mL): Put 25 mL - 50 mL ofurea nitrogen standard solution (U-N 200 µg/mL) in 100-mL volumetric flasks and add
water up to the marked line.
g) Urea nitrogen standard solution for the calibration curve preparation (U-N 1 μg/mL 50 μg/mL): At the time of usage, put 1 mL - 50 mL of urea nitrogen standard solution (UN 0.1 mg/mL) in 100-mL volumetric flasks step-by-step and add water up to the marked
line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 7.5-mm inner diameter 100-mm long stainless steel column tube filled withweak acid ion-exchange resin.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around
190 nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g 10000 × g.
Comment 1 A column is sold under the production name Asahipak ES-502C 7C, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
582

Testing Methods for Fertilizers(2021)(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200 mL-ground-in stopper
Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution (2) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (3).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (4) and use thesupernatant as a sample solution.
Note (2) If there is a possibility that the urea nitrogen (U-N) concentration in the sample
solution will exceed the maximum limit of the calibration curve, dilute apredetermined amount of supernatant with water.
(3) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(4) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 ×g - 10000 × g centrifugal force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line (5) and put it in a 1.5-mL ground-in stopper centrifugal
precipitate tube (3).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (4) and use thesupernatant as a sample solution.
Note (5) If there is a possibility that the urea nitrogen (U-N) concentration in the sample
solution will exceed the maximum limit of the calibration curve, dilute apredetermined amount of precisely adjusted solution with water.
Comment 2 Instead of procedures in (4.1.1) c) - d) or (4.1.2) c) - d), it is allowed to filter witha membrane filter (aperture diameter: no more than 0.5-µm) made of hydrophilic
PTFE and the filtrate can be the sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An
example of measurement conditions is shown below. Set up the measurement conditions
considering it:1) Column: A weak acid ion-exchange resin column (4.0-mm - 7.5-mm inner diameter, 100mm - 150-mm long, 5-µm – 10-µm particle diameter)
2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 3.92 g of potassium dihydrogen phosphate and 0.12 g of phosphoricacid in water to make 1000 mL. Filter with a membrane filter (aperture diameter: no morethan 0.5-µm) made of hydrophilic PTFE.
4) Flow rate: 0.6 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 190 nm
Comment 3 The eluent can be prepared as follows. Dissolve 19.6 g of potassium dihydrogen583

Testing Methods for Fertilizers(2021)

phosphate and 0.584 g of phosphoric acid with water to make 500 mL and store in
a refrigerator. At the time of usage, dilute a predetermined volume of the solution
by a factor of 10 and filter with a membrane filter (aperture diameter: no more than
0.5-µm) made of hydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to theHigh-Performance Liquid Chromatograph, record a chromatogram at a wavelength 190 nm
and obtain a peak height.
2) Prepare a curve for the relationship between the urea nitrogen (U-N) concentration and thepeak height at a wavelength 190 nm of the respective standard solutions for the calibration
curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the urea nitrogen (U-N) content from the peak height using the calibration curve tocalculate the urea nitrogen (U-N) in the analytical sample.
Comment 4 This testing method enables the simultaneous measurement of biuret nitrogen (BN), urea nitrogen (U-N), dicyandiamide nitrogen (Dd-N), guanidine urea (Gd-N)
and guanylurea nitrogen (GU-N). In that case, see 5.10.a Comment 5.
When Asahipak ES-502C 7C is used as a column for HPLC to analyze urea
nitrogen (U-N) in a compound fertilizer containing formaldehyde processed urea(UF), the peak of the urea nitrogen (U-N) and the peak of the impurity components
originating from UF are not separated, so that urea nitrogen (U-N) cannot bemeasured. In this case, the peak of the urea nitrogen (U-N) and the peak of the
impurity components originating from UF are separated by using PRP-X200 as acolumn for HPLC instead to be able to analyze the urea nitrogen(U-N) in thecompound fertilizer containing UF. However, when the PRP-X200 column is used
as a column for HPLC, the simultaneous measurement of urea nitrogen (U-N) andbiuret nitrogen (B-N), etc. is impossible.
Comment 5 Additive recovery testing was conducted using one brand of an acetaldehyde
condensed urea fertilizer, a compound fertilizer, a blended fertilizer, a fluid
compound fertilizer and a home garden-use compound fertilizer respectively. As aresult, the mean recovery rates at the additive level of 6 % (mass fraction) and 3 %(mass fraction) and 0.6 % (mass fraction) were 98.3 % - 102.9 %, 98.9 % - 105.2 %and 92.3 % - 99.9 % respectively.
The results of the repeatability tests on different days using a blended fertilizer, acompound fertilizer and a home garden-use compound fertilizer to evaluate
precision were analyzed by the one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability. Additionally, resultsfrom a collaborative study for testing method validation and its analysis are shownin Table 2.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.03 % (mass fraction).

584

Testing Methods for Fertilizers(2021)

References
1)
Masahiro ECHI, Yasuharu KIMURA and Yuji SHIRAI: Determination of Urea
Nitrogen, Biuret Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl
urea Nitrogen in Fertilizer by High-Performance Liquid Chromatography: A SingleLaboratory Validation, Research Report of Fertilizer, Vol. 10, p. 72 - 85 (2017)2)
Norio FUNAKI and Yasuharu KIMURA: Determination of Urea Nitrogen, Biuret
Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogen in
Fertilizer by High-Performance Liquid Chromatography (HPLC): A Collaborative
Study, Research Report of Fertilizer, Vol. 10, p. 86 - 100 (2017)585

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: An example of the flow sheet for urea nitrogen in fertilizers
is shown below:

586

Testing Methods for Fertilizers(2021)

Reference: The chromatograms of the standard solution for calibration curve preparation of
urea nitrogen are shown below.

Reference diagram 1 HPLC chromatogram of the mixture standard solutions (10 mg/L foreach) for calibration curve preparation
Peak name(1) Urea nitrogen (2) Biuret nitrogen(3) Dicyandiamide nitrogen(4) Guanidine nitrogen(5) Guanylurea nitrogen
Measurement conditions for HPLC
Column: Asahipak ES-502C 7C (7.5-mm inner diameter, 100-mm long, 9-μm
particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)Reference diagram 2 HPLC chromatogram of the urea nitrogen standard solutions (20 mg/L)
and a formaldehyde processed urea fertilizer for calibration curve
preparation
Peak name(1) Urea nitrogen (2) Biuret nitrogen
Measurement conditions for HPLC
Column: PRP-X200 (4.1-mm inner diameter, 150-mm long, 10-µm particle
diameter)Other conditions are according to the example of HPLC measurement conditionsin (4.2) a)587

Testing Methods for Fertilizers(2021)

6.3.c p-dimethylaminobenzaldehide absorptiometry(1) Summary
The testing method is applicable to fertilizers containing urea nitrogen. However,isobutyraldehyde condensed urea fertilizers, formaldehyde processed urea fertilizers, nitrolime,
sludge fertilizers, etc., and special fertilizers are excluded. This testing method is classified as
Type D and its symbol is 6.3.c-2018 or U-N.c-1.
Add water to an analytical sample to extract urea and measure the coloration formed by thereaction with dimethylaminobenzaldehyde by absorbance to obtain urea nitrogen (U-N) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 3.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Coloring reagent solution (1): Dissolve 20 g of p-dimethylaminobenzaldehyde specified in
JIS K 8101 in 1000 mL of ethanol (99.5) specified in JIS K 8101 and 100 mL ofhydrochloric acid specified in JIS K 8180 and leave at rest overnight (2).
c) Urea nitrogen standard solution (U-N 2 mg/mL) (1): Put 0.429 g of urea specified in JIS
K 8731 in a weighing dish and measure the mass to the order of 0.1 mg. Add a small amountof water to dissolve, then transfer to a 100-mL volumetric flask and add water up to themarked line.
d) Urea nitrogen standard solution for the calibration curve preparation (U-N 200µg/mL) (1): Put 10 mL of urea nitrogen standard solution (U-N 2 mg/mL) in a 100-mL
volumetric flask and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) Store in an amber bottle.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Spectrophotometer: A spectrophotometer specified in JIS K 0115b) Magnetic stirrer(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200-mL Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, filter with Type 3 filter paper to make a sample solution.
Comment 1 The procedure in (4.1) is the same as the procedure in (4.1.2) of 6.3.a.
Comment 2 When the determination is affected by the coloring of the sample solution of (4.1)c), add about 0.5 g of active carbon and filter with Type 3 filter paper to make asample solution from which the coloring disappears.
(4.2) Coloring: Conduct coloring as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.5 mg - 5 mg as UN) in a 50-mL volumetric flask.
b) Add 20 mL of coloring reagent solution, and further add water up to the marked line, andthen leave at rest for about 30 minutes.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0115 and as shown below.
Specific measurement procedures are according to the operation method of thespectrophotometer used for the measurement.
588

Testing Methods for Fertilizers(2021)

a) Measurement conditions of the spectrophotometer: Set up the measurement conditionsof the spectrophotometer considering the following.
Detection wavelength: 450 nmb) Calibration curve preparation
1) Put 2.5 mL - 25 mL of urea nitrogen standard solution (U-N 200 µg/mL) in 50-mL
volumetric flasks step-by-step.
2) Conduct the same procedures as (4.2) b) to make U-N 0.5 mg/50 mL - 5 mg/50 mL of urea
nitrogen standard solutions for the calibration curve preparation.
3) Conduct the same procedures as 2) for another 50-mL volumetric flask to make a blank test
solution for the calibration curve preparation.
4) Measure absorbance at a wavelength of 450 nm of the urea nitrogen standard solutions forthe calibration curve preparation using the blank test solution for the calibration curve
preparation as the control.
5) Prepare a curve for the relationship between the urea nitrogen (U-N) concentration and theabsorbance of the urea nitrogen standard solutions for the calibration curve preparation.
c) Sample measurement
1) Regarding the solution in (4.2) b), measure absorbance by the same procedure as b) 4).
2) Obtain the urea nitrogen (U-N) content from the calibration curve to calculate the urea
nitrogen (U-N) in the analytical sample.
Comment 3 Additive recovery testing was conducted using a compound fertilizer, crustacea
grade fertilizer powdery and a preparation sample. As a result, the mean recovery
rates at the additive level of 20 % (mass fraction), 10 % (mass fraction) and 3 %(mass fraction) were 100.0 % - 102.4 %, 100.5 % - 102.0 % and 98.0 % - 103.3 %as urea nitrogen (U-N) respectively.
The results of the repeatability tests on different days using urea, a designatedblended fertilizer and a compound fertilizer to evaluate precision were analyzed
by the one-way analysis of variance. Table 1 shows the calculation results ofintermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method is about 0.2 %(mass fraction).

589

Testing Methods for Fertilizers(2021)

References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.60- 62, Yokendo, Tokyo (1988)
2)
Shinei TAKAHASHI: Determination of urea nitrogen in Fertilizer by Spectrometry,
Research Report of Fertilizer, Vol. 11, p. 54 – 62 (2018)(5)

Flow sheet for testing method: The flow sheet for urea nitrogen in fertilizers is shown
below:

590

Testing Methods for Fertilizers(2021)

6.4 Guanidine nitrogen
6.4.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B andits symbol is 6.4.a-2017 or Gd-N.a-1.
Add water to an analytical sample to extract guanidine, introduce it to a High-Performance
Liquid Chromatograph (HPLC) to isolate it with a weak acid ion-exchange column, and thenmeasure at a wavelength 190 nm to obtain guanidine nitrogen (Gd-N) in an analytical sample. In
addition, the performance of this testing method is shown in Comment 6.
Biuret nitrogen (B-N), dicyandiamide nitrogen (Dd-N), urea nitrogen(U-N) and guanylurea
nitrogen (GU-N) can be simultaneously quantified by using this method. (Refer to Comment 5).
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Potassium dihydrogen phosphate: A JIS Guaranteed Reagent specified in JIS K 9007
or a reagent of equivalent quality.
c) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
d) Guanidine nitrogen standard solution (Gd-N 2 mg/mL) (1): Put 0.515 g of guanidine
sulfate [C2H10N6･H2SO4] (2) in a weighing dish and measure the mass to the order of 0.1
mg. Add a small amount of water to dissolve, then transfer to a 100-mL volumetric flask
and add water up to the marked line.
e) Guanidine nitrogen standard solution for the calibration curve preparation (Gd-N 200µg/mL) (1): Put 10 mL of guanidine nitrogen standard solution (Gd-N 2 mg/mL) in a 100mL volumetric flask and add water up to the marked line.
f) Guanidine nitrogen standard solution (Gd-N 50 µg/mL - 100 µg/mL) (1): Put 25 mL - 50
mL of guanidine nitrogen standard solution (Gd-N 200 µg/mL) in 100-mL volumetric flasks
and add water up to the marked line.
g) Guanidine nitrogen standard solution for the calibration curve preparation (Gd-N 1
μg/mL - 50 μg/mL) (1): At the time of usage, put 1 mL - 50 mL of guanidine nitrogenstandard solution (Gd-N 100 µg/mL) in 100-mL volumetric flasks step-by-step and add
water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity as guanidine sulfate iscommercially sold.
Comment 1 Guanidine sulfate is commercially sold by FUJIFILM Wako Pure Chemical Co.,
Ltd., Kanto Chemical Co., Inc. and Tokyo Chemical Industry Co., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 7.5-mm inner diameter 100-mm long stainless steel column tube filled withweak acid ion-exchange resin.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around
190 nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g 591

Testing Methods for Fertilizers(2021)

10000 × g.
Comment 2 A column is sold under the production name Asahipak ES-502C 7C, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper
Erlenmeyer flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution (3) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (3) If there is a possibility that the guanidine nitrogen (Gd-N) concentration in thesample solution will exceed the maximum limit of the calibration curve, dilute apredetermined amount of supernatant with water.
(4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 ×g - 10000 × g centrifugal force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water (6), and shake to mix.
c) Add water up to the marked line and put it in a 1.5-mL ground-in stopper centrifugal
precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (6) If there is a possibility that the guanidine nitrogen (Gd-N) concentration in thesample solution will exceed the maximum limit of the calibration curve, dilute apredetermined amount of precisely adjusted solution with water.
Comment 3 Instead of procedures in (4.1.1) c) - d) or (4.1.2) c) - d), it is allowed to filter witha membrane filter (aperture diameter: no more than 0.5 µm) made of hydrophilic
PTFE and the filtrate can be the sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An
example of measurement conditions is shown below. Set up the measurement conditions
considering it:1) Column: A weak acid ion-exchange resin column (4.0-mm - 7.5-mm inner diameter,
100-mm - 150-mm long, 5-µm – 10-µm particle diameter)
2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 3.92 g of potassium dihydrogen phosphate and 0.12 g of phosphoricacid in water to make 1000 mL. Filter with a membrane filter (aperture diameter: no more592

Testing Methods for Fertilizers(2021)

than 0.5 µm) made of hydrophilic PTFE.
4) Flow rate: 0.6 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 190 nm
Comment 4 Eluent can be prepared as follows. Dissolve 19.6 g of potassium dihydrogen
phosphate and 0.584 g of phosphoric acid with water to make 500 mL and store in
a refrigerator. At the time of usage, dilute a predetermined volume of the solution
by a factor of 10 and filter with a membrane filter (aperture diameter: no more than
0.5 µm) made of hydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to theHigh-Performance Liquid Chromatograph, record a chromatogram at a wavelength 190 nm
and obtain a peak height.
2) Prepare a curve for the relationship between the guanidine nitrogen (Gd-N) concentrationand the peak height at a wavelength 190 nm of the respective standard solutions for thecalibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1).
2) Obtain the guanidine nitrogen (Gd-N) content from the peak height using the calibration
curve to calculate the guanidine nitrogen (Gd-N) in the analytical sample.
Comment 5 This testing method enables the simultaneous measurement of biuret nitrogen (BN), urea nitrogen (U-N), dicyandiamide nitrogen (Dd-N), guanidine nitrogen (GdN) and guanylurea nitrogen (GU-N). In that case, see 5.10.a Comment 5.
Comment 6 Additive recovery testing was conducted using a preparation sample for aguanylurea fertilizer (one brand). As a result, the mean recovery rates at theadditive level of 3.71 % (mass fraction), 1.85 % (mass fraction) and 0.371 % (massfraction) were 91.2 %, 94.0 % and 100.0 % respectively.
The results of the repeatability tests on different days using a guanylurea fertilizer
to evaluate precision were analyzed by one-way analysis of variance. Table 1
shows the calculation results of intermediate precision and repeatability.
Additionally, results from a collaborative study for testing method validation andits analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimatedto be about 0.02 % (mass fraction).

593

Testing Methods for Fertilizers(2021)

References
1)
Masahiro ECHI, Yasuharu KIMURA and Yuji SHIRAI: Determination of Urea
Nitrogen, Biuret Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl
urea Nitrogen in Fertilizer by High-Performance Liquid Chromatography: A SingleLaboratory Validation, Research Report of Fertilizer, Vol. 10, p. 72 - 85 (2017)2)
Norio FUNAKI and Yasuharu KIMURA: Determination of Urea Nitrogen, Biuret
Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogen in
Fertilizer by High-Performance Liquid Chromatography (HPLC): A Collaborative
Study, Research Report of Fertilizer, Vol. 10, p. 86 - 100 (2017)(5)

Flow sheet for testing method: An example of the flow sheet for guanidine nitrogen in
fertilizers is shown below:594

Testing Methods for Fertilizers(2021)

Reference: The chromatogram of the standard solution for calibration curve preparation of
guanidine nitrogen is shown below.

Reference diagram

HPLC chromatogram of the mixture standard solutions (10 mg/L for
each)

Peak name(1) Urea nitrogen (2) Biuret nitrogen(3) Dicyandiamide nitrogen(4) Guanidine nitrogen(5) Guanylurea nitrogen
Measurement conditions for HPLC
Column: Asahipak ES-502C 7C (7.5-mm inner diameter, 100-mm long, 9-μm
particle diameter)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)595

Testing Methods for Fertilizers(2021)

6.5 Cold buffer solution soluble nitrogen (water-soluble nitrogen)6.5.a Cold buffer solution method(1) Summary
The test method is applicable to formaldehyde processed urea fertilizers. This testing method
is classified as Type A (Def-M) and its symbol is 6.5.a-2017 or Buf(C)-N.a-1.
Add a phosphate solution (cold buffer solution) to an analytical sample to extract, add copper(II) sulfate pentahydrate, sulfuric acid and potassium sulfate, pretreat by the Kjeldahl method tochange cold buffer solution soluble nitrogen to ammonium ion and add a sodium hydroxide
solution to subject to steam distillation. Collect isolated ammonia with 0.25 mol/L sulfuric acidand measure surplus sulfuric acid by (neutralization) titration using a 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution to obtain cold buffer solution soluble nitrogen (water-soluble
nitrogen) in the analytical sample. Or collect isolated ammonia with a boric acid solution andmeasure ammonium ion by (neutralization) titration using 0.25 mol/L sulfuric acid to obtain cold
buffer solution soluble nitrogen (water-soluble nitrogen) in the analytical sample.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 byadding in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5
mL -11 mL of the supernatant in a ground-in stoppered storage container, and add 1000 mLof water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified
in JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours,
then put about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg.
Dissolve in a small amount of water, transfer to a 250-mL volumetric flask, and add water
up to the marked line (1). Put a predetermined amount of the solution in a 200-mL - 300mL Erlenmeyer flask, add a few drops of bromothymol blue solution (0.1 g/100 mL) as
an indicator, and titrate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until thecolor of the solution becomes green. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution by the following formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1 ： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent ofequivalent quality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100
mL of water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL- 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture
solution, and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L
596

Testing Methods for Fertilizers(2021)

sodium hydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following
formula (1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula(2):
Volume (B) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution equivalent to 1 mL of
0.25 mol/L sulfuric acid=V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)
V4 ：
V5 ：
C1 ：
C2 ：

……….

(2)

Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water
to make 1000 mL.
e) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodiumhydroxide specified in JIS K 8576 in water to make 500 mL.
f) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified
in JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
g) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896
in 100 mL of ethanol (95) specified in JIS K 8102.
h) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in
JIS K 8897 in 100 mL of ethanol (95) specified in JIS K 8102.
i) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
j) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green
specified in JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
k) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100mL), add equal volume of bromocresol green solution (0.5 g/100 mL).
l) Phosphate solution: Dissolve 3.63 g of potassium dihydrogen phosphate specified in JIS
K 9007 and 5.68 g of disodium hydrogen phosphate specified in JIS K 9020 in 1000 mL ofwater (5). When it is used, adjust the liquid temperature at about 25 ºC (cold buffer solution).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid)solution in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
(5) pH 7.0 ± pH 0.2
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced witha 0.1 mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
597

Testing Methods for Fertilizers(2021)(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Vertical rotating mixer: A vertical rotating mixer that can vertically rotate a 250-mL
volumetric flask at a rate of 30 - 40 revolutions/min.
b) Steam distillation apparatusc) Digestion flask: A Kjeldahl flask which can be connected to a steam distillation apparatus.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample (6), and put it into a 250 mL- Erlenmeyer flask.
b) Add about 200 mL of phosphate solution and shake to mix at the rate of 30 - 40
revolutions/min for about 30 minutes.
c) Add water up to the marked line.
d) Filter with Type 3 filter paper to make an extract.
Note (6) Prepare the test sample according to Comment 3.
Comment 3 Crush a laboratory sample with a mortar or a pestle, etc. until it completely passes
through an 850 µm aperture sieve.
Comment 4 If there is no possibility for an analytical sample to hydrolyze, it is allowed to use
water instead of a phosphoric acid solution.
Comment 5 The temperature of a solution in the procedure in (4.1) b) - d) should be no morethan 26 ºC.
(4.2) Kjeldahl digestion: Conduct digestion as shown below.
a) Put a predetermined amount of the sample solution (the equivalents of 0.5 g or less as cold
buffer solution soluble nitrogen) in a 300-mL distillation flask.
b) Add 0.1 g of copper (II) sulfate pentahydrate (7) specified in JIS K 8962, and further add 5
mL of sulfuric acid, shake to mix and heat gently to evaporate moisture.
c) After standing to cool, add 1 g of potassium sulfate specified in JIS K 8962 and heat todigest.
d) Ignite further for 30 minutes.
e) After standing to cool, add water while shaking to mix until liquid volume reaches about
30 mL and cool it to make a digestion solution.
Note (7) Crush into powder as appropriate.
(4.3) Distillation: Conduct distillation as shown below. Specific distillation procedures areaccording to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (8) of 0.25 mol/L sulfuric acid in an acceptor, (9) add a few dropsof methyl red−methylene blue mixture solution, and connect this acceptor to a steam
distillation apparatus. Or, put a predetermined amount (8) of boric acid solution (40 g/L) inan acceptor, (9) add a few drops of methyl red−bromocresol green mixture solution, andconnect this acceptor to a steam distillation apparatus.
b) Add a proper amount of sodium hydroxide solution (200 g/L - 500 g/L) (10), and immediately
connect this digestion flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at
a distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in598

Testing Methods for Fertilizers(2021)

the acceptor with a small amount of water, and pool the washing with the distillate.
Note (8) 5 mL - 20 mL(9) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL
beaker with which the distillate outlet of the steam distillation apparatus can be
immersed in 0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(10) An amount sufficient to make the solution strong alkalinity. A blue color will appear.
(4.4) Measurement: Conduct measurement as shown below.
(4.4.1) When 0.25 mol/L sulfuric acid is used in (4.3):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4).
b) Calculate the cold buffer solution soluble nitrogen in the analytical sample by the following
formula:Cold buffer solution soluble nitrogen (% (mass fraction)) in the analytical sample= (B × V6－V7) × C1 × f1 × (V8/V9) × (14.007/W2) × (100/1000)= (B × V6－V7) × C1 × f1 × (V8/V9) × (1.4007/W2)
B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1
mL of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed
for titration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide
solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V8： Constant volume (mL) of the extract in (4.1) c)
V9： Aliquot volume (mL) of the extract subjected to the Kjeldahl digestion in(4.2) a)W2 ： Mass (g) of the analytical sample(4.4.2) When a boric acid solution (40 g/L) is used in (4.3):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomeslight red (11).
b) Calculate the cold buffer solution soluble nitrogen in the analytical sample by the following
formula:Cold buffer solution soluble nitrogen (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (V11/V12) × (14.007/W2) × (100/1000)= V10 × C2 × f2 × (V11/V12) × (2.8014/W2)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV11： Constant volume (mL) of the extract in (4.1) c)
V12： Aliquot volume (mL) of the extract subjected to the Kjeldahl digestion in(4.2) a)W2 ： Mass (g) of the analytical sample
599

Testing Methods for Fertilizers(2021)

Note (11) The endpoint is reached when the color changes from green to light red.
Comment 6 The titration procedures in (2) a) Standardization, (2) c) Standardization and(4.4) can be conducted by an automatic titrator. The setup of the titration program,the determination parameter for the endpoint and vessels such as acceptors areaccording to the specification and the operation method of the automatic titrator
used.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.67- 68, Yokendo, Tokyo (1988)(5)

Flow sheet for cold buffer solution soluble nitrogen testing method: The flow sheets forcold buffer solution soluble nitrogen testing method in formaldehyde processed urea
fertilizers are shown below:
1.00 gWeigh into a 250-mL volumetric flask.
analytical sample←150 mL phosphate solution
Vertical rotating mixer (30 - 40 revolutions/min), for 30
Shaking to mix
minutes← small amount of water
Filtration
Type 3 filter paper
Extract
Figure 1 Flow sheet for cold buffer solution soluble nitrogen testing method
in formaldehyde processed urea fertilizers(Extraction procedure)

600

Testing Methods for Fertilizers(2021)

601

Testing Methods for Fertilizers(2021)

6.6 Heat buffer solution soluble nitrogen (hot-water soluble nitrogen)6.6.a Heat buffer solution method(1) Summary
The testing method is applicable to methylolurea polymerization fertilizers. This testing method
is classified as Type A(Def-M) and its symbol is 6.6.a-2017 or Buf(H)-N.a-1.
Add a heat phosphate solution (heat buffer solution) to an analytical sample to elute heat buffer
solution soluble nitrogen, add copper (II) sulfate pentahydrate, sulfuric acid and potassium
sulfate, pretreat non-dissolved matter by Kjeldahl method to change heat buffer solution soluble
nitrogen to ammonium ion and add a sodium hydroxide solution to subject to steam distillation.
Collect isolated ammonia with 0.25 mol/L sulfuric acid and measure surplus sulfuric acid by(neutralization) titration using a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution to obtain thenitrogen which is insoluble in a heat buffer solution in the analytical sample. Or collect isolated
ammonia with a boric acid solution and measure ammonium ion by (neutralization) titration using
0.25 mol/L sulfuric acid to obtain the nitrogen which is insoluble in a heat buffer solution in theanalytical sample. Subtract the nitrogen which is insoluble in a heat buffer solution from theseparately obtained total nitrogen (T-N) according to the method in 4.1.1 to calculate the nitrogen
which is soluble in a heat buffer solution (hot water-soluble nitrogen).
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 byadding in small portions while cooling, seal tightly and leave at rest for 4 - 5 days. Put 5.5
mL -11 mL of the supernatant in a ground-in stoppered storage container, and add 1000 mLof water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified
in JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours,
then put about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg.
Dissolve in a small amount of water, transfer to a 250-mL volumetric flask, and add water
up to the marked line (1). Put a predetermined amount of the solution in a 200-mL - 300mL Erlenmeyer flask, add a few drops of bromothymol blue solution (0.1 g/100 mL) as
an indicator, and titrate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until thecolor of the solution becomes green. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution by the following formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1 ： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent ofequivalent quality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100
mL of water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL
602

Testing Methods for Fertilizers(2021)- 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture
solution, and titrate with a 0.1 mol/L -0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following
formula (1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula(2):
Volume (B) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution equivalent to 1 mL of
0.25 mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water
to make 1000 mL.
e) Catalyst (5): Mix potassium sulfate specified in JIS K 8962 and copper (II) sulfate
pentahydrate (6) specified in JIS K 8983 in the ratio of 9 to 1.
f) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodiumhydroxide specified in JIS K 8576 in water to make 500 mL.
g) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified
in JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896
in 100 mL of ethanol (95) specified in JIS K 8102.
i) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in
JIS K 8897 in 100 mL of ethanol (95) specified in JIS K 8102.
j) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
k) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green
specified in JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100mL), add equal volume of bromocresol green solution (0.5 g/100 mL).
m) Heat phosphate solution: Dissolve 3.63 g of potassium dihydrogen phosphate specified
in JIS K 9007 and 5.68 g of disodium hydrogen phosphate specified in JIS K 9020 in 1000mL of water (7). When it is used, heat until it reaches boiling point (heat buffer solution).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid)solution in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL - 10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from bluepurple.
(5) A tablet is commercially available.
(6) Crush into powder as appropriate.
603

Testing Methods for Fertilizers(2021)(7) pH 7.0 ± pH 0.2
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced witha 0.1 mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Water bath: A water bath which can boil water.
b) Steam distillation apparatusc) Digestion flask: A Kjeldahl flask which can be connected to a steam distillation apparatus.
d) Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample (8) and put it in a 300-mL tall beaker.
b) Add 100 mL of heat phosphate solution and stir it gently.
c) Cover the tall beaker with a watch glass, and heat in a boiling water bath while stirring at
ten-minute intervals for about 30 minutes.
d) Immediately filter with Type 3 filter paper, transfer the whole non-dissolved matter in a
vessel on the filter paper with 100 mL of heat phosphate solution and wash the nondissolved matter with hot water.
Note (8) Prepare the test sample according to Comment 3.
Comment 3 Crush a laboratory sample with a mortar or a pestle, etc. until it completely passes
through an 850 µm aperture sieve.
(4.2) Kjeldahl digestion: Conduct digestion as shown below.
a) Put the non-dissolved matter in (4.1) d) together with the filter paper into a 300-mL - 500mL digestion flask.
b) Add 5 g - 10 g of catalyst, and further add 20 mL - 40 mL of sulfuric acid, shake to mix andheat gently.
c) After bubbles cease to form, heat until white smoke of sulfuric acid evolves.
d) Ignite until organic matters are completely digested (9).
e) After standing to cool, add a small amount of water, mix well by shaking, transfer to a 250mL - 500-mL volumetric flask with water (10), and further mix by shaking.
f) After standing to cool, add water up to the marked line to make a digestion solution.
Note (9) When the solution has finished changing color, heat further for no less than 2 hours.
(10) When the entire sample solution volume is used in measurement, it is not necessary
to transfer it to a volumetric flask.
(4.3) Distillation: Conduct distillation as shown below. Specific distillation procedures areaccording to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (11) of 0.25 mol/L sulfuric acid in an acceptor (12), add a few
drops of methyl red−methylene blue mixture solution, and connect this acceptor to a steam
distillation apparatus. Or, put a predetermined amount (11) of boric acid solution (40 g/L) in604

Testing Methods for Fertilizers(2021)

an acceptor (12), add a few drops of methyl red−bromocresol green mixture solution, andconnect this acceptor to a steam distillation apparatus.
b) Put a predetermined amount of the digestion solution in a 300-mL distillation flask, add aproper amount of sodium hydroxide solution (200 g/L - 500 g/L) (13), and immediately
connect this distillation flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at
a distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in
the acceptor with a small amount of water, and pool the washing with the distillate.
Note (11) 5 mL - 20 mL(12) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL
beaker with which the distillate outlet of the steam distillation apparatus can be
immersed in 0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(13) An amount sufficient to make the solution strong alkalinity. A blue color will appear.
(4.4) Measurement: Conduct measurement as shown below.
(4.4.1) When 0.25 mol/L sulfuric acid is used in (4.3):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4).
b) Calculate the heat buffer solution soluble nitrogen in the analytical sample by the following
formula:c) Subtract the nitrogen which is insoluble in a heat buffer solution from the separately
obtained total nitrogen (T-N) according to the method in 4.1.1 to calculate the nitrogen
which is soluble in a heat buffer solution (14).
Heat buffer solution soluble nitrogen (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (V8/V9) × (14.007/W2 ) × (100/1000)= (B × V6 － V7) × C1 × f1 × (V8/V9) × (1.4007/W2 )B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1
mL of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed
for titration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide
solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V8： Constant volume (mL) of the digestion solution in (4.2) f)
V9： Aliquot volume (mL) of the digestion solution subjected to distillation in(4.3) b)W2 ： Mass (g) of the analytical sample
Note (14) The total nitrogen (T-N) and the nitrogen which is insoluble in a heat buffer solution
use raw data without rounding numerical value.
(4.4.2) When a boric acid solution (40 g/L) is used in (4.3):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomeslight red (15).
605

Testing Methods for Fertilizers(2021)b) Calculate the heat buffer solution soluble nitrogen in the analytical sample by the following
formula:c) Subtract the nitrogen which is insoluble in a heat buffer solution from the separately
obtained total nitrogen (T-N) according to the method in 4.1.1 to calculate the nitrogen
which is soluble in a heat buffer solution
Heat buffer solution soluble nitrogen (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (V11/V12) × (14.007/W2) × (100/1000)= V10 × C2 × f2 × (V11/V12) × (2.8014/W2)
V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV11： Constant volume (mL) of the digestion solution in (4.2) f)
V12： Aliquot volume (mL) of the digestion solution subjected to distillation in(4.3) b)W2 ： Mass (g) of the analytical sample
Note (15) The endpoint is reached when the color changes from green to light red.
Comment 4 The titration procedures in (2) a) Standardization, (2) c) Standardization and(4.4) can be conducted by an automatic titrator. The setup of the titration program,the determination parameter for the endpoint and vessels such as acceptors areaccording to the specification and the operation method of the automatic titrator
used.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.68- 69, Yokendo, Tokyo (1988)

606

Testing Methods for Fertilizers(2021)(5)

Flow sheet for heat buffer solution soluble nitrogen testing method: The flow sheets forheat buffer solution soluble nitrogen testing method in methylolurea polymerization
fertilizers are shown below:

607

Testing Methods for Fertilizers(2021)

608

Testing Methods for Fertilizers(2021)

6.7 Activity coefficient of nitrogen
6.7.a Buffer solution method(1) Summary
The testing method is applicable to formaldehyde processed urea fertilizers. This testing method
is classified as Type A(Def-M) and its symbol is 6.7.a-2017 or AI-N.a-1.
Add water to an analytical sample to elute cold water-soluble nitrogen, add potassium sulfate
copper (II) sulfate pentahydrate and sulfuric acid, pretreat non-dissolved matter by Kjeldahl
method to change cold water-soluble nitrogen to ammonium ion and add a sodium hydroxide
solution to subject to steam distillation. Collect isolated ammonia with 0.25 mol/L sulfuric acidand measure surplus sulfuric acid by (neutralization) titration using a 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution to obtain cold water insoluble nitrogen in the analytical sample. Or
collect isolated ammonia with a boric acid solution and measure ammonium ion by(neutralization) titration using 0.25 mol/L sulfuric acid to obtain cold water-soluble nitrogen in
the analytical sample. Separately add a heat phosphate solution (heat buffer solution) to an
analytical sample to elute the nitrogen which is soluble in a heat buffer solution and conduct thesame procedures as above to obtain the nitrogen which is insoluble in a heat buffer solution in
the analytical sample. Subtract the nitrogen which is insoluble in a heat buffer solution from cold
water non-dissolved matter and calculate the activity coefficient of nitrogen by dividing thesubtracted value by the cold water non-dissolved matter.
(2) Reagent: Reagents are as shown below.
a) 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (1): Put about 30 mL of water in apolyethylene bottle, dissolve about 35 g of sodium hydroxide specified in JIS K 8576 byadding in small portions while cooling, seal tightly and leave at rest for 4-5 days. Put 5.5
mL -11 mL of the supernatant in a ground-in stoppered storage container, and add 1000 mLof water.
Standardization: Dry sulfamic acid reference material for volumetric analysis specified
in JIS K 8005 by leaving at rest in a desiccator at no more than 2 kPa for about 48 hours,
then put about 2.5 g in a weighing dish, and measure the mass to the order of 0.1 mg.
Dissolve in a small amount of water, transfer to a 250-mL volumetric flask, and add water
up to the marked line (1). Put a predetermined amount of the solution in a 200-mL - 300mL Erlenmeyer flask, add a few drops of bromothymol blue solution (0.1 g/100 mL) as
an indicator, and titrate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until thecolor of the solution becomes green. Calculate the factor of a 0.1 mol/L - 0.2 mol/L sodiumhydroxide solution by the following formula:
Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution (f1)
= (W1 × A × 0.01/97.095) × (V1/V2) × (1000/V3) × (1/C1)
W1 ： Mass (g) of sulfamic acid sampled
A： Purity (% (mass fraction)) of sulfamic acid
V1： Aliquot volume (mL) of sulfamic acid solution
V2： Constant volume (250 mL) of sulfamic acid solution
V3： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solutionb) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent ofequivalent quality.
c) 0.25 mol/L sulfuric acid (1) (2): Add about 14 mL of sulfuric acid to a beaker containing 100
609

Testing Methods for Fertilizers(2021)

mL of water in advance, stir well, and add water to make 1000 mL.
Standardization: Put a predetermined amount (3) of 0.25 mol/L sulfuric acid in a 200-mL- 300-mL Erlenmeyer flask, add a few drops of methyl red−methylene blue mixture
solution, and titrate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4). Calculate the volume of a 0.1 mol/L - 0.2 mol/L
sodium hydroxide solution equivalent to 1 mL of 0.25 mol/L sulfuric acid by the following
formula (1). Or, calculate the factor of 0.25 mol/L sulfuric acid by the following formula(2):
Volume (B) of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1 mL of
0.25 mol/L sulfuric acid= V4/V5………. (1)
Factor of 0.25 mol/L sulfuric acid (f2)
= (f1 × C1 × V4/V5)/(C2 × 2)

……….

