# Techniques of Water-Resources Investigations

of the United States Geological Survey

Chapter Al 

# MEiHODS FOR DETERMINATION OF INORGANIC SUBSTANCES

IN WATER AND FLUVIAL SEDIMENTS

By Marvin J. Flshman and Linda C. Friedman, Editors

First Edition 1970 Second Edition 1979 Third Edition 1989

Book 5 LABORATORY ANALYSIS

## Bromide, titrimetric, hypochlorite oxidatbn

Parameter and Code: Bromide, dissolved, I-1125-85 (mg/L as Br): 71870

1. Application This method may be used to analyze any natural or treated water or brine containing at least 1.Omg/L of bromide. Highly concentrated brines may require dilution.

2. Summary of method 2.1 The determination of bromide involves the determination of bromide andiodide colle& ively, and then the determination of iodide alone; bromide is calculated by difference. Bromide andiodide areoxidixed to bromate and iodate, respectively. by hypochlorite, and the
excess hypochlorite is subsequently decomposed with sodium formate (Kolthoff and others, 1969).

3OCl-1 + Br-1 + BrCgl + 3Cl-1

3OCl-’ + I-’ - IOjl + 3Cl-1

Iodine equivalent to the combined iodate and bromate is then liberated by addition of potassium iodide to an acid solution.

Broil + 61-l + 6H+1+ 31, + 3H,O + Br-1

IOjl + 51-l + 6H+l-, 31, + 3H,O

The liberated iodine is titrated with standard thiosulfate with useof starch asthe indicator.

I, + 2s,og2 - s4052 + 21-l

2.2 Iodide aloneis determined by oxidation to iodate with bromine in a buffered solution. Iodine equivalent to the iodate isthen liberated from addedpotassium iodide andtitrated with thiosulfate as in the combined determination. 3. Interferences Iron, manganese, and organic material interfere with the basic reactions of the method, but their interferences areremoved by preliminary treatment with calcium oxide.

4. Apparatus 4.1 

### Buret, 10-n& capacity. 4.2 

### Iodine mks, 250-n& capacity.

5. Reagents 5.1 

### Acetic acid, 2.2MzMix 125 mL glacial HC,HsO, (sp gr 1.069) with demineralized water and dilute to 1 L. 

### 5.2 Bromine water, saturated: Add to approx 260mL demineralized water slightly more liquid Br2than will dissolve when mixed. Store in a glass-stoppered, a&ink-glass bottle. 6.3 

### Cal&m carbonate,powder, CaCO,. 

### 5.4 Calciumoxide,a&y&us powder, CaO. 

### 6.5 Hydrochloric acid, W Mix 50 mL concentrated HCl (spgr 1.19)with demineralized water and dilute to 100 mL. 

### 5.6 Meth$l redindicatorsolution,0.01g/l00 mL: Dissolve 0.01 g water-soluble methyl red in 100 mL d,emineralizedwater. 

### 5.7 Potassiumfluor&, crystals, KF*2H20. 

### 5.6 Potassiumhypochbrite solution,4.4gL: Dissolve 6.2 g KOH in 109 mL demineralixed water; then saturate the solutiea with bromidefree Cl, while continually cooling and stirring. Store in aglass-s-, a&i&-glass bottle. Prepare fresh daily. 

### 6.9 Potassium iodide, crystals, IOil-free: The KI can be tested for 1091 by dissolving about 0.1g in 5mL demineralized water, acidifying with 1or 2drops concentrated H2SOd(sp gr 1.84),and adding 2to 3mL starch indicator solution. Immediate apeearawe of abIuecolor

111112 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

indicates the presenceof 10~~;slow color formation is due to atmospheric oxidation. 5.10 Sodium acetate solution, 165 g/L: Dissolve 273g NaC,H30,-3H,O in demineralized water and dilute to 1 L. 5.11Sodium chloride, crystals: Freefrom 1-l. IOgl, Br-l, and BrOgl. The NaCl can betested for IO$ and BrOgl by dissolving about 0.1 g in 5mL demineralized water, acidifying with 1

or 2drops concentrated H,SO, (spgr 1.84),and adding 2to 3mL starch indicator solution. Immediate appearance of a blue color indicates presenceof IOil or BrCgl; slow color formation is caused by atmospheric oxidation. 5.12Sodium fonnate solution, 50g/l00 mL: Dissolve 50 g NaHCO, in hot demineralized water anddilute to 100mL. Preparefresh daily. 5.13 Sodium molybdute solution, 1.0 g/l00 mL: Dissolve 1.2 g Na2Mo0,-2H20 in demineralized water and dilute to 100 mL. 5.14 Sodium thiosulfate solution, O.lON: Dissolve 25.0g Na,S,03-5H,O in carbon dioxide-free, demineralized water; add 1g Na,COs and dilute to 1 L. 5.15 Sodium thiosulfate standard solution, O.OlOiVz Dilute 100.0mL O.lOiVNa,S,O, solution to 950 mL with carbon dioxide-free, demineralized water and standardize against KIO, asfollows: Dry approx 0.5 g KIO, for 2 h at 180°C. Cool and dissolve 0.3567 g in demineralized water, and dilute to 1,000 mL. Pipet 25.00 mL of the KIO, solution into a 250-n& iodine flask; then add successively 75 mL demineralized water and0.5g KI crystals. After solution is complete, add ,lO mL 3.6M H,SO,. Allow the stoppered flask to stand 5 min in the dark, andthen titrate with standard Na#,Os solution, adding 2mL starch indicator solution asthe end point is approached (light straw color).

Normality of Na,S,O,= 0.25
mL Na,S,O,

5.16 Starch indicator solution, stable or “thyodene,” powdered (Fisher No. T138 or equivalent). 5.17Sulfuric acid, 3.6M: CAUTIOUSLY add 200 mL concentrated H@O, (sp gr 1.84) to demineralized water, cool, and dilute to 1 L. 6.1 Remove soluble iron, manganese, and organic matter by adding aslight excessof CaO to approx 400mL sample; mix, let stand about 1h, andfilter through adry, moderately retentive filter paper. Discard the first 75 mL of filtrate. 6.2 For the combined Br-1 and 1-l determination, pipet avolume of the filtrate containing less than 5.0 mg Br-l and 1-l (100.0 mL max) into a 250-n& iodine flask, and adjust the volume to approx 100 mL. 6.3 Prepare a blank of approx 100 mL demineralized water, and carry it through the procedure along with the sample. 6.4 Add sufficient NaCl to produce a 3.0 g Cl-l content. 6.5 Add adrop of methyl red indicator solution, andmakethe solution just acidic with 6M HCl. 6.6 Add 10mL KC10 solution, 0.5 mL 6M HCI, andsufficient CaCO, to produce anexcess of approx 0.1 g. 6.7 Heat the solution to boiling and maintain this temperature for about 8 min. 6.8 Reducethe excessKC10 by adding 2mL c NaI-ICO, solution, taking precaution to wash down the sidesofthe flask with asmall amount of hot water. Keepthe solution hot for anadditional 8 min. 6.9 Cool andaddseveral drops of NapMoO solution. If any iron precipitates at this point, add 0.5 g KF*SH,O. 6.10 Add approx 1 g KI and 10 mL 3.6M H,SO,, and let stand 5 min in the dark. 6.11 Titrate the Liberated I, with O.OlN Na$,O, standard solution, adding 2to 3 mL starch indicator solution asthe endpoint is approached. Disregard areturn of the blue color after the end point has been reached. 6.12 For the I-1 determination, pipet a volume of filtrate (step 6.1) containing less than 5.0mg 1-l (100.0mL max) into a250~mL iodine flask, and adjust the volume to approx 100 mL. 6.13 Prepare ablank of 100.0mL demineralized water and carry through the procedure along with the sample. 6.14Add adrop of methyl red indicator solution, and make the solution just acidic with 3.6M H,SO,. cMETHODS FOR DETERMINATION OF INORGANIC SUBSTANCES 113

6.15 Add 15.0 solution, mL 2.2M HC2H302, and-sufficient bromine water to produce alight-yellow color; mix and allow to stand 5 min. 6.16 Reduce the excess Br, by adding NaHCO, solution drop by drop until the yehow tinge in the sample disappears; then addanexcess of 1 mL. 6.17Wash the sidesof the flask with asmall amount ofwater, andblow out Br, vapors with

a syringe and a glass tube inserted into the mouth of the flask. If any iron precipitates at this point, add 0.5 g KI*BH,O. 6.18 Add approx 1 g KI and 10 mL 3.6M H&JO,, and let stand 5 min in the dark. 6.19 Titrate the liberated I, with O.OlOiV Na,S,OS standard solution, adding 2to 3 mL starch indicator solution asthe endpoint is ap proached (light-straw color).Disregard areturn of the blue color after the end point has been reached.

