United States
Environmental Protection
Agency
Method 904.0, Revision 1.0: Radium-228 in Drinking
Water
-------
Questions concerning this document should be addressed to:
Glynda A. Smith, Ph.D.
U.S. EPA, Office of Ground Water and Drinking Water, Standards and Risk Management Division,
Technical Support Center, 26 W. Martin Luther King Dr., Cincinnati, OH 45268
Phone:(513)569-7652
smith.glyiidagepa.gov
Office of Water (MS-140)
EPA 815-B-22-003
March 2022
liars
Glynda A. Smith, Ph.D., U.S. EPA (Cincinnati, OH)
Steven C. Wendelken, Ph.D., U.S. EPA (Cincinnati, OH)
Acknowl*
Robert L. Rosson, General Dynamics Information Technology, Inc. (GDIT), Alexandria, Virginia.
Bob Shannon, Quality Radioanalytical Support, LLC, Grand Marais, Minnesota.
Larry F. Umbaugh (retired), General Dynamics Information Technology, Inc. (GDIT), Alexandria, Virginia.
i
-------
Contents
1 Scope and Application 1
2 Summary of the Method 1
3 Definitions 1
4 Interferences 3
5 Safety 3
6 Equipment and Supplies 3
7 Reagents and Standards 4
8 Sample Collection, Preservation, and Storage 9
9 Quality Control 10
10 Calibration 13
11 Procedure 15
12 Data Analysis and Calculations 18
13 Pollution Prevention 23
14 References 24
ii
-------
1 Scope
1.1 Background
Method 904.0, Revision 1.0 is a method for the determination of radium-228 in drinking water. In this
method the beta activity emitted from actinium-228, which is the decay progeny of radium-228, is
determined and correlated to the radium-228 in a sample. When secular equilibrium is established, the
activity of actinium-228 will be equal to the activity of radium-228.
1.2 Drinking Water Regulatory Requirements
The Code of Federal Regulations (CFR) at 40 CFR 141.66(b) specifies a maximum contaminant level
(MCL) for combined radium-226 and radium-228 of 5 pCi/L. As specified at 40 CFR 141.25(c)(1), the
required detection limit for radium-228 is 1 pCi/L.
1.3 Sensitivity
The sensitivity of the method is a function of sample size, instrument background, counting efficiency,
yield, and counting time.
2 Summary of the Method
The radium isotopes in a drinking water sample are collected by coprecipitation with barium and lead
sulfate and purified by re-precipitation from a basic EDTA solution. After a 36-hour ingrowth of
actinium-228 from radium-228, the actinium-228 is carried on yttrium oxalate, purified and counted for
beta activity. If determination of radium-226 is also desired, the supernatant can be reserved for
analysis by an alternate procedure.
NOTE: This method contains options for carrier standardization, calibration and yield determination. The
laboratory is expected to select an option and incorporate it into their procedure consistently. Switching
options among analytical batches can result in possible QC failures.
3 Definitions
3.1 Activity
Rate of nuclear decay occurring in a body of material, equal to the number of nuclear disintegrations per
unit time.
3.2 Batch, Preparation
A set of up to 20 environmental field samples of the same matrix that are prepared and/or analyzed
together with the same instrumentation and personnel, using the same lot(s) of reagents, with a
maximum time between the start of preparation of the first and last sample in the batch being 24 hours.
3.3 Detection I
The DL for radionuclides in drinking water is defined in 40 CFR 141.25(c) as the radionuclide
concentration that can be counted with a precision of plus or minus 100% at the 95% confidence level
(1.96a, where a is the standard deviation of the net counting rate of the sample).
1
-------
3.4 ID up lit
A second aliquot of a field sample that is processed in the same manner as the samples in the
preparation batch. Analysis of the DUP provides a measure of the precision associated with batch
preparation.
3.5 Field Blank
Samples preserved with reagents that are not provided by the laboratory should be accompanied by a
field blank sample that is preserved in the same manner as the submitted samples. The field blank is a
volume of blank matrix that is placed in a clean sample container, preserved in the field, shipped along
with the samples and subjected to the same analytical procedures as the samples. A sample of the
preservative should also accompany the field samples to determine whether it contributes any
contamination.
3.6 Laboratory Fortified I
The LFB consists of a volume of a blank matrix to which a known activity of a radioisotope has been
added. The LFB is processed in the same manner as the samples in the preparation batch, and its
purpose is to determine whether the methodology is in control, and whether the laboratory is capable
of making accurate measurements. The drinking water LFB activity should be at a level between the
required detection limit and the MCL.
3.7 Laboratoi gent Blank (ILIRB)
The LRB consists of an aliquot of a blank matrix that is processed in the same manner as the samples in
the preparation batch, including exposure to all glassware and equipment that are used in the
preparation batch. The LRB is used to assess the process of handling, preparation and analysis for cross-
contamination and for low-level analytical bias.
3.8 Laboratory Fortified Sample Mat 5M)
An aliquot of a field sample to which a known activity of the radionuclide(s) being measured has been
added. The LFSM is processed in the same manner as the samples in the preparation batch. Its purpose
is to determine whether the sample matrix contributes bias to the results. The native level of the
radionuclide(s) must be determined in an unspiked field sample aliquot in order to correct for levels
already present in a sample that could contribute to the LFSM response. Spike drinking water LFSMs
with a known activity of radium-228 standard that is approximately 10 times the anticipated level in the
samples or approximately 10 times the DL (i.e. 10 pCi/L).
3.9 Laboratory Fortified Sample Matrix Duplicate (LFSMD)
An additional aliquot of a field sample that has the same quantity of radionuclide(s) added to it as the
LFSM. The LFSMD is processed in the same manner as the samples in the preparation batch. It may be
used in place of the DUP to assess preparation batch precision.
3.10 Picocurie (pQ)
The pCi is the quantity of radioactive material producing 2.22 nuclear disintegrations per minute.
3.11 Uncer anting
The component of measurement uncertainty attributable to the random nature of radioactive decay
and radiation counting.
2
-------
3.12 Uinceir indard
An estimate of the measurement uncertainty expressed as one standard deviation.
3.13 Uinceir Danded
An estimate of the uncertainty U of a measurement result y that provides a high level of confidence that
the interval y±U includes the actual value of the quantity being measured. The expanded uncertainty is
typically obtained by multiplying the standard uncertainty by a coverage factor. A coverage factor of
1.96 is routinely used for drinking water analysis and the coverage factor (or confidence level) should be
specified on the sample report.
4 Interferences
4.1 Naturally occurring barium
A significant natural barium content in a sample may bias the barium sulfate chemical yield high
resulting in lower sample activity results.
4.2 Stiron tii u irn-90
The presence of strontium-90 in the water sample will give a positive bias to the radium-228 activity
measured.
4.3 Group 11A elements
High levels of the Group IIA elements (e.g. calcium, strontium) can be a potential problem since the
chemical behavior of these elements mimic that of radium.
5 Safety
The specific toxicity of each reagent used in this method has not been precisely defined. Each chemical
should be treated as a potential health hazard, and exposure to these chemicals should be minimized.
Each laboratory is responsible for maintaining a chemical hygiene plan (CHP) with an awareness of the
appropriate regulations regarding safe handling of chemicals used in this method. A reference file of
safety data sheets (SDSs) should be made available to all personnel involved in the preparation of
samples and their analyses.
6 Equipment and Supplies
6.1 Gas-flow proportional counter
The detector may be either a windowless (internal proportional counter) or a thin window type. The
system should be capable of accommodating counting planchets and be sufficiently free from
background so that required detection levels can be met within a reasonable counting time.
6.2 Stainless steel counting planchets
A planchet should be flat-bottomed, or with concentric rings, with a raised wall to contain the sample
being evaporated.
NOTE: Always use the same type planchet (to maintain the same geometric configuration) for
calibration and sample determinations.
3
-------
6.3 Electric hot plate or hot water bath
6.4 IDir nil 1 ¦ ¦ /ein/heiii II nn|¦
Drying oven capable of maintaining a temperature of 105 °C + 2 °C. Alternately, infrared heat lamps may
be used if a drying oven is not available.
