SW-846 Update V 9320 - 1 Revision 1 

 July 2014 

METHOD 9320 

RADIUM 228

SW-846 is not intended to be an analytical training manual. Therefore, method 

procedures are written based on the assumption that they will be performed by analysts who are 

formally trained in at least the basic principles of chemical analysis and in the use of the subject 

technology. 

In addition, SW-846 methods, with the exception of required method use for the analysis 

of method-defined parameters, are intended to be guidance methods which contain general 

information on how to perform an analytical procedure or technique which a laboratory can use 

as a basic starting point for generating its own detailed standard operating procedure (SOP), 

either for its own general use or for a specific project application. Performance data included in 

this method are for guidance purposes only and must not be used as absolute quality control 

(QC) acceptance criteria for purposes of laboratory QC or accreditation. 

1.0 SCOPE AND APPLICATION 

Please see Appendix A at the back of this document for a summary of revisions to 

Method 9320 (From Revision 0, September 1986). 

 1.1 This method covers the measurement of radium-228 in ground water and, if 

desired, the determination of radium-226 on the same sample. If the level of radium-226 is 

above 3 pCi/L, the sample must also be measured for radium-228. 

 

 1.2 This technique is devised so that the beta activity from actinium-228, which is 

produced by decay of radium-228, can be determined and related to the radium-228 that is 

present in the sample. 

 

 1.3 To quantify actinium-228 and thus determine radium-228, the efficiency of the 

beta counter for measuring the very short half-lived actinium-228 (avg. beta energy of 0.404 

keV) is to be calibrated with a beta source of comparable average beta energy. 

 1.4 Analysts should consult the disclaimer statement at the front of the manual and 

the information in Chapter Two for 1) guidance on the intended flexibility in the choice of 

methods, apparatus, materials, reagents, and supplies; 2) the responsibilities of the analyst for 

demonstrating that the techniques employed are appropriate for the analytes of interest, in the 

matrix of interest, and at the levels of concern. 

 In addition, analysts and data users are advised that, except where explicitly specified in 

a regulation, the use of SW-846 methods is not mandatory in response to Federal testing 

requirements. The information contained in this method is provided by the Environmental 

Protection Agency (EPA) as guidance to be used by the analyst and the regulated community in 

making judgments necessary to generate results that meet the data quality objectives for the 

intended application. 

 1.5 This method is restricted to use by, or under supervision of, properly experienced 

and trained personnel. Each analyst must demonstrate the ability to generate acceptable 

results with this method. 
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2.0 SUMMARY OF METHOD 

 The radium in the water sample is collected by coprecipitation with barium and lead 

sulfate and purified by reprecipitation from EDTA solution. Both radium-226 and radium-228 are 

collected in this manner. After a 36-hr ingrowth of actinium-228 from radium-228, the actinium228 is carried on yttrium oxalate, purified and beta counted. If radium-226 is also desired, the 

activity in the supernatant can be reserved for coprecipitation on barium sulfate, dissolving in 

EDTA and storing for ingrowth in a sealed radon bubbler. 

3.0 DEFINITIONS 

 Refer to Chapter One, Chapter Three, and the manufacturer’s instructions for definitions 

that may be relevant to this procedure. 

4.0 INTERFERENCES 

 4.1 Reagents, glassware, and other sample processing hardware may yield artifacts 

and/or interferences during sample analysis. All of these materials must be demonstrated to be 

free from interferences under the conditions of the analysis by analyzing method blanks. 

Specific selection of reagents may be necessary. Refer to Chapter Three for general guidance 

on glassware cleaning. 

 4.2 As evidenced by the results of the performance studies, the presence of 

strontium-90 in the water sample gives a positive bias to the radium-228 activity measured. 

However, strontium-90 is not likely to be found in ground water, except possibly in monitoring 

wells around a radioactive burial site. 

 

 4.3 Excess barium in the water sample might result in a falsely high chemical yield. 

5.0 SAFETY 

 5.1 This method does not address all safety issues associated with its use. The 

laboratory is responsible for maintaining a safe work environment and a current awareness file 

of OSHA regulations regarding the safe handling of the chemicals specified in this method. A 

reference file of material safety data sheets (MSDSs) should be available to all personnel 

involved in these analyses. 

5.2 Personal protective equipment (PPE) should be worn at all times when in the 

laboratory. PPE requirements include chemical splash goggles and protective clothing and 

gloves. 

5.3 Acetic acid can cause severe skin and eye burns. The liquid and vapors are 

flammable. Carefully follow handling and storage instructions found in its MSDS. 