7. Calculations 7.1 Determine Br-l+I-l in epL asfollows:

Br-1+ I-l(epL) = 1,000 0.01XmL sample 6 X (mL,-mLb)

7.2 Determine 1-l in epL as follows:

I-l(epL)= 1,000 0.01

X - X(mLi-mL& mL sample 6

7.3 Determine Br-l in mg/L as follows:
Br-l(mg/L)=79.91X[epL (H-l+ Br-l)-epL I-‘] where epL= equivalents per liter, mL,= titrant volume for blank determination, mL,= titrant volume for combined determination,

and
mLi= titrant volume for 1-l determination.

8. Report Report bromide, dissolved (71870).concentrations asfollows: lessthan 10mg/L, onedecimal; 10 mg/L and above, two significant figures.

9. Precision Single-operator precision of this method (American Society for Testing and Materials, 1984)may be expressed as follows:

where s* = 0.0044x

S,= single-operator precision, milligrams per liter,
and

X= concentration of bromide, milligrsms per liter.

References

American Society for Testing and Materials, 1984, Annual book of ASTM standards, section 11, water: Philadelphia, v. 11.01, p. 482-90. Kolthoff, I. M., Sandell, E. B., Meehan, E. J., and Bruckenstein, S., 1969, Quantitative chemical analysis (4th ed.): New York, Macmillan, 1199 p.

## Bromide, ion-exchange chromatographic, automated

Parameters and Codes: Bromide, dissolved, I-2057-85 (mg/L as Br): 71870 Bromide, dissolved, I-2058-85 (mg/L as Br): 71870

2. Summary of method Bromide is determined sequentially with six other anions by ion-exchange chromatography. Ions are separated based on their aifinity for the exchange sites of the resin. The separated anions in their acid form are measured using an electrical-conductivity cell. See method I-2067, anions, ion-exchange chromatographic, automated, and method I-2058, anions, ion-exchange chromatographic, low ionic-strength water, automated.

11s

## Bromide, ion-exchange chromatographic-electrochemical, automated

Parameter and Code: Bromide, dissolved, l-2128-85 (mg/L as Br): 71870

1. Application 1.1 This method may beusedto analyze atmospheric precipitation andnatural water containing at least 0.01mg/L of bromide. Samples containing morethan 1mg/L needto bediluted. 1.2 Analyses need to be performed on filtered and unacidified samples.

2. Summary of method Bromide is determined with anion chromatograph using an ion-exchange resin in combination with a specific eluent to separate the anions. After the solution has passedthrough the separator column, the samplestream flows through an electrochemical cell, where afixed potential is applied. Any electroactive species suchasbromide having anoxidation-reduction potential near the applied potential will generate acurrent, which is directly proportional to the concentration of the electroactive species.

3. Interferences 3.1 Chloride is aninterference. When chloride ion passesthrough the detector, acurrent generates because of the formation of silver chloride on the surface of the silver-working electrode. The eluent stream, which removes silver chloride, generates anegative peak. The higher the chloride concentration, the longer it takes for the peak to return to baseline conditions. The effects of chloride at various levels of bromide areshown in tables 5and6.Chloride interferes with bromide if the chloridetobromide ratio is greater than 1,OOO:lfor the analytical rangeof 0.01to 0.1mg/L of bromide. A similar interference is present when the chloridetobromide ratio exceeds5,00&l for the 0.1 to 1.0 mg/L analytical range. Samples containing greater than 2,000mg/L of chloride must first be diluted. 3.2 Sulfite elutes at almost the sametime as bromide, however, this interference will not affect bromide sinceanysulfite in the samplewill havehadtime to oxidize to sulfate before analysis. For example, 10mg/L ofsulfite usually oxidizes to sulfate within 120 h.

4. Apparatus 4.1 Ion Chmmatogmph, Dionex Model 12or equivalent, using the following operating conditions: Sample loop -------- 200 PL Eluent flow rate ---- 138 n&/h (30 percent of full capacity) Samplepump flow rate 50 percent of full capacity 4.1.1 Precolumn, 4X50 mm, fast-run, anionresincolumn (Dionex P/N 030831orequivalent) placed before the separator column to protect the separator column from being fouled by particulates orspeciesstrongly retained by the ionexchange resin. 4.1.2Separator column, 4X250 mm, fast-run, anionseparator column packedwith low-capacity, pellicular, anion-exchangeresin (Dionex P/N 030830 or equivalent) that is styrene divinylbenzenebased.This hasbeenfound to besuitable for resolving fluoride, chloride, nitrite, orthophosphate, bromide, nitrate, and sulfate. 4.2 Pulse dumper, installed just before the injection valve to reduce flow pulsation. 4.3 Electrochemical detector, Dionex or equivalent, consisting of cell and potentiostat. 4.3.1Theelectrochemical cellis installed after the separator ion-exchange column. The cell is composed of a silver-working electrode, a

117118 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

Table S-Recovery of bromide in the presence of chloride for 0.01 to 0.09 mg/L bromide

Bromide O-wW

0.01 .02 .03 .05 .07 .09 10

100 100 100 100 100 20

1El 100 100 100 100 Chloride (me/L)

30 50 Recovery of bromide (percent)

50 40 65 50 loo 60 100 100 100 100 100 100 70 90

10 50 :5 si 40

60 100 66 100 100

Table 6.--Recovery.of bromide in the presence of chloride for 0.01 to 0.09 mg/L bromide

Chloride (mgll)

Bromide O-wW 0.1 .2 .3

:: .6 .7 500 700

100 60 100 100 100 100

100 100 100 100 100 100 100 100 100 100 1000 1500 Recovery of bromide (percent) 70 10 100 75 100 100

100 100 100 100 100 100 100 100 100 100 2mo 2500

0 0 50 10 70 17

100 26

50 100 53 100 57 loo 60 100 61

stainless steelcounter electrode andaAglAgCl reference electrode (NOTE 1). CAUTION: Samples containing oil and greasedamage the membrane. NOTE 1. It is necessary to refill the reference electrode with NaCl solution saturated with AgCl andto replacethe ion-exchangemembrane and membrane gasket when the potentiostat cannot be zeroed (high detector output). This happens when the AgCl in the reference electrode cell is depleted and (or)the membrane is damaged. It is important not to introduce any air bubbleswhile refilling the referenceelectrode andreplacing the membrane; this causesaloss of sensitivity. The silver-working electrode needs to be cleaned once a month. Polish the surface with a small amount of toothpaste on
aKimwipe to removethe gray tarnish, andthen rinse with deionized water. It is desirable to have a spare reference electrode to avoid downtime. If there is difficulty in refilling the reference electrode, contact the manufacturer. 4.3.2 The potentiostat operating conditions

are as follows: Applied potential --- 0.10 V (NOTE 2) Select mode MEAS - ON Select mode +I- -- + Off set multiplier --- Xl uA Meter select ------- Out Put Output range ------ 100 nA/V NOTE 2. The applied potiential setting ofthe potentiostat that gives the optimum sensitivity for bromide will vary with ageandcondition of the reference electrode, and needsto be de termined. 4.4 Autosampkr, Technicon IV or equivalent, using a proportioning pump to deliver water to the wash receptacle. 4.5 Integrator, Spectra Physics SP-4100 or equivalent, using the following operating conditions:

Bromide Bromide 0.01 to 0.1 mg/L 0.1 to 1.0 mgiL Input range 1v 10v Chart speed 1cmlmin 1 cmlmin Calibration 0 (linear) 2 (quadratic fit) PT (Peak threshold) 60,000 1,500 AT (Attenuation) 512 126 PH (Peak height) PW (No. of data A0 A0 samples per bunch) 

# cMETHODS FOR DETERMINATION OF INORGANIC SUBSTANCES 119

4.6 For additional information refer manufacturer’s instruction manual

6. Reagents 5.1 Bromide standard solution I, 1.00mL= 1.00mg Br-l: Dissolve 1.2877g NaBr in demineralized water and dilute to 1,000 mL. 5.2 Bromide sturzcihnlsolution II, 1.00mL= 0.01 mg Br-‘: Dilute 10.0 mL bromide standard solution I to 1,000mL with demineralized water. 5.3 Bromide standard solution III, 1.00 mL= 0.001 mg Br-l: Dilute 100 mL bromide standard solution II to 1,000 mL with demineralized water. 5.4 Bromide working standards: Prepare 1,000 mL eachof a series of bromide working standards by appropriate quantitative dilution of bromide standard solutions II and III.