6.5 Desiccator
6.6 Centrifuge/Centrifuge tubes
6.7 Glassware
Beakers and graduated cylinders of various sizes as appropriate for sample preparation as described in
the method. Vacuum flasks of sufficient capacity to hold filtered sample volumes. Glass or ceramic filter
funnels.
6.8 Pipettes
Pipettes of various sizes.
6.9 Vol ' ic glassware
Volumetric flasks, class A, 100-mL to 2-L
6.10 Analytical balance
The analytical balance should have a readability of 0.1 mg.
6.11 Membrane filters and filter funnel assemblies
Vacuum filter funnel assemblies and membrane filters with 0.45 pim pore diameter. Membrane filters
must be capable of being dissolved in concentrated nitric acid.
6.12 Aclcliitii -in ill IIniters and filter papers (as appropriate for procedural optii -in "
Ashless filter paper. Diameter as appropriate for glass or ceramic filter funnels, including sintered glass
crucibles.
6.13 Optioi II ||i iij merit f -i |-IIII determination
6.13.1 pH meter
Potentiometer with glass electrode, reference electrode, and temperature compensation capability.
6.13.2 pH paper
Short range and wide range.
7 Reagents and Standards
Analytical reagent grade or better chemicals should be used. Commercial reagents are often not tested
for trace radioactivity. Therefore, analysts need to carefully monitor their laboratory reagent blank (LRB)
control charts to identify situations where levels of radioactivity may be present in reagents that could
compromise results.
NOTE: Laboratories can adjust reagent and solution volumes as appropriate to meet testing needs
provided the molar ratios are maintained.
7.1 IDiistii II led/deiK water
Distilled or deionized water meeting the requirements of ASTM Type 1, 2, or 3 reagent water.
4
-------
7.2 Acetic aciicl
Acetic acid, 17.4 M: glacial CH3COOH (conc.), sp.gr. 1.05, 99.8%.
7.3 Acetone
Acetone, reagent grade or better
7.4 Ainiinif Iroxide
Ammonium hydroxide, NH4OH (conc.), sp.gr. 0.90, 56.5%
7.5 Ainiinif Iroxide (6M)
Prepare by adding about 40.5 mL concentrated NH4OH to 50 mL distilled/deionized water and dilute to
100 mL.
7.6 Ainiinif oxalate, saturated
Prepare by adding 10 g (NH4)2C204-H20 to 100 mL boiling distilled/deionized water. Cool.
7.7 Ainiinif oxalate, 5% (inn/v)
Prepare by dissolving 5 g (NH4)2C204-H20 in distilled/deionized water and diluting to 100 mL.
7.8 Ainiinif llfate (200 inng/innIL.)
Prepare by dissolving 20 g (NH4)2S04 in a minimum of distilled/deionized water and dilute to 100 mL.
7.9 Ainiinif I fide, 2% (v/v)
Prepare by diluting 10 mL (NH4)2S (20-24%) to 100 mL with distilled/deionized water.
7.10 Barium carrier (16 nig Ba2
Prepare carrier by dissolving about 2.8 g BaCl2-2H20 in distilled/deionized water, adding 0.5 mL 16 M
HNO3, and diluting to 100 mL with distilled/deionized water. Alternatively, purchase a high purity
commercial barium standard solution and dilute appropriately. Standardize in triplicate using one of the
options described below.
Note: Use the appropriate calculations in Section 12.1 to determine yield.
7.10.1 Standardize according to approach used to determine yield (Section 11.15)
7.10.1:1 Standardize barium based on chemical yield as BaS04
Pipette 2.00 mL carrier solution into a centrifuge tube containing 15 mL water. Add 1 mL 9 M H2S04
(Section 7.28) with stirring and digest precipitate in a hot water bath for 10 minutes. Cool, centrifuge,
and decant supernatant. Wash precipitate with 15 mL water. Centrifuge and decant supernatant.
Transfer the precipitate to a tared stainless steel planchet with a minimum amount of water. Dry under
an infrared lamp or in a 105°C + 2 °C oven, cool in a desiccator and weigh as BaS04. Verify the average
mass is within + 5% of the expected mass with a relative standard deviation among the replicates of
< 5%. Calculate the barium content:
Ba mma/mL= VolumeBai~
Substituting (137.34 g/mole Ba2+/233.404 g/mole BaS04) = 0.5884, and 2.00 mL carrier volume yields:
2+ t (mg BaS04) x (0.5884)
Ba in mg/mL
2.00 mL
5
-------
NOTE: If barium-133 will be used as a tracer for radiochemical analysis, the barium carrier prepared in
Section 7.10 does not need to be separately standardized.
7.10:1.2 Standardize using barium-133 tracer for radiochemical yield
Add barium-133 tracer solution to the prepared barium carrier (Section 7.10) at a level that will yield at
least 6000 - 8000 pCi/100 mL. Pipette 2.00 mL carrier solution into a beaker or centrifuge tube
containing 20 mL basic EDTA reagent (Section 7.13). Add 1 mL ammonium sulfate (200 mg, Section 7.8)
and mix well. Add acetic acid (17.4 M, Section 7.2) until barium sulfate precipitates, then add 2 mL in
excess. Digest precipitate in a hot (near boiling) water bath for about 15 minutes until precipitate
settles. Cool, centrifuge, and decant the supernatant. Wash precipitate with 10 mL distilled/deionized
water. Centrifuge and decant supernatant. Place a 0.45 pim membrane filter in a vacuum filter assembly,
prewet with distilled/deionized water and start vacuum. Transfer the precipitate to the filter using
distilled/deionized water to ensure the transfer is quantitative. Add a small volume of ethanol to the
precipitate and maintain suction to fully dry the precipitate. The filter containing the precipitate should
be mounted and counted in a geometry for which the gamma spectrometer has been properly
calibrated. Ba-133 is counted long enough so about 10,000 counts above background are accumulated.
Verify that the average Ba-133 activity is within + 5% of the expected level with a relative standard
deviation between the replicates of < 5%. This method does not discuss specifications related to
analytical requirements for gamma spectrometers; however, laboratories incorporating barium-133 as a
tracer will be expected to document energy and efficiency calibration as well as performance checks
related to verifying detection efficiency, energy calibration, background, peak resolution, etc.
Calculation of yield using the tracer is discussed in Section 12.1.2.
7.11 Bromocresol green indicator (optional)
Commercially available bromocresol green indicator solution to monitor pH
7.12 Citric acid (1 M)
Prepare by dissolving 21.0 g CeHsOyhhO in distilled/deionized water and dilute to 100 mL.
7.13 I basic reagent (0.25 M)
Prepare by dissolving 20 g NaOH in 750 mL distilled/deionized water, heat and slowly add 93 g
ethylenediamine tetraacetic acid disodium salt dihydrate (CioHi4N2Na208-2H20). Heat and stir until
dissolved, filter through coarse filter paper (Section 6.12) and dilute to 1 L.
7.14 Ethanol (optional)
Ethanol, 95%.
7.15 Lead carrier (15 nig/irnlL)
Prepare by dissolving 2.4 g Pb(N03)2 in a minimum volume of distilled/deionized water, add 0.5 mL 16 N
HN03 and dilute to 100 mL with distilled/deionized water.
7.16 Lead carrier
Dilute 10 mL lead carrier (15 mg/mL) to 100 mL with distilled/deionized water.
7.17 Methyl orange indicator, 0.1% (m/v)
Prepare by dissolving 0.1 g methyl orange indicator in 100 mL distilled/deionized water.
7.18 Nitric acic
Nitric acid, 16 M: HN03 (conc.), sp.gr. 1.42, 70.4%.
6
-------
7.19 Nitric aciicl (6 M)
Prepare by carefully adding 187.5 mL 16 M HN03 to about 300 mL distilled/deionized water. Dilute to
500 mL.