(2)

V4 ：

Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed fortitration
V5： Volume (mL) of 0.25 mol/L sulfuric acid subjected to standardization
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidd) Boric acid solution (40 g/L): Dissolve 40 g of boric acid specified in JIS K 8863 in water
to make 1000 mL.
e) Catalyst (5): Mix potassium sulfate specified in JIS K 8962 and copper (II) sulfate
pentahydrate (6) specified in JIS K 8983 in the ratio of 9 to 1.
f) Sodium hydroxide solution (200 g/L - 500 g/L) (1): Dissolve 100 g - 250 g of sodiumhydroxide specified in JIS K 8576 in water to make 500 mL.
g) Bromothymol blue solution (0.1 g/100 mL): Dissolve 0.1 g of bromothymol blue specified
in JIS K 8842 in 20 mL of ethanol (95) specified in JIS K 8102, add water to make 100 mL.
h) Methyl red solution (0.1 g/100 mL): Dissolve 0.1 g of methyl red specified in JIS K 8896
in 100 mL of ethanol (95) specified in JIS K 8102.
i) Methylene blue solution (0.1 g/100 mL): Dissolve 0.1 g of methylene blue specified in
JIS K 8897 in 100 mL of ethanol (95) specified in JIS K 8102.
j) Methyl red−methylene blue mixture solution: To 2 volumes of methyl red solution (0.1g/100 mL), add 1 volume of methylene blue solution (0.1 g/100 mL).
k) Bromocresol green solution (0.5 g/100 mL): Dissolve 0.5 g of bromocresol green
specified in JIS K 8840 in 100 mL of ethanol (95) specified in JIS K 8102.
l) Methyl red−bromocresol green mixture solution: To a methyl red solution (0.1 g/100mL), add equal volume of bromocresol green solution (0.5 g/100 mL).
m) Heat phosphate solution: Dissolve 1.43 g of potassium dihydrogen phosphate specified
in JIS K 9007 and 9.10 g of dipotassium hydrogen phosphate specified in JIS K 9020 in1000 mL of water (7). When it is used, heat until it reaches boiling point (heat buffer
solution).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) This corresponds to the standard sulfuric acid solution 0.5 M (1/2 sulfuric acid)solution in the Official Methods of Analysis of Fertilizers (1992).
(3) 5 mL -10 mL(4) The endpoint is reached when the color becomes gray-green via dark blue from blue610

Testing Methods for Fertilizers(2021)

purple.
(5) A tablet is commercially available.
(6) Crush into powder as appropriate.
(7) pH 7.5 ± pH 0.2
Comment 1 A 0.1 mol/L - 0.2 mol/L sodium hydroxide solution in (2) a) can be replaced witha 0.1 mol/L sodium hydroxide solution or a 0.2 mol/L sodium hydroxide solution
conforming to ISO/IEC 17025.
Comment 2 0.25 mol/L sulfuric acid in (2) c) can be replaced with 0.25 mol/L sulfuric acidconforming to ISO/IEC 17025.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Water bath: A water bath which can boil water.
b) Steam distillation apparatusc) Digestion flask: A Kjeldahl flask which can be connected to a steam distillation apparatus.
d) Distillation flask: A Kjeldahl flask or round bottom flask that can be connected to a steam
distillation apparatus.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below. Subject the non-dissolved matters of(4.1.1) f) and (4.1.2) d) to (4.2) Kjeldahl digestion respectively.
(4.1.1) Extraction by cold watera) Weigh 1.00 g of an analytical sample (8) and put it in a 50-mL beaker.
b) Add a small amount of ethanol specified in JIS K 8101 to moisten and add 20 mL of waterat 25ºC ± 2ºC to stir.
c) Leave at rest for 15 minutes while stirring at 5-minute intervals.
d) Filter the supernatant with Type 2 filter papere) Wash non-dissolved matter with water at 25ºC ± 2ºC five times and filter the supernatant.
f) Transfer the whole non-dissolved matter on the filter paper using water at 25ºC ± 2ºC andwash the non-dissolved matter using water at the same temperature until filtrate reaches
250 mL.
Note (8) Prepare the test sample according to Comment 3.
Comment 3 Crush a laboratory sample with a mortar or a pestle, etc. until it completely passes
through an 850 µm aperture sieve.
(4.1.2) Extraction by heat phosphate solutiona) Weigh an analytical sample (8) equivalent to 0.12 g of cold non-resolved matter and put it
in a 200-mL tall beaker.
b) Add 100 mL of heat phosphate solution and stir it.
c) Cover the tall beaker with a watch glass, and heat in a boiling water bath while stirring at
ten-minute intervals for about 30 minutes.
d) Immediately filter with Type 2 filter paper (9), transfer the whole non-dissolved matter in a
vessel on the filter paper using boiling water and wash the non-dissolved matter using 100
mL of boiling water.
Note (9) If it takes 4 minutes or more for filtrating, conduct extracting anew according toComment 4.
611

Testing Methods for Fertilizers(2021)

Comment 4 After conducting the procedures in (4.1.2) a) - c), add 1 g of diatomaceous earth
to stir and conduct the procedure in (4.1.2) d).
(4.2) Kjeldahl digestion: Conduct digestion as shown below.
a) Put the non-dissolved matter in (4.1.1) f) and (4.1.2) d) together with the filter paper into
respective 300-mL - 500-mL digestion flasks.
b) Add 5 g - 10 g of catalyst, and further add 20 mL - 40 mL of sulfuric acid, shake to mix andheat gently.
c) After bubbles cease to form, heat until white smoke of sulfuric acid evolves.
d) Ignite until organic matters are completely digested (10).
e) After standing to cool, add a small amount of water, mix well by shaking, transfer to a 250mL - 500-mL volumetric flask with water (11), and further mix by shaking.
f) After cooling is complete, add water up to the marked line to make a digestion solution.
Note (10) When the solution has finished changing color, heat further for no less than 2 hours.
(11) When the entire sample solution volume is used in measurement, it is not necessary
to transfer it to a volumetric flask.
(4.3) Distillation: Conduct distillation as shown below. Specific distillation procedures areaccording to the operation method of the steam distillation apparatus used in measurement.
a) Put a predetermined amount (12) of 0.25 mol/L sulfuric acid in an acceptor (13), add a few
drops of methyl red−methylene blue mixture solution, and connect this acceptor to a steam
distillation apparatus. Or, put a predetermined amount (12) of boric acid solution (40 g/L) inan acceptor (13), add a few drops of methyl red−bromocresol green mixture solution, andconnect this acceptor to a steam distillation apparatus.
b) Put a predetermined amount of the digestion solution in a 300-mL distillation flask, add aproper amount of sodium hydroxide solution (200 g/L - 500 g/L) (14), and immediately
connect this distillation flask to the steam distillation apparatus.
c) Send steam to the distillation flask to heat the solution in the distillation flask, and distill at
a distillation rate of 5 mL/min - 7 mL/min.
d) Stop distilling when the distillate has reached 120 mL - 160 mL.
e) Wash the part of the steam distillation apparatus that came in contact with the solution in
the acceptor with a small amount of water, and pool the washing with the distillate.
Note (12) 5 mL - 20 mL(13) As an acceptor, use a 200-mL - 300-mL Erlenmeyer flask or a 200-mL - 300-mL
beaker with which the distillate outlet of the steam distillation apparatus can be
immersed in 0.25 mol/L sulfuric acid or a boric acid solution (40 g/L).
(14) An amount sufficient to make the solution strong alkalinity. A blue color will appear.
(4.4) Measurement: Conduct measurement as shown below.
(4.4.1) When 0.25 mol/L sulfuric acid is used in (4.3):a) Titrate the distillate with a 0.1 mol/L - 0.2 mol/L sodium hydroxide solution until the colorof the solution becomes gray-green (4).
b) Calculate the cold-water insoluble nitrogen (N1) and the nitrogen which is insoluble in aheat buffer solution (N2) in the analytical sample by the following formula (3):c) Obtain the activity coefficient of nitrogen in the analytical sample by the following formula(4) (15).
Cold water insoluble nitrogen (N1) or the nitrogen which is insoluble in a heat buffer612

Testing Methods for Fertilizers(2021)

solution (N2) (% (mass fraction)) in the analytical sample= (B × V6 － V7) × C1 × f1 × (V8/V9) × (14.007/W2 ) × (100/1000)= (B × V6 － V7) × C1 × f1 × (V8/V9) × (1.4007/W2 )
・・・・・

(3)

B： Volume of 0.1 mol/L -0.2 mol/L sodium hydroxide solution equivalent to 1
mL of 0.25 mol/L sulfuric acidV6： Volume (mL) of 0.25 mol/L sulfuric acid put in the acceptor in (4.2) a)
V7： Volume (mL) of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution needed
for titration
C1： Set concentration (mol/L) of 0.1 mol/L - 0.2 mol/L sodium hydroxide
solution
f1： Factor of 0.1 mol/L - 0.2 mol/L sodium hydroxide solution
V8： Constant volume (mL) of the digestion solution in (4.2) f)
V9： Aliquot volume (mL) of the digestion solution subjected to distillation in(4.3) b)W2 ： Mass (g) of the analytical sample
Activity coefficient of nitrogen (%)= ((N1－ N2)/N1) × 100
N1 ：
N2 ：

・・・・・

(4)

Cold water insoluble nitrogen (% (mass fraction))
Heat buffer solution insoluble nitrogen (% (mass fraction))

Note (15) Cold water insoluble nitrogen (N1) or the nitrogen which is insoluble in a heat buffer
solution (N2) uses raw data without rounding numerical value.
(4.4.2) When a boric acid solution (40 g/L) is used in (4.3):a) Titrate the distillate with 0.25 mol/L sulfuric acid until the color of the solution becomeslight red (16).
b) Calculate the cold-water insoluble nitrogen (N1) and the nitrogen which is insoluble in aheat buffer solution (N2) in the analytical sample by the following formula (5):c) Obtain the activity coefficient of nitrogen in the analytical sample by the formula (4) in(4.4.1) (14).
Cold water insoluble nitrogen (N1) or the nitrogen which is insoluble in a heat buffer
solution (N2) (% (mass fraction)) in the analytical sample= V10 × C2 × 2 × f2 × (V11/V12) × (14.007/W2) × (100/1000)=V10 × C2 × f2 × (V11/V12) × (2.8014/W2)
・・・・・ (3)V10： Volume (mL) of 0.25 mol/L sulfuric acid needed for titration
C2： Set concentration (0.25 mol/L) of 0.25 mol/L sulfuric acidf2： Factor of 0.25 mol/L sulfuric acidV11： Constant volume (mL) of the digestion solution in (4.2) f)
V12： Aliquot volume (mL) of the digestion solution subjected to distillation in(4.3) b)W2 ： Mass (g) of the analytical sample
Note (16) The endpoint is reached when the color changes from green to light red.
Comment 5 The titration procedures in (2) a) Standardization, (2) c) Standardization and613

Testing Methods for Fertilizers(2021)(4.4) can be conducted by an automatic titrator. The setup of the titration program,the determination parameter for the endpoint and vessels such as acceptors areaccording to the specification and the operation method of the automatic titrator
used.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.68- 69, Yokendo, Tokyo (1988)(5)

Flow sheet for the activity coefficient of nitrogen testing method: The flow sheets forthe activity coefficient of nitrogen testing method in formaldehyde processed urea
fertilizers are shown below:

Analytical sample(equivalent to 0.12 g of cold Weigh into a 200-mL tall beaker
water soluble nitrogen)←100 mL heat phosphate solution
Stirring
Heating

Boiling water bathwhile stirring at 10-minute intervals for 30 minutes

Filtration

Type 2 filter paper
Heat buffer solition non-dissolved matter
Transferto the filter paper with water (boiling)←Wash with 100 mL of water (boiling)
Heat buffer solution
non-dissolved matter
Figure 1-2 Flow sheet of the testing method for the activity coefficient of nitrogenin formaldehyde processed urea fertilizers (Extraction procedure by heat phosphate solution (4.1.2))

614

Testing Methods for Fertilizers(2021)

615

Testing Methods for Fertilizers(2021)

6.8 Initial elution rate
6.8.a Standing-in-water method(1) Summary
The testing method is applicable to coated fertilizer. This testing method is classified as TypeA(Def-E) and its symbol is 6.8.a-2017 or SDR.a-1.
An initial elution rate is a quick- acting component of coated fertilizers. Target components
include total nitrogen (T-N), ammoniacal nitrogen (A-N), nitrate nitrogen (N-N), water-soluble
phosphoric acid (W-P2O5), water- soluble potassium (W-K2O) and water-soluble magnesia (WMgO).
Add water to a laboratory sample, leave it at rest while maintaining in water at 30ºC for 24hours and obtain the initial elution flow of a target component. Separately measure thecorresponding component content by 4.1.1, 4.1.2, 4.1.3, 4.2.4, 4.3.3 or 4.6.3. Calculate an initial
elution rate dividing the initial elution flow of a target component by the corresponding
component content.
(2) Reagent: Reagents are as shown below.
a) Reagent solutions for total nitrogen: Reagents corresponding to clauses in 4.1.1 when
determining total nitrogen.
b) Reagent solutions for ammoniacal nitrogen: Reagents corresponding to clauses in 4.1.2
when determining ammoniacal nitrogen.
c) Reagent solutions for nitrate nitrogen: Reagents corresponding to clauses in 4.1.3 when
determining nitrate nitrogen.
d) Reagent solutions for water-soluble phosphoric acid: Reagents corresponding toclauses in 4.2.4 when determining water-soluble phosphoric acid.
e) Reagent solutions for water-soluble potassium: Reagents corresponding to clauses in
4.3.3 when determining water-soluble potassium.
f) Reagent solutions for water-soluble magnesia: Reagents corresponding to clauses in
4.6.4 when determining water-soluble magnesia.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) Incubator: An incubator whose temperature is 30 ºC ± 1 ºC.
b) Total nitrogen: Apparatus and instruments corresponding to clauses in 4.1.1 when
determining total nitrogen.
c) Ammoniacal nitrogen: Apparatus and instruments corresponding to clauses in 4.1.2
when determining ammoniacal nitrogen.
d) Nitrate nitrogen:Apparatus and instruments corresponding to clauses in 4.1.3 when
determining nitrate nitrogen.
e) Water-soluble phosphoric acid: Apparatus and instruments corresponding to clauses in
4.2.4 when determining water-soluble phosphoric acid.
f) Water-soluble potassium: Apparatus and instruments corresponding to clauses in 4.3.3
when determining water-soluble potassium.
g) Water-soluble magnesia: Apparatus and instruments corresponding to clauses in 4.6.4
when determining water-soluble magnesia.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 12.5 g of an analytical sample, and put it into a 300 mL- ground-in stopper
Erlenmeyer flask (1).
b) Add 250 mL of water at 30ºC ± 1ºC, put it into an incubator at 30ºC ± 1ºC and leave it atrest for 24 hours (2).
616

Testing Methods for Fertilizers(2021)c)

Filter with Type 3 filter paper (3) and shake to mix the filtrate to make a sample solution.

Note (1) Since no grinding is conducted and inhomogeneous laboratory samples are used, it
is desirable to heighten the reliability of determined values by conducting tests using
3 - 5 laboratory samples.
(2) Since an initial elution flow is estimated to be higher than usual if the laboratory
sample vibrates in water, water should be added gently. Do not shake to mix thesample solution until the filtering in c) is completed.
(3) Filter most of the solution so that non-dissolved matter remains in the Erlenmeyer
flask.
(4.2) Measurement: Conduct the measurements of the initial elution flow of a target component
as specified in respective clauses in a) - f). In addition, specific measurement procedure foreach component is carried out according to a corresponding clause.
a) Total nitrogen: Get a predetermined amount of sample solution and quantitate the total
nitrogen according to the respective clauses in 4.1.1 to make initial elution flow.
b) Ammoniacal nitrogen: Get a predetermined amount of sample solution and quantitate
ammoniacal nitrogen according to respective clauses in 4.1.2 to make the initial elutionflow.
c) Nitrate nitrogen: Get a predetermined amount of sample solution and quantitate nitrate
nitrogen according to respective clauses in 4.1.3 to make the initial elution flow.
d) Water-soluble phosphoric acid: Get a predetermined amount of sample solution andquantitate water-soluble phosphoric acid according to respective clauses in 4.2.4 to makethe initial elution flow.
e) Water-soluble potassium: Get a predetermined amount of sample solution and quantitate
water-soluble potassium according to respective clauses in 4.3.3 to make the initial elution
flow.
f) Water-soluble magnesia:
Get a predetermined amount of sample solution andquantitate water-soluble magnesia according to respective clauses in 4.6.4 to make theinitial elution flow.
(5) Calculation of initial elution ratea) Calculate an initial elution rate (%) by the following formula using the initial elution flowof a target component obtained in (4.2) and separately determine (4) the corresponding
component content (5).
Initial elution rate (%)= (C1/C2) × 100
C1： Initial elution rate of a target component (% (mass fraction))
C2： Corresponding component content (% (mass fraction))
Note (4) Determine total nitrogen (T-N), ammoniacal nitrogen (A-N), nitrate nitrogen (N-N),
water-soluble phosphoric acid (W-P2O5), water-soluble potassium (W-K2O) or
water-soluble magnesia (W-MgO) in 4.1.1, 4.1.2, 4.1.3, 4.2.4, 4.3.3 or 4.6.4 using
test samples prepared in 2.3 Preparation of test samples.
(5) The initial elution flow and corresponding component content use raw data without
rounding numerical value.
References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers
617

Testing Methods for Fertilizers(2021)(Details), p.288- 290, Yokendo, Tokyo (1988)(6)

Initial elution rate testing method: The flow sheet for initial elution rate testing method
in coated fertilizers is shown below:

618

Testing Methods for Fertilizers(2021)

6.9 Humic acid (Acid insoluble - alkali soluble component)
6.9.a Gravimetric analysis(1) Summary
The testing method is applicable to humic acid chloride fertilizers. This testing method isclassified as Type A(Def-M) and its symbol is 6.9.a-2017 or H-acid.a-1.
Add hydrochloric acid (1+9) to elute acid dissolved matter, filter non-dissolved matter andmeasure the mass of non-dissolved matter to obtain acid non-dissolved matter in the analyticalsample. Separately add hydrochloric acid (1+9) to elute acid dissolved matter, add a sodiumhydroxide solution (10 g/L) to non-dissolved matter to elute alkali dissolved matter, and filter
the non-dissolved matter to obtain acid non-dissolved alkali non-dissolved matter in theanalytical sample. Subtract acid non-dissolved alkali non-dissolved matter from acid dissolved
matter to calculate humic acid (acid insoluble alkali soluble component).
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
(3)
a)
b)
c)

Instruments: Instruments are as shown below:
Shaking apparatus
Drying apparatus: A drying apparatus that can be adjusted to 105 ºC - 110 ºC.
Crucible type glass filter: A crucible type glass filter 1G4 specified in JIS R 3503. Let
it stand to cool in a desiccator after heating at 105 ºC - 110 ºC in advance and measure themass to the order of 1 mg.
d) Ground-in stopper weighing bottles (1): Low-form weighing bottles, 50 mm × 30 mm,
specified in JIS R 3503. Let it stand to cool in a desiccator after heating at 105 ºC - 110 ºC
in advance and measure the mass to the order of 1 mg.
Note (1) Aluminum weighing dishes described in the Handbook of the Feed Analysis
Standards -2009- can also be used.

(4) Test procedures(4.1) Acid non-dissolved matter(4.1.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg and put it in a 100-mL ground-in
stopper centrifugal precipitate tube.
b) Add 50 mL of hydrochloric acid (1+9) and shake to mix by using a shaking apparatus (2)for about 1 hour.
c) Centrifuge at about 1700 × g for about five minutes (3) to remove supernatant (4).
d) Add water to stir (5) and centrifuge at about 1700 × g for about five minutes (3) to remove
supernatant (4).
e) Repeat the procedure in d) 3 times.
Note (2) When using a vertical rotating mixer, it should be adjusted to 30 - 40
revolutions/min.
(3) 16.5-cm of radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4) Remove using Komagome pipet, etc.
(5) Stir with a glass rod, wash non-dissolved matter which may have adhered to the619

Testing Methods for Fertilizers(2021)

glass rod with water and add wash to a centrifugal precipitate tube.
(4.1.2) Measurement: Conduct measurement as shown below.
a) Transfer the whole non-dissolved matter in (4.1.1) e) to a crucible type glass filter and filter
under reduced pressure.
b) Put the non-dissolved matter together with the crucible type glass filter into a drying
apparatus and heat at 105 ºC - 110 ºC for 3 hours.
c) As soon as heating is complete, transfer it to a desiccator and let it stand to cool.
d) After standing to cool, remove the crucible type glass filter from the desiccator and measure
the mass to the order of 1 mg.
(4.2) Acid non-dissolved - alkali non-dissolved matter(4.2.1) Extraction: Conduct extraction as shown below.
a) Weigh 1 g of an analytical sample to the order of 1 mg and put it in a 100-mL ground-in
stopper centrifugal precipitate tube.
b) Add 50 mL of hydrochloric acid (1+9) and shake to mix by using a shaking apparatus (2)for about 1 hour.
c) Centrifuge at about 1700 × g for about five minutes (3) to remove supernatant (4).
d) Add water to stir (5) and centrifuge at about 1700 × g for about five minutes (3) to remove
supernatant (4).
e) Repeat the procedure in d) 3 times.
f) Add 50 mL of sodium hydroxide (10 g/L) and shake to mix by using a shaking apparatus(2)
for about 1 hour.
g) Centrifuge at about 1700 × g for about five minutes (3) to remove supernatant (4).
h) Add water to stir (5) and centrifuge at about 1700 × g for about five minutes (3) to remove
supernatant (4).
i) Repeat the procedure in h) 3 times.
(4.2.2) Measurement: Conduct measurement as shown below.
a) Put the non-dissolved matter together with a ground-in stopper weighing bottle into a drying
apparatus and heat (6).
b) After standing to cool, transfer the non-dissolved matter into the ground-in stopper
weighing bottle.
c) Put the non-dissolved matter together with a ground-in stopper weighing bottle into a drying
apparatus and heat at 105 ºC - 110 ºC for 3 hours.
d) After heating, fit the stopper into the ground-in stoppered weighing bottle, and immediatelytransfer to a desiccator to let it stand to cool.
e) After standing to cool, remove the ground-in stoppered weighing bottle from the desiccator,and measure the mass to the order of 1 mg.
Note (6) Heat at the temperature to enable the procedure in (4.2.2) b).
(5) Calculation of humic acida) Calculate humic acid by the following formula
Humic acid (% (mass fraction))= (A1/W1) × 100 － (A2/W2) × 100

・・・・・

(1)

A1： Mass (g) of the acid non-dissolved matter determined in (4.1.2) d)
W1 ： Mass (g) of the analytical sample sampled in (4.1.1)a)620

Testing Methods for Fertilizers(2021)

A2： Mass (g) of the acid non-dissolved - alkali non-dissolved matter determined in(4.2.2) e)
W2 ： Mass (g) of the analytical sample sampled in (4.2.1)a)References
1)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.316- 317, Yokendo, Tokyo (1988)(6)

Humic acid testing method: The flow sheet for humic acid testing method is shown below:621

Testing Methods for Fertilizers(2021)

622

Testing Methods for Fertilizers(2021)

6.10 Sulfuric acid6.10.1623

Testing Methods for Fertilizers(2021)

6.10.2 Sulfate
6.10.2.a This method is according to 5.29.2 Sulfate analysis in “The Official Methods of Analysis
of Fertilizers 1992”.
References
1)
National Institute for Agro-Environmental Sciences, the Ministry of Agriculture,
Forestry and Fisheries: The Official Methods of Analysis of Fertilizers 1992, p.145 147, Japan Fertilizers Analysis Association, Tokyo (1992)
2)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.285- 286, Yokendo, Tokyo (1988)

624

Testing Methods for Fertilizers(2021)

6.11 Carbon dioxide
6.11.a This method is according to 5.20 Carbon dioxide analysis in “The Official Methods ofAnalysis of Fertilizers 1992”.
References
1)
National Institute for Agro-Environmental Sciences, the Ministry of Agriculture,
Forestry and Fisheries: The Official Methods of Analysis of Fertilizers 1992, p.121 123, Japan Fertilizers Analysis Association, Tokyo (1992)
2)
Masayoshi KOSHINO: Second Revision of The Methods of Analysis of Fertilizers(Details), p.259- 261, Yokendo, Tokyo (1988)

625

Testing Methods for Fertilizers(2021)

7. Nitrification inhibitor
7.1 2-amino-4-chloro-6-methylpyrimidine (AM)
7.1.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing 2-amino-4-chloro-6-methylpyrimidine(AM). This testing method is classified as Type C and its symbol is 7.1.a-2017 or AM.a-1.
Add methanol − water (1+1) to an analytical sample to extract 2-amino-4-chloro-6methylpyrimidine, introduce it into a High-Performance Liquid Chromatograph (HPLC), isolate withan octadecyl silylation silica gel column, and measure at a wavelength 295 nm to obtain 2-amino-4chloro-6-methylpyrimidine (AM) in an analytical sample. In addition, the performance of this testing
method is shown in Comment 6.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
c) Methanol: Methanol used in the eluent of a High-Performance Liquid Chromatograph is aregent of High-Performance Liquid Chromatograph analysis grade or equivalents.
d) 2-amino-4-chloro-6-methylpyrimidine standard solution (1 mg/mL) (1): Put 0.1 g of 2amino-4-chloro-6-methylpyrimidine [C5H6ClN3] (2) in a weighing dish and measure the mass tothe order of 0.1 mg. Add methanol - water (1+1) to dissolve, transfer to a 100-mL volumetricflask and add the same solvent up to the marked line. Store in a refrigerator, and do not use after
6 months after preparation.
e) 2-amino-4-chloro-6-methylpyrimidine standard solution (0.1 mg/mL): In the case of usage,
put 10 mL of 2-amino-4-chloro-6-methylpyrimidine standard solution (1 mg/mL) in a 100-mL
volumetric flask and add methanol - water (1+1) up to the marked line.
f) 2-amino-4-chloro-6-methylpyrimidine standard solution (10 µg/mL - 50 µg/mL) for thecalibration curve preparation: In the case of usage, put 5 mL - 25 mL of 2-amino-4-chloro6-methylpyrimidine standard solution (0.1 mg/mL) for the calibration curve preparation in 50mL volumetric flasks step-by-step and add methanol - water (1+1) up to the marked line.
g) 2-amino-4-chloro-6-methylpyrimidine standard solution (1 µg/mL - 10 µg/mL) for thecalibration curve preparation: In the case of usage, put 2.5 mL - 25 mL of 2-amino-4-chloro6-methylpyrimidine standard solution (20 µg/mL) for the calibration curve preparation in 50mL volumetric flasks step-by-step and add methanol - water (1+1) up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity is commercially sold as 2-amino4-chloro-6-methylpyrimidine.
Comment 1 2-amino-4-chloro-6-methylpyrimidine is commercially sold by FUJIFILM Wako Pure
Chemical Co., Ltd. and Kanto Chemical Co., Inc.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
filled with silica gel, to which octadecyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 295
nm.
626

Testing Methods for Fertilizers(2021)b) Magnetic stirrerc) Centrifugal separator:
A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
e) Acidic alumina cartridge column: Link a 10-mL cylinder to a column (3) that is filled with
500 mg - 1 g of acidic alumina, put 3 mL of methanol and let it flow down.
Note (3) A cartridge with a 3-mL - 6-mL column filled with 500 mg - 1 g of silica gel can be used.
Comment 2 A column is sold under production names such as Inertsil ODS, Mightysil RP-18, Lcolumn ODS, Shim-pack VP-ODS, Silica C18M 4D, Puresil C18, COSMOSIL 5C18MS-II, etc.
Comment 3 An acidic alumina cartridge is commercially sold under production names such as
Bond Elut AL-A, Sep-Pak Alumina-A and Supelclean LC-Alumina-A.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of methanol - water (1+1) and stir it by using a magnetic stirrer for about 30
minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at about 1700 × g centrifugal force for about five minutes (4) and use thesupernatant as an extract (5).
Note (4) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(5) If there is a possibility that the 2-amino-4-chloro-6-methylpyrimidine in the sample
solution exceeds the maximum limit of the calibration curve, dilute a predeterminedamount of extract with methanol water (1+1).
(4.2) Cleanup: Conduct cleanup as shown below:a) Transfer the extract to an acidic alumina cartridge column.
b) Dispose of about the first 3 mL of effluent and then put about the next 2 mL in a test tube.
c) Put the effluent in a 1.5-mL ground-in stopper centrifugal precipitate tube (6).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (7) and use thesupernatant as a sample solution.
Note (6) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(7) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 4 Instead of the procedures in (4.2) c) - d), it is allowed to filter with a membrane filter(aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate can be thesample solution.
Comment 5 The test is possible by the following procedures in the case of fertilizers not containing
organic matters.
627

Testing Methods for Fertilizers(2021)

The procedures in (4.1) c) - d) and (4.2) a) - b) are omitted and “Put the effluent” in(4.2) c) is replaced with the “After allowing to stand still, put the supernatant” tooperate.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph (HPLC) used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph is shown below.
Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter) to which octadecyl chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent: Methanol - water (4+6)4) Flow rate: 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 295 nmb) Calibration curve preparation
1) Inject 10 µL of respective 2-amino-4-chloro-6-methylpyrimidine standard solutions for thecalibration curve preparation to the High-Performance Liquid Chromatograph, record achromatogram at a wavelength 295 nm and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 295 nm of the respective 2-amino-4-chloro-6-methylpyrimidine standard solutions
for the calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain 2-amino-4-chloro-6-methylpyrimidine content from the calibration curve to calculate 2amino-4-chloro-6-methylpyrimidine (AM) in the analytical sample.
Comment 6 Recovery testing was conducted using compound fertilizer (1 sample) and blended
fertilizer (2 samples), as a result, the mean recovery rates of 2-amino-4-chloro-6methylpyrimidine at the concentration level of 1.0 % (mass fraction), 0.4 % (massfraction) and 0.1 % (mass fraction) were 99.1 % - 100.5 %, 99.3 % - 101.6 % and100.2 % - 100.7 %.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005 % (mass fraction).
References
1)
Yuji SHIRAI: The volumetric analysis of 2-amino-4-chloro-6-methylpyrimidine infertilizers with High-Performance Liquid Chromatograph, Validation Report of Fertilizers(in Japanese), 44 (3), p. 26 - 41(1991)

628

Testing Methods for Fertilizers(2021)(5)

Flow sheet for 2-amino-4-chloro-6-methylpyrimidine (AM):The flow sheet for 2-amino-4-chloro-6-methylpyrimidine in fertilizers is shown below:

1.00 g200-mL of ground-in stopper Erlenmeyer flask
analytical sample← 100 mL of methanol-water (1+1)
Stirring
Centrifugal separation
CleanupCentrifugal separation

Magnetic stirrer, 10 minutes
Ground-in stopper centrifugal precipitate tube,
1700 × g , 5 minutes
Acidic alumina cartridge column
Ground-in stopper centrifugal precipitate tube,
8000 × g - 10000 × g , 5 minutes

Sample solution
Measurement
FigureHigh-Performance Liquid Chromatograph

Flow sheet for 2-amino-4-chloro-6-methylprimidine (AM) in fertilizers.

Reference: An example of the HPLC chromatogram of 2-amino-4-chloro-6-methylpyrimidine(AM) standard solution for the calibration curve preparation is shown below.