Bromide standard solutions

(W
10 of III 50 10of of III

5oof II 100 of II Bromide concentration @w/L)
0.01 .05

:A 1.0

5.5 Eluent, 0.003M sodium bicarbonate0.0024M sodium carbonate (NOTE 3):Dissolve 0.2520 g NaHC03 and 0.2544 g Na,C03 in demineralized water and dilute to 1 L. NOTE 3. Eluent concentration may bevaried slightly to obtain the sameretention times for each anion when a new separator column is used. The NaHC03 is subject to thermal decomposition and must be weighed without prior drying.

6. Procedure 6.1 Set up ion chromatographic system according to manufacturer’s instructions. Equilibrate the column with eluent until a stable baselineisobtained. AIIow approx 30min for equilibration. 6.2 Enter appropriate program into the main program controller of the ion chromatograph according to the manufacturer’s instruction. The system is configured sothat the ion chromatograph, controls the autosampler and starts the integrator at the beginning of each sample injection. 6.3 Pressthe LEVEL key of the integrator, which causesthe display of the input voltage. Level the integrator at 10mV or display 1000 by adjusting coarse dial of potentiostat. 6.4 Press the PT EVAL (peak threshold evaluation) key for integrator to evaluate the detector signal for noise and drift. 6.5 Create an information file in the integrator by pressing the DIALOG key. Create File 1for bromide concentrations between 0.1 to 1.0 mg/L using a quadratic fit. Create File 2for bromide concentrations lessthan 0.1mg/L using a single-point calibration with intercept of zero. 6.6 Placeacomplete set of standards in the first positions of the tray, beginning with the least concentrated standard, followed by samples. Place individual standards of differing concentrations in every tenth position ofthe remainder of the tray.

7. Calculations The integrator automatically computes the concentration of bromide in each sample by comparing its peak height or peak areato the analytical curve. Retention time for bromide is approximately 5.4 min.

8. Report Report bromide, dissolved (71870),concentrations asfollows: lessthan 1.0r&L, nearest0.01 mg/L; 1.0 mg/L and above, two significant figures.

9. Precision and accuracy 9.1 Analysis of six test samples 10 times eachby a single operator over aperiod of one month resulted in the following:

Mean Standard deviation (fw3W mLw
0.32 0.005 .22 .005 .24 .005 .30 .008 .50 .008 .049 .002 Relative standard devlatlon (percent)

:f 2.2 2.6 1.6 4.7

9.2 Recovery of bromide addedto ten water samples resulted in the following:120 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

Chloride present VwW

-

4

ii2.28 5.95 4.59 4.78 4.89 5.05 Bromide Bromlds

present added (meW (meW
0.59 .49 .33 .30 .22 .040 .037 .031 .029 .031 .05

.03 .Ol .03 found ReCOVery

(meW (percent)
1.13 1.03 .85 .61 51 .089 .086 .062 .039 .064 108

108 107 103

ii 98 103 100 110 References

Fishman, M. J., and F’yen, G. S., 1979, Determination of selected anions in water by ion chromatography: U.S. Geological Survey Water-Resources Investigations, 79-101, 30 p. Johnson, E. L., and Cathers, E., 1981, Applications of simultaneous detection in IC: 23rd Ftocky Mountain Conference, Denver, Colorado. Small, H., Stevens, T. S.,and Bauman, W. C., 1975,Novel ion exchange chromatographic method using conductimetric detection: Analytical Chemistry, v. 47, p. 1801-09.



# c

## Bromide, calorimetric, fluorescein, automated-segmented flow

Parameter and Code: Bromide, dissolved, l-2129-85 (mg/L as Br): 71870

1. Application This method may beusedto analyze natural water containing from 0.010 to 0.40 mg/L of bromide. Samplescontaining greater concentrations needto be diluted.

2. Summary of method The sample is buffered to pH 5.6 with an aceticacidbuffer solution andthen reactedwith chloramine T to oxidize the bromide to hypobromous acid. The hypobromous acid formed then reacts with fluorescein to form the pink eosin (tetrabromo fluorescein), which is proportional to the bromide concentration.

Br-l + HOC1-, BrOH + Cl-l

BrOH + Fluorescein -t Tetrabromo Fluorescein (pink)

3. Interferences Iodide interferes quantitatively, but in most waters the iodide concentration is negligible. It is recommendedthat adetermination for iodide be performed and that the concentration that is found be subtracted from the apparent bromide concentration. Cyanide, asmuch as0.50 mg/L, andchloride, asmuch as500mg/L, donot interfere. Thiocyanate interferes linearly, but in most waters its concentration is negligible.

4. Apparatus 4.1 Technicon AutoAnalyzer II, consisting of a sampler, proportioning pump, cartridge manifold, calorimeter, voltage stabilizer, recorder, and printer. 4.2 With this equipment the following operating conditions have beenfound satisfactory for the range from 0.010to 0.40mg/L bromide. Absorption cell ----- 50 mm Wavelength _____--- 520 nm Cm _---- ________-- 3()/h (‘J/l)

5. Reagents 5.1 Bromide standard solution I, 1.00mL= 0.100 mg Br-l: Dissolve 0.149 g KBr, dried overnight over concentrated H,SO,, in demineralizedwater anddilute to 1,000mL with demineralized water. 5.2 Bromide stundurd solution II, 1.00mL= 0.010mg Br-l: Dilute 100.0mL bromide standard solution I to 1,000mL with demineralized water. 5.3 Bromide working standards: Prepare a blank and 1000mL eachof aseriesof bromide working standards by appropriate quantitative dilution of bromide standard solution II as follows:

Bromide standard solution II Sromlde concentration

(mL) OWL) 1.0 0.010 5.0 .050 10.0 .lOO 25.0 .250 40.0 .400

5.4 Buffer solution: Dissolve 9.426g NH&l in 500mL demineralized water and add 67 mL glacial aceticacid(sp.gr. 1.06). Add dropwise,5N KOH solution until the pH ofthe solution is 5.6. Dilute to 1,000mL with demineralized water. 5.5 Chloramine-T solution, 0.5 g/l00 mL: Dissolve 0.500 g chloram.ineT in 100 mL of demineralized water. Prepare fresh daily. 5.6 Fluorescein stock solution, 0.125 g/100 mL: Dissolve 0.125gfluorescein in 25mL O.lN NaOH anddilute to 100mL with demineralized water. This solution is stable for one week if stored in a light-proof bottle.

121122 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

5.7 Fluorescein working solution: Pipet 10 mL Fluorescein stock solution into a lOO-mL volumetric flask; dilute to the mark with demineralized water. This solution must beprepared fresh daily. 5.0 Sodium hydroxide solution, 0.1N: Dissolve 4.0 g NaOH in demineralized water and dilute to 1 L with demineralized water. 5.9 Potassium hyclroxide solution, 5.ON: CAUTIOUSLY dissolve 280g KOH in demineralized water, cool, and dilute to 1 L with demineralized water.

6. Procedure 6.1 Set up manifold (fig. 18). 6.2 Allow calorimeter andrecorder to warm up for at least 30 min. 6.3 Adjust the baseline to read zero scale divisions onthe recorder with all reagents, but with demineralized water in the sample line. 6.4 Place acomplete set of standards and a blank in the first positions of the first sample tray, beginning with the most concentrated standard. Place individual standards of differing concentrations in every eighth position of the remainder of this and subsequent sample trays. Fill remainder of eachsample tray with unknown samples. 6.5 Begin analysis. When the peakfrom the most concentrated standard appears on the recorder, adjust the STD CAL control until the flat portion of the peak reads full scale.

7. Calculations 7.1 Prepare an analytical curve by plotting the height of each standard peak versus its respective empirical bromide concentration.