7.20 Nitric aciicl (1 M)
Prepare by carefully adding 62.5 mL 16 M HN03 to about 800 mL distilled/deionized water. Dilute to 1-L.
7.21 Radium-228
Radium-228 standard traceable to a national metrology institute (such as the National Institute of
Standards and Technology [N 1ST]). Prepare a standard working solution equivalent to about 50 pCi
radium-228 per mL to use in preparing laboratory quality control checks.
NOTE: After making a working solution from the standard, verify the concentration by conducting at
least three separate verification measurements to confirm that each individual measurement is within
5% of the expected value.
7.22 Sodium cairb M)
Prepare by dissolving 106 g Na2C03 in distilled/deionized water and dilute to 1 liter.
7.23 Sodium hydroxide (18 M)
Prepare by dissolving 72 g NaOH in about 80 mL distilled/deionized water and dilute to 100 mL.
7.24 Sodium hydroxide (10 M)
Prepare by dissolving 40 g NaOH in about 80 mL distilled/deionized water and dilute to 100 mL.
7.25 Sodium hydroxi
Prepare by dissolving 24 g NaOH in about 80 mL distilled/deionized water and dilute to 100 mL.
7.26 Strontium carrier
Prepare by dissolving 24.16 g Sr(N03)2 in a minimum volume of distilled/deionized water and dilute to 1
liter. When using strontium-89 as the calibrant, standardize the strontium carrier in triplicate by one of
the following options:
7.26.1 Standardize by precipitation as strontium oxalate
Pipet 2-mL of 10 mg/mL strontium carrier into a beaker or centrifuge tube. Dilute with about 20 mL
distilled/deionized water. Add 2 mL concentrated NH4OH, heat to nearly boiling then slowly add 5 mL
saturated ammonium oxalate solution (Secti ). Continue heating in a hot water bath near boiling
for about 15 minutes. Cool, centrifuge, discard supernate. Rinse with a 20 mL volume of
distilled/deionized water, centrifuge and discard supernate. Slurry the strontium oxalate precipitate
with a few mLs distilled/deionized water and quantitatively transfer to a tared planchet. Dry under an
infrared lamp or in a 105 °C + 2 °C oven, cool in a desiccator and weigh. Verify that the average
precipitate mass is within + 5% of the expected level with a relative standard deviation between the
replicates of < 5%.
7.27 Strontium-89 (calibrant)
Strontium-89 NIST-traceable standard solution for detector calibration. Prepare a standard working
solution appropriate for meeting calibration requirements described in Section 10.
NOTE: After making the working solution from the NIST-traceable standard, verify the concentration by
conducting at least three separate verification measurements to confirm that each individual
measurement is within + 5% of the expected value.
7
-------
7.28 Sulfuric aciicl (9 M)
Cautiously mix 1 volume 18 M H2S04 (conc.) with 1 volume of distilled/deionized water.
7.29 Yttrium carrier (18 inng/innIL.)
Add 22.85 g Y203 to an Erlenmeyer flask containing about 20 mL distilled/deionized water. Heat to
boiling. Stir in small volumes of 16 M HN03 to dissolve the Y203. Small additions of water may be
required to replace that lost through evaporation. After total dissolution, add about 70 mL 16 M HN03
and dilute to 1 liter with distilled/deionized water.
7.30 Yttrium cairiri
Dilute 50 mL yttrium carrier (18 mg/mL) to 100 mL with distilled/deionized water. There are two
chemical yield options, either as yttrium oxalate or yttrium oxide. Standardize the yttrium carrier in
triplicate based on the yield option selected:
7.30.1 Standardization based on yttrium oxalate yield
Yttrium oxalate can take the form of multiple hydrates. In order to achieve a uniform nonahydrate
(Y2(C204)3-9HS0), the pH in the final precipitation step should ideally fall in the range of 1.7 -1.9. Verify
the pH and adjust if needed with HN03 or NaOH.
In triplicate: carefully pipet 10.0 mL portions of the yttrium carrier solution into separate centrifuge
tubes. Add 30 mL saturated (NH4)2C204-H20 (Section 7.6) to each centrifuge tube and stir. Digest in a hot
water bath (near boiling) for 30 minutes. Cool in an ice bath. Centrifuge and discard supernate. Slurry
the yttrium oxalate precipitate with a small volume of distilled/deionized water and transfer to a tared
stainless steel planchet. Dry under an infrared lamp or in a 105 °C + 2 °C oven, cool in a desiccator and
weigh. Verify that the average precipitate mass is within + 5% of the expected level with a relative
standard deviation between the replicates of < 5%. Calculate the yttrium concentration:
(mg (Y2(C204)3 ¦ (9H20))) (^9 Y/mg (Y2(C204)3 ¦ (9H20))^j
Volume
_ (mg (Y2(C204)3 ¦ (9H20yj) (0.29448)
1 mL
7.30.2 Standardization based on yttrium oxide yield (in triplicate)
Follow the procedure described in Section 7.30.1, but instead of centrifuging the yttrium oxalate
solution and transferring it to a planchet, allow the solution to cool. Filter the precipitate onto a
quantitative ashless filter paper (e.g Whatman #42 (or equivalent)). Transfer the filter paper and
precipitate to a previously ignited and tared porcelain crucible. Ignite at 800 °C in a muffle oven for one
hour to convert the oxalate to the oxide. Cool and weigh. Verify that the average precipitate mass is
within + 5% of the expected level with a relative standard deviation between the replicates of < 5%.
Calculate the yttrium concentration:
y3+ mg, = (mg YM Ylmg Y203)
mL Volume
_ (mg Y203)(0.78743)
1 mL
Y 3+ mg j
mL
8
-------
7.31 Strontium-yttrium mixed carrier,11in 1 lull -r2+ im'11in 1 ml Y3+
7.31.1 Solution A: yttrium carrier
Pipet a 10-mL aliquot of standardized yttrium carrier (18 mg/mL) into a 100-mL volumetric flask and
dilute with distilled/deionized water.
7.31.2 Solution IB: strontium carrier
Dissolve 0.435 g Sr(N03)2 in a minimum amount of distilled/deionized water and dilute to 100 mL with
distilled/deionized water.
7.31.3 St iro n t i u m -ytt ir i u m m ixed ca ir iri e ir
Combine Solution A and Solution B.
8 Sample Collection, Preservation, and .Storage
8.1 Containers
Collect samples in glass or plastic containers. A sample volume of 1 gallon (approximately 4 liters) is
recommended for collection of drinking water samples, but collection volume is left to the discretion of
the laboratory.
8.2 Sample Collection for Drinking Water
Open the cold water tap and allow the system to flush until the water temperature has stabilized (about
3 to 5 minutes). Collect samples from the flowing system. If the samples are preserved with reagents
(i.e. nitric acid, Section 8.3) that are not provided by the laboratory, they should be accompanied by a
Field Blank (Section 3.5) that is preserved in the same manner as the samples. A sample of the
preservative used in the field should also accompany the samples and Field Blank to the laboratory to
determine the contribution, if any, from the addition of the preservative.
NOTE: This section describes collection of drinking water samples at the entrance to the distribution
system. Other guidance may apply for collection of water samples for other programs.
8.3 Preservation
It is preferred that samples be preserved at the time of collection by adding enough nitric acid to the
sample to bring it to a pH < 2 (e.g. 1-2 mL 16 M HN03 per liter of sample will generally yield a pH < 2).
Alternate concentrations of HN03 are permitted, although the volume added to achieve a pH < 2 should
not exceed 30 mL/L. If the samples are preserved in the field using acid that has not been supplied by
the laboratory, add the same level of acid to a Field Blank (Section 3.5). The pH of all samples must be
verified upon receipt in the laboratory. If the pH is > 2, treat the sample as if it were collected without
preservation as described in Section 8.4.
NOTE: Drinking water samples do not require thermal preservation.
8.4 I npreserved Samples and Storage
If samples are collected without preservation, they must be received by the laboratory within 5 days,
then preserved with 16 M HN03 to a pH < 2 and held in their original containers for a minimum of 16
hours. The 16-hour waiting period helps solubilize finely suspended materials or surface adsorbed
materials. Verify that the pH is < 2 before preparing the samples for analysis.