Reference diagram: HPLC chromatogram of 2-amino-4-chloro-6-methylpyrimidine(AM) standard solution
Measurement conditions for HPLC
Column: Mightysil RP-18 (4.6-mm inner diameter, 150-mm long, 5-µm particle
diameter)
2-amino-4-chloro-6-methylpyrimidine standard solution (the equivalents of 100 ng)
Other conditions are according to the example of HPLC measurement conditions in(4.3) a)629

Testing Methods for Fertilizers(2021)

7.2 1-amidino-2-thiourea (ASU)
7.2.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing 1-amidino-2-thiourea (ASU). This testing
method is classified as Type B and its symbol is 7.2.a-2017 or ASU.a-1.
Add water to an analytical sample to extract 1-amidino-2-thiourea, introduce it into a HighPerformance Liquid Chromatograph (HPLC), isolate with an octadecyl silylation silica gel column,
and measure at a wavelength 262 nm to obtain 1-amidino-2-thiourea (ASU) in an analytical sample.
In addition, the performance of this testing method is shown in Comment 4.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Methanol: Methanol used in the eluent of a High-Performance Liquid Chromatograph is aregent of High-Performance Liquid Chromatograph analysis grade or equivalents.
c) 1-sodium hexasulfonate: A reagent of ion pair chromatography analysis grade or equivalents.
d) Acetic acid: A regent of High-Performance Liquid Chromatograph analysis grade orequivalents.
e) 1-amidino-2-thiourea standard solution (1 mg/mL) (1): Put 0.1 g of 1-amidino-2-thiourea[C2H6N4S] (2) in a weighing dish and measure the mass to the order of 0.1 mg. Add water todissolve, transfer to a 100-mL volumetric flask and add water up to the marked line. Store in arefrigerator, and do not use after 6 months after preparation.
f) 1-amidino-2-thiourea standard solution (0.1 mg/mL): In the case of usage, put 10 mL of 1amidino-2-thiourea standard solution (1 mg/mL) in a 100-mL volumetric flask and add water
up to the marked line.
g) 1-amidino-2-thiourea standard solution (10 µg/mL - 50 µg/mL) for the calibration curve
preparation: In the case of usage, put 5 mL - 25 mL of 1-amidino-2-thiourea standard solution(0.1 mg/mL) in 50-mL volumetric flasks step-by-step and add water up to the marked line.
h) 1-amidino-2-thiourea standard solution (1 µg/mL - 10 µg/mL) for the calibration curve
preparation: In the case of usage, put 2.5 mL - 25 mL of 1-amidino-2-thiourea standard
solution (20 µg/mL) for the calibration curve preparation in 50-mL volumetric flasks step-bystep and add water up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity is commercially sold as 1amidino-2-thiourea.
Comment 1 1-amidino-2-thiourea is sold under the name guanylthiourea by Tokyo Chemical
Industry Co., Ltd, and under the name amidino thiourea by Kanto Chemical Co., Inc.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
filled with silica gel, to which octadecyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 262
nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
630

Testing Methods for Fertilizers(2021)

Comment 2 A column is sold under production names such as Inertsil ODS, Mightysil RP-18, Lcolumn ODS, Shim-pack VP-ODS, Silica C18M 4D, Puresil C18 and COSMOSIL
5C18-MS-II.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution (3) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (3) If there is a possibility that the 1-amidino-2-thiourea concentration in the sample solution
exceeds the maximum limit of the calibration curve, dilute a predetermined amount ofsupernatant with water.
(4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 3 Instead of the procedures in (4.1) c) - d), it is allowed to filter with a membrane filter(aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph (HPLC) is shown
below. Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter) to which octadecyl chemically bonds.
2) Column bath temperature: 30 °C - 45 °C
3) Eluent: Dissolve 0.94 g of sodium 1-hexasulfonic acid in 1000 mL of methanol water (2+8),
adjust to pH 3.15 with acetic acid and filter with a membrane filter (aperture diameter: no morethan 0.5-µm) made of hydrophilic PTFE (1).
4) Flow rate: 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 262 nmb) Calibration curve preparation
1) Inject 10 µL of respective 1-amidino-2-thiourea standard solutions for the calibration curve
preparation to the High-Performance Liquid Chromatograph, record a chromatogram at awavelength 262 nm and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 262 nm of the respective 1-amidino-2-thiourea standard solutions for the calibration
curve preparation.
c) Sample measurement631

Testing Methods for Fertilizers(2021)

1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the 1-amidino-2-thiourea content from the calibration curve to calculate 1-amidino-2thiourea (ASU) in the analytical sample.
Comment 4 Recovery testing with triplicates measurement was conducted using compound
fertilizer (2 samples), as a result, the mean recovery rates of 1-amidino-2-thiourea atthe concentration level of 1.0 % (mass fraction), 0.5 % (mass fraction) and 0.25 %(mass fraction) were 99.0 % - 104.3 %, 97.7 % - 100.7 % and 99.7 % - 101.3 %.
Additionally, results from a collaborative study for test method validation and its
analysis are in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005 % (mass fraction).
Table 1 Analysis resultsof the collaborative study
for the test method validation of 1-amidino-2-thiourea (ASU)
4)
5)
6)
2)
Number of
sr
RSD r
sR
Mean
Sample name
1)
3)
3)
3)
(%)
laboratories
(%)
(%)
(%)
10
0.093
0.009
9.1
0.010
Compound fertilizer 1
10
0.246
0.021
8.6
0.021
Compound fertilizer 2
10
0.511
0.018
3.6
0.025
Compound fertilizer 3
10
0.759
0.039
5.1
0.040
Compound fertilizer 4
10
1.020
0.039
3.8
0.044
Compound fertilizer 5
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

7)

RSD R
(%)
11.2
8.6
4.9
5.3
4.3

References
1)
Kazunori CHIBA： Analysis method of 1-amidino-2-thiourea (ASU) of Nitrification
inhibitor in fertilizers with High-Performance Liquid Chromatograph, Validation Reportof Fertilizers (in Japanese), 43 (4), p. 15 - 22 (1990)
2)
Shigehiro KAI and Erina WATABE: Determination of 1-Amidino-2-thiourea as a
Nitrification Inhibitor in Compound
Fertilizer by High-Performance Liquid
Chromatography: A Collaborative Study, Research Report of Fertilizers, Vol. 6, p. 36 42 (2013)

632

Testing Methods for Fertilizers(2021)(5)

Flow sheet for 1-amidino-2-thiourea: The flow sheet for 1-amidino-2-thiourea in fertilizers isshown below:

1.00 g analytical sample

200-mL ground-in stopper Erlenmeyer flask← 100 mL of water
Stirring

Magnetic stirrer, 10 minutes

Standing still

Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
8000 × g - 10000 × g , 5 minutes

Sample solution
Measurement
FigureHigh-Performance Liquid Chromatograph

Flow sheet for 1-amidino-2-thiourea (ASU) in fertilizers.

Reference: An example of the HPLC chromatogram of 1-amidino-2-thiourea (ASU) standard
solution for the calibration curve preparation is shown below.

Reference diagram: HPLC chromatogram of 1-amidino-2-thiourea (ASU) standard solution
Measurement conditions for HPLC
Column: Mightysil RP-18 (4.6-mm inner diameter, 150-mm long, 5-µm particle
diameter)
1-amidino-2-thiourea standard solution (the equivalents of 200 ng)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)633

Testing Methods for Fertilizers(2021)

7.3 4-amino-1,2,4-triazole hydrochloride (ATC)7.3.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing 4-amino-1,2,4-triazole hydrochloride(ATC) but not containing organic matters. This testing method is classified as Type C and its symbolis 7.3.a-2017 or ATC.a-1.
Add methanol to an analytical sample to extract 4-amino-1,2,4-triazole hydrochloride, introduce it
into a High-Performance Liquid Chromatograph (HPLC), isolate with an aminopropyl silica gelcolumn, and measure at a wavelength 220 nm to obtain 4-amino-1,2,4-triazole hydrochloride (ATC)in an analytical sample. In addition, the performance of this testing method is shown in Comment 4.
(2) Reagent: Reagents are as shown below.
a) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
b) Methanol: Methanol used in the eluent of a High-Performance Liquid Chromatograph is aregent of High-Performance Liquid Chromatograph analysis grade or equivalents.
c) Acetonitrile: Acetonitrile used in the eluent of a High-Performance Liquid Chromatograph isa regent of High-Performance Liquid Chromatograph analysis grade or equivalents.
d) 4-amino-1,2,4-triazole standard solution (1 mg/mL) (1)(2): Put 0.1 g of 4-amino-1,2,4-triazole[C2H4N4] (3) in a weighing dish and measure the mass to the order of 0.1 mg. Add methanol todissolve, transfer to a 100-mL amber volumetric flask and add methanol to the marked line.
Store in a refrigerator, and do not use after 6 months after preparation.
e) 4-amino-1,2,4-triazole standard solution (0.1 mg/mL): In the case of usage, put 10 mL of 4amino-1,2,4-triazole standard solution (1 mg/mL) in a 100-mL volumetric flask and add
methanol up to the marked line.
f) 4-amino-1,2,4-triazole standard solution (10 µg/mL - 50 µg/mL) for the calibration curve
preparation: In the case of usage, put 5 mL - 25 mL of 4-amino-1,2,4-triazole standard solution(0.1 mg/mL) in 50-mL volumetric flasks step-by-step and add methanol up to the marked line.
g) 4-amino-1,2,4-triazole standard solution (1 µg/mL - 10 µg/mL) for the calibration curve
preparation: In the case of usage, put 2.5 mL - 25 mL of 4-amino-1,2,4-triazole standard
solution for the calibration curve preparation (20 µg/mL) in 50-mL volumetric flasks step-bystep and add methanol up to the marked line.
Note (1) The solution contains 1.434 mg/mL as 4-amino-1,2,4-triazole hydrochloride.
(2) This is an example of preparation; prepare an amount as appropriate.
(3) A reagent of no less than 98 % (mass fraction) in purity is commercially sold as 4-amino1,2,4-triazole.
Comment 1 4-amino-1,2,4-triazole is sold under production names such as 4-amino-1,2,4-triazole
by FUJIFILM Wako Pure Chemical Co., Ltd., and Tokyo Chemical Industry Co., Ltd,and 4-amino-4H-1,2,4-triazole by Kanto Chemical Co., Inc.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A column of 4 mm - 6 mm inner diameter and 150 mm - 250 mm long stainlesssteel column tube filled with silica gel, to which amino or amino propyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 220
nm.
634

Testing Methods for Fertilizers(2021)b) Magnetic stirrerc) High speed centrifugal separator:× g.

A centrifugal separator that can work at 8000 × g - 10000

Comment 2 A column is sold under production names such as Hibar LiChrosorb NH2, Inertsil NH2,
Unison UK-Amino, Mightysil NH2, Shim-pack CLC-NH2, Shodex NH-5A, Unisil Q
NH2, etc.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of methanol and stir it with using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put a supernatant solution in a 1.5-mL ground-in stopper centrifugal
precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 3 Instead of the procedures in (4.1) c) - d), it is allowed to filter with a membrane filter(aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph is shown below.
Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter) to which amino or amino propyl chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent: Acetonitrile - methanol (9+1)4) Flow rate: 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 220 nmb) Calibration curve preparation
1) Inject 10 µL of respective 4-amino-1,2,4-triazole standard solutions for the calibration curve
preparation to the High-Performance Liquid Chromatograph, record a chromatogram at awavelength 220 nm and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 220 nm of the 4-amino-1,2,4-triazole standard solutions for the respective
calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the amount of 4-amino-1,2,4-triazole from the calibration curve to calculate 4-amino1,2,4-triazole in the analytical sample.
635

Testing Methods for Fertilizers(2021)

3) Calculate the 4-amino-1,2,4-triazole hydrochloride (ATC) by the following formula.
4-amino-1,2,4-triazole hydrochloride in the analytical sample (% (mass fraction))= A × 1.434
A：

4-amino-1,2,4-triazole hydrochloride in the analytical sample (% (mass fraction))

Comment 4 Recovery testing was conducted using compound fertilizer (2 samples), as a result, themean recovery rates of 4-amino-1,2,4-triazole hydrochloride at the concentration levelof 0.5 % (mass fraction), 0.3 % (mass fraction) and 0.2 % (mass fraction) were 100.2 %- 104.9 %, 100.8 % - 103.0 % and 100.7 % - 104.2 %.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005 % (mass fraction).
References
1)
Koichi SAKAGAMI: Analysis methods of 4-amino-1,2,4-triazole hydrochloride with
High-Performance Liquid Chromatography, Validation Report of Fertilizers (in Japanese),40 (4), p.9 - 16 (1987)(5)

Flow sheet for 4-amino-1,2,4-triazole hydrochloride (ATC): An example of the flow sheet
for 4-amino-1,2,4-triazole hydrochloride in fertilizers is shown below:

1.00 g analytical sample

200-mL ground-in stopper Erlenmeyer flask← 100 mL of Methanol
Stirring

Magnetcic stirrer, 10 minutes

Standing still

Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
8000 × g - 10000 × g , 5 minutes

Sample solution
Measurement
FigureHigh-Performance Liquid Chromatograph

Flow sheet for 4-amino-1,2,4-triazole hydrochloride (ATC) in fertilizers

636

Testing Methods for Fertilizers(2021)

7.4 N-2,5-dichlorophenyl succinamic acid (DCS)
7.4.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing N-2,5-dichlorophenyl succinamic acid
(DCS) but not containing organic matters. This testing method is classified as Type C and its symbolis 7.4.a-2017 or DCS.a-1.
Add methanol - phosphoric acid (996+4) and water to an analytical sample to extract N-2,5dichlorophenyl succinamic acid (DCS), introduce it into a High-Performance Liquid Chromatograph(HPLC), isolate with octadecyl silylation silica gel column, and measure at a wavelength 246 nm toobtain N-2,5-dichlorophenyl succinamic acid (DCS) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 3.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
c) Methanol: Methanol used in the eluent of a High-Performance Liquid Chromatograph is aregent of High-Performance Liquid Chromatograph analysis grade or equivalents.
d) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
e) N-2,5-dichlorophenyl succinamic acid standard solution (1 mg/mL) (1): Put 0.1 g of N-2,5dichlorophenyl succinamic acid [C10H9Cl2NO3] in a weighing dish and measure the mass to theorder of 0.1 mg. Add methanol to dissolve, transfer to a 100-mL volumetric flask and add
methanol to the marked line. Store in a refrigerator, and do not use after 6 months after
preparation.
f) N-2,5-dichlorophenyl succinamic acid standard solution (0.1 mg/mL): In the case of usage,
put 10 mL of N-2,5-dichlorophenyl succinamic acid standard solution (1 mg/mL) in a 100-mL
volumetric flask and add methanol up to the marked line.
g) N-2,5-dichlorophenyl succinamic acid standard solution (10 µg/mL - 50 µg/mL) for thecalibration curve preparation: In the case of usage, put 5 mL - 25 mL of N-2,5-dichlorophenyl
succinamic acid standard solution (0.1 mg/mL) in 50-mL volumetric flasks step-by-step andadd methanol up to the marked line.
h) N-2,5-dichlorophenyl succinamic acid standard solution (1 µg/mL - 10 µg/mL) for thecalibration curve preparation: In the case of usage, put 2.5 mL - 25 mL of N-2,5dichlorophenyl succinamic acid standard solution for the calibration curve preparation (20µg/mL) in 50-mL volumetric flasks step-by-step and add methanol up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
filled with silica gel, to which octadecyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 246
nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
637

Testing Methods for Fertilizers(2021)

Comment 1 A column is sold under production names such as Inertsil ODS, Mightysil RP-18, Lcolumn ODS, Shim-pack VP-ODS, Silica C18M 4D, Puresil C18 and COSMOSIL
5C18-MS-II.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of methanol - phosphate (996+4) and stir it with a magnetic stirrer for about 30
minutes.
c) After allowing to stand still, put a supernatant solution (2) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (3).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (4) and use thesupernatant as a sample solution.
Note (2) If there is a possibility that the N-2,5-dichlorophenyl succinamic acid concentration in
the sample solution exceeds the maximum limit of the calibration curve, dilute apredetermined amount of the outflow solution with methanol.
(3) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(4) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 2 Instead of the procedures in (4.1) c) - d), it is allowed to filter with a membrane filter(aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph is shown below.
Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter) to which octadecyl chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent: Methanol - water (5) (55 + 45)
4) Flow rate: 0.8 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 246 nm
Note(5) Adjust the water used to pH 3 with phosphoric acid in advance.

b) Calibration curve preparation
1) Inject 10 µL of respective N-2,5-dichlorophenyl succinamic acid standard solutions for thecalibration curve preparation to the High-Performance Liquid Chromatograph, record achromatogram at a wavelength 246 nm and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 246 nm of the respective N-2,5-dichlorophenyl succinamic acid standard solution
for the calibration curve preparation.
638

Testing Methods for Fertilizers(2021)c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the N-2,5-dichlorophenyl succinamic acid content from the calibration curve to calculate
N-2,5-dichlorophenyl succinamic acid (DCS) in the analytical sample.
Comment 3 Recovery testing was conducted using compound fertilizer (2 samples) and blended
fertilizer (1 sample), as a result, the mean recovery rates of N-2,5-dichlorophenyl
succinamic acid at the concentration level of 0.4 % (mass fraction), 0.2 % (massfraction) and 0.1 % (mass fraction) were 100.9 % - 101.4 %, 100.8 % - 101.4 % and101.2 % - 103.4 %.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005 % (mass fraction).
References
1)
Akira KUBO: Analysis methods of N-2,5-dichlorophenyl succinamic acid (DCS) of
Nitrification suppression materials in fertilizers with High-Performance Liquid
Chromatograph, Validation Report of Fertilizers (in Japanese), 44 (4), p.25 - 36 (1991).
(5)

Flow sheet for N-2,5-dichlorophenyl succinamic acid (DCS): The flow sheet for N-2,5dichlorophenyl succinamic acid (DCS) in fertilizers is shown below:
1.00 g analytical sample
200-mL ground-in stopper Erlenmeyer flask← 100 mL of methanol phosphoric acid (996+4)
Stirring
Magnetic stirrer, 30 minutes
Standing still
Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
8000 × g - 10000 × g , 5 minutes

Sample solution
Measurement
FigureHigh-Performance Liquid Chromatograph

Flow sheet for N-2,5-dichlorophenyl succinamic acid (DCS) in fertilizers

639

Testing Methods for Fertilizers(2021)

Reference: An example of the HPLC chromatogram of N-2,5-dichlorophenyl succinamic acid
(DCS) standard solution for the calibration curve preparation is shown below.

Reference diagram: HPLC chromatogram of N-2,5-dichlorophenyl succinamic acid
Measurement conditions for HPLC
Column: Mightysil RP-18 (4.6-mm inner diameter, 150-mm long, 5-µm particle
diameter)
N-2,5-dichlorophenyl succinamic acid standard solution (the equivalents of 100 ng)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)640

Testing Methods for Fertilizers(2021)

7.5 Dicyandiamide (Dd)
7.5.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing dicyandiamide (Dd). This testing method isclassified as Type B and its symbol is 7.5.a-2017 or Dd.a-1.
Add water to an analytical sample, leave at rest for a little while and add methanol to extract
dicyandiamide. After removing interfering substances with a silica gel cartridge column, introduce it
into a High-Performance Liquid Chromatograph (HPLC), isolate with an aminopropyl silica gelcolumn, and measure at a wavelength 215 nm to obtain dicyandiamide (Dd) in an analytical sample.
In addition, the performance of this testing method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
c) Methanol: Methanol used in the eluent of a High Performance Liquid Chromatograph is aregent of High Performance Liquid Chromatograph analysis grade or equivalents.
d) Acetonitrile: A reagent of High Performance Liquid Chromatograph analysis grade orequivalents.
e) Dicyandiamide standard solution (1 mg/mL) (1): Put 0.1 g of dicyandiamide [C2H4N4] (2) in aweighing dish and measure the mass to the order of 0.1 mg. Add a small amount of methanol todissolve, transfer to a 100-mL volumetric flask and add the solvent up to the marked line. Storein a refrigerator, and do not use after 6 months after preparation.
f) Dicyandiamide standard solution (0.1 mg/mL): At the time of usage, put 10 mL of
dicyandiamide standard solution (1 mg/ mL) in a 100-mL volumetric flask and add methanol
up to the marked line.
g) Dicyandiamide standard solution (10 µg/ mL - 50 µg/ mL) for the calibration curve
preparation: At the time of usage, put 5 mL - 25 mL of dicyandiamide standard solution (0.1
mg/ mL) in 50-mL volumetric flasks step-by-step and add methanol up to the marked line.
h) Dicyandiamide standard solution (1 µg/mL - 10 µg/mL) for the calibration curve
preparation: In the case of usage, put 2.5 mL - 25 mL of dicyandiamide standard solution forthe calibration curve preparation (20 µg/mL) in 50-mL volumetric flasks step-by-step and add
methanol up to the marked line.
i) Sodium sulfate: A JIS Guaranteed Reagent specified in JIS K 8987 or a reagent of equivalentquality.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % in purity is commercially sold as dicyandiamide.
Comment 1 Dicyandiamide is commercially sold as dicyanodiamide by FUJIFILM Wako Pure
Chemical Co., Ltd. and Kanto Chemical Co., Inc.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A column of 4 mm - 6 mm inner diameter and 150 mm - 250 mm long stainlesssteel column tube filled with silica gel, to which amino or amino propyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 40 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 215
nm.
641

Testing Methods for Fertilizers(2021)b) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
e) Silica gel cartridge column: Link a 10-mL cylinder to the column (3) filled with 500 mg - 1
g of silica gel, add 3 mL of methanol to let it flow down.
Note (3) A cartridge with a 3-mL - 6-mL column filled with 500 mg – 1 g of silica gel can beused.
Comment 2 A column is sold under production names such as Hibar LiChrosorb NH2, Inertsil NH2,
Unison UK-Amino, Mightysil NH2, Shim-pack CLC-NH2, Shodex NH-5A and Unisil
Q NH2.
Comment 3 A silica gel cartridge column is commercially sold under production names such as
Sep-Pak Plus Silica, InertSep Si.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL ground-in stopper Erlenmeyer
flask.
b) Add 1 mL of water (4) and leave at rest for 5 minutes.
c) Add about 100 mL of methanol, and shake to mix by reciprocating vertically at 300 times/min(amplitude of 40 mm) for about 10 minutes.
d) Add an appropriate amount of sodium sulfate (5).
e) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
f) Centrifuge it at about 1700 × g centrifugal force for about five minutes (6) and use thesupernatant (7) as an extract.
Note (4) Mix well until the whole sample comes in contact with water.
(5) About 5 g - 10 g.
(6) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(7) If there is a possibility that the concentration of dicyandiamide in the sample solution
exceeds the maximum limit of the calibration curve, dilute a predetermined amount of
the extract with methanol.
(4.2) Cleanup: Conduct cleanup as shown below:a) Put the extract in a silica gel cartridge column.
b) Dispose of about the first 3 mL of effluent and then put about the next 2 mL in a test tube.
c) Put the effluent in a 1.5-mL ground-in stopper centrifugal precipitate tube (8).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (9) and use thesupernatant as a sample solution.
Note (8) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(9) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
642

Testing Methods for Fertilizers(2021)

Comment 4 Instead of the procedures in (4.2) c) - d), it is allowed to filter with a membrane filter(aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate can be thesample solution.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph is shown below.
Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter) to which amino or amino propyl chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent: Acetonitrile - methanol (6+1)
4) Flow rate: 0.5 mL/min - 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 215 nmb) Calibration curve preparation
1) Inject 10 µL of respective dicyandiamide standard solutions for the calibration curve
preparation to the High-Performance Liquid Chromatograph, record a chromatogram at awavelength 215 nm, and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 215 nm of the respective dicyandiamide standard solutions for the calibration curve
preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain dicyandiamide content from the calibration curve to calculate dicyandiamide (Dd) in theanalytical sample.
Comment 5 Recovery testing was conducted using inorganic compound fertilizer (2 samples) andorganic compound fertilizer (3 samples), as a result, the mean recovery rates at theconcentration level of 2 % (mass fraction) and 0.2% (mass fraction) were 101.2 % 102.6 % and 98.4 % - 100.6 %.
Additionally, results from a collaborative study for test method validation and its
analysis are in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.01 % (mass fraction).

643

Testing Methods for Fertilizers(2021)

Sample name

Table 1 Analysis results of the collaborative study
for the test method validation of dicyandiamide
4)
5)
6)
2)
Number of
sr
RSD r
sR
Mean
1)
3)
3)
3)
laboratories
(%)
(%)
(%)
(%)

7)

RSD R
(%)

Compound fertilizer 1

11

0.263

0.009

3.2

0.019

7.4

Compound fertilizer 2

11

2.04

0.04

1.7

0.07

3.2

Compound fertilizer 3

13

0.548

0.011

2.0

0.033

6.0

Compound fertilizer 4

12

0.423

0.013

3.2

0.022

5.2

Compound fertilizer 5
12
1.02
0.01
1.4
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation

0.04

4.3

References
1)
Masakazu SAIKI: Development of High-Performance Liquid Chromatography for
Determination of Dicyandiamide as a Nitrification Inhibitor in Fertilizer. Research Reportof Fertilizer, Vol. 3, p. 43 - 50 (2010)
2)
Masakazu SAIKI: Determination of Dicyandiamide as a Nitrification Inhibitor in
Fertilizer by High-Performance Liquid Chromatography: Collaborative Study, Research
Report of Fertilizer, Vol. 4, p. 16 - 22 (2011)644

Testing Methods for Fertilizers(2021)(5)

Flow sheet for dicyandiamide: The flow sheet for dicyandiamide in fertilizers is shown.

1.00 g200-mL ground-in stopper Erlenmeyer flask
analytical sample← 1 mL of water
Leave at rest
5 minutes← 100 mL of methanol
Vertical reciprocating shaker
Shaking to mix(300 times/ minute, amplitude of 40 mm), 10 minutes
Anadequate
amount of sodium sulfate←
Ground-in stopper centrifugal precipitate tube,
Centrifugal separation
1700 × g , 5 minutes
CleanupCentrifugal separation

Silica gel cartridge column
1.5-mL ground-in stopper centrifugal precipitate tube,
8000 × g - 10000 × g , 5 minutes

Sample solution
Measurement
FigureHigh-Performance Liquid Chromatograph

Flow sheet for dicyandiamide (Dd) in fertilizers

645Testing Methods for Fertilizers(2021)

0.20

0.18

0.18

0.16

0.16

0.14

0.14

8.605 Dd

0.20

0.12
AU

AU

0.12

8.607 Dd

Reference: Examples of the HPLC chromatogram of dicyandiamide standard solution for thecalibration curve preparation and sample solution (compound fertilizer) are shown
below.

0.10

0.10

0.08

0.08

0.06

0.06

0.04

0.04

0.02

0.02

0.00

0.00
0

2

4

6

8
min

10

12

14

0

1) Standard solution
Reference diagram

2

4

6

8
min

10

12

14

2) Sample solution
HPLC chromatogram of dicyandiamide (Dd)1) Dicyandiamide standard solution (the equivalents of 100 ng (10 µg/ mL, 10 µL) of
dicyandiamide)2) Sample solution (compound fertilizer)
Measurement conditions for HPLC
Column: Inertsil NH2 (4.6-mm inner diameter, 250-mm long, 5-µm particle diameter)
Column oven temperature: 30 °C
Flow rate: 0.5 mL/min
Other conditions are according to the example of HPLC measurement conditions in(4.3) a)646

Testing Methods for Fertilizers(2021)

7.6 2-sulfanilamide thiazole (ST)7.6.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing 2-sulfanilamide thiazole (ST). This testing
method is classified as Type C and its symbol is 7.6.a-2017 or ST.a-1.
Add methanol−water (1+1) to an analytical sample to extract 2-sulfanilamide thiazole, introduce it
into a High-Performance Liquid Chromatograph (HPLC), isolate with an octadecyl silylation silica
gel column, and measure at a wavelength 285 nm to obtain 2-sulfanilamide thiazole (ST) in ananalytical sample. In addition, the performance of this testing method is shown in Comment 6.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
c) Methanol: Methanol used in the eluent of a High-Performance Liquid Chromatograph is aregent of High-Performance Liquid Chromatograph analysis grade or equivalents.
d) 2-sulfanilamide thiazole standard solution (1 mg/mL) (1): Put 0.1 g of 2-sulfanilamide
thiazole [C9H9N3O2S2] (2) in a weighing dish and measure the mass to the order of 0.1 mg. Add
water to dissolve, transfer to a 1000-mL volumetric flask and add methanol−water (1+1) to themarked line. Store in a refrigerator, and do not use after 6 months after preparation.
e) 2-sulfanilamide thiazole standard solution (0.1 mg/mL): In the case of usage, put 10 mL of
2-sulfanilamide thiazole standard solution (100 µg/mL) in a 100-mL volumetric flask and add
methanol−water (1+1) up to the marked line.
f) 2-sulfanilamide thiazole standard solution (10 µg/mL - 50 µg/mL) for the calibration curve
preparation: In the case of usage, put 5 mL - 25 mL of 2-sulfanilamide thiazole standard
solution (0.1 mg/mL) in 50-mL volumetric flasks step-by-step and add methanol - water (1+1)
up to the marked line.
g) 2-sulfanilamide thiazole standard solution (1 µg/mL - 10 µg/mL) for the calibration curve
preparation: In the case of usage, put 2.5 mL - 25 mL of 2-sulfanilamide thiazole standard
solution for the calibration curve preparation (20 µg/mL) in 50-mL volumetric flasks step-bystep and add methanol−water (1+1) up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity is commercially sold as 2sulfanilamide thiazole.
Comment 1 2-sulfanilamide thiazole is sold under the production name sulfathiazole by Tokyo
Chemical Industry Co., Ltd, FUJIFILM Wako Pure Chemical Co., Ltd., and Kanto
Chemical Co., Inc.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
filled with silica gel, to which octadecyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 285
nm.
b) Magnetic stirrerc) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
647

Testing Methods for Fertilizers(2021)

d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
e) Acidic alumina cartridge column: Link a 10-mL cylinder to a column (3) that is filled with
500 mg - 1 g of acidic alumina, put 3 mL of methanol and let it flow down.
Note (3) A cartridge with a 3-mL - 6-mL column filled with 500 mg – 1 g of silica gel can beused.
Comment 2 A column is sold under production names such as Inertsil ODS, Mightysil RP-18, Lcolumn ODS, Shim-pack VP-ODS, Silica C18M 4D, Puresil C18 and COSMOSIL
5C18-MS-II.
Comment 3 An acidic alumina cartridge is commercially sold under production names such as
Bond Elut AL-A, Sep-Pak Alumina-A and Supelclean LC-Alumina-A.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of methanol - water (1+1) and stir it by using a magnetic stirrer for about 15
minutes.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about five minutes (4) and use the supernatant (5)as an extract.
Note (4) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(5) If there is a possibility that the 2-sulfanilamide thiazole concentration in the sample
solution exceeds the maximum limit of the calibration curve, dilute a predeterminedamount of the extract with methanol.
(4.2) Cleanup: Conduct cleanup as shown below:a) Put the extract in an acidic alumina cartridge column.
b) Dispose of about the first 3 mL of effluent and then put about the next 2 mL in a test tube.
c) Put the effluent in a 1.5-mL ground-in stopper centrifugal precipitate tube (6).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (7) and use thesupernatant as a sample solution.
Note (6) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(7) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 4 Instead of the procedures in (4.2) c) - d), it is allowed to filter with a membrane filter(aperture diameter: no more than 0.5-µm) made of PTFE and the filtrate can be thesample solution.
Comment 5 The test is possible by the following procedures in the case of fertilizers not containing
organic matters.
The procedures in (4.1) c) - d) and (4.2) a) - b) are omitted and “Put the effluent” in648

Testing Methods for Fertilizers(2021)(4.2) c) is replaced with the “After allowing to stand still, put the supernatant” tooperate.
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph is shown below.
Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter) to which octadecyl chemically bonds.
2) Column bath temperature: 30 °C - 40 °C
3) Eluent: Methanol−water (2+8)4) Flow rate: 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 285 nmb) Calibration curve preparation
1) Inject 10 µL of respective 2-sulfanilamide thiazole standard solutions for the calibration curve
preparation to the High-Performance Liquid Chromatograph, record a chromatogram at awavelength 285 nm and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 285 nm of the respective 2-sulfanilamide thiazole standard solutions for thecalibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the 2-sulfanilamide thiazole content from the calibration curve to calculate 2sulfanilamide thiazole (ST) in the analytical sample.
Comment 6 Recovery testing was conducted using compound fertilizer (1 sample) and blended
fertilizer (2 sample), as a result, the mean recovery rates of 2-sulfanilamide thiazole atthe concentration level of 1.0 % (mass fraction), 0.4 % (mass fraction) and 0.1 % (massfraction) were 101.2 % - 102.1 %, 99.6 % - 101.7 % and 99.4 % - 101.0 %.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.005 % (mass fraction).
References
1)
Yuji SHIRAI: The volumetric analysis of 2-sulfanilamide thiazole in fertilizers with HighPerformance Liquid Chromatograph, Validation Report of Fertilizers (in Japanese), 44 (1),p. 10 - 20 (1991)

649

Testing Methods for Fertilizers(2021)(5)

Flow sheet for 2-sulfanilamide thiazole (ST): The flow sheet for 2-sulfanilamide thiazole infertilizers is shown below:
1.00 g analytical sample

200-mL ground-in stopper Erlenmeyer flask← 100 mL of methanol - water (1+1)
Stirring

Centrifugal separation

CleanupCentrifugal separation

Magnetic stirrer, 15 minutes
Ground-in stopper centrifugal precipitate tube,
1700 × g , 5 minutes
Acidic alumina cartridge column
Ground-in stopper centrifugal precipitate tube,
8000 × g - 10000 × g , 5 minutes

Sample solution
Measurement
FigureHigh-Performance Liquid Chromatograph

Flow sheet for 2-sulfanilamide thiazole (ST) in fertilizers.

Reference: An example of the HPLC chromatogram of 2-sulfanilamide thiazole (ST) standard
solution for the calibration curve preparation is shown below.

Reference diagram: HPLC chromatogram of 2-sulfanilamide thiazole (ST)
Measurement conditions for HPLC
Column: Mightysil RP-18 (4.6-mm inner diameter, 150-mm long, 5-µm particle
diameter)2-sulfanilamide thiazole standard solution (the equivalents of 200 ng)
Other conditions are according to the example of HPLC measurement conditions in(4.3) a)650

Testing Methods for Fertilizers(2021)

7.7
3,4-Dimethylpyrazole phosphate (DMPP)
7.7.a
High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers containing 3.4-dimethylpyrazole phosphate (DMPP).
However, fertilizers containing organic matters and formaldehyde processed urea fertilizers are
excluded from the scope of application. This testing method is classified as Type D and its symbol is
7.7.a-2021 or DMPP.a-1.
Add water to an analytical sample, agitate to extract, introduce it into a High-Performance Liquid
Chromatograph (HPLC), isolate with an octadecyl silylation silica gel column, and measure at awavelength of 224 nm to obtain 3,4-dimethylpyrazole phosphate (DMPP) in the analytical sample.
Note that the performance of this testing method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Acetonitrile: A regent of High-Performance Liquid Chromatograph analysis grade orequivalents.
c) 3,4-Dimethylpyrazole phosphate (DMPP) standard solution (2 mg/mL) (1): Put 0.200 g of
3,4-dimethylpyrazole phosphate (DMPP) [C5H11N2O4P] (2) in a weighing dish and measure themass to the order of 0.1 mg. Add a small amount of water to transfer to a 100-mL volumetricflask, sonicate using an ultrasonic generator to dissolve, and add water up to the marked line.
d) 3,4-Dimethylpyrazole phosphate (DMPP) standard solution (200 µg/mL) for thecalibration curve preparation (1): Put 20 mL of 3,4-dimethylpyrazole phosphate standard
solution (DMPP 2 mg/mL) in a 200-mL volumetric flask and add water up to the marked line.
e) 3,4-Dimethylpyrazole phosphate (DMPP) standard solutions (50 µg/mL - 100 µg/mL) forthe calibration curve preparation (1): Put 25 mL - 50 mL of 3,4-dimethylpyrazole phosphate(DMPP) standard solution (200 µg/mL) in a 100-mL volumetric flask and add water up to themarked line.
f) 3,4-Dimethylpyrazole phosphate (DMPP) standard solutions (5 µg/mL - 25 µg/mL) for thecalibration curve preparation (1): Put 5 mL - 25 mL of 3,4-dimethylpyrazole phosphatestandard solution (DMPP 100 µg/mL) in 100-mL volumetric flasks step by step and add water
up to the marked line.
g) 3,4-Dimethylpyrazole phosphate (DMPP) standard solutions (0.5 µg/mL - 2.5 µg/mL) forthe calibration curve preparation (1): Put 5 mL - 25 mL of 3,4-dimethylpyrazole phosphatestandard solution (DMPP 10 µg/mL) in 100-mL volumetric flasks step by step and add water
up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate. A DMPP standard
solution is unstable: prepare at least the standard solutions in d) - g) at time of use. The
standard solution prepared in c) is usable for about 1 month when stored refrigerated.
(2) A reagent of no less than 98 % (mass fraction) in purity as 3,4-dimethylpyrazole
phosphate (DMPP) is commercially sold.
Comment 1 3,4-Dimethylpyrazole phosphate is sold by Tokyo Chemical Industry Co., Ltd. It isalso commercially sold as 3,4-dimethylpyrazole phosphate by FUJIFILM Wako Pure
Chemical Co., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4.6-mm inner diameter 150-mm long stainless steel column tube filled with 5µm particle diameter silica gel, to which octadecyl chemically bonds.
651

Testing Methods for Fertilizers(2021)

2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 224
nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
Comment 2 A column is sold under the production name Discovery C18, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Solid test samplea) Weigh 1.0 g of an analytical sample (3), and put it into a 200-mL ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, put the supernatant solution (4) in a 1.5-mL ground-in stopper
centrifugal precipitate tube (5).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (6) and use thesupernatant as a sample solution.
Note (3) Crush the sample immediately after obtaining it.
(4) If there is a possibility that the 3,4-dimethylpyrazole phosphate (DMPP) concentrationin the sample solution exceeds the maximum limit of the calibration curve, dilute apredetermined amount of supernatant with water.
(5) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(6) 7.2-cm – 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8000 × g 10000 × g centrifugal force.
Comment 3 Instead of the procedures in (4.1) c) - d), it is allowed to filter with a membrane filter(pore size: no more than 0.5 µm) made of hydrophilic PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct measurement according to JIS K 0124 and as shown below. Specificmeasurement procedures are according to the operation method of the High-Performance
Liquid Chromatograph (HPLC) used in measurement.
a) Measurement conditions for High Performance Liquid Chromatograph: An example ofmeasurement conditions is shown below. Set up the measurement conditions considering it:1) Column: Octadecyl silylation silica gel column (4.6-mm inner diameter, 150-mm long, 5-µm
particle diameter)
2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 1.56 g of sodium dihydrogen phosphate dihydrate in water to make 1000mL, and mix in 175 mL of acetonitrile. Filter with a membrane filter (pore size: no more than
0.5-µm) made of hydrophilic PTFE.
4) Flow rate: 0.7 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, measurement wavelength: 224 nm
Comment 4 Eluent can be prepared as follows. Dissolve 15.6 g of sodium dihydrogen phosphatewith water to make 1000 mL and store in a refrigerator. At the time of use, dilute apredetermined volume of the solution by a factor of 10, mix in acetonitrile 0.175 folds
652

Testing Methods for Fertilizers(2021)of the volume, and filter with a membrane filter (pore size: no more than 0.5 µm) madeof hydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of standard solutions for the calibration curve preparation to the High-Performance
Liquid Chromatograph, record a chromatogram at a wavelength 224 nm and obtain a peak area.
2) Prepare a calibration curve for the relationship between the concentration and the ratio of peakarea at a wavelength 224 nm of 3,4-dimethylpyrazole phosphate (DMPP).
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1), and obtain a peak area.
2) Obtain the 3,4-dimethylpyrazole phosphate (DMPP) content from the calibration curve, andcalculate 3,4-dimethylpyrazole phosphate (DMPP) in the analytical sample.
Comment 5 Triplicates additive recovery testing was conducted to evaluate trueness using urea,
compound fertilizer, and blended fertilizer (1 brand each) not containing 3,4dimethylpyrazole phosphate (DMPP). As a result, the mean recovery rates at theadditive level of 0.01 % (mass fraction) - 0.5 % (mass fraction) were 96.9 % - 101.3 %.
The results of repeated analyses on different days using urea, mixed nitrogen fertilizer,
compound fertilizer (4 samples), and blended fertilizer were analyzed by the one-way
analysis of variance. Table 1 shows the estimation results of intermediate precision andrepeatability.
Note that the estimated minimum limit of quantification of this testing method wasestimated to be about 0.003 % (mass fraction).
Table 1 Estimation results of repeatability
表1 併行精度及び中間精度の推定結果
and intermediate precision
2)

Name試料名of sample

Test days of 平均値
Mean2)
反復試験
repeatability
1)

3)

sr

4)
3)

1) ）
日数（
(T)T
5

(%)
0.258

(%)
0.0011

混合窒素肥料
Mixed
nitrogen fertilizer

5

0.145

Compoundfertilizer 1
化成肥料1

5

Compoundfertilizer 2
化成肥料2
Compoundfertilizer 3
化成肥料3
Compound fertilizer 4

尿素
Urea

化成肥料4
配合肥料

Blended fertilizer

RSD r
(%)

5)

s I(T)

6)
3)

RSD I(T)
(%)

0.4

(%)
0.00360.00110.8

0.00392.7

0.105

0.00040.4

0.00444.1

50.05330.00040.7

0.00193.5

50.03720.00030.8

0.00123.3

50.03250.00041.4

0.00061.9

50.01840.00042.4

0.0005

2.8

1)1）The
2点併行試験を実施した試験日数
number of test days conducting a duplicate test
2) Mean (the number of test days(T) × the number of2） 平均値 （試験日数（T ）×併行試験数（2））
duplicate testing(2))
質量分率3)3）Mass
fraction

4)
5)
6)
7)

1.4

Repeatability
standard deviation4） 併行標準偏差
Repeatability relative standard deviation5） 併行相対標準偏差Intermediatestandard deviation
6） 中間標準偏差Intermediate
relative standard deviation

7） 中間相対標準偏差

653

7)

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for 3,4-dimethylpyrazole phosphate (DMPP)
in fertilizers is shown below:
1.00 g analytical sample (powdery)

分析試料（粉状）1.00 g

200-mLground-in stopper
Erlenmeyer flask
200 mL
共栓三角フラスコ

mL
mL water
← 100
水 100
Stirring
かき混ぜ

Magnetic
stirrer, 10 minutes
マグネチックスターラー、10分間

Standing
静置still
Centrifugal
separation
遠心分離
Samplesolution
試料溶液
Measurement
測定

Ground-in
stopper centrifugal precipitate
tube,
8000 × g - 10000 × g, 5 minutes
共栓遠心沈殿管、8000×g～10000×g、5分間
Supernatant
上澄み液
LiquidChromatograph
液体クロマトグラフ

Flow sheet for 3,4-dimethylpyrazole phosphate (DMPP) in fertilizers (Extraction procedure (4.1.1) and
図 Figure
肥料中の3,4-ジメチルピラゾールりん酸塩（DMPP）試験法のフローシート（抽出操作（4.1.1）及び測定）
measurement)

Reference: An example of the chromatogram of the standard solution for calibration curve
preparation of 3,4-dimethylpyrazole phosphate (DMPP) is shown below.