### S-Turn 5 Dil I 

### 0.0301n Air \ 0 32mL/min

6.051 in I 4 4AA Waste

-I ,-* n 

## II II .uumw ml

’ Air



### k.32mL/min InI 0.08Oin I wr...p7.8v 250mLImin I Sampler 4 30/h P/lcam

0.0 loin 1 Chloramine T O.O5mL/njin 

# I O.OlOin I Fluorescein Calorimeter
--- ~0 0.05 mL/min n - -,I. Wapte sampler n-1 WMn I 

### Water 150-mm CWII I 

## wazh3.40 

## mL/min -~ receptacle 0 05lin

* 1.OOml I Waste

Jmin I
I I 

# I Recorder Proportioning pump I 

# c

c Figure 18.- Bromide, fluorescein manifoldMETHODS FOR DETERMINATION OF INORGANIC SUBSTANCES 123

7.2 Compute the apparent bromide concentration of each sample by comparing its peak height to the analytical curve. Any baseline drift that may occurmust betaken into account when computing the height of a sample or standard peak. 7.3 Compute the iodide concentration of eachsamplein accordancewith method I- 2371. 7.4 Compute the bromide concentration as follows: Br-l(mg/L)= mg/L apparent concentration-mg/L iodide concentration

8. Report Report bromide, dissolved (71870),concentrations as follows: less than 0.1 mg/L, two decimals; 0.1 mg/L and above, two significant figures.

9. Precision Single-operator precision for dissolved bromide for six samples expressed in terms of percent relative standard deviation is as follows:

Number of replicates
10 10 1

10 10 Concentration

mW
0.010 .050 .lOO .3!x

550 .860 Relative standard deviation (percent)
15.0 10.0

f:8

:::

References

Marti, V. C.,andArozarena, C.E.. 1981,Automated detarmination of bromide in water: proceedings Pittsburgh Conference, No. 734. Thomas, L. C., and ChamberIin. G. J., 1980. Calorimetric chemical analytical methods, 9th: England, The Tinto meter Ltd., p. 111-12. Stager, V. A., and Kolthorf, I. M., 1935,The detection and calorimetric estimation of micro quantities of bromide: Journal of the American Chemical Society, v. LVll. p. 831-3. Zitomer, F. and Lambert, J. L., 1963, Spectrophotometric determination of bromide ion in water: Analytical Chemistry, v. 35, p. 1731-34.

## Cadmium, atomic absorption spectrometric, chelation-extraction

Parameters and Codes: Cadmium, dissolved, l-1136-85 kg/L as Cd): 01025 Cadmium, total recoverable, l-3136-85 Gg/L asCd): 01027 Cadmium, suspended recoverable, l-7136-85 bg/L as Cd): 01026

1. Application 1.1 This method may be used to analyze water and water-suspended sediment containing from 1to 25pg/L ofcadmium. Samplesolutions containing morethan 25pg/L needeither to bediluted prior to chelation-extraction orto be analyzed by the atomic absorption spectrometric direct method. 1.2 Suspended recoverable cadmium is calculated by subtracting dissolved cadmium from total recoverable cadmium. 1.3 Total-recoverable cadmium in watersuspendedsediment needsto undergo apreliminary digestion-solubilization by method I-3485 before being determined. 1.4 If the iron concentration of the sample solution exceeds 25,000 pg/L, determine cadmium by the atomic absorption spectrometric direct method.

2. Summary of method Cadmium is determined by atomic absorption spectrometry following chelation with ammonium pyrrolidine dithiocarbamate (APDC) and extraction with methyl isobutyl ketone (MIBK). The extract is aspirated into the airacetylene flame of the spectrometer.

3. Interferences Concentrations of iron greater than 25,000 pg/L interfere by depressing the cadmium absorption.

4. Apparatus 4.1 Atomic absorption spectrometer equipped with electronic digital readout and automatic zero and concentration controls. 4.2 Refer to the manufacturer’s manual to optimize instrument for the following: Grating ------------ Ultraviolet Wavelength -------- 228.8 nm Source (hollow-cathode

or electrodeless-discharge lamp) ----- Cadmium Ofi,-Jmt _a__-

_______ & Fuel ________----_-- Acetylene Type of flame ------- Oxidizing 4.3 Different burners may beusedaccording to manufacturers’ instructions.

5. Reagents 5.1 Ammonium pyr&dine dithiocarbamate solution, 1g/l00 mL: Dissolve 1gAPDC in 100 mL demineralized water. Prepare fresh daily. 5.2 Cadmium stunduti solution I, 1.00mL= 100pg Cd: Dissolve 0.1000g Cd splatters in a minimum of dilute HNO,. Heat to increaserate of dissolution. Add 10mL concentrated HNO, (spgr 1.41)and dilute to 1000mL with demineralized water. 5.3 Cad&m standard solution II, 1.00 mL= 0.50pgCd:Dilute 5.0mL cadmium standardsolution I and 1mL concentrated HNOz (sp gr 1.41)to 1,000mL with demineralized water. 5.4 Cadmium standard solution III, 1.00 mL=O.O5 pgCd: Immediately beforeuse,dilute 10.0mL cadmium standard solution II to 100.0 mL with acidified water. This standard is used to prepare working standards at time of analysis. 5.5 citric acid-sodium citrate buffersolution: Dissolve 126g citric acid monohydrate and 44 g sodium citrate dihydrate in demineralized water and dilute to 1 L with demineralized water. SeeNOTE 3 before preparation. 5.6 Methyl isobutyl ketone (MIBK).

125126 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

5.7 Potassium hydroxide, 1OM Dissolve 56 g KOH in demineralized water, cool, anddilute to 100 mL. 5.8 Potassium hydroxide solution, 2.5M: Dissolve 14g KOH in demineralized water and dilute to 100 mL (NOTE 1). NOTE 1.Alternately, a2.5M NH,OH solution may be used. Add 167 mL concentrated NH,OH (sp gr 0.90)to 600 mL demineralized water. Cool and dilute to 1 L. 5.9 Water, acidified: Add 1.5 mL concentrated HNO, (sp gr 1.41)to 1 L of demineralized water.

6. Procedure 6.1 Clean all glassware used in this determination with warm, dilute HNO, (1+9) and rinse with demineralized water immediately before use. 6.2 Pipet avolume of sample solution containing less than 2.5 pg Cd (100mL max) into

a 200-n& volumetric flask, and adjust the volume to approx 100 mL. 6.3 Prepare a blank of acidified water and sufficient standards, and adjust the volume of each to approx 100 mL with acidified water. 6.4 With apH meter, adjust the pH of each solution to 2.7 (NOTES 2 and 3) with 2.5M KOH. Shake for 3 min. NOTE 2. For water-suspended sediment samples which have beendigested, add 1to 2 mL 1OMKOH or concentrated NH,OH (spgr 0.90) before pH adjustment. NOTE 3. If an automated titration system is used to adjust the pH, add 2.5 mL citric acidsodium citrate buffer solution prior to pH adjustment. This will prevent over-shooting the end point in poorly buffered samples. 6.5 Add 2.5 mL APDC solution and mix. 6.6 Add 10.0mL MIBK andshakevigorously for 3 min. 6.7 Allow the layers to separate and add demineralized water until the ketone layer is completely in the neck of the flask. 6.8 Aspirate the ketone layer within 1 h. Aspirate the ketone layer ofthe blank to setthe automatic zerocontrol. Usethe automatic concentration control to set the concentrations of standards. Useat least six standards. Calibrate the instrument each time a set of samples is analyzed and check calibration at reasonable intervals.

7. Calculations 7.1 Determine the micrograms per liter of dissolved ortotal recoverable cadmium in each samplefrom the digital display or printer while aspirating each sample. Dilute those samples containing concentrations of cadmium that exceedthe working range of the method; repeat the chelation-extraction and multiply by the proper dilution factors. 7.2 Todetermine the micrograms perliter of suspended recoverable cadmium, subtract dissolved-cadmium concentration from totalrecoverable-cadmium concentration.

6. Report Report cadmium, dissolved (01025), totalrecoverable (01027),andsuspended-recoverable (01026).concentrations asfollows: lessthan 10 pg/L, nearest microgram per liter, 10ClglLand above, two significant figures.