NOTE: Screen sample preservatives used by the laboratory (or by field samplers) for radioactive content
by lot number prior to use, if possible, to verify that preservatives do not introduce radioactive
contamination.
9
-------
NOTE: Drinking water compliance samples must be prepared 'as received' (i.e. not filtered). Other
programs/projects may have alternate requirements. If such programs/projects specify filtration, it must
be performed prior to preservation.
NOTE: The requirement for pH < 2 adequately addresses radionuclides of concern for drinking water
compliance samples; however, that may not be adequate for programs evaluating other radionuclides in
non-drinking water matrices. Other programs should optimize sample preservation as appropriate to
address such radionuclides of concern.
NOTE: The laboratory must have appropriate segregation procedures in place to prevent cross
contamination of samples.
f 11 111: i,n I
9.1 QC Requirements
QC requirements include an Initial Demonstration of Capability (IDC), ongoing Demonstration of
Capability, and ongoing QC requirements that must be met when preparing and analyzing drinking
water compliance samples. This section describes QC parameters, their required frequencies, and
performance criteria that must be met in order to meet EPA quality objectives for drinking water
analyses. These QC requirements are considered the minimum acceptable QC criteria. Laboratories are
encouraged to institute additional QC practices to meet their specific needs.
9.1.1 In II Demonstration of Capability
A successful IDC must be performed by each analyst prior to analyzing any field samples. Before
conducting the IDC, set up and calibrate the instrument as described in Section 10. The IDC consists of
the following: demonstration of low system contamination (Section 9.1.1.1). demonstration of accuracy
(Section 9.1.1.2) and confirmation of method sensitivity through a DL study (Section 9.1.1.3).
NOTE: The primary analyst is responsible for conducting a full DL study along with the demonstration of
low system contamination and demonstration of accuracy. Other analysts/technicians that may also be
responsible for performing the method can document their IDCs by either conducting a DL study or by
evaluating four LRBs (Section 9.1.1.1) and four LFBs (Section 9.1.1.2) and successfully meeting the
specified acceptance criteria.
9.1.1.1 Demonstration of Low System Contamination
Contamination due to sample processing is assessed by preparing and counting at least four LRBs
(Secti ). For drinking water, the LRB volume should be the same as the volume used in establishing
detection capability (Section 9.1.1.3) and representative of typical drinking water sample volumes. LRBs
are prepared and handled like samples following the procedure described in Section 11. Each LRB result
must be below the radium-228 detection limit of 1 pCi/L.
9.1.1.2 Demonstration of Accuracy
Initial demonstration of accuracy is verified by preparing and counting at least four LFBs (Section 3.6)
according to the procedure in Section 11. The recommended LFB fortification with radium-228 standard
is about 2.5 - 5 pCi/L. The average recovery for the LFBs must be within + 20% of the known amount of
added radium-228 activity.
9.1.1.3 Detection Limit Study
Laboratories testing drinking water samples for Safe Drinking Water Act compliance monitoring need to
confirm detection capability by performing a Detection Limit (DL) study. After calibrating the instrument
10
-------
as described in Section 10. fortify seven LFBs with the radium-228 standard at activity concentrations
near the 1 pCi/L required detection limit. Prepare and analyze the LFBs following the procedure
described in Section 11. Calculate the DLs as described in Section 12.5.
NOTE: Further discussion of the drinking water DL procedure along with derivation of the final DL
equation from the 40 CFR 141.25(c) definition can be found in Procedure for Safe Drinking Water Act
Program Detection Limits for Radionuclides, USEPA 815-B-17-003, April 2017.
NOTE: Programs that do not analyze drinking water compliance samples may have alternate detection
capability requirements.
9.1.1.4 Exception for Experienced Analysts
If an analyst has at least one year of experience preparing and analyzing LRBs and LFBs for a
coprecipitation Ra-228 method (such as a previous version of EPA Method 904.0), and there have been
no changes to the instrumentation, previously documented data may be used to fulfill the IDC low
system contamination and accuracy requirements. Ongoing demonstrations of capability (Section 9.1.2)
will verify analyst conformance to the criteria described in this revised method.
9.1.2 Ongoing Demonstration of Capability
Ongoing demonstrations of capability may be fulfilled by repeating the IDC studies described in Sections
9.1.1.1 - 9.1.1.2 annually or by documenting batch QC LRBs and LFBs that an analyst has processed
during the year since the last demonstration of capability. The data for at least four LRBs processed in
different batches can be used to assess sample processing contamination and the data for at least four
LFBs processed in different batches can be used to assess accuracy. The amount of the Ra-228 standard
added to the sample batch LFBs should follow the guidance described in Section 9.I.I.2.
9.2 O in go ii ii leiria
This section summarizes ongoing QC criteria that must be followed when processing and analyzing
drinking water compliance samples.
9.2.1 Calibration Stability and Background Checks
The calibration stability and background of each detector used to count analytical samples is checked
and recorded on control charts each day prior to use to verify the instrument response has not changed
since it was calibrated. During periods when gas proportional counters are idle, check the detector
calibration stability and the background weekly to confirm the ready status of the instrument for sample
measurements.
9.2.1.1 Calibration Stability Check
To verify detector calibration stability, each day prior to sample counting, run a beta QC check source.
The check source does not have to be NIST-traceable but must have a documented count rate. Count
the check source long enough to obtain about 10,000 counts (1% counting uncertainty). Record and
monitor the measurements on a control chart.
9.2.1.2 Background Check
Each day prior to sample counting, run a background check with only a clean planchet in the detector.
Record and monitor background measurements on a control chart.
11
-------
9,2,1,3 Post-run Calibration Stability and Background Checks
After completion of a sample counting batch, run the beta check source and a background check to
verify that the calibration and background did not change significantly while the samples were being
counted.
9.2.2 Control Charts
Analysts are responsible for preparing and maintaining control charts. After a sufficient number of
checks have been obtained (usually at least 20 measurements), calculate the mean values on the control
charts. Establish warning limits at ±2 standard deviations and control limits at ±3 standard deviations
relative to the mean values. Monitor control charts to ensure measurements remain in statistical control
relative to the control limits. Also, monitor control charts to ensure instrument performance does not
change significantly (i.e., drifting or trending of responses) relative to the time of the initial calibration.
NOTE: As opposed to manually plotting data and calculating control limits, most instrument software
provides this capability. Analysts still have a responsibility to monitor the control charts as described
above to ensure that measurements remain in statistical control.
9.2.3 Corrective Action
If instrument control measurements exceed their control limits or exhibit a significant change in
performance, the proportional counter is placed out of service until stability of the system relative to
the initial calibration can be demonstrated.
9.2.4 Laboratory Reagent Blank (ILRIB)
An LRB (Section 3.7) must be prepared with each preparation batch to confirm there is no significant
contamination introduced in processing the batch which would contribute bias to the analytical results.
Ensure that LRB activity does not exceed the regulatory DL as described in Section 9.1.1.1, Record LRB
activities on control charts and monitor for trends that could indicate the need for corrective action.
9.2.5 Laboratory Fortified Blank (LFB)
An LFB (Section 3.6) must be prepared with each preparation batch to assess batch accuracy
independent of compliance sample matrix effects. Fortify with radium-228 standard at a level between
the required detection limit and the MCL, although it is recommended to keep the fortification level
between 2.5 and 5.0 pCi/L since uncertainty at the DL is higher. Accuracy as percent recovery must be
within ±20% of the amount of activity added. If the LFB fails to meet the recovery criterion, the batch is
considered compromised which may be due to contamination, poor precipitation/preparation
technique, etc. Re-prepare the sample batch with new QC checks provided sufficient volume is available.
Otherwise, a new set of samples should be collected. Record and monitor LFB recoveries on control
charts.