Minutes

Reference diagram: HPLC chromatogram of the standard solutions for calibration curb preparation(10 mg/L)
Peak name(1) 3,4-Dimethylpyrazole phosphate (DMPP)
Measurement conditions for HPLC
Column: Discovery C18 (4.6-mm inner diameter, 150-mm long, 5-µm particle
diameter)Other conditions are according to the example of HPLC measurement conditions in(4.2) a).

654

Testing Methods for Fertilizers(2021)

8. Others
8.1 Melamine and its degradation products
8.1.a Gas Chromatography/Mass Spectrometry(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 8.1.a-2017 or Mel.a-1.
Extract melamine and its derivative substances (hereinafter referred to as “melamine derivations”) in
organic matters and fertilizers containing organic matters with diethylamine−water−acetonitrile(1+4+5) and derivatize with BSTFA−TMCS (99+1) and then measure with a Gas Chromatography/
Mass Spectrometer to obtain melamine deviations in an analytical sample. In addition, theperformance of this testing method is shown in Comment 8.
Comment 1 The structural formula of melamine and its degradation products is shown in the figure
1. During the production process of melamine, a by-product that replaces “-NH2” ofR1 - R3 with “-OH” is formed in some cases.

R1
N
R2

N
N

R3

Melamine
Ammeline
Ammelide
Cyanuric acid

R1
NH2
OH
OH
OH

R2
NH2
NH2
OH
OH

R3
NH2
NH2
NH2
OH

MW
126.12
127.10128.09129.07

Figure 1 Structural formula of melamine and its degradation products(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Acetonitrile: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8039 or a reagent of equivalent quality.
c) Diethylamine: A guaranteed reagent or a reagent of equivalent quality.
d) Pyridine (dehydration) (1): A reagent of organic synthesis grade of no less than 99.5 % (massfraction) in purity and no more than 0.05 mg/mL in moisture or a reagent of equivalent quality.
e) Derivatization reagent (2): Bis (trimethylsilyl) trifluoroacetamide−trimethylchlorosilane(99+1).
f) Melamine derivations standard solution (0.5 mg/mL): Put about 0.05 g of melamine[C3H6N6] (3), ammeline [C3H5N5O] (3), ammelide [C3H4N4O2] (3) and cyanuric acid [C3H3N3O3](3)
into a weighing dish and measure the mass to the order of 0.1 mg. Dissolve in a small amountof diethylamine−water (1+4), transfer to a 100 mL volumetric flask respectively, and add thesolvent up to the marked line.
g) Mixture standard solution (50 µg/mL) (3): Put 5 mL of respective melamine derivations
standard solutions (0.5 mg/mL) in 50-mL volumetric flasks and add
diethylamine−water−acetonitrile (1+4+5) up to the marked line.
Note (1) After it is opened once, add a proper amount of sodium sulfate (anhydrous) and seal
tightly to store.
(2) A mixed derivatization reagent is commercially sold under the name BSTFA−TMCS(99+1).
(3) The respective standard reagents of melamine, ammeline, ammelide and cyanuric acidare commercially sold.
655

Testing Methods for Fertilizers(2021)

Comment 2 BSTFA−TMCS (99+1) is sold as 1-mL ampoule by SUPELCO. After it is opened once,
use it on the same day.
Comment 3 The standard reagent of melamine, ammeline, ammelide and cyanuric acid are sold by
FUJIFILM Wako Pure Chemical Co., Ltd. and Kanto Chemical Co., Inc. and Hayashi
Pure Chemical Industries., Ltd.
(3) Instruments: Instruments are as shown below:a) Gas Chromatograph/Mass Spectrometer (GC/MS): GC/MS specified in JIS K 0123 thatsatisfies the following requirements.
1) Gas Chromatograph(i) Sample injector: An injector that enables split less system.
(ii) Capillary column: A capillary column (0.25-mm - 0.32-mm inner diameter and 30-mlong) made of fused silica. 5 % phenyl 95 % methyl polysiloxane chemically bonds to theinner surface of a capillary column with 0.25 µm thickness. The column is according to thespecification of mass spectrometer.
(ii) Carrier gas: High purity helium of no less than 99.999 % (volume fraction) in purity.
2) Mass Spectrometer(i) Ionization method: Electron-Impact ionization (EI) method(ii) Ion detection method: Selected Ion Monitoring (SIM) methodb) Ultrasonic generator: An ultrasonic washer can be used.
c) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
d) Concentrator: A Centrifugal evaporator that can be adjusted to 70 ºC ± 2 ºC.
e) Water bath: Water bath that can be adjusted to 70 ºC ± 2 ºC.
Comment 4 A capillary column is commercially sold under the names such as DB-5ms, Rtx-5ms,
HP-5ms, SLB-5ms, BPX-5, CP-Sil 8CB low Bleed/MS and TC -5HT for GC/MS.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 0.50 g of an analytical sample, and put it into a 200 mL - 200-mL ground-in stopper
Erlenmeyer flask.
b) Add 160 mL - 200 mL of diethylamine−water−acetonitrile (1+4+5), and subject to ultrasonication for about 30 minutes using an ultrasonic generator.
c) Put about 1.5 mL in a 1.5-mL ground-in stopper centrifugal precipitate tube (4), and centrifuge
at 8000 × g - 10000 × g for about 5 minutes (5).
d) Put 1 mL of the supernatant solution in 5-mL - 50-mL volumetric flasks, add
diethylamine−water−acetonitrile (1+4+5) up to the marked line to make an extract.
Note (4) Confirm that the tube is made of polypropylene, etc. to not affect testing results.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 5 Grind until it completely passes through a sieve of 500 µm aperture to prepare the test
sample.
Comment 6 Weigh 0.5 g of an analytical sample, extract with 200 mL of diethylamine – water −acetonitrile (1+4+5). If it is diluted 50 times in the procedure in d), the quantitative
range of melamine derivations in the analytical sample is 0.2 % (mass fraction) - 10 %(mass fraction). In the case of measuring melamine derivations which do not reach the656Testing Methods for Fertilizers(2021)

quantitative range, make the dilution factor in the procedure in d) decrease. In addition,
if the contents of melamine derivations exceed 10 % (mass fraction) respectively, thesampling volume of an analytical sample should be reduced.
(4.2) Derivatization: Conduct derivatization as shown below.
a) Put 0.2 mL of the extract in a 5-mL - 10-mL test tube with a screw stopper.
b) Place a test tube in a concentrator, concentrate under reduced pressure at 70 ºC ± 2 ºC andvaporize the solvent completely (6).
c) Add 0.3 mL of pyridine (dehydration) (1) and 0.2 mL of derivatization reagent (2) to the residue
to mix, and then stopple to seal tightly.
d) After heating in a water bath at 70 ºC ± 2 °C for about 45 minutes (7), let it stand to cool to makea sample solution (8).
Note (6) A spraying type concentrator can be used.
(7) If moisture remains after the procedure in b) or the reagent used in the procedure in c)contains moisture, the reaction of the derivatization in d) does not advance enough insome cases.
(8) If necessary, put the sample solution into a 1.5-mL ground-in stopper centrifugal
precipitate tube (4) to centrifuge at 8000 × g - 10000 × g for about 5 minutes (5).
(4.3) Measurement: Conduct the measurement as indicated in JIS K 0123 and as shown below.
Specific measurement procedures are according to the operation method of the Gas
Chromatograph/Mass Spectrometer used in measurement.
a) Measurement conditions for the Gas Chromatograph/Mass Spectrometer: An example ofmeasurement conditions for the Gas Chromatograph/Mass Spectrometer is shown below. Set
up the measurement conditions considering it:
1) Gas Chromatograph(i) Sample injection method: split less injection method (1min)(ii) Temperature of sample injector: 280 °C(ii) Capillary column: A capillary column (0.25-mm - 0.32-mm inner diameter, 30-m long, 0.25
µm layer thickness) made of fused silica. 5 % phenyl 95 % methyl polysiloxane chemicallybonds to the inner surface of the capillary column.
(iv) Temperature of column bath: 100 °C (1 min) → (15 °C /min) → 320 °C (3 min)(v) Temperature of GC/MS coupling portion: 250 °C(vi) Carrier gas: helium, flow rate: 1.5 mL/min
2) Mass Spectrometer(i) Ionization method: Electron-Impact ionization (EI) method(ii) Ionization voltage: 70 V(iii) Temperature of ion source: 230 °C(iv) Ion detection method: Selected Ion Monitoring (SIM) method(v) Measurement of ion: Shown in table 1657

Testing Methods for Fertilizers(2021)

Table 1 Fragment ion of materials subjected to measurement
Materials
Measured fragment ion (m/z)
to be measured Determination Validation Validation Validation Validation
342
Melamine
344
327
285
213
328
Ammeline
345
343
285
214
344
Ammelide
346
329
214
198
345
Cyanuric acid
347
330
215
188
288
DACP(I.S.)
289
290
273
275
b) Calibration curve preparation
1) Put 5 mL of mixture standard solution (50 µg/mL) in a 50-mL volumetric flask and add
diethylamine−water−acetonitrile (1+4+5) up to the marked line to make a mixture standard
solution (5 µg/mL).
2) Put 1 mL - 20 mL of the mixture standard solution (5 µg/ mL) in 50 mL volumetric flasks stepby-step and add diethylamine−water−acetonitrile (1+4+5) up to the marked line to make a
mixture standard solution (0.1 µg/mL - 2 µg/mL).
3) Conduct the procedures of (4.2) b) - d) for the mixture standard solution (0.1 µg/mL - 2 µg/mL)
to make a mixture standard solution, the equivalents of 0.04 µg/mL - 0.8 µg/mL, for calibration
curve.
4) Inject 1 µL of respective mixture standard solutions for calibration curve to the GC/MS andrecord the chromatogram of ion (m/z) for determination and ion (m/z) for validation of materials
subjected to measurement to obtain a peak area or height.
5) Calculate the peak area ratio or height ratio of ion (m/z) for determination and ion (m/z) for
validation of respective materials subjected to measurement.
6) Prepare a curve for the relationship between the concentration of material subjected tomeasurement and the peak area or height of ion (m/z) for determination of respective mixture
solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 1 µL of the sample solution to the same procedure as in b) 4) - 5) (9).
2) Obtain the content of respective materials subjected to measurement from the calibration curve
to calculate respective materials subjected to measurement in the analytical sample.
Note (9) Confirm that the peak area ratio or height ratio of ion (m/z) for determination to ion(m/z) for validation is within the range of about ± 30 % of the peak area ratio or heightratio for the standard solution. In addition, the peak area ratio or height ratio depends onthe concentration.
Comment 7 If the variation of sensitivity of melamine derivations is observed, conduct
measurement by the following method of a) or b).
a) In the procedure in (4.3) c) 1), inject the sample solution into the GC/MS
predetermined times, and then correct the calibration curve according to (4.3) b)
4) - 6).
b) Add 2,6-diamino-4-chloropyrimidine (the equivalents of 0.5 µg) as an internalreference material to the standard solution and the sample solution, conduct thesame procedures as (4.2) c) - d), (4.3) b) 4) - 6) and c) 1). However, prepare thecalibration curve from the peak area ratio or height ratio of ion (m/z) for
determination of respective materials subjected to measurement and internal658

Testing Methods for Fertilizers(2021)

reference material, and calculate the concentration of respective materials
subjected to measurement in the analytical sample.
Comment 8 Recovery testing of melamine derivations was conducted using soybean meal, fish
meal, fish waste processed fertilizer, mixed organic fertilizer, blended fertilizer andcompound fertilizer, as a result, the mean recovery rates at the additive level of 10 %(mass fraction) and 0.2 % (mass fraction) were 92.1 % - 102.9 % and 90.3 % - 102.2 %.
Note that the minimum limit of quantification of melamine derivations of this test
method was estimated to be about 0.01 % (mass fraction).
References
1)
Yuji SHIRAI, Jun OKI: Validation of Gas Chromatography/Mass Spectrometry for
Determination of Melamine and Its Degradation Products in Fertilizers, Research Reportof Fertilizer, Vol. 1, p. 114 - 121 (2008)

659

Testing Methods for Fertilizers(2021)(5)

Flow sheet for melamine derivations: The flow sheet for melamine derivations in fertilizers
is shown below.
0.50 g analytical sample
200-mL - 300-mL ground-in stopper Erlenmeyer flask← 160 mL - 200 mL of diethylamine - water - acetonitrile (1+4+5)
Ultra-sonication
Ultrasonic generator, 30 minutes
Centrifugal separation

Ground-in stopper centrifugal precipitation tube
8000 × g - 10000 × g, 5 minutes

Extract
Figure 1

Flow sheet for melamine derivations in fertilizers (Extraction procedure)

Extract
Dilution
0.2 mL Aliquot

Put 1 mL in 5-mL - 50-mL volumetric flasks,
add diethylamine−water−acetonitrile (1+4+5) up to the marked line
5-mL - 10-mL test tube with a screw stopper

concentration
Centrifugal evaporator (70 ºC ± 2 ºC)
under reduced pressure/Exsiccation← 0.3 mL of pyridine (dehydration)← 0.2 mL of derivatization reagent (BSTFA−TMCS (99+1))
Stopple and seal.
Derivatization
70 ºC ± 2 ºC, 45 minutes
Standing to cool
Sample solution
Measurement
Figure 2

Gas Chromatograph/Mass Spectrometer

Flow sheet for melamine derivations in fertilizers(Derivatization and measurement procedure)

660

Testing Methods for Fertilizers(2021)

Reference:
An example of the Total Ion Chromatogram (TIC) of GC/MS of the mixture
standard solution for calibration curve preparation of melamine derivations is shown below.
↓a

↓b

↓c

↓d

Figure 3 Total Ion Chromatogram (TIC) of GC/MS for melamine derivations
Measurement conditions of GC/MS
Capillary column: Rtx-5ms (0.25-mm inner diameter, 30-m long, 0.25 µm layer
thickness)
Other conditions are according to the example of HPLC measurement conditions in(4.3) a)Peak name of respective total ion chromatogramsa) Cyanuric acidb) Ammelidec) Ammelined) Melamine
Sample and amount injected into GC/MS
Injected sample: Mixture standard solutions (the equivalents of 2 µg/mL) for thecalibration curve preparation of respective melamine derivations.
Injected amount: 1 µL (the equivalents of 2 ng of respective melamine derivations)661

Testing Methods for Fertilizers(2021)

8.1.b

662

Testing Methods for Fertilizers(2021)

8.1.c High-Performance Liquid Chromatography (Fertilizers not containing organic matters)(1) Summary
This testing method is applicable to fertilizers not containing organic matters. This testing method
is classified as Type B and its symbol is 8.1.c-2017 or Mel.c-1.
Add hydrochloric acid (1+15) to an analytical sample, extract melamine and its degradation
products (hereinafter referred to as “melamine derivations”), introduce them into a High-Performance
Liquid Chromatograph (HPLC), isolate with a silica gel column to which carbamoyl chemicallybonds, and measure at a wavelength 214 nm to obtain melamine derivations in an analytical sample.
In addition, the performance of this testing method is shown in Comment 4.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Acetonitrile: A JIS Guaranteed Reagent specified in JIS K 8032 or a reagent of equivalentquality. In addition, acetonitrile used in the eluent of a High-Performance Liquid
Chromatograph is a reagent of High-Performance Liquid Chromatograph analysis grade.
c) Hydrochloric acid: A guaranteed reagent or a reagent of equivalent quality.
d) Phosphate buffer solution (1): Dissolve 0.237 g of disodium hydrogen-phosphate specified in
JIS K 9020 and 0.520 g of sodium dihydrogen-phosphate dihydrate specified in JIS K 9009 inwater to make 1000 mL (2). If it is used for the eluent of a High-Performance Liquid
Chromatograph, filter with a membrane filter (pore size: no more than 0.5-µm) made ofhydrophilic PTFE.
e) Melamine derivations standard solution (0.5 mg/mL): Put about 0.05 g of melamine[C3H6N6] (3), ammeline [C3H5N5O] (3), ammelide [C3H4N4O2] (3) and cyanuric acid [C3H3N3O3](3)
into a weighing dish and measure the mass to the order of 0.1 mg. Dissolve them with a small
amount of hydrochloric acid (1+15), transfer to 100 mL volumetric flasks respectively, and add
the solutions up to the marked line.
f) Mixture standard solution (50 µg/mL) (1): Put 5 mL of respective melamine derivations
standard solutions (0.5 mg/mL) in 50-mL volumetric flasks and add acetonitrile - phosphatebuffer solutions (4+1) up to the marked line.
g) Mixture standard solution for calibration curve preparation (1 µg/mL - 5 µg/mL): In thecase of usage, put 1 mL - 5 mL of mixture standard solution (50 µg /mL) in 50-mL volumetricflasks step-by-step and add acetonitrile−phosphate buffer solutions (4+1) up to the marked line.
h) Mixture standard solution for calibration curve preparation (0.05 µg/mL - 0.5 µg/mL): In
the case of usage, put 2.5 mL - 25 mL of mixture standard solution (1 µg /mL) in 50-mL
volumetric flasks step-by-step and add acetonitrile−phosphate buffer solutions (4+1) up to themarked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) The phosphate buffer solution becomes pH 6.7 ± pH 0.2.
(3) The respective standard reagents of melamine, ammeline, ammelide and cyanuric acidare commercially sold.
Comment 1 The standard reagent of melamine, ammeline, ammelide and cyanuric acid are sold by
FUJIFILM Wako Pure Chemical Co., Ltd. and Kanto Chemical Co., Inc. and Hayashi
Pure Chemical Industries., Ltd.
(3)a)

Instruments: Instruments are as shown below:
High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
663

Testing Methods for Fertilizers(2021)

filled with silica gel, to which carbamoyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 40 ºC ± 1 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 214nm.
b) Ultrasonic generator: An ultrasonic washer can be used.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
Comment 2 A column is sold under the production name TSKgel Amide-80, etc. A column that has
been confirmed to be able to completely separate melamine, ammeline, ammelide andcyanuric acid should be used.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 0.50 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of hydrochloric acid (1+15) and conduct ultra-sonication for about 30 minutes
using an ultrasonic generator.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about five minutes (4) and use the supernatant as
an extract.
e) Put 5 mL of the extract (5) into a 50-mL volumetric flask, and add an acetonitrile−phosphatebuffer solution (4+1) up to the marked line to dilute.
f) Put dilution liquid in a 1.5-mL ground-in stopper centrifugal precipitate tube (6).
g) Centrifuge at 8000 × g - 10000 × g for about 5 minutes (7) to make supernatant as a sample
solution
Note (4) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(5) If there is a possibility that the concentration of melamine derivations in the sample
solution exceeds the maximum limit of the calibration curb, the amount of a supernatantsolution to be transferred should be1 mL - 2.5 mL.
(6) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(7) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 3 Instead of the procedures in (4.1) f) - g), it is allowed to filter with a membrane filter(pore size: no more than 0.5-µm) made of hydrophilic PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph:An
example of measurement conditions for the High-Performance Liquid Chromatograph is shown
below. Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
664Testing Methods for Fertilizers(2021)

particle diameter column) to which carbamoyl chemically bonds.
2) Column bath temperature: 40 °C ± 1 °C
3) Eluent: Acetonitrile - phosphate buffer solution (4+1)
4) Flow rate: 1 mL/min
5) Detection unit: An absorptiometric detector, a measurement wavelength: 214 nmb) Calibration curve preparation
1) Inject 10 µL of respective mixture standard solutions for calibration curve preparation into theHigh-Performance Liquid Chromatograph, record a chromatogram at a wavelength 214 nm andobtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 214 nm of respective mixture solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the melamine derivations content from the calibration curve to calculate respective
melamine derivations in the analytical sample.
Comment 4 Recovery testing was conducted using 3 brands of nitrolime, 1 brand of compound
fertilizer containing nitrolime, 2 brands of compound fertilizers not containing
nitrolime, 1 brand of ammonium sulfate and 1 brand of urea, as a result, the recovery
rates of melamine derivations at the concentration level of 4 % (mass fraction) and
0.1 % (mass fraction) were 90.5 % - 106.3 % and 92.2 % - 107.0 %.
Additionally, results from a collaborative study for test method validation and its
analysis are in Table 1.
Note that the minimum limit of quantification of the test method was estimated to beabout 0.02 % (mass fraction) for melamine and cyanuric acid and about 0.01 % (massfraction) for ammeline and ammelide. In the case of ammelide and cyanuric acid, thesufficient reproducibility was observed in the range of 0.188 % (mass fraction) 1.10 % (mass fraction) and 0.105 % (mass fraction) - 1.15 % (mass fraction)
respectively.

665

Testing Methods for Fertilizers(2021)

Agrichemical
name

Table 1 Analysis resultsof the collaborative study
for the test method validation of melamine deivations
3)
4)
5)
6)
2)
Number of
sr
RSD r
sR
RSD R
Mean
Sample name1)
7)
7)laboratories(%) (%)7)
(%)
(%)
(%)

Melamine

Nitrolime 1
9
2.83
0.04
1.4
Nitrolime 2
10
0.391
0.003 0.89
0.845
0.019 2.2
Compound fertilizer containing nitrolime
Compound ferttilizer
11
0.198
0.005 2.6
Ammonium sulfate
100.0343 0.0015 4.5Ammeline
Nitrolime 1
9
1.60
0.02
1.3
Nitrolime 2
10
0.105
0.001 1.3
9
0.629
0.027 4.3
Compound fertilizer containing nitrolime
Compound ferttilizer
11
0.195
0.004 2.1
Ammonium sulfate
100.0346 0.0013 3.7
Ammelide
Nitrolime 1
9
1.10
0.02
2.1
Nitrolime 2
11
0.361
0.008 2.2
9
0.188
0.004 2.2
Compound fertilizer containing nitrolime
Compound ferttilizer
11
0.718
0.028 3.9
Ammonium sulfate
11
0.0345 0.0031 8.9
Cyanuric acid Nitrolime 1
9
1.15
0.06
4.8
Nitrolime 2
10
0.390
0.018 4.5
9
0.105
0.003 2.9
Compound fertilizer containing nitrolime
Compound ferttilizer
9
0.788
0.026 3.2
Ammonium sulfate
100.0365 0.0015 4.2
1) Number of laboratories used in analysis
2) Gross mean (n = number of laboratories × number of repeated tests (2))3) Repeatability standard deviation
4) Repeatability relative standard deviation
5) Reproducibility standard deviation
6) Reproducibility relative standard deviation
7) Mass fraction

0.12
0.023
0.036
0.012
0.0040
0.06
0.002
0.023
0.009
0.0024
0.08
0.023
0.014
0.052
0.0056
0.09
0.029
0.014
0.054
0.0067

4.3
5.8
4.2
6.2
11.6
3.8
2.3
3.7
4.5
6.9
7.6
6.5
7.5
7.2
16.1
7.7
7.4
13.2
6.8
18.3

References
1)
Etsuko BANDO and Yuji SHIRAI: Validation of High-Performance Liquid
Chromatography (HPLC) for Determination of Melamine and Its Related Substances in
Fertilizer, Research Report of Fertilizer, Vol. 6, p. 27 - 35 (2013)
2)
Etsuko BANDO and Sigehiro KAI: Determination of Melamine and Its Related
Substances in Fertilizer by High-Performance Liquid Chromatography (HPLC): A
Collaborative Study, Research Report of Fertilizer, Vol. 7, p. 10 - 21 (2014)666

Testing Methods for Fertilizers(2021)(5)

Flow sheet for melamine derivations: The flow sheet for melamine derivations in fertilizers
is shown below.

0.50 g analytical sample
200-mL ground-in stopper Erlenmeyer flask←100 mL of hydrochloric acid (1+15）
Ultra-sonication
Ultrasonic generator, 30 minutes
Centrifugal separation

DilutionCentrifugal separation

Ground-in stopper centrifugal precipitation tube
1700 × g, 5 minutes
Put 5 mL in a 50-mL volumetric flask,
add acetonitrile−phosphate buffer solution (4+1) up to the marked line
Ground-in stopper centrifugal precipitation tube
8000 × g - 10000 × g, 5 minutes

Sample solution
Measurement

High-Performance Liquid Chromatograph

Figure Flow sheet for melamine derivations in fertilizers

667

Testing Methods for Fertilizers(2021)

Reference: An example of the HPLC chromatogram of the mixture standard solution for calibration
curve preparation of melamine derivations is shown below.

Time

Reference diagram: HPLC chromatogram of melamine derivations
The names of materials for respective peaks(1) cyanuric acid(2) ammelide(3) melamine(4) ammeline
Measurement conditions for HPLC
Column: TSKgel Amide-80 (4.6-mm inner diameter, 250-mm long, 5-µm particle
diameter)Mixture standard solutions (respective equivalents of 10 ng (1 µg/mL, 10 µL)) for
calibration curve preparation of respective melamine derivations
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)668

Testing Methods for Fertilizers(2021)

8.1.d High-Performance Liquid Chromatography (Fertilizers containing organic matters)(1) Summary
This testing method is applicable to organic fertilizers and fertilizers containing organic matters.
This testing method is classified as Type D and its symbol is 8.1.d-2017 or Mel.d-1.
Add water to an analytical sample to extract melamine, introduce it into a High-Performance
Liquid Chromatograph (HPLC), isolate with a silica gel column to which carbamoyl chemicallybonds, and measure at a wavelength 214 nm to obtain melamine in an analytical sample. However,cyanuric acid, ammelide and ammeline which are melamine derivations are excluded fromcomponents subjected to measurement. In addition, the performance of this testing method is shownin Comment 4.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Acetonitrile: A JIS Guaranteed Reagent specified in JIS K 8032 or a reagent of equivalentquality. In addition, acetonitrile used in the eluent of a High-Performance Liquid
Chromatograph is a reagent of High-Performance Liquid Chromatograph analysis grade.
c) Phosphate buffer solution (1): Dissolve 0.237 g of disodium hydrogen-phosphate specified in
JIS K 9020 and 0.520 g of sodium dihydrogen-phosphate dihydrate specified in JIS K 9009 inwater to make 1000 mL (2). If it is used for the eluent of a High-Performance Liquid
Chromatograph, filter with a membrane filter (pore size: no more than 0.5-µm) made ofhydrophilic PTFE.
d) Melamine standard solution (0.5 mg/mL) (1): Put 0.05 g of melamine [C3H6N6] (3) in aweighing dish and measure the mass to the order of 0.1 mg. Dissolve it with a small amount ofwater, transfer to a 100 mL volumetric flask and add the solution up to the marked line.
e) Melamine standard solution (50 µg/mL) (1): Put 5 mL of melamine solution (0.5 mg/mL) in
a 50-mL volumetric flask and add acetonitrile - phosphate buffer solutions (82+18) up to themarked line.
f) Melamine standard solution for calibration curve preparation (1 µg/mL - 5 µg/mL): In thecase of usage, put 1 mL - 5 mL of melamine standard solution (50 µg /mL) in 50-mL volumetricflasks step-by-step and add acetonitrile−phosphate buffer solutions (82+18) up to the marked
line.
g) Melamine standard solution for calibration curve preparation (0.05 µg/mL - 0.5 µg/mL):
In the case of usage, put 2.5 mL - 25 mL of melamine standard solution (1 µg/ mL) in 50-mL
volumetric flasks step-by-step, add acetonitrile−phosphate buffer solutions (82+18) up to themarked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) The phosphate buffer solution becomes pH 6.7 ± 0.2.
(3) A standard reagent as melamine is commercially sold.
Comment 1 A standard reagent of melamine is sold by FUJIFILM Wako Pure Chemical Co., Ltd.,
Kanto Chemical Co., Inc. and Hayashi Pure Chemical Industries., Ltd.
(3) Instruments: Instruments are as shown below:a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4-mm - 6-mm inner diameter 150-mm - 250-mm long stainless steel column tube
filled with silica gel, to which carbamoyl chemically bonds.
2) Column bath: A column bath whose temperature can be adjusted to 40 ºC ± 1 ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 214
669

Testing Methods for Fertilizers(2021)

nm.
b) Ultrasonic generator: An ultrasonic washer can be used.
c) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
d) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
Comment 2 Column is sold under the production name TSKgel Amide-80, etc. A column which
has actually isolated melamine, ammeline, ammelide and cyanuric acid should be used.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 0.50 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and conduct ultra-sonication for about 10 minutes using an ultrasonic
generator.
c) After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
d) Centrifuge it at 1700 × g centrifugal force for about 10 minutes (4) and use the supernatant as
an extract.
e) Put 5 mL of the extract (5) into a 50-mL volumetric flask, and add an acetonitrile−phosphatebuffer solution (82+18) up to the marked line to dilute.
f) Put dilution liquid in a 1.5-mL ground-in stopper centrifugal precipitate tube (6).
g) Centrifuge at 8000 × g - 10000 × g for about 5 minutes (7) to make supernatant as a sample
solution
Note (4) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(5) If there is a possibility that the concentration of melamine derivations in the sample
solution exceeds the maximum limit of the calibration curb, the aliquot volume to betaken of a supernatant solution should be 1 mL - 2.5 mL.
(6) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(7) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 3 Instead of the procedures in (4.1) f) - g), it is allowed to filter with a membrane filter(pore size: no more than 0.5 µm) made of hydrophilic PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions for the High-Performance Liquid Chromatograph is shown below.
Set up the measurement conditions considering it:1) Column: A silica gel column (4-mm - 6-mm inner diameter, 150-mm - 250-mm long, 5-µm
particle diameter column) to which carbamoyl chemically bonds.
2) Column bath temperature: 40 °C ± 1 °C
3) Eluent: Acetonitrile - phosphate buffer solution (82+18)
4) Flow rate: 1 mL/min
670

Testing Methods for Fertilizers(2021)

5) Detection unit: An absorptiometric detector, measurement a wavelength: 214 nmb) Calibration curve preparation
1) Inject 10 µL of respective melamine standard solutions for calibration curve preparation into
the High-Performance Liquid Chromatograph, record a chromatogram at a wavelength 214 nm
and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height at awavelength 214 nm of respective melamine solutions for the calibration curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the melamine content from the calibration curve to calculate melamine in the analyticalsample.
Comment 4 Additive recovery testing was conducted to evaluate trueness using rape seed meal,
soybean meal, compound fertilizer containing lime nitrogen and organic matter,compound fertilizer containing organic matter and blended fertilizer containing
organic matter (1 brand for each). As a result, the mean recovery rates at the additive
level of 2 % (mass fraction), 0.4 % (mass fraction) and 0.1 % (mass fraction) were
94.6 % - 99.8 %, 92.4 % - 98.5 % and 93.1 % - 98.4 % respectively.
The results of the repeatability tests on different days using soybean meal andcompound fertilizer containing organic matter, to evaluate precision were analyzed by
one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.02 % (mass fraction).
Table 1 Analysis results of the repeatability tests on different days of melamine
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Soybean meal
5
1.91
0.03
1.7
0.04
2.2
Compound fertilizer containing organic matter
51) The number of test days conducting a duplicate test
2) Mean (the number of test days(T )×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

0.100
0.001
1.4
0.002
2.5
6) Intermediate standard deviation
7) Intermediate relative standard deviation

References
1)
Etsuko FUNAMIZU: Determination Method for Melamine in Organic Fertilizer andFertilizer Containing Organic Matter using High-Performance Liquid Chromatograph(HPLC), Research Report of Fertilizers, Vol. 9, p. 33 - 42 (2016)

671

Testing Methods for Fertilizers(2021)(5)

Flow sheet for melamine derivations: The flow sheet for melamine derivations in fertilizers
is shown below.

0.50 g analytical sample
200-mL ground-in stopper Erlenmeyer flask←100 mL of water
Ultra-sonication
Ultrasonic generator, 30 minutes
Centrifugal separation
DilutionCentrifugal separation

Ground-in stopper centrifugal precipitation tube
1700 × g, 10 minutes
Put 5 mL in a 50-mL volumetric flask,
add acetonitrile−phosphate buffer solution (82+18) up to the marked line
Ground-in stopper centrifugal precipitation tube
8000 × g - 10000 × g, 5 minutes

Sample solution
Measurement

High-Performance Liquid Chromatograph

Figure Flow sheet for melamine in fertilizers containing organic matter

Reference: An example of the HPLC chromatogram of the standard solution for calibration curve
preparation of melamine is shown below.