5.4 Ammonium hydroxide is corrosive; carefully follow handling and storage instructions 

found in its MSDS. 
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6.0 EQUIPMENT AND SUPPLIES 

 The mention of trade names or commercial products in this manual is for illustrative 

purposes only, and does not constitute an EPA endorsement or exclusive recommendation for 

use. The products and instrument settings cited in SW-846 methods represent those products 

and settings used during method development or subsequently evaluated by the Agency. 

Glassware, reagents, supplies, equipment, and settings other than those listed in this manual 

may be employed provided that method performance appropriate for the intended application 

has been demonstrated and documented. 

 This section does not list all common laboratory glassware (e.g., beakers and flasks) 

that might be used. 

 6.1 Gas-flow proportional counting system (low-background beta <3 cpm). 

 6.2 Electric hot plate. 

 6.3 Centrifuge. 

 6.4 Membrane filters: Matricel 47-mm. 

 6.5 Drying lamp. 

 6.6 Stainless steel counting planchets. 

 6.7 Analytical balance. 

7.0 REAGENTS AND STANDARDS 

 7.1 Reagent-grade chemicals, at a minimum, should be used in all tests. Unless 

otherwise indicated, all reagents conform to the specifications of the Committee on Analytical 

Reagents of the American Chemical Society, where such specifications are available. Other 

grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity 

to permit its use without lessening the accuracy of the determination. 

 7.2 Reagent water -- Reagent water must be interference free. All references to 

water in this method refer to reagent water unless otherwise specified. 

 7.3 Acetic acid (17.4 N), glacial CH3COOH (concentrated) sp. gr. 1.05, 99.8%. 

 7.4 Ammonium hydroxide (15 N), NH4OH (concentrated) sp. gr. 0.90, 56.6%. 

 7.5 Ammonium oxalate (5%): Dissolve 5 g (NH4)2C2O4 • H2O in reagent water and 

dilute to 100 mL. 

 7.6 Ammonium sulfate (200 mg/mL): Dissolve 20 g (NH4)2SO4 in reagent water and 

dilute to 100 mL. 

 7.7 Ammonium sulfide (2%): Dilute 10 mL (NH4)2S (20-24%), to 100 mL with reagent 

water. 

 7.8 Barium carrier (16 mg/mL), standardized: Dissolve 2.846 g BaCl2 • 2H2O in 

reagent water, add 0.5 mL 16 N HNO3, and dilute to 100 mL with Type II water. 
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 July 2014 

 7.9 Citric acid (1 M): Dissolve 19.2 g C6H8O7 • H2O in reagent water and dilute to 

100 mL. 

 

 7.10 EDTA reagent, basic (0.25 M): Dissolve 20 g NaOH in 750 mL reagent water, 

heat, and slowly add 93 g disodium ethylenedinitriloacetate dihydrate (Na2C10H14O8N2 • 2H2O) 

while stirring. After the salt is in solution, filter through coarse filter paper, and dilute to 1 liter. 

 7.11 Lead carrier (15 mg/mL): Dissolve 2.397 g Pb(NO3)2 in reagent water, add 0.5 

mL 16 N HNO3, and dilute to 100 mL with reagent water. 

 7.12 Lead carrier (1.5 mg/mL): Dilute 10 mL lead carrier (15 mg/mL) to 100 mL with 

reagent water. 

7.13 Standard strontium-89 tracer solution. 

8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE 

 Sample collection, preservation, and storage requirements may vary by EPA program 

and may be specified in a regulation or project planning document that requires compliance 

monitoring for a given contaminant. Where such requirements are specified in the regulation, 

follow those requirements. In the absence of specific regulatory requirements, use the following 

information as guidance in determining the sample collection, preservation, and storage 

requirements. 

 

 8.1 All samples must have been collected in a manner which addresses the 

considerations discussed in Chapter Nine of the SW-846 manual. 

 8.2 It is recommended that samples be preserved at the time of collection by adding 

enough 1 N HNO3 to the sample to bring it to pH 2 (15 mL 1 N HNO3 per liter of sample is 

usually sufficient). If samples are to be collected without preservation, they should be brought 

to the laboratory within 5 days, then preserved, and held in the original container for a minimum 

of 16 hr before analysis or transfer of the sample. See also Note to Paragraph 7.2 below. 

 8.3 All sample containers must be prewashed with acids, water, and metal-free 

detergents, if necessary, depending on the use history of the container. For further information 

see Chapter Three. 

 8.4 The container choice should be plastic (rather than glass) to prevent loss due to 

breakage during transportation and handling. 