9.2.6 Laboratory Fortified Sample Matrix (LFSM)
Prepare one LFSM (Section 3.8) per preparation batch. Spike the LFSM with a known activity of radium-
228 standard that is approximately 10 times the anticipated level in the samples or at least 10 times the
DL (i.e. 10 pCi/L). Accuracy as percent recovery must be within ±30% of the amount of activity added. If
the LFSM fails to meet the recovery criterion, re-prepare the sample batch with new QC checks provided
sufficient volume is available. Otherwise, flag sample results in the batch as possibly biased low or high
(as the LFSM result indicates) due to matrix effects. Record and monitor LFSM recoveries on control
charts.
12
-------
9.2.7 Duplicate (DUIP) or Laboratory Fortified Sample Matrix Duplicate (LFSMD)
Batch precision is assessed through preparation of either a DUP (Section 3.4) or a LFSMD (Section 3.9)
with every preparation batch. The LFSMD is spiked at the same level as the LFSM. Precision is assessed
by calculating the relative percent difference (RPD). RPD must be < 20%. If the RPD exceeds 20%, and a
duplicate sample measurement is < 5X the DL, calculate the normalized absolute difference (NAD).
Calculations for the RPD and NAD are provided in Section 12.6. A sample/DUP or LFSM/LFSMD that fail
the batch precision criteria may be an indication of a lack of sample homogeneity and the samples in the
preparation batch should be reported with a qualifier indicating the measurement has questionable
precision. If a client requires unqualified results, prepare a new sample batch with new QC checks
provided sufficient volume is available. Otherwise, a new set of samples should be collected. Record and
monitor RPD and NAD on control charts.
9.2.3 Field Blair sded)
If a Field Blank (Section 3.5) is provided with the samples, prepare and analyze it to confirm that field-
supplied preservative does not contribute uncertainty to the analytical results.
10 Calibration
10.1 Instrument Setup
Establish voltage plateaus and appropriate operating conditions as recommended by the instrument
manufacturer. Perform a calibration stability check and background check as described in Section 9.2.1
following instrument set-up, anytime operating voltage is changed, following instrument repairs, and
after gas bottle changes. If QC checks fail, take corrective action (which may entail re-establishing
instrumental operating conditions and recalibration).
10.2 Detector Background
Detector chamber background levels must be determined to provide for background subtraction in
activity calculations and verification that the instrument is free of contamination. A clean, empty
planchet is counted (for each detector in the counting system) for at least the same length of time that
typical samples are expected to be counted.
10 „ 2 „ 1 IBa c Ikgiro u n d S u bt ira ct i o n
For drinking water compliance samples, background subtraction measurements should be performed
with each batch of samples, however a long weekly count as described in Section 10.2.2 is also
acceptable. If desired, the background subtraction measurement can substitute as either the pre- or
post-background check as described in Section 9.2.1.
NOTE: Other programs that do not analyze drinking water compliance samples may have alternate
background subtraction counting frequencies, as appropriate.
10.2.2 Multiple Detector Systems
There are counting systems that have multiple single detectors and the batch is counted on several
different detectors. For such systems, the laboratory may establish a control chart with a weekly long
background count. On a daily basis, count a clean planchet before and after analyzing a drinking water
compliance batch for a shorter time (at least ten minutes). Plot the short background measurements on
the longer background control chart. If the short background measurements are in statistical control of
the long background (i.e., within + 3 standard deviations of the mean long background measurements),
then the weekly long background count can be used for background subtraction.
13
-------
10.3 Geometry Considerations
Initial calibration involves preparation of a mass-efficiency curve. There are two calibration options for
Ra-228 determination as described in Section 10.4 - using Sr-89 as the calibration surrogate or using Ra-
228 and calibrate relative to Ac-228. Either option is acceptable, however analysts must be cognizant of
the short half-life of actinium-228 (6.15 hours) and the requirement to meet the regulatory detection
limit. The geometry of the calibration sources prepared for the mass-efficiency curve needs to be the
same as that of the prepared sample and QC planchets (i.e., prepare and mount calibration sources in
the same manner as samples).
10.4 1 -ill! -I atiioii !iI-1 II /elopnieint of Mass-Efficiency Curve
The acceptable yttrium yield (as yttrium oxalate nonahydrate, Y2(C204)3-9H20) is 70-110%. The target
100% yield is about 30.5 mg when 9 mg standardized yttrium carrier (Section 7.30) is used. Based on the
recovery acceptance criterion, the relative yttrium oxalate mass range is approximately 21.4 mg (70%)
to 33.6 mg (110%). Therefore, efficiency calibration sources should be prepared that bracket the mass
range.
10.4.1 Sr-89 Callibirant
Standard Sr-89 can be used as a beta energy surrogate for calibration in place of Ac-228. Generate a
strontium oxalate mass range that brackets the acceptable yttrium oxalate mass range.
10.4.1.1 Preparation of Sr-89 Efficiency Calibration Sources as Strontium Oxalate Monohydrate
Assuming 100% yield, 1.5 mL of 10 mg/mL strontium carrier will yield 33 mg strontium oxalate
monohydrate. Prepare at least four centrifuge tubes that contain varying amounts of standardized
strontium carrier (10 mg/ml, Section 7.26) that will bracket the mass range. To each tube, add
approximately 1000 dpm Sr-89 standard and dilute with about 20 mL distilled/deionized water. Add 2
mL concentrated NH4OH (Section 7.4), heat to nearly boiling then slowly add 5 mL saturated ammonium
oxalate solution (Section 7.6) to each tube. Heat the tubes in a hot water bath for 15 minutes. Remove
the tubes from the bath and allow to cool. Centrifuge and discard the supernates. Rinse each strontium
oxalate precipitate with about 20 mL distilled/deionized water. Centrifuge and discard the supernate.
Slurry each strontium oxalate precipitate with a few mLs distilled/deionized water and quantitatively
transfer each precipitate to separate tared planchets. Dry under an infrared lamp or in a 105 °C + 2 °C
oven, cool in a desiccator and weigh to determine the mass of strontium oxalate recovered. Count as
described in Section 10.5. Calculate efficiency standard yields as described in Section 12.1.5.
10.4.2 Ra-228 Callibirant (measured as Ac-228)
Standard Ra-228 is used as the calibrant to establish beta mass efficiencies over a range of precipitate
weights as described in Section 10.4.2.1 below. After a 36-hour ingrowth of Ac-228, the Ac-228 is carried
on yttrium oxalate. The final yield can be based on either yttrium oxalate or yttrium oxide; however,
counting Ac-228 is performed using the yttrium oxalate precipitate. Therefore, prepare a set of at least
four calibration sources that will bracket the minimum and maximum allowable masses for Ac-228
carried on yttrium oxalate based on a yield of 70-110% (21.4 mg to 33.6 mg yttrium oxalate
nonahydrate).
10.4.2.1 Preparation of Ra-228 Calibration Standards
Pipet approximately 1500-2000 dpm Ra-228 standard into at least four separate 50-mL centrifuge tubes.
Pipet variable volumes of 9 mg/mL standardized yttrium carrier (Section 7.30) covering the range of
about 0.5 - 1.5 mL (to fully encompass the yield range) into the tubes. To each tube, add 5 mL 18 M
14
-------
NaOH, stir well and digest the tubes in a hot water bath until yttrium hydroxide coagulates. Centrifuge
and discard supernates. Note the time of the yttrium hydroxide precipitation - this marks the end of the
Ac-228 ingrowth and beginning of Ac-228 decay. Move quickly from this point forward. Dissolve
precipitate with lmLIM HN03 (Section 7.20). Put tubes in hot water bath for a few minutes to make
sure samples are clear. Dilute the contents of each tube to a 5-mL volume with distilled/deionized water
and add 2 ml 5% ammonium oxalate (Section 7.7) to each centrifuge tube and stir. Heat for just a few
minutes to coagulate oxalate precipitate (excessive heating can cause dissolution of the precipitate back
into solution). Centrifuge and discard the supernate. Slurry the yttrium oxalate precipitate with a small
volume of distilled/deionized water and transfer to a tared stainless steel planchet. Dry under an
infrared lamp or in a 105 °C + 2 °C oven. Cool in a desiccator and weigh to determine the mass of yttrium
oxalate recovered. Count as described in Section 10.5.