9. Precision 9.1 Precision for dissolved cadmium for 22 samples within the range of 2to 17pg/L may be expressed as follows:

S,= 0.213X - 0.111

where s,= overall precision, micrograms per liter, and X= concentration of cadmium, micrograms per liter. The correlation coefficient is 0.6914. 9.2 Precision for dissolved cadmium for four of the 22 samplesexpressedin terms ofthe percent relative standard deviation is asfollows:

Number of laL7oratorles 6 11 6 12 Relative standard deviation (percent)

;: 17 34

9.3 It is estimated that the percent relative standard deviation for total recoverable and suspendedrecoverable cadmium will begreater than that reported for dissolved cadmium.

## Cadmium, atomic absorption spectrometric, direct

Parameters and Codes: Cadmium, dissolved, l-l 135-85 bg/L asCd): 01025 Cadmium, total recoverable, l-3135-85 bg/L as Cd): 01027 Cadmium, suspended recoverable, l-7135-85 bg/L as Cd): 01028 Cadmium, recoverable-from-bottom-material, l-5135-85 bglg as Cd): 01028

1. Application 1.1 This method may be used to analyze water and water-suspended sediment containing at least 10pg/L of cadmium. Sample solutions containing morethan 250pg/L needeither to bediluted or to be read on a less expanded scale.Sample solutions containing lessthan 10 pg/L needto beanalyzed by the atomic absorp tion spectrometric chelationextraction method, providing that the interference limits discussed in that method are not exceeded. 1.2 Suspended recoverable cadmium is calculated by subtracting dissolved cadmium from total recoverable cadmium. 1.3 This method may beusedto analyxehottom material containing at least 1 pg/g of cadmium. 1.4 Total recoverable cadmium in watersuspended sediment needsto undergo preliminary digestion-solubilization by method I-3486, and recoverable cadmium in bottom material needs to undergo preliminary digestion-solubilixation by method I-5486 beforebe ing determined.

2. Summary of method Cadmium is determined by atomic absorption spectrometry by direct aspiration of the sample into anair-acetylene flame without preconcentration or pretreatment of the sample.

3. Interferences 3.1 Individual concentrations of sodium (9,000mg/L), potassium (9,000mg/L), magnesium (4,500mg/L), sulfate (9,000mg/L), chloride (9,000 mg/L), nitrate (100 mg/L), iron (4X10” rg/L), andcobalt, nickel, copper,zinc, lead,and chromium (10,000 M/L each)do not interfere. Greaterconcentrations ofeachconstituent were not investigated. 3.2 Calcium at concentrations greater than 1,000 mg/L suppresses the cadmium absorp tion. At 2,000mg per liter of calcium, the suppression is approximately 19 percent.

4. Apparatus 4.1 Atomic absorption spectrometer equipped with electronic digital readout and automatic zero and concentration controls. 4.2 Refer to the manufacturer’s manual to optimize instrument for the following: Grating ,----------- Ultraviolet Wavelength ----- --- 253.8 m Source (hollow-cathode lamp) A,,- _---_ -_- Cadmium
Oi&& I,--e---w--- fi

fiel --- --___--__-__ Acetylene Type of flame ------- Oxidizing 4.3 The Perkin-Elmer, flathead, single-slot burner allows aworking rangeof 10to 250pg/L. Different burners may be used according to manufacturers’ instructions.

5. Reagents 6.1 Cadmium standad solution I, 1.00mL= 100pg Cd: Dissolve 0.1000g Cd splatters in a minimun of dilute HNOs. Heat to increaserate of dissolution. Add 10mL concentrated HNOa (spgr 1.41)anddilute to 1,000mL with demineralized water. 5.2 Cadmium standard solution II, 1.00 mL= 1.0pgmcd:

Dilute 10.0mL cadmium standardsolution I and 1mL concentrated HNO, (sp gr 1.41)to 1,000mL with demineralized water.

127128 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS (01026), concentrations as follows: less than 5.3 Cadmium working standards: Preparea seriesofat least six working standards containing from 10to 250 pg/L of cadmium by appropriate dilution of cadmium standard solutions I and II with acidified water. Preparefreshdaily. 5.4 Water, acidified: Add 1.5 mL concentrated HNO, (spgr 1.41)to aliter of deminerslized water. 1,000 ClglL, nearest 10 rg/L; 1,000 pg/L and above,two significant figures. 8.2 Report cadmium, recoverable-frombottom-material (01028), concentrations as follows: less than 10 pglg, nearest microgram per gram; 10 pglg and above, two significant
figUlW.

6. Procedure Aspirate the blank (acidified water) to setthe automatic zerocontrol. Usethe automatic concentration control to set the concentrations of standards. Useat least six standards. Calibrate the instrument each time a set of samples is analyzed andcheckcalibration at reasonableintC?rVdS.

7. Calculations 7.1 Determine the micrograms per liter of dissolved or total recoverable cadmium in each samplefrom the digital display or printer while aspirating each sample Dilute those samples containing cadmium concentrations that exceed the working range of the method and multiply by the proper dilution factors. 7.2 lb determine micrograms per liter suspendedmcoverablecadmium, subtract dissolvedcadmium concentration from total-recoverablecadmium concentration. 7.3 lb determine micrograms per gram of cadmium in bottom-material samples, first determine the micrograms per liter of cadmium in each sample as in paragraph 7.1;then 9. Precision 9.1 Thestandard deviation for dissolved cadmium within the range of 2.8to 18.4 pg/L for 21 samples was found to be independent of concentration. The 95-percent confidence inter val for the averagestandard deviation of 3.57 pg/L ranged from 3.24 to 3.95 pg/L. 9.2 Precision for dissolved cadmium for five of the 21 samples expressed in terms of the percent relative standard deviation is as follows:

Number of Mean Ralatlve standard deviation laboratories .&gQ (percent)

12 2.8 124 17 4.8 50 15 10.7 19 15 15.7 24 5 18.4 71

m/L CdX mL of original digest

Cd klg)= 1,000

wt of sample (g) 9.3 It is estimated that the percent relative standard deviation for total recoverable and suspended recoverable cadmium and for recoverable cadmium from bottom material will be greater than that reported for dissolved cadmium. 9.4 Precision for total recoverable cadmium expressedin terms ofthe percent relative standarddeviation for two watersuspended sediment mixtures is as follows:

a. Report 8.1 Report cadmium, dissolved (01025),totalrecoverable(01027),and suspended-recoverable Number of
laboratorles

13 9 Mean

&gg5.4 15.8 Relative standard davlatlon (percent)

ii 

# c,

c

## Cadmium, atomic absorption spectrometric, graphite furnace

Parameter and Code: Cadmium, dissolved, l-1137-85 (pa/L as Cd): 01025

1. Application 1.1 This method may beusedto determine cadmium in low ionic-strength water and pre cipitation. With deuterium background correction and a 20-rL sample, the method is applicable in the range from 0.02 to 1.0 pg/L. With Zeeman background correction and a 20-rL sample, the method is applicable in the range from 0.1 to 3.0 pg/L. Sample solutions that contain cadmium concentrations exceeding the upper limits must bediluted or preferably be analyzed by the atomic absorption spectrometric direct orchelation- extraction method

or by the atomic emission spectrometric ICP method. 1.2 Theanalytical rangeanddetection limits

canbeincreasedor possibly decreasedby varying thevolume of sampleinjected orthe instrumental settings. Purification of reagents and

use of ASTM Type 1water (Method D-1193, American Society for Testing and Materials, 1984)may result in lower detection limits.

2. Summary of method Cadmium is determined by atomic absorption spectrometry in conjunction with agraphite furnace containing a graphite platform (Hinderberger andothers, 1981).A sampleis placed on the graphite platform and amatrix modifier is added. The sample is then evaporated to dryness,charred, andatomized using high-temperature ramping. Theabsorption signal generated during atomization is recorded and compared with standards.

3. Interferences 3.1 Interferences in low ionic-strength samples, such asprecipitation, normally are quite low. In addition, the use of the graphite platform reducesthe effects of many interferences. Cslcium (25mg/L), magnesium (8n&L), sodium (20 mg/L), sulfate (34 mg/L), and chloride (25 mg/L) do not interfere. Greater concentrations of these constituents were not investigated. 3.2 Precipitation samples ususlly contain very low concentrations of cadmium. Special precautionary measuresmust beemployed during both sample collection and laboratory determination to prevent contribution from contamination.