←melamine

Reference diagram: HPLC chromatogram of melamine
Measurement conditions for HPLC
Column: TSKgel Amide-80 (4.6-mm inner diameter, 250-mm long, 5-µm particle
diameter)Melamine standard solution (the equivalents of 10 ng (1 µg/mL, 10 µL) for each)
Other conditions are according to the example of HPLC measurement conditions in(4.2) a)672

Testing Methods for Fertilizers(2021)

8.2 Clopyralid and its degradation products
8.2.a High-Performance Liquid Chromatography/Tandem Mass Spectrometry(Simultaneous analysis of three components for clopyralid, etc.)(1) Summary
This testing method is applicable to compost and composted sludge fertilizers. This testing method isclassified as Type B and its symbol is 8.2.a-2017 or CLP.a-1.
Extract clopyralid, aminopyralid and picloram with methanol under alkaline condition, refine with acleanup cartridge by taking advantage of characteristics that the behavior of elution varies between
acidity and alkaline, and then measure with a High-Performance Liquid Chromatograph/Tandem
Mass Spectrometer (LC-MS/MS) to obtain clopyralid, aminopyralid and picloram in an analyticalsample. In addition, the performance of this testing method is shown in Comment 6.
Comment 1 Structural formulas of clopyralid, aminopyralid and picloram are as shown in Figure
1.

Figure 1 Structural formula of clopyralid, aminopyralid and picloram(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557. Note that water of A4 should be used as theeluent which is introduced to a High-Performance Liquid Chromatograph/Tandem Mass
Spectrometer.
b) Acetonitrile: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8039 or a reagent of equivalent quality.
c) Methanol:
A JIS Guaranteed Reagent specified in a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer or a reagent of equivalent quality.
d) Methanol: Methanol used in the eluent of a High-Performance Liquid Chromatograph/ Tandem
Mass Spectrometer is a reagent of LC-MS analysis grade or equivalents.
e) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
f) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
g) Ammonia solution: A JIS Guaranteed Reagent of 28 % (mass fraction) specified in JIS K
8085 or a reagent of equivalent quality.
h) formic acid: A JIS Guaranteed Reagent specified in JIS K 8264 or a reagent of equivalentquality.
i) Ammonia solution (0.0028 % (mass fraction)) (1): Add 0.1 mL of ammonia solution to 1000mL of water.
j) Respective agrichemical standard solutions (0.1 mg/mL) (1): Put about 0.01 g of clopyralid[C6H3Cl2NO2] (2), aminopyralid [C6H4Cl2N2O2] (2) and picloram [C6H3Cl3N2O2] (2) in weighing
673

Testing Methods for Fertilizers(2021)

dishes and measure the mass to the order of 0.1 mg. Dissolve with a small amount ofacetonitrile, transfer to 100-mL volumetric flasks and add the solvent up to the marked line.
k) Mixture standard solution (100 ng/mL) (1): Dilute a predetermined amount of respective
agrichemical standard solutions (0.1 mg/mL) with formic acid (1+1000) to prepare mixture
standard solution (100 ng/mL).
l) Mixture standard solution for calibration curve preparation (5 ng/mL - 50 ng/mL) (1): In
the case of usage, put 2.5 mL - 25 mL of mixture standard solution (100 ng/mL) in 50 mL
volumetric flasks step-by-step, and add formic acid (1+1000) up to the marked line.
m) Mixture standard solution for calibration curve preparation (0.5 ng/mL - 5 ng/mL) (1): In
the case of usage, put 2.5 mL - 25 mL of mixture standard solution (10 ng/mL) in 50 mL
volumetric flasks step-by-step, and add formic acid (1+1000) up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A standard reagent is commercially sold.
Comment 2 Standard reagents of clopyralid, aminopyralid and picloram are sold by FUJIFILM
Wako Pure Chemical Co., Ltd., Kanto Chemical Co., Inc. and Hayashi Pure Chemical
Industries., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph/Mass Spectrometer：A high-performance liquid
chromatograph/tandem mass spectrometer specified in JIS K 0136 that satisfies the following
requirements.
1) High-Performance Liquid Chromatograph(i) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
(ii) Column: A 2-mm - 3-mm inner diameter 50-mm - 150-mm long 1.6-µm - 2.2-µm particle
diameter stainless steel column tube filled with silica gel to which octadecyl chemicallybonds. The specification is according to the mass spectrometer specification.
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Ion detection method: Selected Reaction Monitoringb) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
c) Manifoldd) Centrifugal separator: A centrifugal separator that can work at about 1700 × g.
e) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
f) Concentrator: An evaporator that can adjust to 40 ºC ± 2 ºC.
g) Copolymer cartridge column:
A divinylbenzene-N-vinylpyrrolidone copolymer minicolumn (200 mg)
Comment 3 Column is sold under the production name ACQUITY UPLC HSS C18, etc.
Comment 4 A copolymer cartridge is sold under the production names such as Oasis HLB 6cc (200mg) and Oasis PRiME HLB Plus Short Cartridge (225 mg).
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample, and put it into a 200-mL - 300-mL ground-in stopper
Erlenmeyer flask.
674

Testing Methods for Fertilizers(2021)

b)
c)
d)

Add 1 mL of sodium hydroxide solution (40 g/L) and 99 mL of methanol (3), and shake to mix
by reciprocating vertically at 300 times/min (amplitude of 40 mm) for about 30 minutes.
After allowing to stand still, put a supernatant solution in a 50-mL ground-in stopper centrifugal
precipitate tube.
Centrifuge it at about 1700 × g centrifugal force for about five minutes (4) and use thesupernatant as an extract.

Note (3) It is also allowed to add 100 mL of sodium hydroxide solution (40 g/L) − methanol[1+99](4) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
Comment 5 Grind until it completely passes through a sieve of 500 µm aperture to prepare the test
sample.
(4.2) Cleanup (1) (5): Conduct cleanup (1) as shown below.
a) Wash a copolymer cartridge column with about 5 mL of methanol and 5 mL of water in advance.
b) Place a 100-mL round-bottom flask (6) under the cartridge column, put 5 mL or 7 mL (7) of theextract in the cartridge column and allow the extract to overflow until the surface of the liquidreaches the top of the packing materials.
c) Add about 5 mL of sodium hydroxide solution (0.4 g/L) − methanol (1+1) to the cartridge
column 2 times and allow the liquid to overflow in the same manner in b).
d) Add 5 mL of methanol.
Note (5) Use a pressure reducing device in the procedure in (4.2) and (4.3) as appropriate.
(6) When pretreating many analytical samples, a free-standing type vessel that can containa solution with a liquid volume of 20 mL may be used. In this case, instead of procedured), put an effluent into a round-bottle flask, wash the vessel 2 times with 2.5 mL of
methanol and add washing to the previous effluent.
(7) When using Oasis HLB 6cc (200 mg), add 5 mL of the extract 2 times.
(4.3) Cleanup (2) (5): Conduct cleanup (2) as shown below.
a) Wash a new copolymer cartridge column with about 5 mL of acetonitrile and 5 mL ofhydrochloric acid (1+120) in advance.
b) Concentrate the effluent in (4.2) d) under reduced pressure to 5 mL or less on a water bath at
no more than 40 °C.
c) Add 3 mL of hydrochloric acid (1 +11), put the concentrated effluent into the cartridge column
and allow the effluent to overflow until the surface of liquid reaches the top of packing
materials.
d) Wash a round-bottom flask with about 5 mL of hydrochloric acid (1+120) 2 times and add
washing into the cartridge column successively.
e) Then, add about 5 mL of hydrochloric acid (1+120) − acetonitrile (9+1) and about 5 mL ofwater into the cartridge column successively and allow the liquid to overflow.
f) Place a 5-mL volumetric flask under the cartridge column, add 4 mL of ammonia solution(0.0028 % (mass fraction)) − acetonitrile (9+1) to the cartridge column and allow clopyralid,aminopyralid and picloram to elute quickly.
g) Add formic acid (1+1000) up to the marked line (8) and put it in 1.5-mL ground-in stopper
centrifugal precipitate tube (9).
h) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (10) and use thesupernatant as a sample solution
675

Testing Methods for Fertilizers(2021)

Note (8) If there is a possibility that the clopyralid, aminopyralid and picloram concentration in
the sample solution exceed the maximum limit of the calibration curve, dilute apredetermined amount of effluent with formic acid (1 +1000).
(9) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(10) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
(4.4) Measurement: Conduct the measurement as indicated in JIS K 0136 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph/Tandem Mass Spectrometer used in measurement.
a) The measurement conditions of the High-Performance Liquid Chromatograph/Tandem
Mass spectrometer: An example of measurement conditions for the High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer is shown below. Set up the measurement
conditions considering it:
1) High-Performance Liquid Chromatograph(i) Column: A silica gel column (2-mm - 3-mm inner diameter, 50-mm - 150-mm long, 1.6µm - 2.2-µm particle diameter column) to which octadecyl chemically bonds.
(ii) Flow rate: 0.2 mL/min - 0.5 mL/min(iii) Eluent: A: Formic acid (1+1000) B: Methanol:(iv) Gradient: 0 min (5 %B) → 5 min (60 %B) → 6 min (95 %B) → 7 min (5 %B)(v) Temperature of column bath: 40 °C(vi) Injection volume: 5 µL
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Mode: Positive(iii) Monitor ion: Shown in table 1
Table 1Monitor ion of respective agrichemicals
Mass-to-charge ratio (m /z )Substance namePrecursor ion

Product ion

Product ion(Determination)(Validation)

Clopyralid

192

146

110

Aminopyralid

207

161

189

Picloram

241

195

223

b) Calibration curve preparation
1) Inject 5 μL of respective mixture standard solutions for calibration curve into the LC-MS/MS,
record the chromatograms of ion (m/z) for determination and ion (m/z) for validation of
clopyralid, aminopyralid and picloram and obtain respective peak areas.
2) Calculate the peak area ratio or height ratio of ion (m/z) for determination and ion (m/z) for
validation of clopyralid, aminopyralid and picloram.
3) Prepare a curve for the relationship between the agrichemical concentration and the peak areaof ion (m/z) for determination of respective mixture standard solutions for the calibration curve
preparation.

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Testing Methods for Fertilizers(2021)c) Sample measurement
1) Subject 5 µL of the sample solution to the same procedure as in b) 2) - 3) (11).
2) Obtain the content of material subjected to measurement from the calibration curve to calculate
the concentration of the material subjected to measurement in the analytical sample.
Note (11) Confirm that the peak area ratio or height ratio of ion (m/z) for determination to ion(m/z) for validation is within the range of about ± 30 % of the peak area ratio or heightratio for the standard solution. In addition, the peak area ratio or height ratio depends onthe concentration.
Comment 6 Additive recovery testing of clopyralid, aminopyralid and picloram was conductedusing cow dung compost (2 kinds), composted sludge fertilizers containing cow dung
(2 kinds) and composted sludge fertilizers containing swine manure (1 kind), as a result,the mean recovery rates at the additive level of 1000 µg/kg, 400 µg/kg and 40 µg/kg
were 78.1 % - 90.0 %, 81.0 % - 117.6 % and 71.2 % - 101.3 % respectively.
Additionally, results from a collaborative study for testing method validation and its
analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 10 µg/kg for clopyralid, aminopyralid, and picloram.

677

Testing Methods for Fertilizers(2021)

Table 2 Analysis results of the collaborative study
for the test method validation of clopyralid and its degradation products
3)
4)
5)
6)
2)
Number of
Agrichemical
sr
RSD r
sR
RSD R
Mean
Sample name1)
namelaboratories (µg/kg) (µg/kg) (%)(µg/kg)
(%)
10
128
6
4.5
21
16.4
Clopyralid Compost 1
10
835
41
4.9
100
11.9
Compost 2
9
16.2
1.7
10.6
5.2
31.8
Composted sludge fertilizer 1
10
89.6
11.3
12.6
11.3
12.6
Composted sludge fertilizer 2
10
339
28
8.3
28
8.3
Composted sludge fertilizer 3
8
324
15
4.5
39
12.0
Aminopyralid Compost 1
8
21.2
5.2
24.7
6.4
30.3
Compost 2
7
5.39
1.41
26.2
2.22
41.2
Composted sludge fertilizer 1
10
701
146
20.8
263
37.6
Composted sludge fertilizer 2
9
59.5
8.9
15.0
16.6
28.0
Composted sludge fertilizer 3
10
840
50
5.9
175
20.8
PicloramCompost 1
9
37.7
3.5
9.4
10.3
27.3
Compost 2
9
90.2
11.1
12.3
30.3
33.5
Composted sludge fertilizer 1
8
341
19
5.6
67
19.8
Composted sludge fertilizer 2
8
182
16
8.6
56
31.0
Composted sludge fertilizer 3
1) Number of laboratories used in analysis
2) Grossl mean (n = number of laboratories × number of repeated tests (2))3) Repeatability standard deviation
4) Repeatability relative standard deviation
5) Reproducibility standard deviation
6) Reproducibility relative standard deviation

References1)
Toshiharu YAGI, Yuko SEKINE, Yuji SHIRAI: Determination of Clopyralid in
Fertilizer by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS),
Research Report of Fertilizer Vol. 3, p. 51 - 59 (2010)
2)
Hisanori ARAYA, Toshiharu YAGI, Yoshimi HASHIMOTO and Yuji SHIRAI:
Determination of Clopyralid, Aminopyralid and Picloram in Compost and Composted
Sludge Fertilizer by Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS),
Research Report of Fertilizer Vol. 7, p. 1 - 9 (2014)3)
Kenji KOZUKA, Mayu OSHIMA, Yoshimi HASHIMOTO, Naoko TAMARU, and Yuji
SHIRAI: Determination of Clopyralid, Aminopyralid and Picloram in Compost andComposted Sludge Fertilizer by Liquid Chromatography-Tandem Mass Spectrometry(LC-MS/MS): A Collaborative Study, Research Report of Fertilizer Vol. 10, p. 61 - 71
(2017)

678

Testing Methods for Fertilizers(2021)(5)

Flow sheet for clopyralid and its derivative substances: The flow sheet for clopyralid and its
derivative substances in compost and composted sludge fertilizer is shown below:

5.00 g analytical sample
200-mL - 300-mL ground-in stopper Erlenmeyer flask← 1 mL of sodium hydroxide solution (4 g/L)
← 99 mL of methanol
Vertical reciprocating shaker
shaking to mix(300 times/ minute, amplitude of 40 mm), 30 minutes
Centrifugal separation

50 mL centrifugal precipitate tube, 1700 × g, 5 minutes

Extract
Figure 1 Flow sheet for clopyralid and its derivative substances in compostand composted sludge fertilizers (Extraction procedure)
Extract
Aliquot(5 mL or 10 mL)
copolymer cartridge column (1)(Wash with about 5 mL of methanol, then 5 mL of water in advance）[Collection, 100-mL round-bottom flask]← About 5 mL of sodium hydroxide solution (0.4 g/L) - methanol [1+1] × 2 times[Collection, same as above vessel]← About 5 mL of methanol
Concentration
40 ºC, until the volume reaches about 5 mLunder reduced pressure← 3 mL of hydrochloric acid (1+11)
copolymer cartridge column (1)Cleanup (2)(Wash with about 5 mL of acetonitrile,then 5 mL of hydrochloric acid (1+120) in advance)← Wash the vessel 2 times with about 5mL of hydrochloric acid (1+120)← Wash with about 5mL of hydrochloric acid (1+120) -acetonitrile [9+1]← Wash with about 5mL of water← 4 mL of ammonia solution (0.0028 w/v %)- acetonitrile [9+1][Elute, 5-mL volumetric flask]
Precise adjustment← Formic acid (1+1000) (up to the marked line)
1.5-mL ground-in stopper centrifugal precipitate tube,
Centrifugal separation
8000 × g - 10000 × g , 5 minutes
Cleanup (1)Measurement

High-Performance Liquid Chromatograph/Tandem Mass Spectrometer

Figure 2 Flow sheet for clopyralid and its derivative substances in compostand composted sludge fertilizers (Cleanup (1), cleanup (2) and measurement procedure)

679

Testing Methods for Fertilizers(2021)

References: An example of the Selected Reaction Monitoring chromatograms of the mixture
standard solution for calibration curve preparation and the sample solution (cow dung
compost) is shown below
Peak No.

2

3

Intensity / arb.units

10

Retention Time / min

5

Peak No.1: Picloram
No.2: Aminopyralid
No.3: Clopyralid
Reference diagram: SRM chromatograms of respective agrichemicals
Mixture standard solution (the equivalents of 200 pg as respective
agrichemicals)
LC-MS/MS measurement conditions
Column: ACQUITY UPLC HSS C18 (2.1-mm inner diameter, 100-mm long, 1.8-µm
particle diameter)
Flow rate: 0.4 mL/min
Capillary voltage: 1.0 kV
Temperature of ion source: 120 °C
Desolvation temperature: 400 °C
Cone voltage: Shown in reference table
Collision energy: Shown in reference table
Other conditions are according to the examples of the measurement conditions in (4.4)a) LC-MS/MS.

680

Testing Methods for Fertilizers(2021)

681

Testing Methods for Fertilizers(2021)

8.2.b High-Performance Liquid Chromatography/Tandem Mass Spectrometry(Microanalysis for clopyralid (1))(1) Summary
This testing method is applicable to compost and composted sludge fertilizers. This testing method isclassified as Type B and its symbol is 8.2.b-2018 or CLP.b-1.
Extract clopyralid in compost and composted sludge fertilizer with methanol under alkaline condition,refine with a cleanup cartridge and dichloromethane by taking advantage of characteristics that the
behavior of elution varies between acidity and alkaline then measure with a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer (LC-MS/MS) to obtain clopyralid in an analyticalsample. In addition, the performance of this testing method is shown in Comment 8.
Comment 1 Structural formula of clopyralid is as shown in Figure 1.

Figure 1 Structural formula of clopyralid(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557. Note that water of A4 should be used as theeluent which is introduced to a High-Performance Liquid Chromatograph/Tandem Mass
Spectrometer.
b) Acetonitrile: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8039 or a reagent of equivalent quality.
c) Methanol: A reagent of agricultural chemicals residue/PCB testing grade (concentration: noless than 300) or a reagent of equivalent quality.
d) Methanol:
Methanol used in the eluent of a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer is a reagent of LC-MS analysis grade orequivalents.
e) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
f) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
g) Ammonia solution: A JIS Guaranteed Reagent of 28 % (mass fraction) specified in JIS K
8085 or a reagent of equivalent quality.
h) Formic acid: A JIS Guaranteed Reagent specified in JIS K 8264 or a reagent of equivalentquality.
i) Formic acid: Formic acid used in the eluent of a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer is a reagent of LC-MS analysis grade orequivalents.
j) Dichloromethane: A reagent of agricultural chemicals residue/PCB testing grade(concentration: no less than 300) specified in JIS K 8117 or a reagent of equivalent quality.
k) Sulfuric acid: A JIS Guaranteed Reagent specified in JIS K 8951 or a reagent of equivalentquality.
l) Acetone: A reagent of agricultural chemicals residue/PCB testing grade (concentration: noless than 300) specified in JIS K 8040 or a reagent of equivalent quality.
682

Testing Methods for Fertilizers(2021)m) Ammonia solution (0.0028 % (mass fraction)) (1): Add 0.1 mL of ammonia solution to 1000mL of water.
n) Clopyralid standard solution (0.1 mg/mL) (1): Put about 0.01 g of clopyralid [C6H3C12NO2](2)
in a weighing dish and measure the mass to the order of 0.1 mg. Dissolve with a small amountof acetonitrile, transfer to 100-mL volumetric flasks and add the solvent up to the marked line.
o) Clopyralid standard solution (100 ng/mL) (1): Dilute a predetermined amount of clopyralid
standard solution (0.1 mg/mL) with formic acid (1+1000) to prepare a clopyralid standard
solution (100 ng/mL).
p) Clopyralid standard solution for calibration curve preparation (5 ng/mL - 50 ng/mL) (1):In the case of usage, put 2.5 mL - 25 mL of clopyralid standard solution (100 ng/mL) in 50 mL
volumetric flasks step-by-step, and add formic acid (1+1000) up to the marked line.
q) Clopyralid standard solution for calibration curve preparation (0.5 ng/mL - 5 ng/mL) (1):In the case of usage, put 2.5 mL - 25 mL of clopyralid standard solution (10 ng/mL) in 50 mL
volumetric flasks step-by-step, and add formic acid (1+1000) up to the marked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A standard reagent is commercially sold.
Comment 2 A standard reagent of clopyralid is sold by FUJIFILM Wako Pure Chemical Co., Ltd.,
Kanto Chemical Co., Inc. and Hayashi Pure Chemical Industries., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph/ Mass Spectrometer： A high-performanceliquid chromatograph/tandem mass spectrometer specified in JIS K 0136 that satisfies thefollowing requirements.
1) High-Performance Liquid Chromatograph(i) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
(ii) Column: A 2-mm - 3-mm inner diameter 50-mm - 150-mm long 1.6-µm - 2.2-µm particle
diameter stainless steel column tube filled with silica gel to which octadecyl chemicallybonds. The specification is according to the mass spectrometer specification.
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Ion detection method: Selected Reaction Monitoringb) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
c) Manifoldd) Centrifugal separator: A centrifugal separator that can work at 700 × g - 2000 × g.
e) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
f) Concentrator: An evaporator that can adjust to 40 ºC ± 2 ºC.
g) Copolymer cartridge column: A divinylbenzene-N-vinylpyrrolidone copolymer mini column(200 mg or 335 mg)h) Filter: A funnel for filtering under reduced pressure (compatible filter diameter: 60 mm)i) Glass fiber filter paper: A filter paper made of glass fiber (filter diameter: 60 mm) that cankeep particle diameter 0.8 µm.
j) Test tube mixer: Vortex mixer
Comment 3 Column is sold under the production name ACQUITY UPLC HSS C18, etc.
Comment 4 A copolymer cartridge is sold under the production names such as Oasis HLB 6cc (225683

Testing Methods for Fertilizers(2021)mg) and Oasis PRiME HLB Plus Short Cartridge (225 mg).
Comment 5 A funnel for filtering under reduced pressure is sold under the production nameKIRIYAMA Funnel SB-60, KIRIYAMA Funnel SU-60, etc.
Comment 6 A glass fiber filter is sold under the production name Glass filter paper GFP-60, etc.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample to the order of 1 mg and put it in a 100-mL centrifugal
precipitate tube with a screw cap (3) (4).
b) Add 50 mL of sodium hydroxide solution (40 g/L) − methanol [1+99] and shake to mix byreciprocating vertically at 300 times/min (amplitude of 40 mm) for about 30 minutes.
c) Centrifuge at about 1700 × g for about 3 minutes (5) and put the supernatant in a 100-mL
Erlenmeyer flask.
d) Add 40 mL of sodium hydroxide solution (40 g/L) − methanol [1+99] to residue and shake tomix by reciprocating vertically at 300 times/min (amplitude of 40 mm) for about 30 minutes.
e) Centrifuge at about 1700 × g for about five minutes (5).
f) Filter supernatant in c) and e) under reduced pressure with a filter that places a glass fiber filter
paper to a 100-mL short-neck volumetric flask as an acceptor (6).
g) Wash the vessel and residue with a small amount of sodium hydroxide (40 g/L)−methanol[1+99] several times and put the washing in the previous filter to filter under pressure.
h) Add sodium hydroxide solution (40 g/L) - methanol [1+99] to the marked line to make anextract.
Note (3) A vessel used for an extract procedure should be made of glass or polypropylene and it
can be used with a shaker and a centrifugal separator.
(4) A 100-mL - 200-mL ground-in stopper or screw cap Erlenmeyer flask can also be used.
In this case, however, suspension should be transferred to a ground-in stopper or screw
cap centrifugal precipitate tube before the procedure c) and e).
(5) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(6) An Erlenmeyer flask can also be used. In this case, however, filtrate should betransferred to a 100-mL volumetric flask before the procedure h).
Comment 5 Grind until it completely passes through a sieve of 500 µm aperture to prepare the test
sample.
(4.2) Cleanup (1) (7): Conduct cleanup (1) as shown below.
a) Wash a cartridge column with about 5 mL of methanol and 5 mL of water in advance.
b) Place a 100-mL round-bottom flask (8) under the cartridge column, put 9 mL (9) of the extract in
the cartridge column and allow the extract to overflow until the surface of the liquid reaches
the top of the packing materials.
c) Add about 5 mL of sodium hydroxide solution (0.4 g/L) − methanol [1+1] to the cartridge
column 2 times and allow the liquid to overflow in the same manner in b).
d) Add 5 mL of methanol.
Note (7) Use a pressure reducing device in the procedure in (4.2) and (4.3) as appropriate.
(8) When making a pretreatment of many analytical samples, a free-standing type vesselthat can contain a solution with a liquid volume of 20 mL may be used. In this case,instead of procedure d), put an effluent into a round-bottle flask, wash the vessel 2 times
with 2.5 mL of methanol and add washing to the previous effluent.
684

Testing Methods for Fertilizers(2021)(9) When using Oasis HLB 6cc (200 mg), add 5 mL of the extract 2 times.
(4.3) Cleanup (2) (7): Conduct cleanup (2) as shown below.
a) Wash a new cartridge column with about 5 mL of acetonitrile and 5 mL of hydrochloric acid
(1+120) in advance.
b) Concentrate the effluent in (4.2) d) under reduced pressure to 5 mL or less on a water bath at
no more than 40 °C.
c) Add 3 mL of hydrochloric acid (1 +11), put the concentrated effluent into the cartridge column
and allow the effluent to overflow until the surface of liquid reaches the top of packing
materials.
d) Wash a round-bottom flask with about 5 mL of hydrochloric acid (1+120) 2 times and add
washing into the cartridge column successively to allow the liquid overflow.
e) Then, add about 5 mL of hydrochloric acid (1+120) − acetonitrile (9+1) and about 5 mL ofwater into the cartridge column successively and allow the liquid to overflow.
f) Place a 10-mL cone shaped centrifugal precipitate tube with a screw cap (10) under the cartridge
column, add 4 mL of ammonia solution (0.0028 % (mass fraction)) − acetonitrile [9+1] to thecartridge column and allow clopyralid to elute.
Note (10)The part under 2 mL from the bottom forms a cone shape.

(4.4) Cleanup (3): Conduct cleanup (3) as shown below.
a) Add 0.1 mL of sodium hydroxide (40 g/L) to the elute in (4.3) f) and shake to mix by using atest tube mixer.
b) Add about 2 mL of dichloromethane, and shake to mix using a test tube mixer for about 30
minutes.
c) Centrifuge at about 740 × g for about 3 minutes (11) and remove a low layer by using a Pasteur
pipet (12) or a syringe.
d) Repeat the procedure in b) - c) 1 time.
e) Add about 0.15 mL of sulfuric acid (1+2), and shake to mix using a test tube mixer.
f) Add about 2 mL of dichloromethane, and shake to mix using a test tube mixer for about 30
minutes (13).
g) Centrifuge at about 740 × g for about five minutes (11) and put a low layer in a 50mL roundbottle flask by using a Pasteur pipet (14) or a syringe.
h) Repeat the procedure in f) - g) 2 times. Note that lower layers are added to the same roundbottle flask.
i) Add 5 mL of acetone.
j) Concentrate under reduced pressure in a water bath of no more than 40 ºC until most of theelute exsiccates and send a nitrogen gas to exsiccate.
k) Add 1 mL of formic acid (1+1000) and transfer it to a 1.5-mL ground-in stopper centrifugal
precipitate tube (15).
l) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (16) and use thesupernatant as a sample solution
Note (11) 16.5-cm of rotor radius and 2000 rpm of revolutions makes about 740 × g centrifugal
force. Confirm the permissible range of centrifugal force of a 10-mL cone shaped bottle
centrifugal precipitate tube with a screw cap used.
(12) When using a Pasteur pipet, use the same Pasteur pipet through a series of proceduresin c) - d).
(13) Disperse dichloromethane sufficiently. If a shaking to mix process is conducted while
dichloromethane layer remains caked, the extraction efficiency of clopyralid
685

Testing Methods for Fertilizers(2021)

deteriorates and measurements are affected.
(14) When using a Pasteur pipet, use the same Pasteur pipet through a series of proceduresin g) - h). Do not use the Pasteur pipet used in Note (12).
(15) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(16) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
(17) If there is a possibility that the clopyralid concentration in the sample solution exceed
the maximum limit of the calibration curve, dilute a predetermined amount of effluent
with formic acid (1 +1000).
Comment 6 As an alternative to the procedures in (4.4) k) - l), filtration is allowed with a membranefilter (pore size: no more than 0.5 µm) made of hydrophilic PTFE or conduct
centrifugal filtration with a centrifugal type filter unit (Ultrafree-MC PVDF membrane(0.22 µm), etc.) and the filtrate can be the sample solution.
Comment 7 When further concentration is required to ensure minimum quantitation, dissolve
concentrated matters in the procedure in j) by adding acetone, transfer to a nitrogenconcentration tube with the same solvent and send a nitrogen gas to exsiccate. Then
add 0.2 mL of formic acid (1+1000) and conduct centrifugal filtration with acentrifugal type filter unit (Ultrafree-MC PVDF membrane (0.22 µm), etc.) and thefiltrate can be the sample solution. In this case, don not conduct the procedure in i).
(4.5) Measurement: Conduct the measurement as indicated in JIS K 0136 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph/Mass Spectrometer used in measurement.
a) The measurement conditions of the High-Performance Liquid Chromatograph/Mass
spectrometer: An example of measurement conditions for the High-Performance Liquid
Chromatograph/Mass Spectrometer is shown below. Set up the measurement conditions
considering it:
1) High-Performance Liquid Chromatograph(i) Column: A silica gel column (2-mm - 3-mm inner diameter, 50-mm - 150-mm long, 1.6µm - 2.2-µm particle diameter column) to which octadecyl chemically bonds.
(ii) Flow rate: 0.2 mL/min - 0.5 mL/min(iii) Eluent: A: Formic acid (1+1000) B: Methanol:(iv) Gradient: 0 min (5 %B) → 5 min (60 %B) → 6 min (95 %B) → 7 min (5 %B)(v) Temperature of column bath: 40 °C(vi) Injection volume: 5 µL
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Mode: Positive(iii) Monitor ion: Precursor ion m/z 192
Product ion m/z 146 for determination, m/z 110 for validationb) Calibration curve preparation
1) Inject 5 μL of respective clopyralid standard solutions for calibration curve into the HighPerformance Liquid Chromatograph/Tandem Mass Spectrometer, record the chromatograms ofion (m/z) for determination and ion (m/z) for validation of clopyralid and obtain respective peakareas.
2) Calculate the peak area ratio or height ratio of ion (m/z) for determination and ion (m/z) for686

Testing Methods for Fertilizers(2021)

validation of clopyralid.
3) Prepare a curve for the relationship between the agrichemical concentration and the peak areaof ion (m/z) for determination of respective mixture standard solutions for the calibration curve
preparation.
c) Sample measurement
1) Subject 5 µL of the sample solution to the same procedure as in b) 2) - 3) (18).
2) Obtain the clopyralid content from the calibration curve to calculate clopyralid in the analyticalsample.
Note (18) Confirm that the ratio against the peak area ratio or height ratio of the standard solution
is within the range of about ± 30 %. In addition, the peak area ratio or height ratio may
depend on the concentration.
Comment 8 Additive recovery testing of clopyralid was conducted using cow dung compost (1kinds), as a result, the mean recovery rates at the additive level of 50 µg/kg, 10 µg/kg
and 2 µg/kg were 78.9 %, 78.3 % and 71.5 % respectively. In addition, additive
recovery testing of clopyralid was conducted using swine manure compost, poultry
manure compost and composted sludge fertilizer (1 sample for each), as a result, themean recovery rates at the additive level of 200µg/kg, 2 µg/kg and 80µg/kg were
88.6 %, 81.2 % and 94.2 % respectively.
Additionally, results from a collaborative study for testing method validation and its
analysis are shown in Table 1.
Note that the minimum limit of quantification of this testing method was estimated to
be about 2 µg/kg for clopyralid.
Table 1 Analysis results of the collaborative study
for the test method validation of clopyralid
3)
4)
5)
6)
Number of Mean2)
sr
RSD r
sR
RSD R
Sample name1)laboratories(µg/kg) (µg/kg)(%)(µg/kg)
(%)
10
128
10
7.9
15
11.4
Cow dung compost 1
10
2.28
0.35
15.3
0.40
17.6
Cow dung compost 2
9
22.5
2.3
10.3
3.4
15.3
Swine manure compost
9
1.20
0.06
5.0
0.14
12.0
Poultry manure compost
9
48.1
1.2
2.5
5.6
11.6
Composted sludge fertilizer
1) Number of laboratories used in analysis
2) Grossl mean (n = number of laboratories × number of repeated tests (2))3) Repeatability standard deviation
4) Repeatability relative standard deviation
5) Reproducibility standard deviation
6) Reproducibility relative standard deviation

References
1)
National Research and Development Agency: Institute for Agro-Environmental Sciences,
National Agriculture and Food Research Organization: High-sensitive analysis forclopyralid in cow dung compost (Reference method)< http://www.naro.affrc.go.jp/publicity_report/pub2016_or_later/pamphlet/tech-pamph/078229.html>
687

Testing Methods for Fertilizers(2021)

2)

3)

(5)

Kohei ITO, Kenji KOZUKA, Keisuke AOYAMA, Yuji SHIRAI: Validation of
Microanalysis Determination of Clopyralid in Compost and Composted Sludge Fertilizer
by Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS), Research Reportof Fertilizer Vol. 11, p. 63 – 74 (2018)
Kohei ITO, Kenji KOZUKA, Satono AKIMOTO, Satoko SAKAIDA, Mayu OSHIMA,
Nobuhito NAKAMURA, Yuji SHIRAI: Microanalysis Determination of Clopyralid in
Compost and Composted Sludge Fertilizer by Liquid Chromatography/Tandem Mass
Spectrometry (LC-MS/MS): A Collaborative Study, Research Report of Fertilizer Vol. 11,
p. 75 – 85 (2018)

Flow sheet for clopyralid: The flow sheet for clopyralid in compost is shown below:
5.00 g100-mL centrifugal precipitate tube with a screw cap
analytical sample← 50 mL of sodium hydroxide solution (40 g/L)−methanol [1+99]
Shaking to mix
Vertical reciprocating shaker (300 reciprocations/min, amplitude of 40 mm), for 30 minutes
Centrifugal separation

1700× g , 5 minutes

Transfer supernatant［Acceptor, 100-mL Erlenmeyer flask］（Supernatant）（Residue）← 40 mL of sodium hydroxide solution (40 g/L)−methanol [1+99]
Shaking
30 minutes
Centrifugal separation

1700× g , 5 minutes

Filter under
Glass fiber filter paper
reduced pressure［Acceptor, 100-mL short-neck volumetric flask］←Wash the vessel and residue with a small amount of
sodium hydroxide (40 g/L)−methanol [1+98]←Sodium hydroxide solution (40 g/L)−methanol [1+99]
Extract

Figure 1

Flow sheet for clopyralid in compostand composted sludge fertilizers (Extraction procedure)

688

Testing Methods for Fertilizers(2021)

Extract
Aliquot (10 mL)
copolymer cartridge column (1)(Wash with about 5 mL of methanol, then 5 mL of water in advance）[Collection, 100-mL round-bottom flask]← About 5 mL of sodium hydroxide solution (0.4 g/L)−methanol [1+1] × 2 times[Collection, same as above vessel]← About 5 mL of methanol
Concentration
40 ºC, until the volume reaches about 5 mLunder reduced pressure← 3 mL of hydrochloric acid (1+11)
copolymer cartridge column (2)Cleanup (2)(Wash with about 5 mL of acetonitrile,then 5 mL of hydrochloric acid (1+120) in advance)
Wash
thevessel2
times with about 5mL of hydrochloric acid (1+120)←← Wash with about 5mL of hydrochloric acid (1+120)−acetonitrile [9+1]← Wash with about 5mL of water← 4 mL of ammonia solution (0.0028 % (mass fraction))−acetonitrile [9+1][Elute, 10-mL centrifugal precipitate tube]
Elute
Cleanup (1)Figure 2 Flow sheet for clopyralid in compost and composted sludge fertilizers(Cleanup (1) and cleanup (2) procedure)

689

Testing Methods for Fertilizers(2021)

EluateCleanup (3)← 0.1 mL of sodium hydroxide (40 g/L)
VortexShaking to mix← 2 mL of dichloromethane
Vortex, 30 seconds
Shaking to mix
Centrifugal separation

740 × g (2000 rpm, 165 mm), 3 minutes

Remove a low layer

Pasteur pipet or micro syringe

Repeat 1 time
← 0.15 mL of sulfuric acid (1+2)
Shaking to mix
Vortex← 2 mL of dichloromethane
Vortex, 30 seconds

Shaking to mix

Centrifugal separation

740 × g (2000 rpm, 165 mm), 3 minutes
Pasteur pipet or micro syringe

Transfer a low layer［Acceptor, 50-mL round-bottle flask］
Repeat 2 times←5 mL of acetone
Concentration
under reduced pressure

40 °C

Exsiccation

Nitrogen← 1 mL of formic acid (1+1000)
Ground-in stopper centrifugal precipitate tube,
Centrifugal separation
8000 × g - 10000 g, 5 minutes
Supernatant
Measurement

High-Speed Liquid Chromatograph/Mass Spectrometer

Figure 3 Flow sheet for clopyralid in compost and composted sludge fertilizers(Cleanup (3) and measurement procedure)

690

Testing Methods for Fertilizers(2021)

Intensity /References: An example of the Selected Reaction Monitoring chromatogram of clopyralid standard
solution for calibration curve preparation is shown below

Retention Time / min

Reference diagram: SRM chromatograms of clopyralid
Clopyralid standard solution (the equivalents of 100 pg as clopyralid)
LC-MS/MS measurement conditions
1) Column: ACQUITY UPLC HSS C18 (2.1-mm inner diameter, 100-mm long, 1.8µm particle diameter)
Flow rate: 0.4 mL/min
Capillary voltage: 1.0 kV
Temperature of ion source: 120 °C
Desolvation temperature: 400 °C
Cone voltage: 20 V
Collision energy: 20 eV for determination, 30 eV for validation
Other conditions are according to the examples of the measurement conditions in (4.4)a) LC-MS/MS.