10.5 Counting
Count the prepared efficiency standards until at least 10,000 total counts greater than background
(where the background should be less than 1-2% of the total counts above background) have been
accumulated.
10.6 Generate Curve
Prepare the mass-efficiency curve and generate the best curve fit by plotting the efficiency of the
radionuclide standard as calculated in Section 12.3 along the y-axis vs. the measured precipitate mass
along the x-axis.
10.7 Annual Verification
Annual verification of efficiency calibration is required. Due to the half-lives associated with the
calibrants, it is not appropriate to save the prepared calibration sources for reuse to verify the
calibration. As a result, prepare new sources as described in either Section 10.4.1.1 or 10.4.2.1. For the
calibration verification to be acceptable, the original measurements of each efficiency standard should
lie within the range defined by the uncertainty of the new efficiency standards calculated at the 95%
confidence level.
NOTE: Evaluate a beta check source standard after instrument repair and after gas bottle changes. If the
check source indicates a change in instrument performance, verify with a recount. If the recount still
indicates a problem, then corrective action is warranted. Re-establish instrument parameters and
recalibrate.
| | ! ! ! J
11.1 Citric Acid Addition
To a 1-L acid-preserved drinking water sample, add 5 mL 1 M citric acid (Section 7.12) and a few drops
methyl orange indicator. The solution should be red.
11.2 Ad ers
Add 10 mL lead carrier (150 mg, Section 7.15), 2 mL standardized strontium carrier (20 mg, Section
7.26), 2 mL standardized barium carrier (32 mg, Section 7.10) and 1 mL yttrium carrier (18 mg, Section
7.29). Stir well. Heat to a low boil and digest for 30 minutes.
NOTE: If barium-133 is used for yield determination, add the tracer to the barium carrier as described in
Section 7.10.1.2.
15
-------
11.3 Precipitate PbSCUand BaSClf
Add concentrated NH4OH (Sectic ) until a definite yellow color is obtained (pH > 4.4), then add a few
drops in excess. Precipitate lead and barium sulfates by adding 9 M H2S04 (Section 7.28) until the red
color reappears, then add 0.25 mL excess. Add 5 mL (NH4)2S04 (1 g, Section 7.8). Stir frequently and
maintain a sub-boiling temperature of about 90 °C for 30 minutes.
11.4 Isolate Precipitate
Allow precipitate to settle and cool slightly. Filter with suction through a metricel membrane filter (GA-6,
0.45 pirn, or equivalent). Transfer any remaining precipitate in the container to the filter using a strong
jet of distilled/deionized water. Place the filter in a glass beaker and add 10 mL 16 M HN03 (Section
7.18) to dissolve the filter. Heat gently until the filter completely dissolves. Transfer the precipitate to a
centrifuge tube with a small amount of 16 M HN03. Centrifuge and discard the supernate. Wash the
precipitate with about 15 mL 16 M HN03, centrifuge and discard the supernate. Wash the precipitate
once more with 15 mL 16 M HN03, centrifuge and discard the supernate.
11.5 Dissolve Precipitate with Basil >llutiion
Dissolve the precipitate by adding 25 mL basic EDTA reagent (Sectic ). Heat in a hot water bath and
stir well. Add a few drops 10 M NaOH (Sectic ) if precipitate does not readily dissolve.
11.6 Precipitate BaSCli
Add 1 mL strontium-yttrium mixed carrier (Section 7.31) and stir thoroughly. Add a few drops of 10 M
NaOH (Section 7.24) if any precipitate forms. Add 1 mL (NH4)2S04 (200 mg, Section 7.8) and stir
thoroughly. Add 17.4 M CH3COOH (Secti ) slowly until precipitation begins. If desired, add a few
drops of bromocresol green indicator. Continue to add up to 2 mL additional acetic acid to ensure
complete precipitation. Check the pH because this step is pH-dependent by either watching the
bromocresol green indicator or using an appropriate pH paper strip. Acidification releases
barium/radium from the EDTA complex, but if the pH drops below about 4.5, the lead that is bound
within the EDTA complex will begin to be released. Digest in a hot water bath until the precipitate
settles. Centrifuge and discard the supernate.
NOTE: If pH is monitored using the bromocresol green indicator, the appropriate endpoint is green. It is
recommended that analysts become familiar with recognizing the appropriate color of a pH 4.5 solution
by adjusting a solution of similar composition to pH 4.5 using a pH meter.
11.7 Isolate Precipitate
Add 20 mL basic EDTA reagent (Section 7.13). heat in a hot water bath and stir until precipitate
dissolves. Repeat procedure described in Section 11.6. Note the time of the final BaS04 precipitation;
this is the beginning of Ac-228 ingrowth.
11.8 Dissolve Precipitate, Add Carriers and Allow Ac-228 Ingrowth
Add 20 mL basic EDTA reagent (Section 7.13) to the precipitate, heat in a hot water bath and stir to
dissolve the precipitate. Add 1.0 mL standardized yttrium carrier (9 mg, Section 7.30) and 1 mL lead
carrier (1.5 mg, Sectii ). If any precipitate forms, dissolve by adding a few drops of 10 M NaOH
(Section 7.24). Cap the centrifuge tube and allow Ac-228 ingrowth for at least 36 hours.
11.9 Scavenge Ingrown 212Pb
At the end of the ingrowth period, add 0.3 mL (NH4)2S (Section 7.9) and stir well. Add 10 M NaOH
(Section 7.24) dropwise with vigorous stirring until black lead sulfide precipitates, then add 10 drops
16
-------
excess. Stir intermittently for about ten minutes. Centrifuge and decant the supernate (which contains
barium, yttrium and Ac-228) into a clean centrifuge tube. Dispose of the PbS precipitate. To the
supernate in the centrifuge tube, add 1 mL lead carrier (1.5 mg, Section 7.16), 0.1 mL (NH4)2S (Section
7.9) and a few drops of 10 M NaOH (Section 7.24). Repeat lead sulfide precipitation as before.
Centrifuge and filter the supernate through a Whatman #42 (or equivalent) filter paper into a clean
centrifuge tube. Rinse the filter with a small amount of distilled/deionized water. Dispose of the PbS
residue. Proceed without delay to the final separation and count to minimize Ac-228 decay.
11.10 Precipitate
Add 5 mL 18 M NaOH (Section 7.23) to the filtrate, stir well and digest in a hot water bath until yttrium
hydroxide coagulates. Centrifuge, decant the supernate into a clean beaker or centrifuge tube, and save
for barium yield determination and, if desired, radium-226 analysis. Note the time of yttrium hydroxide
precipitation; it marks the end of Ac-228 ingrowth and the beginning of Ac-228 decay.
11.11 IP u r i f y P r e c i p i t a t e
Dissolve the precipitate in about 2 mL 6 M HN03 (Section 7.19). Heat and stir in a hot water bath about
five minutes. Add 5 mL distilled/deionized water and reprecipitate yttrium hydroxide with 3 mL 10 M
NaOH (Section 7.24). Heat and stir in a hot water bath until precipitate coagulates. Centrifuge and add
supernate to the beaker/centrifuge tube for barium yield determination (Section 11.10 above).
11.12 Precipitate Y2(C204)-9(H20)
Dissolve yttrium hydroxide precipitate with 1 mL 1 M HN03 (Section 7.20). Heat in a hot water bath for a
few minutes. Dilute to a 5-mL volume with distilled/deionized water. Add 2 mL 5% ammonium oxalate
(Secti ). Heat in a hot water bath for a few minutes to coagulate the precipitate. Be careful in this
step because prolonged heating can cause partial dissolution of the precipitated yttrium oxalate back
into solution. Centrifuge and discard supernate.
