oERA
United States
Environmental Protection
Agency
Method 900.0, Revision 1.0: Gross Alpha and Gross Beta
Radioactivity in Drinking Water
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Questions concerning this document should be addressed to:
Glvnda 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-18-002
February 2018
Authors
Glynda A. Smith, Ph.D., U.S. EPA (Cincinnati, OH)
Steven C. Wendelken, Ph.D., U.S. EPA (Cincinnati, OH)
Ac kin o1
Katie Adams, Inorganic Chemistry Technical Lead, US EPA Region 10 Laboratory, Port Orchard,
Washington.
Andy Eaton, Ph.D., Eurofins Eaton Analytical, Inc., Monrovia, California.
John Griggs, Ph.D., National Analytical Radiation Environmental Laboratory (NAREL), Office of Radiation
and Indoor Air (ORIA), USEPA.
Keith McCroan, Ph.D., National Analytical Radiation Environmental Laboratory (NAREL), Office of
Radiation and Indoor Air (ORIA), USEPA.
Bahman Parsa, Ph.D., Environmental and Chemical Laboratory Services, PHEL/PHILEP, New Jersey
Department of Health.
Bob Read, Ph.D., Environmental Chemistry Laboratory, Division of Laboratory Services, Tennessee
Department of Health.
Robert L. Rosson, CSRA, LLC, Alexandria, Virginia.
Bob Shannon, Quality Radioanalytical Support, LLC, Grand Marais, Minnesota.
Larry F. Umbaugh, CSRA, LLC, Alexandria, Virginia.
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Contents
1 Scope and Application 1
2 Summary of the Method 2
3 Definitions 2
4 Interferences 3
5 Safety 4
6 Equipment and Supplies 5
7 Reagents and Standards 5
8 Sample Collection, Preservation, and Storage 6
9 Quality Control 7
10 Calibration 10
11 Procedure 13
12 Data Analysis and Calculations 14
13 Pollution Prevention 20
14 References 20
15 SOP for Preparation of Radiochemistry Synthetic Water Solids (SWS) Matrix 21
16 Tables 25
17 References 25
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1 Scope and/ :ation
1.1 Background
Method 900.0, Revision 1.0 is a method for the determination of gross alpha and gross beta particle
activities in water. The method is a screening technique for monitoring water for alpha and beta particle
activities and thereby determining the necessity for further analysis.
From a regulatory standpoint, this method may be used as a screening procedure for monitoring
drinking water samples for alpha and beta particle activities according to the limits set forth in the Code
of Federal Regulations (CFR) and 40 CFR 141.26. As specified at 40 CFR 141.25(c)(1) and 141.25(c)(2), the
required detection limits (DLs) for gross alpha and gross beta are 3 pCi/L and 4 pCi/L, respectively.
1.2 Applicability
This method is applicable to the measurement of alpha emitters having energies above 3.9
megaelectronvolts (MeV) and beta emitters having maximum energies above 0.1 MeV. Samples
containing radionuclides of maximum beta particle energy less than 0.1 MeV, such as Ni-63, Pb-210, Ra-
228, and Pu-241, cannot be effectively screened using this method. In the presence of dissolved or
suspended solids, alpha emitter and mid-range energy beta emitter radiation can be significantly
attenuated. Thus, sample self-absorption calibrations are necessary to determine sample-specific
counting efficiencies (alpha and beta) to minimize bias.
1.3 Detection Limitations
The minimum limit of activity concentration to which this method is applicable depends on sample size,
counting system characteristics, background, and counting time.
1.4 Gross Alpha
In this method, solids are not separated from the samples, but are the end result of evaporating the
water fraction. As a result, high solids levels can be a limiting factor for method sensitivity. For gross
alpha determination, the maximum (uniformly distributed) solids thickness should be < 5 mg/cm2. As an
example, if a laboratory uses a counting planchet with a 2-inch diameter (20 cm2), a volume of water
containing 100 mg of dissolved solids would be the maximum volume that could be evaporated and
counted for gross alpha activity. Guidance for estimating an appropriate sample volume is provided in
Section 10.4.1.
1.5 Gross Beta
Gross beta activity determination is less affected by the presence of solids; a maximum (uniformly
distributed) solids thickness of up to 10 mg/cm2 can be tolerated. The absorption of alpha particles by
solids is more significant than that of beta particles. Thus, solids thickness of < 5 mg/cm2 is a limiting
factor if a laboratory performs simultaneous gross alpha and gross beta determination.
1.6 Solids Limitations
This method provides a rapid screening measurement to indicate whether more specific analyses are
required. For waters with high solids content (> 500 mg/L), a co-precipitation method is recommended
for determining gross alpha activity. For drinking water samples, using a smaller sample volume to
reduce the solids loading is only acceptable as long as the regulatory DLs can still be achieved.