691

Testing Methods for Fertilizers(2021)

8.2.c High-Performance Liquid Chromatography/Tandem Mass Spectrometry(Microanalysis for clopyralid (2))(1) Summary
This testing method is applicable to compost and composted sludge fertilizers. This testing method
is classified as Type B and its symbol is 8.2.c-2021or CLP.c-2.
Extract clopyralid in compost and composted sludge fertilizer with methanol under alkalinecondition, refine with two kinds of cleanup cartridge by taking advantage of characteristics that the
behavior of elution varies between acidity and alkaline then measure with a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer (LC-MS/MS) to obtain clopyralid in an analyticalsample. In addition, the performance of this testing method is shown in Comment 9.
Comment 1 Structural formula of clopyralid is as shown in Figure 1.

Figure 1 Structural formula of clopyralid(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557. Note that water of A4 should be used as theeluent which is introduced to a High-Performance Liquid Chromatograph/Tandem Mass
Spectrometer.
b) Acetonitrile: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8039 or a reagent of equivalent quality.
c) Methanol: A reagent of agricultural chemicals residue/PCB testing grade (concentration: noless than 300) or a reagent of equivalent quality. Note that a regent of LC-MS analysis grade
or equivalents should be used as the eluent which is introduced to a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer.
d) Sodium hydroxide: A JIS Guaranteed Reagent specified in JIS K 8576 or a reagent ofequivalent quality.
e) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
f) Ammonia solution: A JIS Guaranteed Reagent of 28 % (mass fraction) specified in JIS K
8085 or a reagent of equivalent quality.
g) Formic acid: A JIS Guaranteed Reagent specified in JIS K 8264 or a reagent of equivalentquality. Note that a regent of LC-MS analysis grade or equivalents should be used as the eluent
which is introduced to a High-Performance Liquid Chromatograph/Tandem Mass
Spectrometer.
h) Ammonia solution (0.0028 % (mass fraction)) (1): Add 0.1 mL of ammonia solution to 1000mL of water.
i) Clopyralid standard solution (0.1 mg/mL) (1): Put about 0.01 g of clopyralid [C6H3C12NO2](2)
in a weighing dish and measure the mass to the order of 0.1 mg. Dissolve with a small amountof acetonitrile, transfer to 100-mL volumetric flasks and add the solvent up to the marked line.
j) Clopyralid standard solution (100 ng/mL) (1): Dilute a predetermined amount of clopyralid
standard solution (0.1 mg/mL) with formic acid (1+1000) to prepare clopyralid standard
solution (100 ng/mL).
692

Testing Methods for Fertilizers(2021)k)l)Clopyralid standard solution for calibration curve preparation (5 ng/mL - 50 ng/mL) (1):In the case of usage, put 2.5 mL - 25 mL of clopyralid standard solution (100 ng/mL) in 50 mL
volumetric flasks step-by-step, and add formic acid (1+1000) up to the marked line.
Clopyralid standard solution for calibration curve preparation (0.5 ng/mL - 5 ng/mL) (1):In the case of usage, put 2.5 mL - 25 mL of clopyralid standard solution (10 ng/mL) in 50 mL
volumetric flasks step-by-step, and add formic acid (1+1000) up to the marked line.

Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A standard reagent is commercially sold.
Comment 2 A standard reagent of clopyralid is sold by FUJIFILM Wako Pure Chemical Co., Ltd.,
Kanto Chemical Co., Inc. and Hayashi Pure Chemical Industries., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph/Mass Spectrometer ： A high-performanceliquid chromatograph/tandem mass spectrometer specified in JIS K 0136 that satisfies thefollowing requirements.
1) High-Performance Liquid Chromatograph(i) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
(ii) Column: A 2-mm - 3-mm inner diameter 50-mm - 150-mm long 1.6-µm - 2.2-µm particle
diameter stainless steel column tube filled with silica gel to which octadecyl chemicallybonds. The specification is according to the mass spectrometer specification.
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Ion detection method: Selected Reaction Monitoringb) Vertical reciprocating shaker: A vertical reciprocating shaker that can shake a 250-mL
volumetric flask using an adapter to reciprocate vertically at a rate of 300 reciprocations/min(amplitude of 40 mm).
c) Manifoldd) Centrifugal separator: A centrifugal separator that can work at 700 × g - 2000 × g.
e) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
f) Concentrator: An evaporator that can adjust to 40 ºC ± 2 ºC.
g) Copolymer cartridge column: A cartridge column whose syringe barrel (12 mL) is filledwith a divinylbenzene-N-vinylpyrrolidone copolymer (500 mg) or cartridge column whosesyringe barrel (20 mL) is filled with an N-containing vinyl polymer-containing
styrenedivinylbenzene composite polymer (500 mg).
h) Zirconia coated silica gel cartridge column: A cartridge column whose syringe barrel (6mL) is filled with silica gel (500 mg) coated by zirconia group.
Comment 3 A column is sold under production names such as CQUITY UPLC HSS C18,ACQUITY UPLC HSS C18, ACQUITY UPLC HSS T3, InertSustain AQ-C18, Shimpack Scepter C18-120, C18U 2B, and ZORBAX Eclipse Plus C18.
Comment 4 A copolymer cartridge column is sold under the production names Oasis HLB 12cc
(500 mg), InertSep HLB FF 500 mg/20 mL, etc.
Comment 5 A zirconia coated silica gel cartridge column is commercially sold under production
names HybrideSPEⓇ-Phospholipid (500 mg), etc.
(4)

Test procedures
693

Testing Methods for Fertilizers(2021)(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2.00 g of an analytical sample and put it in a 50-mL centrifugal precipitate tube with ascrew cap (3).
b) Add 50 mL of sodium hydroxide solution (40 g/L) − methanol [1+99] and shake to mix byreciprocating vertically at 300 times/min (amplitude of 40 mm) for about 30 minutes.
c) Centrifuge at about 1700 × g for about 5 minutes (4) and put the supernatant in a 200-mL roundbottle flask(5).
d) Add 10 mL of sodium hydroxide solution (40 g/L) − methanol [1+99] to residue and shake tomix.
e) Centrifuge it at about 1700 × g centrifugal force for about 5 minutes (4), and add the supernatantto the supernatant of c) (5).
f) Conduct the procedures in d) – e) two times, wash the solution attached at the connecting partof the round-bottom flask with methanol to add, and use it as an extract.
Note (3) A vessel used for an extract procedure should be made of glass or polypropylene and it
can be used with a shaker and a centrifugal separator.
(4) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(5) Transfer by decantation.
Comment 6 Grind until it completely passes through a sieve of 500 µm aperture to prepare the test
sample.
Comment 7 In the procedure in (4.2), to reduce the factors of the copolymer cartridge column
being clogged, rotate the centrifugal precipitate tube with a screw cap to remove thesample attached to the wall prior to the centrifugal separation operation in c) and e),
and pay attention not to include solid materials to the extent possible when transferringor adding the supernatant.
(4.2) Cleanup (1) (6): Conduct cleanup (1) as shown below.
a) Wash a copolymer cartridge column with about 5 mL of acetonitrile and 5 mL of hydrochloric
acid (1+120) in advance.
b) Concentrate the extract under reduced pressure to 3 mL or less on a water bath at no more than
40 °C.
c) Add 3 mL of hydrochloric acid (1+11) and transfer it to a 10-mL ground-in stopper centrifugal
precipitate tube (7) (hereinafter in this section simply “centrifugal precipitate tube”) (8).
d) Centrifuge at about 740 × g for about five minutes (9).
e) Put the supernatant into the cartridge column (8) and allow the effluent to overflow until thesurface of liquid reaches the top of packing materials.
f) Wash the round-bottom flask with about 5 mL of hydrochloric acid (1+120), and add thewashing into the centrifugal precipitate tube (8) (10).
g) Centrifuge at about 740 × g for about five minutes.
h) Wash the round-bottom flask with about 5 mL of hydrochloric acid (1+120), and add thewashing into the centrifugal precipitate tube (8) (10).
i) Centrifuge at about 740 × g for about five minutes (9).
j) Add the supernatant and the washings into the cartridge column successively and allow theliquid overflow.
k) Repeat the procedure in h) - j) 2 times.
l) Then, add about 10 mL of hydrochloric acid (1+120) - acetonitrile (9+1) and about 5 mL ofwater into the cartridge column successively and allow the liquid to overflow.
694

Testing Methods for Fertilizers(2021)m) Place a 10-mL ground-in stopper tube under the cartridge column, add 8 mL of ammonia
solution (0.0028 % (mass fraction)) - acetonitrile [9+1] to the cartridge column and allow
clopyralid to elute.
n) Add 2 mL of formic acid (1+1000) to the effluent and mix well.
Note (6) Use a pressure reducing device or pressurize in the procedure in (4.2) and (4.3) asappropriate.
(7) A centrifugal precipitate tube with a screw cap may be used.
(8) The same Pasteur pipet, etc. should be used in a series of procedures.
(9) 16.5-cm of rotor radius and 2000 rpm of revolutions makes about 740 × g centrifugal
force. The permissible range of centrifugal force of a 10-mL ground-in stopper
centrifugal precipitate tube used to be confirmed.
(10) To reduce the factors of the copolymer cartridge column being clogged, pay attention
not to disturb the centrifugal precipitate to the extent possible.
(4.3) Cleanup (2) (5): Conduct cleanup (2) as shown below.
a) Wash a zirconia coated silica gel cartridge column with about 5 mL of acetonitrile and 5 mL offormic acid (1+1000) in advance.
b) Put the solution in (4.2) f) into the cartridge column (6) and allow the effluent to overflow until
the surface of liquid reaches the top of packing materials.
c) Wash a ground-in stopper tube with about 5 mL of acetonitrile, put the washing to the same
cartridge and allow the effluent to overflow until the surface of liquid reaches the top of packing
materials.
d) Place a 50-mL round-bottom flask (8) under the cartridge column, add 10 mL of formic acidacetonitrile [2+98] (9) to the cartridge column and allow the solution to elute.
e) Concentrate the elute under reduced pressure in a water bath of no more than 40 ºC until mostof the elute exsiccates and send a nitrogen gas to exsiccate.
f) Add 4 mL of formic acid (1+1000) and put a predetermined amount of the solution in a groundin stopper centrifugal precipitate tube (10).
g) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (11) to make thesample solution (12).
Note (8) When making a pretreatment of the multicomponent of an analytical sample, a 10-mL
test tube may be used. In this case, before the procedure in e), put the eluate into a 50mL round-bottle flask, wash the previous test tube 2 times with 2.5 mL of acetonitrile
and add the washing to the previous eluate.
(9) Prepare at the time of usage. Using the solution that has passed one day after the
preparation affects the measurement results.
(10) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(11) 7.2-cm – 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
(12) If there is a possibility that the clopyralid concentration in the sample solution exceed
the maximum limit of the calibration curve, dilute a predetermined amount of the sample
solution with formic acid (1 +1000).
Comment 8 Instead of the procedures in (4.3) f) - g), it is allowed to filter with a membrane filter(pore size: no more than 0.5 µm) made of hydrophilic PTFE and the filtrate can be thesample solution.
695

Testing Methods for Fertilizers(2021)(4.4) Measurement: Conduct the measurement as indicated in JIS K 0136 and as shown below.
Specific measurement procedures are according to the operation method of the High-Performance
Liquid Chromatograph/ Mass Spectrometer used in measurement.
a) The measurement conditions of the High-Performance Liquid Chromatograph/Mass
spectrometer: An example of measurement conditions for the High-Performance Liquid
Chromatograph/Mass Spectrometer is shown below. Set up the measurement conditions
considering it:
1) High-Performance Liquid Chromatograph(i) Column: A silica gel column (2-mm - 3-mm inner diameter, 50-mm - 150-mm long, 1.6µm – 3.0-µm particle diameter column) to which octadecyl chemically bonds.
(ii) Flow rate: 0.2 mL/min - 0.5 mL/min(iii) Eluent: A: Formic acid (1+1000) B: Methanol:(iv) Gradient: 0 min (5 %B) → 5 min (60 %B) → 6 min (95 %B) → 7 min (5 %B)(v) Temperature of column bath: 40 °C(vi) Injection volume: 5 µL
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Mode: Positive(iii) Monitor ion: Precursor ion m/z 192
Product ion m/z 146 for determination, m/z 110 for validationb) Calibration curve preparation
1) Inject 5 μL of respective clopyralid standard solutions for calibration curve preparation into theHigh-Performance Liquid Chromatograph/Tandem Mass Spectrometer, record thechromatograms of ion (m/z) for determination and ion (m/z) for validation of clopyralid andobtain respective peak areas (13).
2) Calculate the peak area ratio or height ratio of ion (m/z) for determination and ion (m/z) for
validation of clopyralid.
3) Prepare a curve for the relationship between the clopyralid concentration and the peak area ofion (m/z) for determination of respective clopyralid standard solutions for the calibration curve
preparation.
c) Sample measurement
1) Subject 5 µL of the sample solution to the same procedure as in b) 1) - 2) (14).
2) Obtain the content of material subjected to measurement from the calibration curve to calculate
the concentration of the material subjected to measurement in the analytical sample.
Note (13) According to the sensitivity of an instrument, ion for determination may be regarded as
ion for validation and vice versa.
Note (14) Confirm that the peak area ratio or height ratio of ion (m/z) for determination to ion(m/z) for validation is within the range of about ± 30 % of the peak area ratio or heightratio for the standard solution. In addition, the peak area ratio or height ratio may varydepending on the concentration.
Comment 9 The comparison of the measurement value (yi ： 1.5 µg/kg – 88.5 µg/kg) of
microanalysis for clopyralid (2) and the measurement value (xi) of microanalysis forclopyralid (1) was conducted to evaluate trueness using cow dung compost (5 samples),horse dung compost (2 samples), swine manure compost (4 samples), poultry manure696

Testing Methods for Fertilizers(2021)

compost (4 samples) and composted sludge fertilizer (5 samples). As a result, a
regression equation was y=−0.43+1.005x and its correlation coefficient (r) was 0.996.
The results of the repeatability tests on different days using compost and composted
sludge fertilizers were analyzed by one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability.
Additionally, results from a collaborative study for testing method validation and its
analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 2 µg/kg for clopyralid.
Table 1 Analysis results of the collaborative study
for the test method validation of clopyralid
3)
4)
Number of Mean2)sr
RSD r
Sample name1)laboratories (mg/kg) (mg/kg)
(%)
5
87.2
3.6
4.1
Cow dung compost
5
2.79
0.29
10.3
Swine manure compost
5
20.5
0.8
3.8
Poultry manure compost
5
6.27
0.36
5.8
Composted sludge fertilizer
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of repeated tests (2))3) Repeatability standard deviation
4) Repeatability relative standard deviation
5) Reproducibility standard deviation
6) Reproducibility relative standard deviation

5)

6)

sR

RSD R

(mg/kg)
3.6
0.29
3.2
0.46

(%)
4.1
10.3
15.8
7.3

References
1)
Nobuhito NAKAMURA, Kenji KOZUKA and Yuji SHIRAI: Improvement ofMicroanalysis Determination of Clopyralid in Compost and Composted Sludge Fertilizer
by Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS), Research Reportof Fertilizer Vol. 12, p. 69 – 83 (2019)697

Testing Methods for Fertilizers(2021)(5)

Flow sheet for clopyralid: The flow sheet for clopyralid in compost and composted sludge fertilizer is shown
below:
2.00 g analytical sample

50-mL centrifugal precipitate tube with a screw cap (A)← 25 mL of sodium hydroxide solution (40 g/L)−methanol [1+99]
Shaking to mix

Vertical reciprocating shaker (300 reciprocations/min, amplitude of 40 mm), for 30 minutes

Centrifugal separation

1700 × g , 5 minutes

Transfer (supernatant)

Acceptor, 200-mL round-bottom flask (B)(Supernatant)(Residue)<Repeat procedures inside the frame 2 times>← 10 mL of sodium hydroxide solution (40 g/L)−methanol [1+99]
Shaking to mix
Centrifugal separation(Residue)

Shake manuallyCentrifugal precipitate tube with a screw cap (A), 1700 × g , 5 minutes(Supernatant)
Add up (Supernatant)

Extract
Figure 2-1

Flow sheet for clopyralid in compost and composted sludge fertilizers (Extraction procedure)

698

Testing Methods for Fertilizers(2021)
Extract
Concentration under
reduced pressure

40 °C, round-bottom flask (B), not more than 3 mL

← 3 mL of hydrochloric acid (1+11)
Transfer
Centrifugal separation

Acceptor, 10-mL centrifugal precipitate tube with a screw cap (C)740 × g , 5 minutes(Supernatant)(Residue)<Repeat procedures inside the frame 2 times>← Wash the round-bottom flask (B) with about 5 mL of hydrochloric acid (1+120)
Transfer
Centrifugal separation(Residue)Centrifugal precipitate tube with a screw cap (C)Centrifugal precipitate tube with a screw cap (C), 1700 × g , 5 minutes(Supernatant)
Add (Supernatant) successively

Cleanup (1)Copolymer cartridge column(Wash with about 5 mL of acetonitrile, then about 5 mL of hydrochloric
acid (1+120) in advance)← Wash with about 10 mL of hydrochloric acid (1+120)−acetonitrile [9+1]← Wash with about 5 mL of water← 8 mL of ammonia solution (0.0028 % (mass fraction))−acetonitrile [9+1][Elute, 10-mL ground-in stopper centrifugal precipitate tube (D)]Eluate← 2 mL of formic acid (1+1000)
MixingCleanup (2)Zirconia coated silica gel column(Wash with about 5 mL of acetonitrile, then about 5 mL of formic acid
(1+1000) in advance)← Wash the ground-in stopper centrifugal precipitate tube (D) with about 5 mL of acetonitrile← 10 mL of formic acid−acetonitrile (2+98)[Elute, 50-mL round-bottom flask (E)]
Concentration under
reduced pressure

40 °C

Exsiccation

Nitrogen← 4 mL of formic acid (1+1000)
Centrifugal separation

1.5-mL ground-in stopper centrifugal precipitate tube (F), 8000 × g - 10000 × g , 5 minutes

Sample solution

Supernatant

Measurement

High-Performance Liquid Chromatograph/Tandem Mass Spectrometer

Figure 2-2 Flow sheet for clopyralid in compost and composted sludge fertilizers(Cleanup (1), cleanup (2) and measurement procedures)

699

Testing Methods for Fertilizers(2021)

References: An example of the Selected Reaction Monitoring chromatogram of a clopyralid standard
solution for calibration curve preparation is shown below.

Reference diagram: SRM chromatograms of clopyralid
Clopyralid standard solution (the equivalents of 50 pg as clopyralid)
LC-MS/MS measurement conditions
Column: ACQUITY UPLC HSS C18 (2.1-mm inner diameter, 100-mm long, 1.8-µm particle
diameter)Flow rate: 0.4 mL/min
Capillary voltage: 1.0 kV
Temperature of ion source: 120 °C
Desolvation temperature: 400 °C
Cone voltage: 20 V
Collision energy: 20 eV for determination, 30 eV for validation
Other conditions are according to the examples of the measurement conditions in (4.4) a) LCMS/MS.

700

Testing Methods for Fertilizers(2021)

8.3 Residue agrichemicals (multicomponent)
8.3.1 Residue agrichemicals multicomponent analysis (1)8.3.1.a High-Performance Liquid Chromatography/Tandem Mass Spectrometry(1) Compounds subjected to analysis Abamectin: abamectin B1a, ivermectin: 22, 23-dihydroavermectin B1a (Another name: ivermectin B1a), eprinomectin: eprinomectin B1a, rotenone:
rotenone, piperonylbutoxide: piperonylbutoxide, pyrethrin: pyrethrin I and pyrethrin II(2) Summary
This testing method is applicable to fluid home garden-use compound fertilizer and fluid
compound fertilizer. This testing method is classified as Type B and its symbol is 8.3.1.a-2017 or AGC-1.a-1.
Dissolve respective agricultural chemicals in fertilizers with acetonitrile and water, and extract.
Refine by using 2 kinds of cleanup cartridge, and then measure with a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer (LC-MS/MS) to obtain compounds subjected to analysis
in an analytical sample. In addition, the performance of this testing method is shown in Comment 3.
(3) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Acetonitrile: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8039 or a reagent of equivalent quality.
c) Methanol: A JIS Guaranteed Reagent specified in JIS K 8891 or a reagent of equivalentquality.
d) Methanol:
Methanol used in the eluent of a High-Performance Liquid
Chromatograph/Tandem Mass Spectrometer is a reagent of LC/MS analysis grade orequivalents.
e) Ethyl acetate: A JIS Guaranteed Reagent specified in JIS K 8361 or a reagent of equivalentquality.
f) Toluene: A JIS Guaranteed Reagent specified in JIS K 8680 or a reagent of equivalent quality.
g) Ammonium formate: A JIS Guaranteed Reagent (no less than 95 % (mass fraction) in purity)
or a reagent of equivalent quality.
h) Ammonium formate solution (0.1 mol/L) (1): Add 6.306 g of ammonium formate into 1000mL of water.
i) Ammonium formate solution (0.1 mmol/L) (1): Add 1mL of ammonium formate solution (0.1mol/L) into 1000 mL water.
j) Formic acid: A JIS Guaranteed Reagent specified in JIS K 8264 or a reagent of equivalentquality.
k) Formic acid solution (0.1 v/ v %) (1): Add 1 mL of formic acid to 1,000 mL of water.
l) Acetonitrile formate solution (0.1 v/v %) (1): Add 1 mL of formic acid to 1,000 mL ofacetonitrile.
m) Respective agricultural chemicals standard solutions (0.1 mg/mL) (1): Put about 0.01 g ofabamectin [C48H72O14] (2), ivermectin [C48H74O14] (2), eprinomectin [C50H75NO14] (2), rotenone[C23H22O6] (2), piperonylbutoxide [C19H30O5] (2) and pyrethrin [pyrethrin I: C21H28O3 andpyrethrin II: C22H28O5] (2) in a weighing dish, and measure the mass to the order of 0.1 mg.
Dissolve with a small amount of methanol, transfer to a 100-mL volumetric flask and add thesolvent up to the marked line. (However, 0.1 mg/mL of pyrethrin contains total of pyrethrin
I/II)n) Mixture standard solution (10 µg/mL): Transfer 10 mL of respective agricultural chemical
standard solutions to a 100-mL volumetric flask and add methanol up to the marked line.
o) Mixture standard solution (1000 ng/mL): Transfer 10 mL of mixture standard solution (10µg/mL) to a 100-mL volumetric flask and add methanol up to the marked line.
701

Testing Methods for Fertilizers(2021)p)q)

Mixture standard solution for calibration curve preparation (50 ng/mL - 500 ng/mL): In
the case of usage, put 2.5 mL - 25 mL of mixture standard solution (1000 ng/ mL) in 50-mL
volumetric flasks step-by-step, and add methanol up to the marked line.
Mixture standard solution for calibration curve preparation (5 ng/mL - 50 ng/mL): In thecase of usage, put 2.5 mL - 25 mL of mixture standard solution (100 ng/ mL) in 50-mL
volumetric flasks step-by-step, and add methanol up to the marked line.

Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A standard reagent is commercially sold.
Comment 1 A standard reagent of respective agricultural chemicals is sold by FUJIFILM Wako
Pure Chemical Co., Ltd., Kanto Chemical Co., Inc. and Hayashi Pure Chemical
Industries., Ltd.
(4) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph/Mass Spectrometer ： A high-performanceliquid chromatograph/tandem mass spectrometer specified in JIS K 0136 that satisfies thefollowing requirements.
1) High-Performance Liquid Chromatograph(i) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
(ii) Column: A 2-mm - 3-mm inner diameter 50-mm - 150-mm long 1.6-µm - 3.0-µm particle
diameter stainless steel column tube filled with silica gel to which octadecyl chemicallybonds. The specification is according to the mass spectrometer specification (3).
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Ion detection method: Selected Reaction Monitoringb) Ultrasonic generator: An ultrasonic washer can be used.
c) Concentrator: An evaporator whose temperature can be adjusted up to 40 ºC.
d) Porous diatomaceous earth cartridge column: A column that is filled with the porous
diatomaceous earth (capacity: 5 mL) (4)e) Graphite carbon-NH2 laminate cartridge column: A 6-mL cylinder on which 500 mg ofgraphite carbon and 500 mg of aminopropyl silylation silica gel is laminated (5).
Note (3) The column is sold under the names ACQUITY UPLC HSS C18, etc.
(4) The column is sold under the names Chem Elut (5 mL), etc.
(5) The column is sold under the names Envi-carb/LC-NH2 (500 mg/500 mg, 6 mL), etc.
(5) Test procedures(5.1) Extraction: Conduct extraction as shown below.
a) Put about 5.00 mL (6) of an analytical sample into a 10-mL volumetric flask.
b) Add 3 mL of acetonitrile to the same volumetric flask, and add water up to the marked line toshake to mix well.
c) Conduct ultra-sonication for about 30 minutes using an ultrasonic generator (7) to make anextract.
Note (6) After measuring the specific gravity of sample, calculate the concentration of materials
subjected to measurement in the analytical sample.
(7) Note that the volume of the solution may expand as a result of ultra-sonication. It is
recommended to leave it at room temperature for a while when it expands.
702

Testing Methods for Fertilizers(2021)

Comment 2 The specific gravity (density) can be calculated by placing a 10-mL volumetric flask
on an electric balance, aligning the scale to zero, putting 5.00 mL of the analyticalsample in the volumetric flask and reading the weighing value.
(5.2) Cleanup (1): Conduct cleanup (1) as shown below.
a) Put 5 mL of extract into a porous diatomaceous earth cartridge column and keep it in the column
for about 5 minutes.
b) Place a 100-mL round-bottom flask under the same cartridge column, add about 5 mL of ethyl
acetate into the same cartridge column 4 times successively and allow the solution to elute until
the surface of the solution reaches the top of packing materials (8).
c) After conducting vacuum concentration of elute in a water bath of no more than 40 ºC until
most of the elute exsiccate, send a nitrogen gas to exsiccate the elute (9), and add 2 mL ofacetonitrile−toluene (3+1) to dissolve the residue.
Note (8) Confirm the solution to elute before conducting the testing.
(9) There is a possibility for agricultural chemicals to vaporize if it is exsiccated excessively.
(5.3) Cleanup (2): Conduct cleanup (2) as shown below.
a) Wash the graphite carbon-NH2 laminate cartridge column with about 10 mL ofacetonitrile−toluene (3+1) in advanceb) Place a 100-mL round-bottom flask under the same cartridge column, put the solution in (5.2)c) in the same cartridge column, and allow the solution to overflow until the surface of thesolution reaches the top of packing materials.
c) Wash the vessel with about 5 mL of acetonitrile−toluene (3+1) 5 times and add washing to thesame cartridge successively to allow it to overflow.
d) After conducting vacuum concentration of elute in a water bath of no more than 40 ºC until
most of the elute exsiccates, send a nitrogen gas to exsiccate the elute (10), and add 2 mL of
methanol (11) to dissolve the residue. Put a predetermined amount of the solution precisely anddilute with methanol exactly by a factor of 5 to make the solution as a sample solution.
Note (10) There is a possibility for agricultural chemicals to vaporize if it is exsiccated excessively.
(11) If there is a possibility that the concentration of agricultural chemicals in the sample
solution exceeds the maximum limit of the calibration curve, dilute a predeterminedamount of the sample solution with methanol.
(5.4) Measurement: Conduct the measurement as indicated in JIS K 0136 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph/Mass Spectrometer used in measurement.
a) The measurement conditions of the High-Performance Liquid Chromatograph/Mass
spectrometer: An example of measurement conditions for the High-Performance Liquid
Chromatograph/Mass Spectrometer is shown below. Set up the measurement conditions
considering it:
1) High-Performance Liquid Chromatograph(i) Column: A silica gel column (2-mm - 3-mm inner diameter, 50-mm - 150-mm long, 1.6µm - 3.0-µm particle diameter column) to which octadecyl chemically bonds.
(ii) Flow rate: 0.2 mL/min - 0.5 mL/min(iii) Eluent: A: Ammonium formate solution (0.1 mmol/L) − formic acid solution (0.1 v/v%)[1+1]
B: Acetonitrile formate solution (0.1 v/v%)(iv) Gradient: 0 min (50 %B) → 15 min (95 %B) → 20 min (98 %B) → 30 min (50 %B)
703

Testing Methods for Fertilizers(2021)(v) Temperature of column bath: 40 °C(vi) Injection volume: 5 µL
2) Mass Spectrometer(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Mode: Positive(iii) Monitor ion: Shown in Table 1
Table 1 表1
Monitorion of respective agrichemicals
各農薬のモニターイオン
Mass-to-charge
m /z ）(m/z)
質量イオン比（ratio

Agrichemicals
農薬名プロダクトイオン
Production

915

Production
プロダクトイオン(determination)
（定量用）
305
307
186

395
356
329
373

213
177
161
161

192
147
133
133

Precursorion
プレカーサーイオン

アバメクチンB1a
Abamectin
B1a
Ivermectin
B1aイベルメクチンB1aEprinomectin
B1a
エプリノメクチンB1a
Rotenone
ロテノン
Piperonylbutoxide
ピペロニルブトキシド
PyrethrinⅠ
ピレトリンⅠ
PyrethrinⅡ
ピレトリンⅡ

891
893(validation)
（確認用）
567
551
298

b) Calibration curve preparation
1) Inject 5 μL of respective mixture standard solutions for calibration curve preparation into theHigh-Performance Liquid Chromatograph/Tandem Mass Spectrometer, record thechromatograms of ion (m/z) for determination and ion (m/z) for validation of materials subjected
to measurement.
2) Calculate the peak area ratio or height ratio of ion (m/z) for determination and ion (m/z) for
validation of respective materials subjected to measurement.
3) Prepare a curve for the relationship between the concentration of material subjected tomeasurement and the peak area or height of ion (m/z) for determination of respective mixture
solutions for the calibration curve preparation. Prepare a calibration curve when the sample ismeasured.
c) Sample measurement
1) Subject 5 µL of the sample solution to the same procedure as in b) 2) - 3) (12).
2) Obtain the content of materials subjected to measurement from the calibration curve of the peakarea or height to calculate materials subjected to measurement in the analytical sample.
Note (12) Confirm that the peak area ratio or height ratio of ion (m/z) for determination to ion(m/z) for validation is within the range of about ± 30 % of the peak area ratio or heightratio for the standard solution. In addition, the peak area ratio or height ratio depends onthe concentration.
(5.5)
Calculation
Calculate the respective concentration of agricultural chemicals in the analytical sample by thefollowing formula. in the analytical sample by the following formula:
Respective concentration of agricultural chemicals in the analytical sample (µg/kg)
704

Testing Methods for Fertilizers(2021)= (A × B × 10) /C
A： Concentration (ng/mL) of respective materials subjected to measurement in the final
sample solution obtained from the calibration curve
B： Dilution factor in the case that the final sample solution is further diluted because it
exceeds the upper limit of the calibration curve.
C： Specific gravity of the analytical sample (density) (g/mL)
Comment 3 Recovery testing was conducted using fluid home garden-use compound fertilizer (3kinds) and fluid compound fertilizer (2 kinds), as a result, the mean recovery rates at
the additive level of 4000 µg/kg and 400 µg/kg (However, 4000 µg/kg and 400 µg/kg
of pyrethrin contain total of pyrethrin I/II) were 77.0 % - 104.5 % and 85.6 % - 107.9 %respectively.
Additionally, results from a collaborative study for test method validation and its
analysis are shown in Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 10 µg/kg for each of the agrichemicals.

705

Testing Methods for Fertilizers(2021)

References1)
Toshiharu YAGI, Masayuki YAMANISHI, Yuji SHIRAI: Simultaneous Determination ofAgricultural chemicals in Fluid Fertilizer by Liquid Chromatography/Tandem Mass
Spectrometry, Research Report of Fertilizer, Vol. 4, p. 36 - 48 (2011)2)
Toshiharu YAGI, Masayuki YAMANISHI, Yuji SHIRAI and Masato SHIBATA:
Simultaneous Determination of Six Kind of Agricultural Chemicals in Fluid Fertilizer by
Liquid Chromatograph-Tandem Mass Spectrometer (LC-MS/MS): A Collaborative Study,
Research Report of Fertilizer, Vol. 5, p. 48 - 59 (2012)706

Testing Methods for Fertilizers(2021)(6)

Flow sheet for simultaneous analysis of 6 kinds of agrichemicals: The flow sheet for
simultaneous analysis of 6 kinds of agrichemicals in fertilizer is shown below.
5.00 mL analytical sample
10-mL volumetric flask← About 3 mL of acetonitrile← Water (up to the marked line)
Ultra sonication
5 minutes
Extract
Figure 1 Flow sheet for residue agrichemicals multicomponent analysis((1) : simultaneous analysis of 6 kinds of agrichemicals) in fertilizers(Extraction procedure)707

Testing Methods for Fertilizers(2021)

Reference: An example of the Selected Reaction Monitoring chromatograms of a mixture standard
solution for calibration curve preparation and a sample solution (fluid home gardenuse compound fertilizer) are shown below.