9.0 QUALITY CONTROL 

 9.1 Refer to Chapter One for guidance on quality assurance (QA) and QC protocols. 

When inconsistencies exist between QC guidelines, method-specific QC criteria take 

precedence over both technique-specific criteria and Chapter One criteria; technique-specific 

QC criteria take precedence over Chapter One criteria. Any effort involving the collection of 

analytical data should include development of a structured and systematic planning document, 

such as a Quality Assurance Project Plan (QAPP) or a Sampling and Analysis Plan (SAP), 

which translates project objectives and specifications into directions for those that will implement 

the project and assess the results. 
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 Each laboratory should maintain a formal quality assurance program. The laboratory 

should also maintain records to document the quality of the data generated. Development of inhouse QC limits for each method is encouraged. Use of instrument specific QC limits is 

encouraged, provided such limits will generate data appropriate for use in the intended 

application. All data sheets and quality control data should be maintained for reference or 

inspection. 

9.2 Initial demonstration of proficiency (IDP). 

The initial demonstration of method proficiency must be performed prior to independently 

running an analytical method, and should be repeated if other changes occur (e.g., instrument 

repair, significant change in procedure, and change in analyst). An IDP must consist of 

replicate reference samples from each sample preparation and determinative method 

combination it utilizes by generating data of acceptable accuracy and precision for target 

analytes in a clean reference matrix taken through the entire preparation and analysis. 

 9.3 Sample QC for preparation and analysis 

The laboratory must also have procedures for documenting the effect of the matrix on 

method performance (precision, bias, and sensitivity). At a minimum, this should include the 

analysis of QC samples including a method blank, a matrix spike (MS), a laboratory control 

sample (LCS), and a duplicate sample in each analytical batch. Any method blanks, LCS, MS 

samples, and duplicate samples should be subjected to the same preparatory and instrument 

determination procedures as those used on actual samples (see Sec. 11.0). 

 

10.0 CALIBRATION AND STANDARDIZATION 

 Counter efficiency: The beta counter may be calibrated with actinium-228 or strontium89 (t1/2 = 51 d). Strontium-89 has an average beta energy of 0.589 KeV. A standard strontium89 tracer solution can be used to determine beta efficiencies over a range of precipitate weights 

on the stainless steel planchet. 

11.0 PROCEDURE 

 11.1 For each liter of water add 5 mL 1 M C6H8C7 • H2O and a few drops of methyl 

orange indicator. The solution should be red. 

NOTE: At the time of sample collection add 2 mL 16 N HNO3 for each liter of water. 

 11.2 Add 10 mL lead carrier (15 mg/mL), 2 mL strontium carrier (10 mg/mL), 2.0 mL 

barium carrier (16 mg/mL), 1 mL yttrium carrier (18 mg/mL) and stir well. Add 15 N NH4OH until 

a definite yellow color is obtained; then add a few drops excess. Heat to incipient boiling and 

maintain at this temperature for 30 min. 

 11.3 Precipitate lead and barium sulfates by adding 18 N H2SO4 until the red color 

reappears. Then add 0.25 mL excess. Add 5 mL (NH4)2SO4 (200 mg/mL) for each liter of 

sample. Stir frequently and keep at a temperature of about 90°C for 30 min. 

 11.4 Cool slightly; then filter with suction through a 47-mm matricel membrane filter 

(GA6, 0.45-micron pore size). Make a quantitative transfer of precipitate to the filter by rinsing 

last particles out of beaker with a strong jet of water. 
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 11.5 Carefully place filter with precipitate in the bottom of a 250-mL beaker. Add 

about 10 mL 16 N HNO3 and heat gently until the filter completely dissolves. Transfer the 

precipitate into a polypropylene centrifuge tube with an additional 16 N HNO3. Centrifuge and 

discard supernatant. 

 11.6 Wash the precipitate with 15 mL 16 N HNO3, centrifuge, and discard supernatant. 

Repeat this washing a second time. 

 11.7 Wash the precipitate with 10 mL reagent water, centrifuge, and discard 

supernatant. 

 11.8 Add 25 mL basic EDTA reagent, heat in a hot-water bath, and stir well. Add a 

few drops 10 N NaOH if the precipitate does not readily dissolve. 

 11.9 Add 1 mL strontium-yttrium mixed carrier and stir thoroughly. Add a few drops 

10 N NaOH if any precipitate forms. 

 11.10 Add 1 mL (NH4)2SO4 (200 mg/mL) and stir thoroughly. Add 17.4 N acetic acid 

until the barium sulfate precipitates. Then add 2 mL excess. Digest in a hot water bath until 

precipitate settles. Centrifuge and discard supernatant. 