NOTE: If yttrium yield is determined relative to yttrium oxalate (as opposed to optionally converting the
yttrium oxalate to yttrium oxide), reproducibility and accuracy in the mass of the final oxalate
precipitate depends upon carefully reproducing the acid and base amounts used in the procedural steps
described in Sections 11.12 and 11.13. A pH of 1.7 - 1.9 in the solution from which yttrium oxalate is
being precipitated is required in order to obtain a uniform 9-hydrate (Y2(C204)-9 H20) precipitate.
11.13 Pu irify Preci pitate
Add 10 mL distilled/deionized water, 6 drops 1 M HN03 (Section 7.20) and 6 drops 5% ammonium
oxalate (Secti ). Heat in a hot water bath for a few minutes. Centrifuge and discard supernate.
11.14 Prepare Planchet and Count
Preparation of the final precipitate for counting depends on the manner in which yield will be
determined, either as the oxalate or the oxide:
11.14.1 Procedure based on determining yield as yttrium oxalate
Slurry the yttrium oxalate precipitate with a minimum of distilled/deionized water and transfer
quantitatively to a tared stainless steel planchet. Dry under a heat lamp or in a 105 °C + 2 °C oven until a
constant weight is obtained. Count in a low-background gas flow proportional counter to determine
beta activity. Determine yttrium recovery as described in Section 12.1.3.
17
-------
11.14.2 Procedure based on determining yield as yttrium oxide
Place an ashless cellulose or glass fiber filter in a filter assembly and quantitatively transfer the yttrium
oxalate precipitate to the filter using distilled/deionized water to ensure transfer is complete. Add a
small volume of acetone to the precipitate to facilitate drying. Place the filter containing the precipitate
in a gas flow proportional counter to determine beta activity of the Ac-228. After counting, transfer the
filter to a tared crucible. Ignite at 800 °C for 1 hour in a muffle oven to convert the oxalate to the oxide.
Cool completely and weigh the crucible. Determine the yttrium recovery as described in Section 12.1.4.
11.15 Barium Yield
Procedure followed is based on either gravimetric chemical yield of BaS04 or radiochemical yield of Ba-
133 tracer:
11.15.1 Procedure based on gravimetric chemical yield determination
To the combined supernate collected in Sections 11.10 and 11.11. add 4 mL 16 M HN03 (Section 7.18)
and 2 mL ammonium sulfate (400 mg, Section 7.8), stirring well after each addition. Add 17.4 M acetic
acid (Section 7.2) slowly until barium sulfate precipitates, then add 2 mL in excess. Digest in a hot water
bath until precipitate settles. Centrifuge and discard supernate. Add 20 mL basic EDTA reagent (Section
), heat in hot water bath and stir until precipitate dissolves. Add a few drops of 10 M NaOH (Section
7.24) if needed to ensure dissolution of the precipitate. Add 1 mL ammonium sulfate (400 mg, Section
7.8) and stir well. Add 17.4 N acetic acid until barium sulfate precipitates, then add 2 mL in excess.
Digest in a hot water bath until precipitate settles. Centrifuge and discard supernate. Wash precipitate
with about 10 mL distilled/deionized water. Centrifuge and discard the supernate. Slurry the precipitate
in a small volume of distilled/deionized water and transfer quantitatively to a tared stainless steel
planchet. Dry under a heat lamp or in a 105 °C + 2 °C oven until a constant weight is obtained.
Determine barium recovery as described in Section 12.1.1.
11.15.2 Procedure based on radiochemical yield using Ba-133 tracer
Precipitate barium sulfate as described in Section 11.15.1 above. Instead of transferring precipitate to a
planchet, place a 0.45 um membrane filter in a vacuum filter assembly, prewet with distilled/deionized
water and start vacuum. Transfer the precipitate to the filter using distilled/deionized water to ensure
transfer is quantitative. Add a small volume of ethanol to the precipitate and maintain suction to fully
dry the precipitate. Place the filter containing the precipitate in a planchet and count in a gamma
spectrometer detector. Determine barium recovery as described in Section 12.1.2.
I I '.»!.» / iiji1 , !! ,,ik! ¦ J. ill
12.1 Yield Calculations
12.1.1 Barium Chemical Yield (Precipitate)
The chemical yield for the barium carrier is calculated as follows:
(mg BaS04)(0.5884)
Theoretical Yield, Std. Ba in mq/mL =
2.0 mL
Theoretical yield of barium sulfate must be determined based on the standardized concentration of the
barium carrier (Sectic 1.1). If the standardized carrier concentration is 16 mg/mL, then the
theoretical 100% yield of barium sulfate would be 54.38 mg.
The fractional yield would thus be:
18
-------
(ms - mv)
54.38
Where
ms= mass of planchet with the dried barium sulfate precipitate, mg
mp= mass of planchet, mg
54.38 = mass of barium sulfate precipitate if all the added barium carrier (32 mg) is recovered. If the
standardized concentration of the barium carrier differs from the 16 mg/mL prepared in Section 7.10,
adjust the theoretical Ba2+ concentration accordingly.
12.1.2 Barium Radiochemical Yield (Ba-133 Tracer)
Alternately to the chemical yield calculated in Section 12.1.1, radiochemical yield based on addition of
barium-133 as a tracer is calculated using the following equation:
A
Y = —
As
Where
Am= Activity of Ba-133 measured in the sample, pCi/mL
As= Activity of standardized Ba-133 solution, pCi/mL
12.1.3 Yttrium Yield (as Yttrium Oxalate Nonahydrate)
The yield for yttrium oxalate is calculated as follows:
3+ , {mg Y2(C204)3 ¦ 9H2O)(0.29948)
Theoretical Yield for Std. Y , in mg/mL =
1.0 mL
If the standardized yttrium carrier concentration is 9 mg/mL, then the theoretical 100% yield of yttrium
oxalate nonahydrate would be 30.56 mg.
The fractional yield would be:
(ms - mp)
30.56
Where
ms= mass of planchet with the dried yttrium oxalate nonahydrate precipitate, mg
mp= mass of planchet, mg
30.56 = mass of yttrium oxalate nonahydrate precipitate if all the added yttrium carrier (9 mg) is
recovered. If the standardized concentration of the yttrium carrier differs from the 9 mg/mL prepared in
Section 7.30, adjust the theoretical Y3+ concentration accordingly.
12.1.4 Yttrium Yield (as Yttrium Oxide)
The yield for yttrium oxide is calculated as follows:
3_i_ . (mgY203W78743)
Theoretical Yield for Std. Y , in mg/mL =
1.0 mL
If the standardized yttrium carrier concentration is 9 mg/mL, then the theoretical 100% yield of yttrium
oxide would be 11. 43 mg.
The fractional yield would be:
(ms - mp)
11.43
Where
ms= mass of planchet with the dried yttrium oxide precipitate, mg
mp= mass of planchet, mg
19
-------
11.43 = mass of yttrium oxide precipitate if all the added yttrium carrier (9 mg) is recovered. If the
standardized concentration of the yttrium carrier differs from the 9 mg/mL prepared in Section 7.30,
adjust the theoretical Y3+ concentration accordingly
12.1.5 Strontium Oxalate Monohydrate (Efficiency Calibration Yields)
Calibration with Sr-89 and determination of detector efficiency entails determination of strontium
oxalate monohydrate yield. For any given mass of strontium carrier used in preparing efficiency
standards (i.e., 1.0 mL of 10 mg/mL strontium carrier results in 10 mg Sr2+), multiply by 2.211 in order to
determine the theoretical yield of strontium oxalate monohydrate precipitate. Assess fractional yield for
each standard and calculate efficiency as described in Section 12.3.1.
12.2 Count Rate
The net count rate, Rx, for any single count (sample, background, standard) is generically calculated as
R
* ts tB
where
Rx = Net count rate in counts per minute
Nx = Number of counts observed over the sample counting period
ts = Duration of the sample counting period (i.e., live time) in minutes
Bx = Number of counts observed over the background counting period
tB = Duration of the background counting period (i.e., live time) in minutes
The standard uncertainty ("one-sigma") of Rx is then given by
Nx Bx
u(Rx)= -j + -j
y Ls lB
The square of the standard uncertainty is denoted by u2(Rx).