Peak No.
1
2
3

5
6
7

Intensity / arb.units

40Retention Time / min

20 0Retention Time / min

20

Peak No.1: AbamectinB1a
No.2: IvermectinB1a
No.3: Eprinomectin B1a
No.4: Rotenone
No.5: Piperonylbutoxide
No.6: Pyrethrin I
No.7: Pyrethrin II

1) Mixed standard solution
Reference diagram:

2) Sample solution

Selected Reaction Monitoring chromatograms of respective agriculturalchemicals1) Mixture standard solution (the equivalents of 2,500 pg as respective agrichemicals)(For pyrethrin, the equivalents of 2,500 pg of the total of pyrethrin I/II)
2) Sample solution (fluid home garden-use compound fertilizer, additive of the equivalents of 400µg/ kg in the sample)(For pyrethrin, the equivalents of 400 µg/kg of the total of pyrethrin I/II)
LC-MS/MS measurement conditions
Column: ACQUITY UPLC HSS C18 (2.1-mm inner diameter, 100-mm long, 1.8-µm
particle diameter)
Flow rate: 0.2 mL/min
Capillary voltage: 3.0 kV
Temperature of ion source: 120 °C
Desolvation temperature: 400 °C
Cone voltage: Shown in Table 1708

Testing Methods for Fertilizers(2021)

Collision energy: Shown in reference table
Other conditions are according to the examples of the measurement conditions in (5.4)a) LC-MS/MS and the reference table.
Reference
table
参考表

Parameters of mass spectrometer
質量分析計のパラメーター

Mass-to-charge
ratio
(m/z)
m /z
質量イオン比（）

Agrichemicals
農薬名

プレカーサー プロダクトイオン
コーン電圧
Production プロダクトイオン
Production Conevoltage
Precursorion(determination)(validation)
(V)
イオン
（定量用）
（確認用）
（V）
891
305
567
20
アバメクチンB1a
Abamectin
B1a
893
307
551
25
Ivermectin
B1aイベルメクチンB1aEprinomectin
B1a
915
186
298
20
エプリノメクチンB1a
Rotenone
35
395
213
192
ロテノン
Piperonylbutoxide20
ピペロニルブトキシド
356
177
147
PyrethrinⅠ
20
ピレトリンⅠ
329
161
133
PyrethrinⅡ
20
ピレトリンⅡ
373
161
133

709

コリジョン
Collision
エネルギー
energy
eV）
（(eV)

25
25
20
25
15
10
10

Testing Methods for Fertilizers(2021)

8.3.2 Residue agrichemicals multicomponent analysis (2)8.3.2.a Gas Chromatography(1) Compounds subjected to analysis β-HCH (β-BHC), γ-HCH (γ-BHC), o,p'-DDD, p,p'-DDD,o,p'-DDE, p,p'-DDE, o,p'-DDT, p,p'-DDT,aldrin,endrin, dieldrin, trans-chlordane, cischlordane,trans-nonachlor,cis-nonachlor,heptachlor,heptachlor
epoxideandhexachlorobenzene(2) Summary
This testing method is applicable to compost and straw, raw materials of compost. This testing
method is classified as Type D and its symbol is 8.3.2.a-2017 or AG-C-2.a-1.
Extract respective agricultural chemicals in fertilizers or raw materials with acetonitrile and water,refine by using a porous diatomaceous earth column, a gel permeation chromatograph and a synthetic
magnesium silicate cartridge column, and then measure with an electron capture detector equipped
gas chromatograph to obtain compounds subjected to analysis in an analytical sample. In addition,
the performance of this testing method is shown in Comment 7.
(3) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Acetonitrile: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8039 or a reagent of equivalent quality.
c) Hexane: A reagent of agricultural chemicals residue/PCB testing grade (concentration: noless than 300) specified in JIS K 8825 or a reagent of equivalent quality.
d) Sodium chloride: A reagent of agricultural chemicals residue/PCB testing grade or a reagentof equivalent quality.
e) Cyclohexane: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) or a reagent of equivalent quality.
f) Acetone: A reagent of agricultural chemicals residue/PCB testing grade (concentration: noless than 300) specified in JIS K 8040 or a reagent of equivalent quality.
g) Diethyl ether: A reagent of agricultural chemicals residue/PCB testing grade (concentration:no less than 300) specified in JIS K 8357 or a reagent of equivalent quality.
h) 2,2,4-trimethylpentane: A reagent of High-Performance Liquid Chromatograph analysis grade
or a reagent of equivalent quality.
i) Respective agricultural chemicals standard solutions (0.2 mg/mL) (1): Put about 0.02 g of
β-HCH (β-BHC)［C6H6Cl6］(2), γ-HCH (γ-BHC)［C6H6Cl6］(2), o,p'-DDD［C14H10Cl4］(2), p,p'DDD［C14H10Cl4］(2), o,p'-DDE［C14H8Cl4］(2), p,p'-DDE［C14H8Cl4］, o,p'-DDT［C14H9Cl5］(2), p,p'-DDT［C14H9Cl5］,aldrin［C12H8Cl6］,endrin［C12H8Cl6O］, dieldrin［C12H8Cl6O］(2), trans-chlordane［C10H8Cl6］(2), cis-chlordane［C10H8Cl6］(2), trans-nonachlor［C10H5Cl9］(2), cis-nonachlor［C10H5Cl9］(2), heptachlor［C10H5Cl7］(2), heptachlor epoxide［C10H5Cl7O］(2)
and hexachlorobenzene［C6Cl6］(2) to a weighing dish, and measure the mass to the order of
0.1 mg. Dissolve them with 20 mL of acetone, transfer to 100 mL volumetric flasks respectively,
and add 2,2,4-trimethylpentane up to the marked line.
j) Mixture standard solution (1 µg/mL) (1): Transfer 1 mL of respective agricultural chemicals
standard solutions to a 100-mL volumetric flask and add 2,2,4-trimethylpentane-acetone (4+1)
up to the marked line.
k) Mixture standard solution for calibration curve preparation (0.02 µg/mL - 0.2 µg/mL) (1):In the case of usage, put 1 mL - 10 mL of mixture standard solution (1 µg/mL) in 50 mL
volumetric flasks step-by-step, and add 2,2,4-trimethylpentane−acetone (4+1) up to the markedline.
l) Mixture standard solution for calibration curve preparation (0.005 µg/mL - 0.02 µg/mL)(1): In the case of usage, put 2.5 mL - 10 mL of mixture standard solution (0.1 µg/mL) in 50 mL
710

Testing Methods for Fertilizers(2021)

volumetric flasks step-by-step, and add 2,2,4-trimethylpentane−acetone (4+1) up to the marked
line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A standard reagent is commercially sold.
Comment 1 A standard reagent of respective agricultural chemicals is sold by FUJIFILM Wako
Pure Chemical Co., Ltd., Kanto Chemical Co., Inc. and Hayashi Pure Chemical
Industries., Ltd.
(4) Apparatus and instruments: Apparatus and instruments are shown below.
a) Gas Chromatograph (GC): GC specified in JIS K 0114 that satisfies the following
requirements.
1) Sample injector: An injector that enables split less system.
2) Capillary column: A capillary column (0.25-mm inner diameter and 30-m long) made of
fused silica. 14 % cyanopropylphenyl -86 % dimethyl polysiloxane chemically bonds to theinner surface of a capillary column with 0.25 µm thickness.
3) Detection unit: Electron capture detector (ECD)b) Gel Permeation Chromatograph (GPC): Preparative liquid chromatograph specified in JIS
K 0135 that satisfies the following requirements. No detector is required.
1) Sample injector: A sample injector that can inject 5 mL of sample solution.
2) Column: A 20-mm inner diameter 300-mm long stainless-steel column tube filled withstyrendivynylbenzene copolymer system hard gel3) Guard column: A 20-mm inner diameter 100-mm long stainless steel column tube filled withstyrendivynylbenzene copolymer system hard gel
4) Fraction collector: A fraction collector that can set up a fraction to which agrichemicalcomponents elute.
c) Shaking apparatusd) Concentrator: An evaporator whose temperature can be adjusted up to 40 ºC.
e) Filter: A funnel for filtering under reduced pressure (compatible filter diameter: 60 mm)f) Porous diatomaceous earth cartridge column: A column that is filled with the porous
diatomaceous earth (capacity: 20 mL).
g) Synthetic magnesium silicate cartridge column: A cartridge column that is filled with 910
mg of synthetic magnesium silicate.
h) Membrane filters: Made of PTFE (pore size is no more than 0.5 μm)
Comment 2 Column for GC is sold under the production name DB-1701, Rtx-1701, SPB-1701, etc.
A column which has actually isolated compounds subjected to analysis should be used.
Comment 3 GPC is an aliquot liquid chromatograph that collects a fraction of a material subjected
to measurement sieved and isolated by packing materials of the column for GPC
according to the size of the molecule of the material. A column for GPC is sold under
the production name Shodex CLNpak EV-2000 AC, etc. In addition, a guard column
for GPC is sold under the production name Shodex CLNpak EV-G AC, etc.
Comment 4 A funnel for filtering under educed pressure is sold under the production nameKIRIYAMA Funnel SB-60, KIRIYAMA Funnel SU-60, etc.
Comment 5 A porous diatomaceous earth cartridge is commercially sold under production nameChem Elut (20 mL), etc.
Comment 6 Synthetic magnesium silicate is commercially sold under the production names suchas Sep-Pak Florisil Plus Long Cartridge (910 mg).
Comment 7 A membrane filter is sold under the production name HLC-DISK 25 Solvent system
711

Testing Methods for Fertilizers(2021)(pore size: 0.45 µm), DISMIC 25JP050, Millex FH (diameter: 25 mm, pore size: 0.45µm), etc.
(5) Test procedures(5.1) Extraction: Conduct extraction as shown below.
a) Weigh 5.00 g of an analytical sample, and put it into a 200-mL ground-in stopper Erlenmeyer
flask.
b) Add 20 mL of acetonitrile−water (3 +1) to moisten.
c) After leaving at rest for ten minutes, add 100 mL of acetonitrile and shake to mix for about 30
minutes.
d) Place a 300-mL round-bottom flask under the filter and filtrate the extract under reducedpressure with a filter paper (type 5 B)e) Conduct cleanup of the previous Erlenmeyer flask and residue with 50 mL of acetonitrile
successively, similarly filtrate under reduced pressure and pool with the filtrate in d) to makean extract.
(5.2) Cleanup (1): Conduct cleanup (1) as shown below.
a) Concentrate under reduced pressure in a water bath of no more than 40 ºC until most of theextract exsiccates.
b) Add 20 mL of sodium chloride saturated solution, put it into a porous diatomaceous earth
cartridge column and leave it at rest for about 5 minutes.
c) Place a 300-mL round-bottom flask under the same cartridge column, wash the vessel 3 times
with about 20 mL of hexane to add the washing to the same cartridge column successively andallow the solution to elute until the surface of the solution reaches the top of packing materials.
d) Further add about 60 mL of hexane into the same cartridge and allow the solution to elute until
the surface of the solution reaches the top of packing materials.
e) After concentrating the eluate under reduced pressure in a water bath of no more than 40 ºC
until most of the eluate exsiccates, send a nitrogen gas to exsiccate the eluate (3), and add 10 mLof cyclohexane−acetone (4+1) to dissolve the residue.
f) Filter with a membrane filter (pore size: no more than 0.5 μm).
Note (3) There is a possibility for agricultural chemicals to vaporize if it is exsiccated excessively.
(5.3) Cleanup (2): Conduct cleanup (2) as shown below.
a) Inject 5 mL of the filtrate in (5.2) e) into a gel permeation chromatograph and take a fraction
eluted from respective agrichemicals which are determined according to the procedure
condition in b) into a 100-mL round-bottom flask.
b) Procedure conditions for the Gel Permeation Chromatograph: An example of procedure
conditions for the Gel Permeation Chromatograph is shown below. Set up the measurement
conditions considering it:1) Column: A styrendivynylbenzene copolymer column (20-mm inner diameter, 300-mm long,
15-µm particle diameter)
2) Guard column: A styrendivynylbenzene copolymer column (20-mm inner diameter, 100mm long, 15-µm particle diameter)
3) Eluent: Cyclohexane-acetone (4 +1)
4) Flow rate: 5 mL/min
5) Aliquot fraction: 70 mL -120 mLc) After concentrating the eluate under reduced pressure in a water bath of no more than 40 ºC
until most of the eluate exsiccates, send a nitrogen gas to exsiccate the eluate (3), and add 2 mLof hexane to dissolve the residue.
712

Testing Methods for Fertilizers(2021)(5.4) Cleanup (3): Conduct cleanup (3) as shown below.
a) Conduct cleanup of a synthetic magnesium silicate cartridge column (910 mg) with about 5 mLof hexane.
b) Place a 50-mL round-bottom flask under the same cartridge column, put the solution in (5.3) c)to the same cartridge column, and allow the solution to overflow until the surface of the solution
reaches the top of packing materials.
c) Wash the vessel with about 2 mL of hexane 2 times and add washing to the same cartridge
successively to allow it to overflow.
d) Further add about 15 mL of hexane−diethyl ethel (9+1) into the same cartridge and allow
respective materials subjected to measurement to elute.
e) After concentrating the eluate under reduced pressure in a water bath of no more than 40 ºC
until most of the eluate exsiccates, send a nitrogen gas to exsiccate the eluate (3). And add 1 mLof 2,2,4-trimethylpentane−acetone (4+1) (4) to dissolve the residue, making a sample solution.
Note (4) If there is a possibility that the concentration of respective agricultural chemicals in thesample solution exceed the maximum limit of the calibration curve, dilute apredetermined amount of the sample solution with 2,2,4-trimethylpentane−acetone(4+1).
(5.4) Measurement: Conduct the measurement as indicated in JIS K 0114 and as shown below.
Specific measurement procedures are according to the operation method of the Gas
Chromatograph used in measurement.
a) The measurement conditions of the Gas Chromatograph: An example of measurement
conditions for the Gas Chromatograph is shown below. Set up the measurement conditions
considering it:1) Sample injection method: split less injection method (1min)
2) Temperature of sample injector: 250 °C
3) Capillary column: A capillary column (0.25-mm inner diameter, 30-m long, 0.25 µm layer
thickness) made of fused silica. 14 % cyanopropylphenyl−86 % dimethyl polysiloxane
chemically bonds to the inner surface of the capillary column with 0.25 µm thickness.
4) Column bath temperature: 60 °C (1 min) → (20 °C/min) → 180 °C→ (2 °C/min) →260 °C→ (5 °C/min) → 275 °C (1 min)5) Carrier gas: helium, Flow rate: 1.5 mL/min
6) Addition gas: Nitrogen, Flow rate: 60 mL/min
7) Detection unit: Electron capture detector (ECD)
8) Detector temperature: 280 °Cb) Calibration curve preparation
1) Inject 1 µL of respective mixture standard solutions for calibration curve preparation into theGC, record a chromatogram and obtain a peak area or height.
2) Prepare a curve for the relationship between the concentration and the peak area or height ofrespective mixture solutions for the calibration curve preparation. Prepare a calibration curvewhen the sample is measured.
c) Sample measurement
1) Subject 1 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the content of materials subjected to measurement from the calibration curve of the peakarea or height to calculate materials subjected to measurement in the analytical sample.
713

Testing Methods for Fertilizers(2021)

Comment 8 Recovery testing of compounds subjected to analysis in compost was conducted, as aresult, the mean recovery rates at the additive level of 20 µg/kg and 50 µg/kg were
82.1 % - 118.1 % and 62.5 % - 120.2 % respectively. The results of the repeatability
tests on different days using compost to evaluate precision were analyzed by one-way
analysis of variance. Table 1 shows the calculation results of intermediate precisionand repeatability. Note that α-HCH (α-BHC), δ-HCH (δ-BHC), and oxychlordane,
which were subjected to simultaneous analysis, were excluded from the compounds
subjected to analysis because sufficient recovery rates were not obtained.
Note that the minimum limit of quantification for respective agrichemicals of the test
method is no more than 20 µg/kg.

References
1)
Tomoharu NOZAKI: Determination of Organic Chloride Pesticides in Composts using
Gas Chromatography-Electron Capture Detector (GC-ECD), Research Report of
Fertilizers, Vol. 10, p. 41 - 60 (2017)714

Testing Methods for Fertilizers(2021)(6)

Flow sheet for simultaneous analysis of chloride pesticides: The flow sheet for simultaneous
analysis of chloride pesticides in fertilizer is shown below.

715

Testing Methods for Fertilizers(2021)

716

Testing Methods for Fertilizers(2021)

8.4 Sodium
8.4.a Flame atomic absorption spectrometry(1) Summary
This testing method is applicable to fertilizers containing organic matters. This testing method isclassified as Type D and its symbol is 8.4.a-2017 or Na.a-1.
Pretreat an analytical sample with incineration and hydrochloric acid, spray into an acetylene−air
flame, and measure the atomic absorption with sodium at a wavelength of 589.0 nm or 589.6 nm toobtain sodium (Na) in an analytical sample. In addition, the performance of this testing method isshown in Comment 3.
(2) Reagent: Reagents are as shown below.
a) Hydrochloric acid: A JIS Guaranteed Reagent specified in JIS K 8180 or a reagent ofequivalent quality.
b) Sodium standard solution (Na 1 mg/mL) (1): Heat sodium chloride specified in JIS K 8150 at
600 ºC ± 10 ºC for about 1 hour, let it stand to cool in a desiccator, and weigh 2.542 g to aweighing dish. Dissolve in a small amount of water, transfer to a 1000-mL volumetric flask,
and add water up to the marked line.
c) Sodium standard solution (Na 0.1 mg/mL) (1): Put 20 mL of sodium standard solution (Na 1
mg/mL) in a 200-mL volumetric flask, and add hydrochloric acid (1+23) up to the marked line.
d) Sodium standard solutions (Na 1 µg/mL - 10 µg/mL) for the calibration curve preparation(2): Put 2.5 mL - 25 mL of sodium standard solution (Na 0.1 mg/mL) in 250-mL volumetricflasks step-by-step, and add hydrochloric acid (1+23) up to the marked line (2).
e) Blank test solution for the calibration curve preparation: Hydrochloric acid (1+23) usedin the procedures in d) (3).
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) When using a device model which cannot degrade the sensitivity of the device by tilting
the burner head, conduct the model appropriate dilution. (For example, 0.1 µg/mL - 4µg/mL)(3) When preserving, use a container, which can be sealed tightly, made of material such as
polypropylene, PTFE that sodium hardly elutes.
Comment 1 Instead of the sodium standard solution in (2) b), a sodium standard solution (Na 0.1
mg/mL 1 mg/mL or 10 mg/mL for Atomic Absorption Spectrometry traceable to
National Metrology can also be used.
(3) Instruments: Instruments are as shown below:a) Flame atomic absorption spectrometer: An atomic absorption spectrometer specified in JIS
K 0121.
1) Light source: A sodium hollow cathode lamp
2) Gas: Gas for heating by flame(i) Fuel gas: acetylene(ii) Auxiliary gas: Air sufficiently free of dust and moisture.
b) Electric furnace: An electric furnace that can be adjusted to 550 ºC ± 5 ºC.
c) Hot plate or sand bath: A hot plate whose surface temperature can be adjusted up to 250 ºC.
Adjust the amounts of gas and silica sand of a sand bath so that the sand bath temperature canbe set to 250 ºC.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
717

Testing Methods for Fertilizers(2021)a) Weigh 5.00 g of an analytical sample and put it in a 200-mL - 300-mL tall beaker.
b) Put the tall beaker in an electric furnace, and heat gently to char (4).
c) Ignite at 550 ºC ± 5 ºC for no less than 4 hours to incinerate (4).
d) After standing to cool, moisten the residue with a small amount of water, gradually add about
10 mL of hydrochloric acid, and further add water to make 20 mL.
e) Cover the tall beaker with a watch glass, and heat on a hot plate or a sand bath to boil for about
5 minutes.
f) After standing to cool, transfer the solution to a 250-mL - 500-mL volumetric flask with waterg) Add water up to the marked line.
h) Filter with Type 3 filter paper to make a sample solution.
Note (4) Example of charring and incineration procedure: After raising the temperature fromroom temperature to about 250 °C in 30 minutes to 1 hour, continue heating for about 1
hour and further raise to 550 °C in 1 to 2 hours.
Comment 2 A sample solution obtained in the procedure in (4.1) is also applicable to thecomponents shown in Annex B.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0121 and as shown below.
Specific measurement procedures are according to the operation method of the Atomic
absorption spectrometer used in measurement.
a) Measurement conditions for the Atomic absorption spectrometer: Set up the measurement
conditions for the Atomic absorption spectrometer considering the following:
Analytical line wavelength: 589.0 nm or 589.6 nmb) Calibration curve preparation
1) Spray the sodium standard solutions for the calibration curve preparation and the blank test
solution for the calibration curve preparation into a flame, and read the indicated value at awavelength of 589.0 nm or 589.6 nm.
2) Prepare a curve for the relationship between the sodium concentration and the indicated valueof the sodium standard solutions for the calibration curve preparation and the blank test solution
for the calibration curve preparation.
c) Sample measurement
1) Put a predetermined amount of the sample solution (the equivalents of 0.1 mg - 1 mg as Na) (5)in a 100-mL volumetric flask.
2) Add hydrochloric acid (1+23) to the marked line.
3) Subject to the same procedure as in b) 1) to read the indicated value.
4) Obtain the sodium content from the calibration curve, and calculate the sodium (Na) in theanalytical sample.
Note (5) Sample a predetermined amount of sample solution according to the device model in
Note (2).
Comment 3 Additive recovery testing with triplicates measurement was conducted using fish
caked powder, fish waste processed fertilizers, rape seed meal and its powder,composted sludge fertilizers and compost, as a result, the mean recovery rate at theadditive concentration of sodium in the range of 1 % (mass fraction) - 10 % (massfraction) was 97.0 % - 103 %.
The results of the repeatability tests on different days using fish caked powder (sample
to which sodium chloride is added) and compost to evaluate precision were analyzed
718

Testing Methods for Fertilizers(2021)

by one-way analysis of variance. Table 1 shows the calculation results of intermediate
precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.02 % (mass fraction).

References
1) Kimie KATO, Masaki CHIDA and Toshifumi FUJITA:
Method Validation for
Determination of Sodium in Fertilizer by Atomic Absorption Spectrometry , Research
Report of Fertilizers, Vol. 8, p. 61 - 69 (2015)(5)

Flow sheet for sodium testing method: The flow sheet for sodium testing method in fertilizers
is shown below:
5.00 g analytical sample
Charring
Incineration

Weigh into a 200-mL - 300-mL tall beaker.
Heat gently
550 ºC ± 5 ºC, no less than 4 hours

Standing to coolRoom temperature← A small amount of water, moisten the residue← About 10 mL of hydrochloric acid
← Water (up to about 20 mL)
Heating
Cover with a watch glass, and boil for 5 minutes.
Standing to coolRoom temperature

Transfer
250-mL - 500-mL volumetric flask, water← Water (up to the marked line)
Filtration
Type 3 filter paper
Sample solution
Figure 1 Flow sheet for sodium in fertilizers (Extraction procedure)

719

Testing Methods for Fertilizers(2021)

Sample solution
Aliquot(predetermined amount)

100-mL volumetric flask, water←Hydrochloric acid (1+23) (up to the marked line)
Measurement
Atomic absorption spectrometer(589.0 nm or 589.6 nm)
Figure 2 Flow sheet for sodium in fertilizers (Measurement procedure)720

Testing Methods for Fertilizers(2021)

8.5 Guanylurea nitrogen
8.5.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type B and its
symbol is 8.5.a-2017 or GU-N.a-1.
Add water to an analytical sample to extract guanylurea, introduce it to a High-Performance Liquid
Chromatograph (HPLC) to isolate it with a weak acid ion-exchange column, and then measure at awavelength 190 nm to obtain guanylurea nitrogen (GU-N) in an analytical sample. In addition, theperformance of this testing method is shown in Comment 6.
Biuret nitrogen (B-N), dicyandiamide nitrogen (Dd-N), urea nitrogen(U-N) and guanidine nitrogen(Gd-N) can be simultaneously quantified by using this method. (Refer to Comment 5).
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557.
b) Potassium dihydrogen phosphate: A JIS Guaranteed Reagent specified in JIS K 9007 or areagent of equivalent quality.
c) Phosphoric acid: A JIS Guaranteed Reagent specified in JIS K 9005 or a reagent ofequivalent quality.
d) Guanylurea nitrogen standard solution (GU-N 2 mg/mL) (1): Put 0.540 g of guanylurea
sulfate [C4H12N8O2･H2SO4] (2) in a weighing dish and measure the mass to the order of 0.1 mg.
Add a small amount of water to dissolve, then transfer to a 100-mL volumetric flask and add
water up to the marked line.
e) Guanylurea nitrogen standard solution (GU-N 200 µg/mL): Put 10 mL of guanylurea
nitrogen standard solution (GU-N 2 mg/mL) in a 100-mL volumetric flask and add water up to
the marked line.
f) Guanylurea nitrogen standard solution (GU-N 50 µg/mL - 100 µg/mL): Put 25 mL - 50 mL
of guanylurea nitrogen standard solution (GU-N 200 µg/mL) in 100-mL volumetric flasks andadd water up to the marked line.
g) Guanylurea nitrogen standard solution for the calibration curve preparation (GU-N 1
μg/mL - 50 μg/mL): At the time of usage, put 1 mL - 50 mL of guanylurea nitrogen standard
solution (GU-N 100 µg/mL) in 100-mL volumetric flasks step-by-step and add water up to themarked line.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A reagent of no less than 98 % (mass fraction) in purity as guanylurea sulfate iscommercially sold.
Comment 1 Guanylurea sulfate is commercially sold by Kanto Chemical Co., Inc. and Tokyo
Chemical Industry Co., Ltd.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 7.5-mm inner diameter 100-mm long stainless steel column tube filled with weakacid ion-exchange resin.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45ºC.
3) Detection unit: An absorptiometric detector that can measure at a wavelength around 190
nm.
b) Magnetic stirrerc) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
721

Testing Methods for Fertilizers(2021)

× g.
Comment 2 A column is sold under the production name Asahipak ES-502C 7C, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
(4.1.1) Powdery test samplea) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of water and stir it by using a magnetic stirrer for about 10 minutes.
c) After allowing to stand still, transfer a supernatant solution (3) to a 1.5-mL ground-in stopper
centrifugal precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (3) If there is a possibility that the guanylurea nitrogen (GU-N) concentration in the sample
solution will exceed the maximum limit of the calibration curve, dilute a predeterminedamount of supernatant with water.
(4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement.
(5) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
(4.1.2) Fluid test samplea) Weigh 1.00 g of an analytical sample, and put it in a 100-mL volumetric flask.
b) Add about 50 mL of water, and shake to mix.
c) Add water up to the marked line (6) and pit it in a 1.5-mL ground-in stopper centrifugal
precipitate tube (4).
d) Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (5) and use thesupernatant as a sample solution.
Note (6) If there is a possibility that the guanylurea nitrogen (GU-N) concentration in the sample
solution will exceed the maximum limit of the calibration curve, dilute a predeterminedamount of precisely adjusted solution with water.
Comment 3 Instead of procedures in (4.1.1) c) - d) or (4.1.2) c) - d), it is allowed to filter with amembrane filter (aperture diameter: no more than 0.5-µm) made of hydrophilic PTFE
and the filtrate can be the sample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of a High-Performance
Liquid Chromatograph (HPLC) used in measurement.
a) Measurement conditions for a High-Performance Liquid Chromatograph (HPLC): An
example of measurement conditions is shown below. Set up the measurement conditions
considering it:1) Column: A weak acid ion-exchange resin column (4.0-mm - 7.5-mm inner diameter, 100mm - 150-mm long, 5-µm – 10-µm particle diameter)
2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 3.92 g of potassium dihydrogen phosphate and 0.12 g of phosphoric acidin water to make 1000 mL. Filter with a membrane filter (aperture diameter: no more than 0.5722

Testing Methods for Fertilizers(2021)µm) made of hydrophilic PTFE.
4) Flow rate: 0.6 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 190 nm
Comment 4 Eluent can be prepared as follows. Dissolve 19.6 g of potassium dihydrogen phosphateand 0.584 g of phosphoric acid with water to make 500 mL and store in a refrigerator.
At the time of usage, dilute a predetermined volume of the solution by a factor of 10
and filter with a membrane filter (aperture diameter: no more than 0.5-µm) made ofhydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for the calibration curve preparation to the HighPerformance Liquid Chromatograph, record a chromatogram at a wavelength 190 nm andobtain a peak height.
2) Prepare a curve for the relationship between the guanylurea nitrogen (GU-N) concentration andthe peak height at a wavelength 190 nm of the respective standard solutions for the calibration
curve preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the guanylurea nitrogen (GU-N) content from the peak height using the calibration curve
to calculate guanylurea nitrogen (GU-N) in the analytical sample.
Comment 5 This testing method enables the simultaneous measurement of biuret nitrogen (B-N),
urea nitrogen (U-N), dicyandiamide nitrogen (Dd-N), guanidine urea (Gd-N) andguanylurea nitrogen (GU-N). In that case, see 5.10.a Comment 5.
Comment 6 Additive recovery testing was conducted using a preparation sample for a guanylurea
fertilizer (one brand). As a result, the mean recovery rates at the additive level of
36.7 % (mass fraction), 35.2 % (mass fraction) and 33.4 % (mass fraction) were
103.8 %, 104.6 % and 105.6 % respectively.
The results of the repeatability tests on different days using a guanylurea fertilizer toevaluate precision were analyzed by one-way analysis of variance. Table 1 shows thecalculation results of intermediate precision and repeatability. Additionally, resultsfrom a collaborative study for testing method validation and its analysis are shown in
Table 2.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.006 % (mass fraction).

723

Testing Methods for Fertilizers(2021)

Table 2 Analysis results of the collaborative study
for the test method validation of guanylurea nitrogen
Number of Mean2) sr4) RSD r5) s R6) RSD R7)
Sample name
1)
3)
3)
3)
laboratories
(%)
(%)
(%)
(%)
(%)
Compound fertilizer 1
12
2.20
0.09
4.2
0.17
7.7
Compound fertilizer 2
11
4.38
0.07
1.5
0.19
4.3
Compound fertilizer 3
11
5.83
0.08
1.4
0.52
8.9
Compound fertilizer 4
12
7.43
0.43
5.7
0.78
10.5
Guanylurea fertilizer
12
30.3
0.4
1.5
1.1
3.6
1) Number of laboratories used in analysis
2) Mean (n = number of laboratories × number of samples (2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation
6) Reproducibility standard deviation
7) Reproducibility relative standard deviation
References
1)
Masahiro ECHI, Yasuharu KIMURA and Yuji SHIRAI: Determination of Urea Nitrogen,
Biuret Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogenin Fertilizer by High-Performance Liquid Chromatography: A Single-Laboratory
Validation, Research Report of Fertilizer, Vol. 10, p. 72 - 85 (2017)2)
Norio FUNAKI and Yasuharu KIMURA: Determination of Urea Nitrogen, Biuret
Nitrogen, Dicyandiamide Nitrogen, Guanidine Nitrogen and Guanyl urea Nitrogen in
Fertilizer by High-Performance Liquid Chromatography (HPLC): A Collaborative Study,
Research Report of Fertilizer, Vol. 10, p. 86 - 100 (2017)724

Testing Methods for Fertilizers(2021)(5)

Flow sheet for testing method: The flow sheet for guanylurea nitrogen in fertilizers is shown
below:

1.00 g analytical sample(powdery)

200-mL ground-in stopper Erlenmeyer flask← 100 mL of water
Extraction

Stir to mix, 10 minites

Standing still

Centrifugal separation

Ground-in stopper centrifugal precipitate tube,
8000 ×g - 10000 ×g , 5 minutes

Sample solution

Supernatant

Measurement

Liquid Chromatograph

Figure 1

Flow sheet for guanylurea nitrogen in fertilizers(Extraction procedure (4.1.1) and mesurement)

1.00 g analytical sample
100-mL volumetric flask(Fluid)← About 50 mL of water
Extraction

Shake to mix← Water (up to the marked line)
Ground-in stopper centrifugal precipitate tube,
Centrifugal separation
8000 ×g - 10000 ×g , 5 minutes
Sample solution

Supernatant

Measurement

Liquid Chromatograph

Figure 2 Flow sheet for guanylurea nitrogen in fertilizers(Extraction procedure (4.1.2) and mesurement)725

Testing Methods for Fertilizers(2021)

Reference:

An example of the chromatogram of the standard solution for calibration curve
preparation of guanylurea nitrogen is shown below.

Reference diagram:

HPLC chromatogram of the mixture standard solutions forcalibration curb preparation (10 mg/L for each)Peak name(1) Urea nitrogen(2) Biuret nitrogen(3) Dicyandiamide nitrogen(4) Guanidine nitrogen(5) Guanylurea nitrogen
Measurement conditions for HPLC
Column: Asahipak ES-502C 7C (7.5-mm inner diameter, 100-mm long, 9-μm particle
diameter)Other conditions are according to the example of HPLC measurement conditions in(4.2) a)726

Testing Methods for Fertilizers(2021)

8.6 Uric acid8.6.a High-Performance Liquid Chromatography(1) Summary
This testing method is applicable to fertilizers. This testing method is classified as Type D and its
symbol is 8.6.a-2018 or U-acid.a-1.
Add phosphate solution (pH 8) to an analytical sample to extract uric acid, introduce it to a HighPerformance Liquid Chromatograph (HPLC) to isolate it with a multi-mode ODS (reverse phase +strong anion-exchange + strong cation-exchange + normal phase) column, and then measure at awavelength 290 nm to obtain uric acid (U-acid) in an analytical sample. The performance of thistesting method is shown in Comment 5.
(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A3 specified in JIS K 0557. Note that water of A4 should be used as theeluent which is introduced to a High-Performance Liquid Chromatograph.
b) Potassium dihydrogenphosphate: A reagent specified in JIS K 9007 or a reagent ofequivalent quality.
c) Disodium hydrogenphosphate: A reagent specified in JIS K 9020 or a reagent of equivalentquality.
d) Phosphate solution: Dissolve 9.073 g of potassium dihydrogenphosphate in water to make1000 mL and dissolve 9.464 g of disodium hydrogenphosphate in water to make 1000 mL. Mix
these solutions so that pH 8.0 ± 0.1 is reached.
e) Lithium carbonate solution: Dissolve 0.739 g of lithium carbonate (Li2CO3) of no less than
99 % (mass fraction) in purity in water to make 1000 mL.
f) Uric acid standard solution (U-acid 1 mg/mL) (1): Put 0.100 g of uric acid in a weighing dishand measure the mass to the order of 0.1 mg. Dissolve it with a small amount of lithium
carbonate solution, transfer to a 100 mL volumetric flask and add the solution up to the markedline.
g) Uric acid standard solution for the calibration curve preparation (U-acid 100 µg/mL): Put
10 mL of uric acid standard solution (U-acid 1 mg/mL) in a 100-mL volumetric flask and add
the phosphate solution up to the marked line.
h) Uric acid standard solution for the calibration curve preparation (U-acid 10 µg/mL - 50
µg/mL): Put 10 mL - 50 mL of uric acid standard solution (U-acid 100 µg/mL) in a 100-mL
volumetric flask and add the phosphate solution up to the marked line.
i) Uric acid standard solution for the calibration curve preparation (U-acid 0.1 μg/mL - 5
μg/mL): At the time of usage, put 1 mL - 50 mL of uric acid standard solution (U-acid 10
μg/mL) in 100-mL volumetric flasks step-by-step and add the phosphate solution up to themarked line.
j) Ammonium acetate: A reagent specified in JIS K 8359 or a reagent of equivalent quality.
k) Methanol: A reagent of High-Performance Liquid Chromatograph analysis grade or a reagentof equivalent quality.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph: A high-performance liquid chromatographspecified in JIS K 0124 that satisfies the following requirements.
1) Column: A 4.6-mm inner diameter 250-mm long stainless steel column tube filled with silica
gel, to which octadecyl, ion-exchange group for strong acidity and strong basic anion-exchangegroup of a 3-µm particle diameter chemically bond.
2) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
727

Testing Methods for Fertilizers(2021)

3) Detection unit: An absorptiometric detector that can measure at a wavelength around 290
nm.
b) Water bath: Water bath that can be adjusted to 60 ºC ± 2 ºC.
c) Magnetic stirrerd) Centrifugal separator: A centrifugal separator that can work at 1700 × g.
e) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
Comment 1 A column is sold under the production name Scherzo SS-C18, etc.
(4) Test procedures(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 1.00 g of an analytical sample, and put it into a 200 mL- ground-in stopper Erlenmeyer
flask.
b) Add 100 mL of phosphate solution (2) and heat for 30 minutes while shaking to mix (3) at every
10 minutes in a water bath at 60 ºC ± 2 ºC.
c) Immediately stir it by using a magnetic stirrer for about 10 minutes.
d) After allowing to stand still, put supernatant in a 15-mL or 50-mL ground-in stopper centrifugal
precipitate tube (4), and centrifuge at 1700 × g for about 5 minutes (5).
e) Put the supernatant (6) in a 1.5-mL ground-in stopper centrifugal precipitate tube (4), andcentrifuge at 8000 × g - 10000 × g for about 5 minutes (7) to make supernatant as a sample
solution.
Note (2) Use a silicone stopper instead of a glass stopper as the solution is heated.
(3) Steam easily expels silicon stoppers, so while lightly holding down the stopper from the
top with your finger, shake it so that the water drops on the inside of the flask comedown as much as possible. In addition, conduct this procedure before and after theheating procedure.
(4) The ground-in stopper centrifugal precipitate tube should be made of polypropylene,
etc. to not affect the measurement(5) 7.2 cm - 18.9-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g
centrifugal force.
(6) If there is a possibility that the uric acid (U-acid) concentration in the sample solution
will exceed the maximum limit of the calibration curve, dilute a predetermined amountof supernatant with phosphate solution.
(7) 7.2-cm - 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
Comment 2 Instead of the procedures in (4.1) e), it is allowed to filter with a membrane filter (poresize: no more than 0.5-µm) made of hydrophilic PTFE and the filtrate can be thesample solution.
(4.2) Measurement: Conduct the measurement as indicated in JIS K 0124 and as shown below.
Specific measurement procedures are according to the operation method of the HighPerformance Liquid Chromatograph used in measurement.
a) Measurement conditions for the High-Performance Liquid Chromatograph: An example
of measurement conditions is shown below. Set up the measurement conditions considering it:1) Column: A silica gel column (4.6-mm inner diameter, 250-mm long, 3-μm particle diameter),to which octadecyl, ion-exchange group for strong acidity and strong basic anion-exchangegroup chemically bond728

Testing Methods for Fertilizers(2021)

2) Column bath temperature: 40 °C
3) Eluent (1): Dissolve 1.54 g of ammonium acetate with water to make 1000 mL. Get 900 mL of
the solution to mix with 100 mL of methanol. Filter with a membrane filter (aperture diameter:
no more than 0.5-µm) made of hydrophilic PTFE.
4) Flow rate: 0.4 mL/min
5) Injection volume: 10 µL
6) Detection unit: An absorptiometric detector, a measurement wavelength: 290 nm
Comment 3 Eluent can be prepared as follows. Dissolve 15.4 g of ammonium acetate with water
to make 1000 mL and store in a refrigerator. At the time of usage, dilute apredetermined volume of the solution by a factor of 10 to mix with methanol of volume
ratio 1/9 and filter with a membrane filter (aperture diameter: no more than 0.5-µm)
made of hydrophilic PTFE.
b) Calibration curve preparation
1) Inject 10 µL of respective standard solutions for calibration curve preparation into the HighPerformance Liquid Chromatograph, record a chromatogram at a wavelength 290 nm andobtain a peak area or height.
2) Prepare a curve for the relationship between the uric acid (U-acid) concentration and the peakarea or height at a wavelength 290 nm of respective standard solutions for the calibration curve
preparation.
c) Sample measurement
1) Subject 10 μL of the sample solution to the same procedure as in b) 1)
2) Obtain the uric acid (U-A) content from the peak area or height using the calibration curve tocalculate the uric acid (U-A) in the analytical sample.
Comment 4 In addition to uric acid, allantoin and allantoic acid can be measured simultaneously
by this measurement method (when using a Scherzo SS-C18 column). Note that thedetection wavelength of allantoin and allantoic acid is 210 nm.
Comment 5 Additive recovery testing was conducted using one brand of a compound fertilizer, acomposted sludge fertilizer, a mixed compost compound fertilizer and compost. As aresult, the mean recovery rates at the additive level of 0.1 % (mass fraction), 0.01 %(mass fraction) and 0.005 % (mass fraction) were 92.4 % - 101.8 %, 85.3 % - 105.0 %and 92.5 % - 114.1 % respectively.
The results of the repeatability tests on different days using one brand of a compound
fertilizer, a composted sludge fertilizer, a mixed compost compound fertilizer andcompost to evaluate precision were analyzed by one-way analysis of variance. Table 1
shows the calculation results of intermediate precision and repeatability.
Note that the minimum limit of quantification of this testing method was estimated to
be about 0.0008 % (mass fraction).