 11.11 Add 20 mL basic EDTA reagent, heat in a hot-water bath, and stir until precipitate 

dissolves. Repeat steps 7.9 and 7.10. (Note time of last barium sulfate precipitation as this is 

the beginning of the actinium-228 ingrowth time.) 

 11.12 Dissolve the precipitate in 20 mL basic EDTA reagent as before; then add 1.0 mL 

yttrium carrier (9 mg/mL) and 1 mL lead carrier (1.5 mg/mL). If any precipitate forms, dissolve 

by adding a few drops 10 N NaOH. Cap the polypropylene tube and age at least 36 hr. 

 11.13 Add 0.3 mL (NH4)2S and stir well. Add 10 N NaOH dropwise with vigorous 

stirring until lead sulfide precipitates. Then add 10 drops excess. Stir intermittently for about 10

min. Centrifuge and decant supernatant into a clean tube. 

 11.14 Add 1 mL lead carrier (1.5 mg/mL), 0.1 mL (NH4)2S and a few drops 10 N NaOH. 

Repeat precipitation of lead sulfide as before. Centrifuge and filter supernates through 

Whatman #42 filter paper into a clean tube. Wash filter with a few mL water. Discard residue. 

 11.15 Add 5 mL 18 N NaOH, stir well and digest in a hot water bath until yttrium 

hydroxide coagulates. Centrifuge and decant supernates into a beaker. Save for barium yield 

determination (step 7.20). (Note time of yttrium hydroxide precipitation as this is the end of the 

actinium-228 ingrowth time and beginning of actinium-228 decay time.) 

 11.16 Dissolve the precipitate in 2 mL 6 N HNO3. Heat and stir in a hot water bath 

about 5 min. Add 5 mL water and re-precipitate yttrium hydroxide with 3 mL 10 N NaOH. Heat 

and stir in a hot water bath until precipitate coagulates. Centrifuge and add this supernate to 

the supernate produced in step 7.15 in order to determine barium yield. 

 11.17 Dissolve precipitate with 1 mL 1 N HNO3 and heat in hot water bath a few 

minutes. Dilute to 5 mL and add 2 mL 5% (NH4)2C2O4 • H2O. Heat until mixture coagulates, 

then centrifuge and discard supernatant. 

 11.18 Add 10 mL water, 6 drops 1 N HNO3 and 6 drops 5% (NH4)2C2O4 • H2O. Heat 

and stir in a hot-water bath a few minutes. Centrifuge and discard supernatant. 
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 11.19 To determine yttrium yield, transfer quantitatively to a tared stainless steel 

planchet with a minimum amount of water. Dry under an infrared lamp to a constant weight and 

count in a low-background beta counter. 

 11.20 To the supernatant from step 7.15, add 4 mL 16 N HNO3 and 2 mL (NH4)2SO4

(200 mg/mL), stirring well after each addition. Add 17.4 N acetic acid until barium sulfate 

precipitates. Then add 2 mL excess. Digest on a hot plate until precipitate settles. Centrifuge 

and discard supernatant. 

 11.21 Add 20 mL basic EDTA reagent, rest in a hot-water bath, and stir until precipitate 

dissolves. Add a few drops 10 N NaOH if precipitate does not readily dissolve. 

 11.22 Add 1 mL (NH4)2SO4 (200 mg/mL) and stir thoroughly. Add 17.4 N acetic acid 

until barium sulfate precipitates. Then add 2 mL excess. Digest in a hot-water bath until 

precipitate settles. Centrifuge and discard supernatant. 

 11.23 Wash precipitate with 10 mL water. Centrifuge and discard supernatant. 

 11.24 Transfer precipitate to a tared stainless steel planchet with a minimum amount of 

water. Dry under an infrared lamp and weigh for barium yield determination. 

12.0 DATA ANALYSIS AND CALCULATIONS 

 12.1 Results need to be reported in units commensurate with their intended use and 

all dilutions need to be taken into account when computing final results. 