4. Apparatus 4.1 Atomic absorption spectrometer, for use at 228.8nm andequippedwith background correction, digital integrator to quantitate peak areas,graphite furnace with temperature programmer, and automatic sample injector. The programmer must havehigh-temperature ramping and stopped-flow capabilities. 4.1.1 Referto the manufacturer’s manual to optimize instrumental performance.The aualytical ranges reported in paragraph 1.1arefor a 20-PL sample with 5 CCL of matrix modifier (NOTE 1). NOTE 1.A 20-rL samplegenerally requires 30
sto dry. Samples that have acomplex matrix may require alonger drying andcharring time. 4.1.2 Graphite furnace, capable of reaching temperatures sufficient to atomize the element of interest. Warning: dial settings frequently

areinaccurate and newly conditioned furnaces require temperature calibration. 4.1.3 Graphite tubesandplatforms. Pyrolyt ically coatedgraphite tubes andsolid pyrolytic graphite platforms are recommended. 4.2 Labware. Many trace metals at very low concentrations have been found to sorb very rapidly to glassware. To preclude this,

129130 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

fluorinated ethylene propylene (FEP) orTeflon labware may be used. Alternately, glassware, particularly flasks and pipets, may betreated with silicone anti-wetting agentsuchasSurfacil (Pierce Chemical Co., Rockford, IL, 61105)according to the manufacturer’s instructions. Autosampler cups must becheckedfor contamination. Lancer (1831Olive St., St. Louis, MO, 63103)polystyrene disposable cups have been found to be satisfactory after acid rinsing. Alternately, reuseableTeflon or FEP cupsmay be used. 4.3 Argon, standard, welder’s grade, commercially available. Nitrogen may also be used if recommended by the instrument manufacturer.

5. Reagents 5.1 Cadmium standu~ solution I, 1.00mL= 1,000pg Cd: Dissolve 1.0000g Cd splatters in

a minimum of dilute HNO,. Heat to increase rate of dissolution. Add 10 mL high-purity concentrated HNO, (sp gr 1.41). Ultrex or equivalent, and dilute to 1,000 mL with Type 1water. 5.2 Cadmium standard solution II, 1.00 mL= 10.0 pg Cd: Dilute 10.0 mL cadmium standard solution I to 1,000 mL (NOTE 2). NOTE 2.Useacidified Type 1water (paragraph 5.7)to make dilutions. All standards must be stored in sealedTeflon or FEP containers. Each container must be rinsed twice with a small volume of standard before being filled. Standards stored for 6 months in FEP containers yielded values equalto thoseoffreshly prepared standards. 5.3 Cadmium standard solution III, 1.00 mL= 0.100 pg Cd: Dilute 10.0 mL cadmium standard solution II to 1,000 mL. This standard is usedto prepareworking standards serially at time of analysis. 5.4 Cadmium standard solution IV, 1.00 mL= 0.001 pg Cd: Dilute 10.0 mL cadmium standard solution III to 1,000mL. This standard also is used to prepare working standards serially at time, of analysis. 5.5 Matrix modifier solution, 40g NH4HzP04/L: Add 40.0 g NH,H,P04 to 950 mL Type 1water, mix, and dilute to 1,000mL. Analyze 20CCL

of matrix modifier for cadmium contamination. If the cadmium reading is more absorbanceseconds, purify the solution by chelation with ammonium pyrrolidine dithiocarbamate (APDC) and extraction with methyl isobutyl ketone (MIBK) (NOTE 3). Analyze 20rL of the purified solution. Repeat extractions until the cadmium level is reduced to the acceptable level. DO NOT ADD ACID TO THE PURIFIED MATRIX MODIFIER SOLUTION. NOTE 3. To purify matrix modifier solution, pour the solution into a Teflon or FEP container. Add 0.25g APDC for eachliter of solution. While stirring, adjust the solution to pH 2.9by dropwise addition of concentrated HNO, (sp gr 1.41).Transfer portions of the solution to aseparatory funnel, add 100mL MIBK/liter of solution, and shakevigorously for at least 5 min. Frequently, vent the funnel in ahood.Collect theextracted solution in the FEP container. Repeat the extraction with 50 mL MIBK/liter of solution. Because MIBK can dissolve some plastic autosampler cups, boil the solution for at least 10 min in a silicone-treated or acidrinsed container covered with awatchglass to
remove MIBK. 5.6 Nitric acid, concentrated, high-purity, c

_ (spgr 1.41):J. T. Baker “Ultrex” brand HNOs hasbeenfound to beadequately pure; however, each lot must be checked for contamination. Analyze acidified Type 1water for cadmium. Add an additional 1.5 mL of concentrated HNO,/liter of water, and repeat analysis. The integrated signal should not increase by more than 0.001 absorbance-seconds. 5.7 Watet, acidified, Type 1: Add 1.5 mL high-purity, concentrated HNO, (spgr 1.41)to each liter of water. 5.8 Water, Type 1

6. Procedure 6.1 Systematically clean and rinse work
areaswith deionized water on aregular schedule. Use alaminar flow hoodor a“clean room” environment during sample transfers. Ideally, the autosampler and the graphite furnace should be in a clean environment. 6.2 Soak autosampler cups at least overnight in a 1+l solution of Type 1 water and high-purity nitric acid. 6.3 Rinse the sample cups twice with sample beforefilling. Placecupsin sampletray and cMETHODS FOR DETERMINATION OF INORGANIC SUBSTANCES 131

cover.Adjust sampler sothat only the injection tip contacts the sample. 6.4 In sequence, inject 20-PL aliquots of blank and working standards plus 5 CCL of modifier each and analyze. Analyze the blank and working standards twice. Construct the analytical curve from the integrated peak areas (absorbance-seconds). Generally, the curve should be linear to a peak-absorbance (peakheight) value of 0.40 absorbance units. 6.5 Similarly, inject andanalyzethe samples twice. Every tenth sample cup should contain either a standard or a reference material. 6.6 Restandatdizeasrequired.Minor changes of values for known samples usually indicate deterioration of the furnace tube, contact rings, and/orplatform. A major variation usually indicateseither autosampler malfunction orresidue buildup from a complex matrix in a previous sample.

7. Calculations Determine the micrograms per liter of cadmium in each sample from the digital display
orprinter output. Dilute thosesamplescontaining concentrations of cadmium that exceedthe working range ofthe method; repeat the analysis,andmultiply by the proper dilution factors.

8. Report Report cadmium, dissolved (01025),concentrations asfollows: lessthan 1.0pg/L, nearest 0.01CcglL

for deuterium background correction

or nearest 0.1pg/L for Zeemanbackground correction; 1.0 pg/L and above, two significant figures for both deuterium background correction and Zeeman background correction.

9. Precision 9.1 Analysis of five samples six times each by a single operator using deuterium background correction is as follows:

Mean Standard deviation Relative standard deviation WL) &BU (percent)

0.030 0.004 6.9 .106 .004 4.0 ,249 .009 3.4 .499 .OlO 2.0 1.005 .013 1.3
9.2 Analysis of four samples by a single operator using Zeeman background correction 

# B is as follows: Relative standard Number of Mean Standard deviation devlatlon replicates be/L) WL) (percent)

~~ 4 0.50 0.115 23 12 1.60 .060 3.6 6 2.10 .089 4.2 14 3.14 .074 2.4

9.3 The precision and bias for the Zeeman background correction weretested ondeionized water and tap water (specific conductance 280 PSIcm). A known amount of cadmium was addedto eachsample,andsingle-operator precision and bias for six replicates are asfollows:

Amount Amount added found bw) (rsw
Deionized water Standard devlatlon biw Relative

standard devlatlon (percent) Recovery

(percent)

5f5

E 6:5
Tap water 2.25

77 0.05

.05 2.2 t;

4.53 42 .15

7 i:X

3.0 91

85 5.63 .08 1.4 87

f:!5 2.05

5 .08

41 3.9

7 2 5.00 4.52 .12 90

X:E 3.90

522 .15

41 f.i

7:9 75

80

9.4 Theprecision andbiasfor the deuterium background method were tested on deionized water and tap water (specific conductance 280 @/cm). A known amount of cadmium was addedto eachsample,andsingleoperator precision and bias for six replicates are asfollows:

Amount Amount added found (rm be/L)
Deionized water
::825 2.55

72

tx 4.70

97

6:5 5.83
Tap water Standard deviation be-)

0.31 .15

.30 44

.33 Relative

standard deviation (percent)

12

i::

::: Recovery

(percent)

98

t:

it

2.6 ‘3.03 1.0 33 117

3.25 ,2.83 .25 50 4.53 7 if

::: ,5.48

4.23 .21

15 5:o

2.7 t:

81 4

9.5 Interlaboratory precision for dissolved cadmium for 16 samples within the range of132 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

0.62 to 16.2 PglL, without regard to type of background correction anduseof matrix modifiers, if any, may be expressed as follows:

ST= 0.282X + 0.022

where S,= overall precision, micrograms per liter, and X= concentration of cadmium, micrograms per liter. The correlation coefficient is 0.9157.