729

Testing Methods for Fertilizers(2021)
Table 1 Analysis results of the repeatability tests on different days of uric acid
2)
4)
6)
5)
7)
Test days ofMeansrs I(T)RSD r
RSD I(T)Name of sample
1)
3)
3)
3)
repeatability (T)
(%)
(%)
(%)
(%)
(%)
Compound fertilzier
7
0.09890.00060.6
0.00151.6
70.01020.00010.7
0.00042
4.2
Composted sludge fertilizer
7
0.09320.00040.5
0.00161.7
70.00938 0.00009
0.9
0.000313.3
Mixed compost compound
70.09240.00040.40.0015
1.7
fertilizer
70.00921 0.00005
0.6
0.00032
3.5
Compost
7
0.101
0.001
1.3
0.00292.8
70.00966 0.00018
1.8
0.00049
5.0
1) The number of test days conducting a duplicate test
6) Intermediate standard deviation
2) Mean (the number of test days(T )7) Intermediate relative standard deviation
×the number of duplicate testing(2))3) Mass fraction
4) Repeatability standard deviation
5) Repeatability relative standard deviation

References
1)
Norio FUNAKI: Determination of Uric Acid in Fertilizer by High Performance Liquid
Chromatography, Research Report of Fertilizer, Vol. 11, p. 86 – 105 (2018)(5)

Flow sheet for testing method: The flow sheet for uric acid in fertilizers is shown below:

730

Testing Methods for Fertilizers(2021)
Reference: An example of the chromatogram of the standard solution for calibration curve preparation ofuric acidis shown below.

min

Reference diagram:

HPLC chromatogram of the uric acid standard solution for
calibration curve preparation (50 µg/mL)

Peak name(↓) Uric acid
Measurement conditions for HPLC
Column: Scherzo SS-C18 (4.6-mm inner diameter, 250-mm long, 3-µm particle
diameter)Other conditions are according to the example of HPLC measurement conditions in(4.2) a)731

Testing Methods for Fertilizers(2021)

8.7 Organofluorine compounds
8.7.a High-Performance Liquid Chromatography/Tandem Mass Spectrometry(1) Summary
This testing method is applicable to compost and composted sludge fertilizers. This testing method
is classified as Type D and its symbol is 8.7.a-2021 or PFC.a-1.
Extract organofluorine compounds (perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic
acid (PFOA)) in sludge fertilizers with methanol under acidic condition, refine using two kinds ofcleanup cartridges, and then measure using a High-Performance Liquid Chromatograph/Tandem
Mass Spectrometer (LC-MS/MS) to obtain PFOS and PFOA in the analytical sample. Note that theperformance of this testing method is shown in Comment 14.
Comment 1 Structural formulas of PFOS and PFOA are as shown in Figure 1-1 and Figure 1-2.

Figure 1-1
FF

Structural formula of PFOS
F

F

F

C

C

C
F

F

Figure 1-2

C

C
F

O

F
C

C
F

F

F

C
F

F

OH
F

Structural formula of PFOA

(2) Reagent, etc.: Reagents and water are as shown below.
a) Water: Water of A4 specified in JIS K 0557.
b) Acetonitrile: A reagent of LC-MS analysis grade or equivalents.
c) Methanol: A reagent of agricultural chemicals residue/PCB testing grade (concentration: noless than 300) or a reagent of equivalent quality.
f) Ammonia solution: A JIS Guaranteed Reagent of 28 % (mass fraction) specified in JIS K
8085 or a reagent of equivalent quality.
e) Formic acid: A JIS Guaranteed Reagent of no less than 98 % (mass fraction) specified in JIS
K 8264 or a reagent of equivalent quality.
f) Ammonium acetate solution (1 mol/L):
A regent of High-Performance Liquid
Chromatograph analysis grade or equivalents.
g) Ammonium acetate solution (10 mmol/L) (1): Add water to 10 mL of ammonium acetate
solution (1 mol/L) to make 1000 mL.
h) PFOS standard stock solution: A standard solution of PFOS [C8HF17SO3] with known
concentration and uncertainty (2).
i) PFOA standard stock solution: A standard solution of PFOA [C8HF15O2] with known
concentration and uncertainty (2).
j) PFOS standard solution (1 µg/mL) (1): Dilute a predetermined amount of PFOS standard stock
solution with methanol to prepare a PFOS standard solution (1 µg/mL).
732

Testing Methods for Fertilizers(2021)k) PFOA standard solution (1 µg/mL) (1): Dilute a predetermined amount of PFOA standard
stock solution with methanol to prepare a PFOA standard solution (1 µg/mL).
l) Mixed standard solution (100 ng/mL) (1): Dilute a predetermined amount of PFOS standard
solution (1 µg/mL) and PFOA standard solution (1 µg/mL) with methanol - water (1+1) toprepare a mixed standard solution (100 ng/mL).
m) Mixed standard solution (10 ng/mL) (1): Dilute a predetermined amount of mixed standard
solution (100 ng/mL) with methanol - water (1+1) to prepare a mixed standard solution (10ng/mL).
n) Mixed standard solution (1 ng/mL) (1): Dilute a predetermined amount of mixed standard
solution (10 ng/mL) with methanol - water (1+1) to prepare a mixed standard solution (1 ng/mL).
o) 13C-labeled PFOS internal standard stock solution: A standard solution of 13C4-PFOS[C8HF17SO3] or 13C8-PFOS [C8HF17SO3] with known concentration and uncertainty (2).
p) 13C-labeled PFOA internal standard stock solution: A standard solution of 13C4-PFOA[C8HF15O2] or 13C8-PFOA [C8HF15O2] with known concentration and uncertainty (2).
q) 13C-labeled PFOS internal standard solution (1 µg/mL) (1): Dilute a predetermined amountof 13C-labeled PFOS internal standard stock solution with methanol to prepare a PFOS internal
standard solution (1 µg/mL).
r) 13C-labeled PFOA internal standard solution (1 µg/mL) (1): Dilute a predetermined amountof 13C-labeled PFOA internal standard stock solution with methanol to prepare a PFOA internal
standard solution (1 µg/mL).
s) 13C-labeled mixed internal standard solution (200 ng/mL) (1): Dilute a predetermined amountof 13C-labeled PFOS internal standard solution (1 µg/mL) and 13C-labeled PFOA internal
standard solution (1 µg/mL) with methanol to prepare a 13C-labeled mixed internal standard
solution (200 ng/mL).
t) 13C-labeled mixed internal standard solution (20 ng/mL) (1): Dilute a predetermined amountof 13C-labeled mixed internal standard solution (200 ng/mL) with methanol - water (1+1) toprepare a 13C-labeled mixed internal standard solution (20 ng/mL).
u) Mixed standard solutions for calibration curve preparation (0.1 ng/mL - 50 ng/mL) (1): Put
1 mL - 5 mL of mixed standard solution (100 ng/ mL) in 20-mL volumetric flasks step-by-step,
add 1 mL of 13C-labeled mixed internal standard solution (20 ng/mL) to each of them, and add
methanol - water (1+1) up to the marked line.
Put 1 mL - 5 mL of mixed standard solution (10 ng/ mL) in 20-mL volumetric flasks step-bystep, add 1 mL of 13C-labeled mixed internal standard solution (20 ng/mL), and add methanol water (1+1) up to the marked line for each of them.
Put 1 mL - 5 mL of mixed standard solution (1 ng/ mL) in 20-mL volumetric flasks step-bystep, add 1 mL of 13C-labeled mixed internal standard solution (20 ng/mL) to each of them, andadd methanol - water (1+1) up to the marked line.
v) 13C-labeled mixed internal standard solution (20 ng/mL) for adding analytical sample (1):Dilute a predetermined amount of 13C-labeled mixed internal standard solution (200 ng/mL)with methanol to prepare a 13C-labeled mixed internal standard solution (20 ng/mL) for adding
analytical sample.
Note (1) This is an example of preparation; prepare an amount as appropriate.
(2) A standard reagent is commercially sold.
Comment 2 Molecules in a PFOS standard stock solution, PFOA standard stock solution, 13Clabeled PFOS internal standard stock solution and 13C-labeled PFOA internal standard
stock solution shall be primarily linear.
Comment 3 A PFOS standard stock solution, PFOA standard stock solution, 13C-labeled PFOS
733

Testing Methods for Fertilizers(2021)

internal standard stock solution and 13C-labeled PFOA internal standard stock solution
are sold by Wellington Laboratories Inc., Cambridge Isotope Laboratories, Inc.,
FUJIFILM Wako Pure Chemical Co., Ltd., and GL Sciences Inc.
Comment 4 A HPLC grade ammonium acetate solution (1 mol/L) is sold by FUJIFILM Wako Pure
Chemical Co., Ltd. and Kanto Chemical Co., Inc.
(3) Apparatus and instruments: Apparatus and instruments are shown below.
a) High-Performance Liquid Chromatograph/Mass Spectrometer: A high-performanceliquid chromatograph/tandem mass spectrometer specified in JIS K 0136 that satisfies thefollowing requirements.
1) High-Performance Liquid Chromatograph:(i) Column bath: A column bath whose temperature can be adjusted to 30 ºC - 45 ºC.
(ii) Column: A 2-mm - 3-mm inner diameter 50-mm - 150-mm long 1.6-µm - 3.0-µm particle
diameter stainless steel column tube filled with silica gel to which octadecyl chemicallybonds. The specification is according to the mass spectrometer specification.
2) Mass Spectrometer:(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Ion detection method: Selected Reaction Monitoringb) Ultrasonic generator: An ultrasonic washer can be used.
c) Manifoldd) Centrifugal separator: A centrifugal separator that can work at 700 × g - 2000 × g.
e) High speed centrifugal separator: A centrifugal separator that can work at 8000 × g - 10000
× g.
f) Test tube mixer: Vortex mixerg) Weak anion exchange polymer cartridge column: A cartridge column whose syringe barrel(6 mL) is filled with polymer (500 mg) to which weak anion exchange groups bond.
h) Graphite carbon cartridge column: A cartridge column filled with 400 mg of graphite
carbon.
i) 50-mL centrifugal precipitate tube with a screw cap: A 50-mL test tube with a screw cap
made of polypropylene that can be used in a centrifugal separator.
j) 50-mL test tube with a screw cap: A 50-mL test tube with a screw cap made ofpolypropylene that has a line marked at 50 mL.
k) 15-mL test tube with a screw cap: A 15-mL test tube with a screw cap made ofpolypropylene.
l) Graduated test tube: A 7-mL - 10-mLtest tube that has lines marked at 0.5 mL and 1 mL.
m) Vial for standard solution and sample solution: A 0.3-mL - 1-mL vial with a screw cap
made of polypropylene.
Comment 5 A column is sold under the production name InertSustain C18, etc.
Comment 6 A weak anion exchange polymer cartridge column is sold under the production names
InertSep MA-2 500 mg/6 mL, Oasis WAX 6 cc (500 mg), etc.
Comment 7 A graphite carbon cartridge column is sold under the production names InertSep Slim
GC 400 mg, etc.
Comment 8 A test tube with a 50 mL line (ASTM Standard E1272 Class A (± 0.25 mL)) is soldunder the production name DigiTUBEs, etc. Since an internal standard solution isadded, the solution does not have to be accurately 50 mL in the procedure in (4.1) f).
Comment 9 The containers, whole pipettes, Pasteur pipettes, and piston pipette tips used in i) - l)shall be washed with methanol specified in JIS K 8891 and allow the methanol toevaporate.
734

Testing Methods for Fertilizers(2021)

Comment 10 For containers used in i) - k) and m), screw caps made of polyethylene orpolypropyrene shall be used. To prevent contamination, do not use packings ofpolytetrafluoroethylene resin, etc.
(4) Test procedure(4.1) Extraction: Conduct extraction as shown below.
a) Weigh 2.00 g of an analytical sample and put it in a 50-mL centrifugal precipitate tube with ascrew cap.
b) Put 1 mL of 13C-labeled mixed internal standard solution (20 ng/mL) for adding analyticalsample.
c) Add 15 mL of methanol and 0.1 mL of formic acid and conduct ultra-sonication for 20 minutes
using an ultrasonic generator.
d) Centrifuge it at about 1700 × g centrifugal force for about 5 minutes (3), and add the supernatant
to a 50-mL test tube with a screw cap (4).
e) Repeat the procedure in c) - d) 2 times and add up the supernatants.
f) Add methanol to the 50 mL line to make an extract.
g) As a blank test, conduct the procedures in b) - f) using another centrifugal precipitate tube witha screw cap to prepare an extract for blank test.
Note (3) 16.5-cm of rotor radius and 3000 rpm of revolutions makes about 1700 × g centrifugal
force.
(4) Transfer by decantation.
Comment 11 Grind until it completely passes through a sieve of 500 µm aperture to prepare the test
sample.
(4.2) Cleanup (5): Conduct cleanup as shown below:a) Successively wash the weak anion exchange polymer cartridge column with about 5 mL ofammonia solution (6) - methanol (1+100), about 5 mL of methanol, and then about 5 mL of
methanol - water (1+1) in advance.
b) Wash the graphite carbon cartridge column with about 5 mL of methanol in advance.
c) Put 5 mL of the extract in (4.1) f) in a 15-mL test tube with a screw cap, add 5 mL of water,
shake to mix, put it into the weak anion exchange polymer cartridge column and allow theeffluent to overflow until the surface of liquid reaches the top of packing materials.
d) Wash the test tube with a screw cap with about 5 mL of methanol - water (1+1), put the washing
to the same column and allow the effluent to overflow until the surface of liquid reaches the topof packing materials.
e) Add about 5 mL of methanol twice, and allow the effluent to overflow until the surface of liquidreaches the top of packing materials.
f) Connect (8) the graphite carbon cartridge column washed in b) under the weak anion exchange
polymer cartridge column.
g) Add 2 mL of ammonia solution (6) - methanol (1+100), and allow the effluent to overflow until
the surface of liquid reaches the top of packing materials.
h) Place a graduated test tube under the cartridge column, add 4 mL of ammonia solution (6) methanol (1+100) to the cartridge column and allow PFOS and PFOA to elute.
i) Gently spray nitrogen gas onto the eluate to concentrate it to the 0.5 mL line.
j) Add a small amount of water (9), and shake to mix using a test tube mixer (10).
k) Further add water to the 1 mL line, shaking to mix using a test tube mixer, and put it in a 1.5mL ground-in stopper centrifugal precipitate tube.
735

Testing Methods for Fertilizers(2021)

Centrifuge it at 8000 × g - 10000 × g centrifugal force for about five minutes (11) and use thesupernatant as a sample solution.
m) Conduct the procedures in a) - l) using the extract for blank test in (4.1) g) in place of the extractin (4.1) f) in the procedure in c) to prepare a blank test solution.
l)Note (5) Use a pressure reducing device or pressurize in the procedure in (5) c) and d) as
appropriate.
(6) Use an ammonia solution with an ammonia concentration of 28 % (mass fraction).
(7) Put methanol into the graphite carbon cartridge column using a reservoir.
(8) Remove the reservoir of the graphite carbon cartridge column and directly connect it to
the weak anion exchange polymer cartridge column.
(9) About 0.4 mL.
(10) Dissolve precipitates.
(11) 7.2-cm – 8.9-cm of rotor radius and 10000 rpm of revolutions makes about 8100 × g 10000 × g centrifugal force.
(4.3) Measurement: Conduct measurement according to JIS K 0136 and as shown below. Specificmeasurement procedures are according to the operation method of the High-Performance
Liquid Chromatograph/ Mass Spectrometer used in measurement.
a) The measurement conditions of the High-Performance Liquid Chromatograph/Mass
spectrometer: An example of measurement conditions for the High-Performance Liquid
Chromatograph/Mass Spectrometer is shown below. Set up the measurement conditions
considering it:
1) High-Performance Liquid Chromatograph:(i) Column: A silica gel column (2-mm - 3-mm inner diameter, 50-mm - 150-mm long, 1.6µm - 3.0-µm particle diameter column) to which octadecyl chemically bonds.
(ii) Flow rate: 0.2 mL/min～0.5 mL/min(iii) Eluent: A: Ammonium acetate solution (10 mmol/L)
B: Acetonitrile(iv) Gradient:
0 min (40 %B)→1.5 min (40 %B)→10 min (100 %B)→12 min(100 %B)→12.1 min (40 %B)(v) Temperature of column bath: 40 °C(vi) Injection volume: 5 µL
2) Mass Spectrometer:(i) Ionization method: Electro-Spray Ionization (ESI) method(ii) Mode: Negative(iii) Monitor ion: Shown in Table 1736

Testing Methods for Fertilizers(2021)

Comment 12 If peaks of impurities originating from the mobile phase or the High-Performance
Liquid Chromatograph/Mass Spectrometer appear at the retention time of PFOS or
PFOA, it is desirable to take a measure to eliminate their influence on themeasurement by, for example, attaching a delay column (2-mm - 4.6-mm innerdiameter 10-mm - 50-mm long stainless steel column tube filled with silica gel towhich octadecyl chemically bonds or with highly pure activated carbon) between theeluent supply pump and the inlet of the solution to be measured to separate them fromthe peaks of PFOS and PFOA in the test solution. A delay column is sold under the
production name Delay Column for PFAS, etc.
b) Calibration curve preparation
1) Inject 5 μL of respective mixed standard solutions for calibration curve preparation into theHigh-Performance Liquid Chromatograph/Tandem Mass Spectrometer, record thechromatograms of ion (m/z) for determination and ion (m/z) for validation of PFOS, PFOA,
13
C-labeled PFOS, and 13C-labeled PFOA, and obtain respective peak areas.
2) Calculate the ratio of peak area of ion (m/z) for determination for PDOS and PFOA and peakarea of ion (m/z) for validation for 13C-labeled PFOS and 13C-labeled PFOA.
3) Calculate the ratio of peak areas of ion (m/z) and ion (m/z) for validation for PFOS, PFOA, 13Clabeled PFOS, and 13C-labeled PFOA.
4) Prepare a calibration curve for the relationship between the concentrations of PFOS and PFOA
and the peak area ratio derived in 2).
c) Sample measurement
1) Subject 5 µL of the sample solution in (4.2) l) to the same procedure as in b) 1) - 3) (12).
2) Obtain the PFOS and PFOA concentrations in the sample solution from the calibration curve,and calculate the PFOS and PFOA concentrations in the analytical sample.
d) Blank test sample measurement
1) Subject 5 µL of the blank test solution in (4.2) m) to the same procedure as in b) 1) - 3) (13).
2) Obtain the PFOS and PFOA concentrations in the blank test solution from the calibration curve,and confirm that they are below the lower limit of the calibration curve concentration range (0.5ng/mL).
Note (12) Confirm that the peak area ratio of ion (m/z) for determination to ion (m/z) for validation
is within the range of about ± 30 % of the peak area ratio for the standard solution. In
addition, the peak area ratio may vary depending on the concentration.
Comment 13 If the PFOS and PFOA concentrations in the blank test solution obtained in d) 2) are
not lower than the lower limit of the calibration curve concentration range, investigate
the cause, reduce the blank value to the level that does not affect the measurement,
prepare a blank test solution again and redo the test.
Comment 14 Additive recovery testing was conducted to evaluate trueness using sewage sludge
fertilizer, industrial sludge fertilizer, and composted sludge fertilizer (1 brand each).
As a result, the mean recovery rates at the additive levels of 200 µg/kg, 20 µg/kg and2 µg/kg were 96.5 % - 101.1 %, 93.8 % - 96.5 % and 83.3 % - 102.1 % for PFOS and100.4 % - 107.3 %, 92.3 % - 96.0 % and 99.7 % - 102.7 % for PFOA, respectively.
The results of the repeatability tests on different days using human waste sludge
fertilizer and composted sludge fertilizer were analyzed by one-way analysis ofvariance. Table 2 shows the calculation results of intermediate precision andrepeatability.
Note that the minimum limit of quantification of this testing method was estimated to737

Testing Methods for Fertilizers(2021)

be about 0.5 µg/kg for PFOS and PFOA.

(5)

Flow sheet for organofluorine compounds: The flow sheet for organofluorine compounds insludge fertilizers is shown below:

738

Testing Methods for Fertilizers(2021)
Extract
Aliquot (5 mL)

Acceptor, 15-mL PP test tube with a screw cap (C)← 5 mL of water
MixingCleanup

Weak anion exchange polymer cartridge column(Wash with about 5 mL of ammonia solution (28 % (mass fraction))methanol (1+100), about 5 mL of methanol, and then about 5 mL ofwater in advance)← Wash the test tube with a screw cap (C) with 5 mL of methanol-water (1+1)← Wash with 5 mL of methanol
Connection of cartridge
columns(Connect the graphite carbon cartridge column (wash with about 5
mL of methanol in advance) under the weak anion exchange polymer
cartridge column)← 2 mL of ammonia solution (28 % (mass fraction))−methanol [1+100] [Discard]← 4 mL of ammonia solution (28 % (mass fraction))−methanol [1+100] [Elute,graduated test tube (D)]Concentration

Gently spray nitrogen gas, down to the 0.5 mL line

← A small amount (about 0.4 mL) of water
MixingTest tube mixer← Water, up to the 1 mL line
MixingCentrifugal separation

Test tube mixer
1.5-mL ground-in stopper centrifugal precipitate tube (E), 8000 × g 10000 × g , 5 minutes

Sample solution

Supernatant

Measurement

High-Performance Liquid Chromatograph/Tandem Mass Spectrometer

Figure 2-2 Flow sheet for organofluorine compounds in sludge fertilizers (Cleanup and measurement
procedures)

739

Testing Methods for Fertilizers(2021)

References: An example of the Selected Reaction Monitoring chromatograms of product ion for
determination of mixed standard solution for calibration curve preparation and sample
solution is shown below .

Standard solution (20 ng/mL as PFOS)
Sample solution (composted sludge fertilizer)
Reference diagram 1: MRM chromatograms of PFOS

Standard solution (20 ng/mL as PFOA)
Sample solution (composted sludge fertilizer)
Reference diagram 2: MRM chromatograms of PFOA
LC-MS/MS measurement conditions
Column for separation: InertSustain C18 (2.1-mm inner diameter, 150-mm long, 3µm particle diameter)
Delay column: Delay column for PFAS (3-mm inner diameter, 30-mm long)
Flow rate: 0.2 mL/min
Probe voltage: -1 kV
DL temperature: 200 °C
Heat block temperature: 300 °C
Interface temperature: 300 °C
Nebulizing gas rate: 3 L/min
740

Testing Methods for Fertilizers(2021)

Drying gas rate: 5 L/min
Heating gas rate: 15 L/min
Other conditions are according to the examples of the measurement conditions in (4.3)a) LC-MS/MS and the reference table.

741

Explanation of Testing Methods for Fertilizers (2021)

Explanation of Testing Methods for Fertilizers (2021)“The Official Methods of the Analysis of Fertilizers” stipulated by the National Institute forAgro-Environmental Sciences (currently the National Agriculture and Food Research
Organization) of the Ministry of Agriculture, Forestry and Fisheries (herein after referred to asMAFF) is adopted for the MAFF Public Notices (Prescribing for the official specifications fornormal fertilizers pursuant to the Fertilizer Regulation Act, etc.) which prescribes the quality or
the labeling method of fertilizers, and contributes to maintaining the quality of and securing thesafety of fertilizers. On February 28, 2020, according to the amendment of these MAFF Public
Notices, “Testing Methods for fertilizers” were adopted as the official methods of analysis for
effective components, harmful components, etc., as stipulated by the Incorporated Administrative
Agency: Food and Agricultural Materials Inspection Center (herein after referred to as “FAMIC”)“Testing Methods for Fertilizers” collected simple testing methods using new analytical
instruments and the performance results of testing methods for new ingredients and fertilizers.
The contents were edited and made public by FAMIC based on the views of experts and MAFF
officers in the technical committee for fertilizers, etc. established at FAMIC.
In the course of editing the “Testing Methods for Fertilizes”, attention was paid to thefollowing amendment points to make the description easier to understand: Reagents and instruments
used should be clarified by specifying JIS standards, etc., certified standard solutions and titrant have beenrevised for ease of use and operation flow sheets for respective testing methods have been appended

in order for analysts to work easily. In addition, a testing method type specified by the validationlevel (Citrate-soluble phosphoric acid 4.2.3.a: Ex. Type B) and its symbol indicating theamendment year or revision history (Citrate-soluble phosphoric acid 4.2.3.a: Ex. 4.2.3.a-2018 or
C-P.a-2) were described in the “Summary”. Also, as for the testing methods whose validation
was conducted, the results of trueness and precision were listed in the “Comments”.
In the “Testing Methods for Fertilizers (2021)”, as a result of the investigation and researchissues by FAMIC, (1) testing methods which were newly studied in FY2020 were added, (2)extraction procedures and measurement procedures (including expansion of scope) were added
to existing testing methods, (3) the classification of the testing methods carried out incollaborative studies and whose validation was confirmed by multiple laboratories was revised
to Type B, and (4) some descriptions were revised according to indications by the technicalcommittee for fertilizers, etc.
In addition, upon revising to the “Testing Methods for Fertilizers (2021)”, following suit theexample set by the Japanese Industrial Standards (JIS), (5) content that is difficult to be included
in descriptions of a testing method due to, for example, a large amount of information was newly
arranged as annexes. When an annex provides standards, it is indicated as (Standards). When anannex provides reference information, it is indicated as (Reference).

Explanation－1

Explanation of Testing Methods for Fertilizers (2021)(1) Newly added testing methods
7.7 3,4-Dimethylpyrazole phosphate (DMPP)
7.7.a High-Performance Liquid
Chromatography
8.7 Organofluorine compounds
8.7.a High-Performance Liquid Chromatography/Tandem
Mass Spectrometry(2) Testing methods to which procedures, etc. were added
4.1.2 Ammoniacal nitrogen
4.1.2.a Distillation method
4.1.3 Nitrate nitrogen
4.1.3.c Phenol sulfuric acid method
4.3.1 Total potassium
4.3.1.a Flame atomic absorption spectrometry or flame photometry
4.3.2 Citric acid-soluble potassium
4.3.2.a Flame atomic absorption spectrometry or
flame photometry
4.3.3 Water-soluble potassium
4.3.2.a Flame atomic absorption spectrometry or flame
photometry
4.6.1 Total magnesia
4.6.1.a Flame atomic absorption spectrometry
4.6.2 Acid-soluble magnesia
4.6.2.a Flame atomic absorption spectrometry
4.6.3 Citric acid-soluble magnesia
4.6.3.a Flame atomic absorption spectrometry
4.6.4 Water-soluble magnesia
4.6.4.a Flame atomic absorption spectrometry
4.7.2 Citric acid-soluble manganese
4.7.2.a Flame atomic absorption spectrometry
4.7.3 Water-soluble manganese 4.7.3.a Flame atomic absorption spectrometry
5.2 Arsenic
5.2.c ICP Mass Spectrometry
5.3 Cadmium
5.3.c ICP Mass Spectrometry
5.4 Nickel
5.4.c ICP Mass Spectrometry
5.5 Chromium
5.5.c ICP Mass Spectrometry
5.6 Lead
5.6.c ICP Mass Spectrometry(3) Testing methods whose classification was revised to Type B
4.5.3 Citric acid-soluble lime
4.5.3.a Flame atomic absorption spectrometry
4.12.2 Acid-soluble sulfur
4.12.2.a Ion Chromatography
8.2 Clopyralid and its degradation products
8.2.c High-Performance Liquid
Chromatography/Tandem Mass Spectrometry (Microanalysis for clopyralid (2))(4) Revised descriptions• For extractor, “rotary shaker” was changed to “vertical rotating mixer,” and “constanttemperature rotary shaker” was changed to “constant-temperature vertical rotating mixer.”
For the extraction procedure, only “shake to mix” was used as a phrase about shaking tomix (in the previous Japanese versions, multiple expressions meaning “shake to mix” wereused).
• Among the measurement conditions of high-performance liquid chromatograph/mass
spectrometer used in high-performance liquid chromatograph mass spectrometry and highperformance liquid chromatograph/tandem mass spectrometry, those that depend on themodel of mass spectrometer, namely, capillary voltage, temperature of ion source,
desolvation temperature, cone temperature, and collision energy, were removed from the
Explanation－2

Explanation of Testing Methods for Fertilizers (2021)

descriptions in the body, and described in the measurement conditions for example
chromatograph shown as an example instead.
(5) New establishment of annexes• New establishment of annexes for Testing Methods for Fertilizers• Annex A (Standards) Procedure to validate characteristics of testing methods• Annex B (Reference) List of extraction methods for main components, etc.
• Annex C1 (Reference) Standard solution, etc. preparation methods in simultaneous
analysis using ICP optical emission spectrometer• Annex C2 (Reference) Standard solution, etc. preparation methods in simultaneous
analysis using ICP mass spectrometer• Annex D (Reference) Example IC column used for acid-soluble sulfur

Further, information, such as consistency and revised contents between “Testing Methods for
Fertilizers (2021)” and “Official Methods of Analysis of Fertilizers (1992)”, was put together inthe “Changes in the Testing Methods for Fertilizers (2021) (latest information is shown in red)and performance evaluation of the Testing Methods for Fertilizers (2020)” (Reference material).
These testing methods are utilized for inspection and investigation by FAMIC. FAMIC hopesthat the testing methods will help people engaged in the production/quality control and products
inspection of fertilizers to ensure the quality of their activities.
We are grateful to the members of the Testing Methods for Fertilizers Technical Committee
and the Testing Methods for Fertilizers and Sampling Methods Study Group for their helpfuladvice and timely guidance regarding technical issues on the occasion of making the “Testing
Methods for Fertilizers (2021)”.

Explanation－3

Explanation of Testing Methods for Fertilizers (2021)

Testing Methods for Fertilizers Technical Committee in FY2020(Without honorifics, as of March 3, 2021)(Members)
AIZAKI Mayumi

Public Interest Incorporated Foundation: The Fertilization Research
Foundation
ISAGAWA Satoshi
General Incorporated Foundation: Japan Food Research Laboratories
IMAGAWA Toshiaki Public Interest Incorporated Foundation: Japan Fertilizer and Feed
Inspection Association
KAWASAKI Akira
National Research and Development Agency: National Agriculture andFood Research Organization
KUROIWA Takayoshi National Research and Development Agency: The National Institute ofAdvanced Industrial Science and Technology
NOGUCHI Akira
Incorporated Educational Institution: Nihon University
FUJIMORI Eiji
Ministry of the Environment: National Environmental Research andTraining Institute
YAZIMA Kazuyuki
General Incorporated Association: Niigata Prefectural Institute of
Public Health and Environmental Sciences
YASUI Akemi
National Research and Development Agency: National Agriculture andFood Research Organization
WATANABE Takahiro National Institute of Health Sciences(Related persons)
URANO Tsuyoshi
Plant Products Safety Division, Food Safety and Consumer Affairs
Bureau, Ministry of Agriculture, Forestry and Fisheries
NOJIMA Yuki
Plant Products Safety Division, Food Safety and Consumer Affairs
Bureau, Ministry of Agriculture, Forestry and Fisheries

Testing Methods for Fertilizers Technical Committee Testing Methods for Fertilizers andSampling Methods Study Group in FY2021(Without honorifics, as of June 30, 2021)(Members)
IMAGAWA Toshiaki
KAWASAKI Akira
FUJIMORI Eiji
YASUI Akemi
YOSHIDA Mitsuya(Related persons)Public Interest Incorporated Foundation: Japan Fertilizer and Feed
Inspection Association
National Research and Development Agency: National Agriculture andFood Research Organization
Ministry of the Environment: National Environmental Research andTraining InstituteNational Research and Development Agency: National Agriculture andFood Research Organization
General Incorporated Foundation: Japan Food Research Laboratories

Explanation－4

Explanation of Testing Methods for Fertilizers (2021)

INOUE NaoKASHIMA Shinichi

Plant Products Safety Division, Food Safety and Consumer Affairs
Bureau, Ministry of Agriculture, Forestry and Fisheries
Plant Products Safety Division, Food Safety and Consumer Affairs
Bureau, Ministry of Agriculture, Forestry and Fisheries

Explanation－5