Nx Bx
u2(Rx) = -^ + -j
Ls lB
12.3 Efficiency
The beta counting mass-efficiency (self-absorption) calibration is established as described in Section 10.
Calculate efficiencies as based on calibrant as follows:
12.3.1 Sr-89
Rp \ /i
Pm V^StdQS)/
where
£pm = Beta Efficiency determined for mass m
Rp = Net count rate of the Sr-89 standard, counts per minute
^std(/3) = Activity of the Sr-89 standard, disintegrations per minute, at midpoint of the count
Y = Strontium oxalate yield (as calculated in Section 12.1.5)
A = Sr-89 decay constant, (0.0137 day"1)
12.3.2 IRa-228
Rt
AstdiP)/ ^Ba X Yy
Ll
Ye
ts
1 — e-Aits_
20
-------
where
£pm = Beta Efficiency determined for mass m
Rp = Net count rate, counts per minute
^std(/3) = Activity of the Ra-228 standard, disintegrations per minute
yBa = Barium Yield (as calculated in Section 12.1)
Yy = Yttrium Yield (as calculated in Section 12.1)
A1 = Ac-228 decay constant, (0.1127 hr"1)
tx = Beginning of Ac-228 ingrowth
t2 = Beginning of Ac-228 decay
t3 = Beginning of sample count
ts = Sample count time
12.4 Radium-228 Activiii lertainty
Calculate the radium-228 activity concentration for each sample.
i i r i i r X, t.
228D„ a n -
Ra Activity pCi/L = ¦
] [_^ I [ ^ 1 f.
£p x V x 2.22 x YBa x Yy
where
Rp = Net beta count rate, counts per minute
£p = Beta efficiency, cpm/dpm
V = Volume of sample aliquot, in liters
2.22 = Conversion factor from dpm to pCi
yBa = Barium Yield (as calculated in Section 12.1)
Yy = Yttrium Yield (as calculated in Section 12.1)
A1 = Ac-228 decay constant, (0.1127 hr"1)
A2 = Ra-228 decay constant, (0.1205 yr1)
1 = Beginning of Ac-228 ingrowth
2 = Beginning of Ac-228 decay
= Beginning of sample count
= Sample count time
= Time when sample was collected
The radium standard counting uncertainty and expanded counting uncertainty (95 % confidence) are
calculated as:
( , ^u~(Rft) l i r l i r A,ts i r l
^ £p x 7 x 2.22 x YBa xYyX .1 — [l — [e-;i2(t2-to)
^95% = 1-96 X u(cp)
where
u(cp) = Radium standard counting uncertainty ("one-sigma") in pCi/L
U95o/o = Expanded counting uncertainty (95 % confidence) in pCi/L
1.96 = Coverage factor for 95 % level of confidence
Rp = Net beta count rate, counts per minute
£p = Beta efficiency, cpm/dpm
V = Volume of sample aliquot, in liters
21
-------
2.22 = Conversion factor from dpm to pCi
yBa = Barium Yield (as calculated in Section 12.1)
Yy = Yttrium Yield (as calculated in Section 12.1)
= Ac-228 decay constant, (0.1127 hr"1)
X2 = Ra-228 decay constant, (0.1205 yr"1)
1 = Beginning of Ac-228 ingrowth
2 = Beginning of Ac-228 decay
= Beginning of sample count
= Sample count time
= Time when sample was collected
12.5 Safe Drinking Water Act Detection Limit
The detection limit (DL) requirement for drinking water compliance samples is defined in Section 3.3 and
determination of method detection capability is described in Section 9.I.I.3. From the definition, the
equation in Section 12.5.1 can be derived (see reference 7 in Section 14).
12.5.1 DL Equation
The single sample drinking water detection limit is calculated as:
1.962
2 ts
DL =
)] [l - e-AitJ [;
ep x V x 2.22 x YBa xYy Ll — eLl — e~^^l L
where
ts = Sample count time
tB = Background count time
B = Number of background counts
Ep = Beta efficiency, cpm/dpm
V = Volume of sample aliquot, in liters
2.22 = conversion factor from dpm to pCi
yBa = Barium Yield (as calculated in Section 12.1)
Yy = Yttrium Yield (as calculated in Section 12.1)
= Ac-228 decay constant, (0.1127 hr"1)
X2 = Ra-228 decay constant, (0.1205 yr1)
= Beginning of Ac-228 ingrowth
t2 = Beginning of Ac-228 decay
t3 = Beginning of sample count
ts = Sample count time
t0 = Time when sample was collected
12.5.2 DL Study
The DL study described in Section 9.1.1.3 consists of seven replicate laboratory fortified blanks that are
prepared and counted as specified in the method. The replicate results are assessed using a chi-square
statistic to test whether the relative standard deviation of the results exceeds the maximum value
allowed at the required DL.
Calculate the mean of the measured values and the chi-square statistic as follows:
22
-------
7 = 1
And
Where
n = Number of replicate measurements
= Activity fortified in sample replicates
To be deemed acceptable, the value of^2 should be less than or equal to the 99th percentile of the^2
distribution with (n-1) degrees of freedom.
12.6 Relative Percent Difference Calculation
As described in Section 9.2.7, relative percent difference (RPD) is used to evaluate precision of duplicate
measurements. The RPD is calculated as
where
As = Net activity of the first aliquot of sample
Adup = Net activity of the measurement obtained from a second aliquot of the same sample
If a duplicate sample measurement has an activity < 5x the detection limit and the calculated RPD > 20%,
calculate the normalized absolute difference (NAD). The NAD of the two measurements made from the
same sample assesses whether they are within 2 standard deviations of their aggregate measurement
uncertainty of each other. Calculate the NAD as
where
As = Net activity of the first aliquot of sample
Adup = Net activity of the measurement obtained from a second aliquot of the same sample
u\As) = Square of the standard counting uncertainty ("one-sigma") associated with As
u2(Adup) = Square of the standard counting uncertainty ("one-sigma") associated with Adup
If the NAD is less than or equal to 2, then the two measurements are within 2 standard deviations of
each other and therefore acceptable. If, however, the NAD exceeds 2, it is unacceptable since it means
there is > 2 standard deviations of difference between the two measurements drawn from the same
sample. Recount the sample and duplicate. If RPD/NAD evaluation still fails, a new sample and duplicate
should be prepared.
The procedures described in this method generate relatively small amount of waste since only small
amounts of reagents are used. The matrices of concern are finished drinking water or source water.
Laboratory waste practices must be conducted consistent with the laboratory's radioactive materials
license and all applicable rules and regulations, and that laboratories protect the air, water, and land by
RPD = ——Adup\ X 100 %
NAD =
13 Pollution Prevention
23
-------
minimizing and controlling all releases from fume hoods and bench operations. Also, compliance is
required with any sewage discharge permits and regulations, particularly the hazardous waste
identification rules and land disposal restrictions.
14 References
1. Standard Methods for the Examination of Water and Wastewater, 22nd Ed., American Public
Health Association, Washington, D.C. (2011).
2. Manual for the Certification of Laboratories Analyzing Drinking Water, Criteria and Procedures
Quality Assurance, 5th Ed., USEPA 815-R-05-004, January 2005.
3. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP), NTIS PB2004-
105421, July 2004.
4. Goldin, A. S., Determination of Dissolved Radium. Anal. Chem. 33, 406-409 (March 1961).
5. Kirby, H. W., Decay and Growth Tables for the Naturally Occurring Radioactive Series, Anal.
Chem., 26, 1063-1071 (1954).
6. Sill, C. W., Determination of Radium-226 in Ores, Nuclear Wastes and Environmental Samples by
High-Resolution Alpha Spectrometry, Nuclear and Chemical Waste Management, 7, 239-256
(1987).
7. Procedure for Safe Drinking Water Act Program Detection Limits for Radionuclides, USEPA 815-B-
17-003. April 2017.
24
------- |