References

American Society for Testing and Materials, 1984,Annual book of ASTM standards, section 11,water: PhiIadelphi4 v. 11.01, p. 39-41. Cooksey,M., andBamett. W. B., 1979,Matrix modification andthe method ofadditions in fhunelessatomic absorption: Atomic Absorption Newsletter, v. 18, p. 101-6. Femandez, F. J., Beatty, M. M., and Bamett, W. B., 1981, Use of the L’vov platform for furnace atomic absorp tion applications: Atomic Spectroscopy, v. 2,p. 16-21. Hinderberger, E. J., Kaiser, M. L., and Koirtyohann, S. It., 1981,Furnace atomic absorption analysis of biological samples using the L’vov platform and matrix modi% ation: Atomic Spectroscopy, v. 2, p. l-11. Manning, D. C., and Slavin, W., 1983,The determination of trace elements in natural waters using the stabihred temperature platform furnace: Applied Spectroscopy,

v. 37. p. l-11. Ottaway, J. M., 1982, A revolutionary development in graphite furnace atomic absorption: Atomic Spectra scopy, v. 3, p. 89-92. Slavin, W., Carnrick, G. R., and Marming, D. C., 1982, Magnesium nitrate asamatrix modifier In the stabilised temperature platform furnace: AnaIyticai Chemistry, v. 54. p.621-4.



# c

c

## Cadmium, atomic emission spectrometric, ICP

Parameter and Code: Cadmium, dissolved, l-1472-85 (pg/L as Cd): 01025

2. Summary of method metric method utilizing an induction-coupled Cadmium is determined simultaneously argon plasma as an excitation source. See with several other constituents on a single method I-1472, metals, atomic emission specsample by a direct-reading emission spectro- trometric, ICP.

133

## Cadmium, total-in-sediment, atomic absorption spectrometric, direct

Parameter and Code: Cadmium, total, l-5474-55 (mglkg as Cd): none assigned

2. Summary of method hotplate at 200°C. Cadmium is determined on A sediment sample is dried, ground, and the resulting solution by atomic absorption homogenized. The sample is digested with a spectrometry. Seemethod I-5474, metals, macombination of nitric, hydrofluoric, and per- jor andminor, total-in-sediment, atomic absorpchloric acids in a Teflon beaker heated on a tion spectrometric, direct.

135

## Calcium, atomic absorption spectrometric, direct

Parameters and Codes: Calcium, dissolved, l-1152-85 (mg/L as Ca): 00915 Calcium, total recoverable, l-3152-85 (mg/L as Ca): none assigned Calcium, suspended recoverable, l-7152-85 (mg/L as Ca): 81357 Calcium, recoverable-from-bottom-material, dry wt l-5152-85 (mglkg as Ca): 00917

1. Application 1.1 This method may beusedto analyze atmospheric precipitation, water, brines, and water-suspended sediment. 1.2 Two analytical rangesfor calcium areincluded: from 0.01 to 5.0 mg/L and from 1.0to 60 mg/L. Sample solutions containing calcium concentrations greater than 60mg/L needto be diluted. 1.3 Suspendedrecoverable calcium is calculated by subtracting dissolved calcium from total recoverable calcium. 1.4 This method may beusedto analyzebottom material containing at least 10 mglkg of calcium. 1.5 Total recoverable calcium in water-suspendedsediment needsto undergo preliminary digestion-solubilization by method I-3485, and

To aspirator recoverable calcium in bottom material needs to undergo preliminary digestion-solubilization by method I-5485 before being determined.

2. Summary of method 2.1 Calcium isdetermined by atomic absorption spectrometry (Fishman andDowns, 1966). Lanthanum chloride is added to mask interferences. 2.2 This proceduremay beautomated by the addition of a sampler, a proportioning pump, and a strip-chart recorder or printer or both (fig. 19).

3. Interferences 3.1 Phosphate, sulfate, andaluminum interferebut aremasked by the addition of lanthanum. Silica also reportedly interferes. Because

Waste

wash receptacle

Figure lg.-Calcium manifold

137138 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

low calcium values result if the pH of the sampleis above7,standards areprepared in hydra chloric acid solution andsamplesarepreserved in the field with use of nitric acid solution. Concentrations of magnesium greater than 1,000 mg/L also cause low calcium values. 3.2 Nitrate interferes, but in the presenceof lanthanum chloride-hydrochloric acid solution at least 2,000mg/L can betolerated. The addition of nitric acidto the samplecausesnoprob. lem in the following procedure.

4. Apparatus 4.1 Atomic absorption spectrometer equipped with electronic digital readout and automatic zero and concentration controls. 4.2 Refer to the manufacturer’s manual to optimize instrument for the following:

Grating __-_-

_______ Visible Wavelength -------- 422.7 nm Source (hollow-cathode

lamp) --------

____ C&urn

Oxidant ---

_________ Ah

Fuel

______ ----

_____ Acetylene Type of flame ------- Slightly reducing 4.3 The50.mm (2-m.),flathead burner allows
a working range of 0.01 to 5.0 mg/L. This burner, rotated 90“, allows aworking range of 1.0 to 60 mg/L. 4.4 Different burners may beusedaccording to manufacturers’ instructions. A nitrous oxide-acetylene flame will provide two to five times greater analytical sensitivity andfreedom from chemical interferences; however, sodium
or potassium chloride must beaddedto control ionization of calcium.

5. Reagents 5.1 Calcium standard solution, 1.00 mL= 0.500mg Ca:Suspend 1.250g CaC03, dried at 180“Cfor 1hbeforeweighing, in demineralized water anddissolve cautiously with aminimum of dilute HCl. Dilute to 1,000 mL with demineralized water. 5.2 Calcium working standards: Prepare at least six working standards containing either from 0.01 to 5.0 mg/L or from 1.0 to 60 mg/L of calcium by diluting the calcium standard solution. To each working standard add 1.0 mL of LaCls solution for each 10 mL standard. Similarly, prepare ademineralized water blank. 5.3 Lanthanum chloride solution, 87 g/L: Mix 29 g of LazO, with a few milliliters of demineralized water to form a slurry. Slowly add250mL concentrated HCl (spgr 1.19)while stirring (reaction may beviolent) to dissolve the La,O,. Dilute to 500 mL with demineralized water.

6. Procedure 6.1 Add 1.0 mL of LaCls solution per 10.0 mL of sample solution. 6.2 Aspirate the blank to set the automatic
zero control. Use the automatic concentration control to set the concentrations of standards. Useat least six standards. Calibrate the instrument eachtime asetof samplesis analzyedand check calibration at reasonable intervals.

7. Calculations 7.1 Determine the milligrams per liter of dissolved ortotal recoverable calcium in eachsample from the digital display or printer while aspirating each sample. Dilute those samples containing calcium concentrations that exceed the working range of the method and multiply q\ by the proper dilution factors. 7.2 To determine milligrams per liter of suspended recoverable calcium, subtract dissolved-calcium concentration from total-recoverable-calcium concentration. 7.3 To determine milligrams per kilogram of calcium in bottom-material samples,first determine the milligrams per liter of calcium in each sample as in paragraph 7.1; then J

mg/L CaXmL of original digest

Ca (mg/kg)= 1000

wt of sample (kg)

8. Report 8.1 Report calcium, dissolved (00915),totalrecoverable (none assigned), and suspendedrecoverable (81357),concentrations asfollows: less than 1.0 mg/L, two decimals; 1.0 to 10 mg/L, onedecimal; 10mg/L andabove,two significant figures. 8.2 Report calcium, recoverable-from-bottom-material (00917),concentrations asfollows: lessthan 1,000mg/kg, nearest 10mglkg; 1,000 mg/kg and above, two significant figures. aMETHODS FOR DETERMINATION OF INORGANIC SUBSTANCES 139

9. Precision 9.1 Precision for dissolved calcium for 37 samples within the range of 0.84 to 184mg/L may be expressed as follows:

s,= 0.087X - 0.249

where

S,= overall precision, milligrams per liter, and X= concentration of calcium, milligrams per liter. The correlation coefficient is 0.8632. 9.2 Precision for dissolved calcium for five ofthe 37samplesexpressedin terms ofthe percent relative standard deviation is as follows:

Number of Mean Relative standard deviation laboratorles mW (percent)

20 0.84 24 14 10.7 6 45 50.1 8

110 184 9.3 Precision for dissolved calcium within the rangeof0.05to 5.0mg/L in terms ofthe percent relative standard deviation by a single operator is as follows:

Number of Mean Relative standard deviation replicates mm (percent)

-_

I 0.052 40.4

1.02 5.9

: 1.85 10.3

5.05 1.0

9.4 It is estimated that the percent relative standard deviation for total recoverable and suspendedrecoverable calcium andfor recoverable calcium from bottom material will be greater than that reported for dissolved calcium.