 

 12.2 Calculate the radium-228 concentration, D, in picocuries per liter as follows: 

D		

C

2.22		EVR	




1 − 

		 	

1

1 − 

		

1



NOTE: 





 is a factor to correct the average count rate to the count rate at 

the beginning of counting time. 

 where: 

 C = Average net count rate, cpm; 

E = Counter efficiency, for actinium-228, or comparable beta energy 

nuclide; 

V = Liters of sample used; 

R = Fractional chemical yield of yttrium carrier (Step 11.18) multiplied 

by fractional chemical yield of barrier carrier (Step 11.23); 

2.22 = Conversion factor from disintegrations/minute to picocuries; 

λ = The decay constant for actinium-228 (0.001884 min-1); 
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 July 2014 

t1 = The time interval (in min) between the first yttrium hydroxide 

precipitation in Step 11.14 and the start of the counting time; 

t2 = The time interval of counting in min; and 

t3 = The ingrowth time of actinium-228 in min measured from the last 

barium sulfate precipitation in Step 11.10 to the first yttrium 

hydroxide precipitation in Step 11.14. 

13.0 METHOD PERFORMANCE 

 Performance data and related information are provided in SW-846 methods only as 

examples and guidance. The data do not represent required performance criteria for users of 

the methods. Instead, performance criteria should be developed on a project-specific basis, 

and the laboratory should establish in-house QC performance criteria for the application of this 

method. Performance data must not be used as absolute QC acceptance criteria for laboratory

QC or accreditation.

Performance data examples and guidance for this method currently are not currently available. 

14.0 POLLUTION PREVENTION 

 14.1 Pollution prevention encompasses any technique that reduces or eliminates the 

quantity and/or toxicity of waste at the point of generation. Numerous opportunities for pollution 

prevention exist in laboratory operations. The EPA has established a preferred hierarchy of 

environmental management techniques that places pollution prevention as the management 

option of first choice. Whenever feasible, laboratory personnel should use pollution prevention 

techniques to address their waste generation. When wastes cannot be feasibly reduced at the 

source, the Agency recommends recycling as the next best option. 

 14.2 For information about pollution prevention that may be applicable to laboratories 

and research institutions consult Less is Better: Laboratory Chemical Management for Waste 

Reduction, a free publication available from the American Chemical Society (ACS), Committee 

on Chemical Safety, 

http://portal.acs.org/portal/fileFetch/C/WPCP_012290/pdf/WPCP_012290.pdf. 

15.0 WASTE MANAGEMENT 

 The EPA requires that laboratory waste management practices be conducted consistent 

with all applicable rules and regulations. Laboratories are urged to protect air, water, and land 

by minimizing and controlling all releases from hoods and bench operations, complying with the 

letter and spirit of any sewer discharge permits and regulations, and by complying with all solid 

and hazardous waste regulations, particularly the hazardous waste identification rules and land 

disposal restrictions. For further information on waste management, consult The Waste 

Management Manual for Laboratory Personnel available from the ACS at the address listed in 

Sec. 14.2. 
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16.0 REFERENCES 

1. A.E. Greenberg, J.J. Connors, and D.J. Jenkens, eds., Standard Methods for the 

Examination of Water and Wastewater, 15th ed., American Public Health Assoc., 

Washington, D.C., Method 707, p. 600, 1980. 

2. J.O. Johnson, Determination of Radium 228 in Natural Waters. Radiochemical Analysis 

of Water. U.S. Geol. Surv., Water Supply Paper 1696-G. U.S. Govt. Printing Office, 

Washington, D.C., 1971. 

3. H.L. Krieger, Prescribed Procedures for Measurement of Radioactivity in Drinking Water, 

Environmental Monitoring and Support Laboratory, U.S. EPA, Cincinnati, OH, EPA600/4-75-008, 1976. 

17.0 TABLES, DIAGRAMS, FLOW CHARTS, AND VALIDATION DATA 

 The following pages contain figures that provide illustration for the procedures of this 

method. 

 
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METHOD 9320 

RADIUM-228

 
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METHOD 9320 

RADIUM-228

 
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METHOD 9320 

RADIUM-228
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Appendix A 

Summary of Revisions to Method 9320 (From Revision 0, September 1986)

1. Improved overall method formatting for consistency with new SW-846 methods style 

guidance. 

2. Extensively reformatted “REAGENTS AND STANDARDS” section and to meet current 

SW-846 method guidelines. 

3. Updated and expanded “QUALITY CONTROL” section for better adherence to current 

SW-846 method guidelines and for improved alignment with current universal practices for 

published analytical methods. 

4. In Section 9.2, the recommendation of an initial demonstration of proficiency for analysts 

and instrumentation and/or procedure changes was added. 

5. The Section 11.7 was added; instructing a reagent water wash after the two HNO3 washes 

in Sec. 11.6. This step will help prevent and reduce interferences later in the procedures 

and analysis. 

6. The revision number was changed to one and the date published to July 2014.