Reference

Fishman, M. J., and Downs, S. C., 1966, Methods for analysis of selected metals in water by atomic absorption: U.S. Geological Survey Water-Supply Paper 1540-C. p. C26-C28.

## Calcium, atomic absorption spectrometric, direct-EPA

Parameter and Code: Calcium, total recoverable, l-3153-65 (mg/L as Ca): 00916

1. Application 1.1 This method may be used to analyze water-suspended sediment. Sample solutions containing from 0.1to 60mg/L of calcium may be analyzed without dilution; whereas, those containing more than 60 mg/L need to be diluted. 1.2 For ambient water, analysis may be made on a measured portion of the acidified water-suspended sediment sample. 1.3 For all other waters, including domestic and industrial effluent, the atomic absorption procedure must be preceded by a digestionsolubilization asspecifiedbelow. In caseswhere the analyst is uncertain about the type of sample,the digestion-solubilization procedure must be used.

2. Summary of method 2.1 Calcium is determined by atomic absorption spectrometry (Fishman and Downs, 1966). Lanthanum chloride is added to mask interferences. 2.2 Effluent samples must undergo a pre liminary nitric acid digestion followed by a hydrochloric acid solubilization.

3. Interferences 3.1 Phosphate, sulfate, and aluminum interfere but are masked by the addition of lanthanum. Silica reportedly also interferes. Becauselow calcium values result if the pH of the sample is above 7, standards areprepared in hydrochloric acid solution and samples are preservedinthefield with useofnitric acidsolution. Concentrations of magnesium greater than 1,000 mg/L also cause low calcium values. 3.2 Nitrate interferes, but in the presenceof lanthanum chloride-hydrochloric acid solution, at least 2,000mg/L canbetolerated. The addition of nitric acid to the sample as a preservative atthetime of collection causesnoproblem in the following procedure. Samples should be evaporatedjust to dryness following nitric acid digestion to avoid any possible nitrate interference.

4. Apparatus 4.1 Atomic absorption spectrometer equipped with electronic digital readout and automatic zero and concentration controls. 4.2 Refer to the manufacturer’s manual to optimize instrument for the following:

Grating __-- ______-_ Visible Wavelength -------- 422.7 nm Source (hollow-cathode

1-p)

____ --

______ Calcium

Oxidant

____ --_-__-- fi

Fuel --___---

____ -_- Acetylene Type of flame ------- Slightly reducing 4.3 Different burners may beusedaccording to manufacturers’ instructions. A nitrous oxid&acetylene flameprovides 2to 5times greater sensitivity and freedom from chemical interferences;however,sodiumorpotassium chloride must beaddedto control ionization of calcium.

5. Reagents 5.1 Calcium standard solution, 1.00 mL= 0.500mg Ca:Suspend 1.250g CaC03, dried at 180“Cfor 1hbeforeweighing, in demineralized water anddissolve cautiously with aminimum of dilute HCl. Dilute to 1,000mL with demineralized water. 5.2 Calcium working standards: Prepare a seriesof at least six working standards containing from 0.1to 60mg/L of calcium by dilution of calcium standard solution. To eachworking

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### 142 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

standard add 

### 1.0mL of LaCls solution for each 10 mL of standard. 5.3 Hydrochloric acid, 6M: Dilute 500 mL concentrated HCl (sp gr 1.19) to 1 L with demineralized water. 5.4 Hydrochloric acid, 0.3M: Dilute 25 mL concentrated HCl (spgr 1.19)to 1L with demineralized water. 5.5 Lanthanum chloride solution, 87 g/L: Mix 29g La,Os with afew milliliters of demineralized water to form aslurry. Slowly add250 mL concentrated HCl (spgr 1.19)while stirring (reaction may beviolent) to-dissolve the LazO,. Dilute to 500 mL with demineralized water. 5.6 Nitric acid, concentrated (sp gr 1.41).



### 6. Procedure 6.1 Transfer the entire sample to a beaker. 6.2 Rinse the sample bottle with 3nil., con

### centratedHNO, for each100mL of sampleand add to the beaker. Prepare ablank using 3mL concentrated HNO, per 100mL demineralized water. 6.3 Evaporate samplesandblank to dryness
on ahotplate, making sure the samples do not boil. 6.4 Coolandaddanadditional 3mL concentrated HNO, to the beaker. Cover with a watchglass, return to the hotplate, and gently reflux the sample. 6.5 Continue heating, adding additional acid

asnecessary,until the digestion is complete (indicated by a light-colored residue). Evaporate just to dryness. 6.6 Add 6mL 6M HCl solution per 100mL of original sample andwarm the beaker to dissolve the residue. 6.7 Wash the watchglass and beaker with demineralized water and filter the sample (Whatman No. 41 or equivalent), rinsing the filter with hot, 0.3M HCl. Dilute to the original volume with demineralized water. 6.8 Add 1.0mL lanthanum chloride solution per 10.0 mL of sample. 6.9 Aspirate the blank to set the automatic
zero control. Use the automatic concentration control to set the concentrations of standards. Useat least six standards. Calibrate the instrument eachtime asetof samplesis analyzed and check calibration at reasonable intervals.

7. Calculations Determine the milligrams per liter of total recoverable calcium in each sample from the digital display or printer while aspirating each sample. Dilute those samples containing calcium concentrations that exceedtheworking rangeofthe method andmultiply by the proper dilution factors.

8. Report Report calcium, total-recoverable (00916), concentrations as follows: less than 10 mg/L,

onedecimal; 10mg/L andabove,two significant figures.

9. Precision It isestimated that the percent relative standard deviation for total recoverable calcium over the range of the method will begreater than 8 percent.

References

Fishman, M. J., and Downs, S. C., 1966, Methods for analysis of selected metals in water by atomic absorp tion: U.S. Geological Survey Water-Supply Paper 1540-C,p. C26-C28. U.S. Environmental Protection Agency, 1979,Methods for chemical analysis ofwater andwastes: Cincinnati, U.S. Environmental Protection Agency, p. 215.1-1.

## Calcium, atomic emission spectrometric, ICP

Parameter and Code: Calcium, dissolved, l-1472-85 (mg/L as Ca): 00915

2. Summary of method method utilizing an induction-coupled argon Calcium is determined simultaneously plasma as an excitation source. See method with severalother constituents onasingle sam- I-1472, metals, atomic emission spectrometric, ple by adirect-reading emission spectrometric ICP.

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## Calcium, total-in-sediment, atomic absorption spectrometric, direct

Parameters and Codes: Calcium, total, l-5473-85 (mglkg as Ca): none assigned Calcium, total, l-5474-85 (mglkg as Ca): none assigned

2. Summary of method 2.1 A sediment sample is dried, ground, and homogenized. The sample is then treated and analyzed by one of the following techniques. 2.1.1 The sample is fused with a mixture of lithium metaborate and lithium tetraborate in

a graphite crucible in a muffle furnace at 1000“C.Theresulting beadisdissolved in acidified, boiling, demineralizedwater, andcalcium is determined by atomic absorption spectrometry. See method I-5473, metals, major, total in sediment, atomic absorption spectrometric, direct. 2.1.2The sample is digested with acombination of nitric, hydrofluoric, andperchloric acids in a Teflon beaker heated on a hotplate at 200“C. Calcium is determined onthe resulting solution by atomic absorption spectrometry. Seemethod I-5474, metals, major and minor, total-in-sediment, atomic absorption spectrometric, direct.

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