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1,7 Tii /eints for Gross Alpha
The time intervals involved between sampling and preparation and between preparation and counting
can have a significant impact on the gross alpha results. If the gross alpha contribution due to Ra-226 is
the primary concern, hold the samples 2-3 weeks before preparation. Keeping in mind that the drinking
water gross alpha maximum contaminant level is 15 pCi/L minus activity contributed by uranium and
radon, samples need to be counted as soon as possible after preparation to ensure that the screening
results are optimized for Ra-226 by minimizing the ingrowth of Rn-222 and its alpha-emitting decay
progeny. On the other hand, some state regulations require sample preparation and counting as soon as
possible; analysis of a sample for gross alpha activity within 48 hours of sample collection will minimize
Ra-224 decay, an isotope with a half-life of 3.64 days. Thus, it is incumbent upon the laboratory to verify
the client's analytical requirements prior to preparing and counting samples. The gross beta
determination is not affected by the same timing issues.
2 Summary of the Method
An aliquot of a preserved drinking water sample is evaporated to a small volume and transferred
quantitatively in a uniform distribution to a tared stainless steel counting planchet. The sample residue
is dried to a constant weight and then counted for alpha and/or beta activity. Counting efficiencies for
both alpha and beta particle activities are determined from counting efficiency vs. sample solids
standard curves (see Section 10).
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 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 Limit (DL)
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).
3.4 D up II k
A second aliquot of a field sample that is processed in exactly 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 IFiieId Blank
Samples preserved with reagents that are not provided by the laboratory should be accompanied by a
radioactive-free 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
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sample of the preservative should also accompany the field samples to determine whether it
contributes any contamination.
3.6 Laboratory Fortified
For gross alpha and gross beta analyses, the LFB consists of a volume of a blank matrix to which a known
activity of a radioisotope is added. The LFB is prepared and analyzed and results calculated exactly like a
sample, and its purpose is to determine whether the methodology is in control, and whether the
laboratory is capable of making accurate measurements.
3.7 Laboratory Reagent Blank (LIRIB)
For gross alpha and gross beta analyses, the LRB consists of an aliquot of a blank matrix that is prepared
and analyzed and results calculated exactly like a sample, 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 Matrix (LFSM)
An aliquot of a field sample that has a known activity of the radionuclide(s) being measured added to it.
The LFSM is prepared and analyzed and results calculated in exactly 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.
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 prepared and analyzed and results calculated exactly as for the LFSM. It is used in
place of the DUP to assess preparation batch precision when non-detects are frequent.
3.10 Picocurie (pCi)
The pCi is the quantity of radioactive material producing 2.22 nuclear disintegrations per minute.
3.11 Uncertainty, Counting
The component of measurement uncertainty attributable to the random nature of radioactive decay
and radiation counting.
3.12 Uncertainty, Standard
An estimate of the measurement uncertainty expressed as one standard deviation.
3.13 Uncer .Minded
An estimate of the uncertainty Uof 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.
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4.1 Moisture
Moisture associated with the sample residue may interfere with this method. Some salts in the dried
residue may be hygroscopic. Proper drying of the sample residue and mass accuracy are essential to
ensure accurate application of correction for attenuation of radiation.
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4.2 Volatility
Radionuclides that are volatile under the sample preparation conditions of this method will not be
reliably measured (e.g., tritium and radioiodine).
4.3 Static charge
Elevated and unstable count rates may be observed in very dry samples due to the accumulation of
static charge causing count rates above the level of radioactivity that is actually present. Accumulation
of static charge may occur especially when conditions of low humidity exist in the laboratory.
4.4 Non-uniform sample residues
Non-uniformity in preparation of the sample residue relative to preparation of the standards used for
calibration interferes with the accuracy and precision of the method.
4.5 Sample re s i due th i c Ik in e s s
Sample residue thickness on the planchet needs to be no more than 5 mg/cm2 for gross alpha
determination and no more than 10 mg/cm2 for gross beta determination.
4.6 Callii birant
Alpha and/or beta energy differences between the radionuclides in the sample and the standards used
for the detection efficiency and crosstalk calibrations of the detector can result in bias in the alpha
and/or beta activity determinations.
4.6.1 Alpha Calibrations
For alpha calibrations, thorium-230 is the preferred calibrant. If natural uranium is used as the calibrant
in alpha calibration, progeny will include the beta emitters Th-234 and Pa-234m which can interfere with
the determination of crosstalk on the beta plateau and impact the calibrated alpha-to-beta crosstalk
values.
4.6.2 Beta Calibrations
For beta calibrations, strontium-90/yttrium-90 is the preferred calibrant solution; cesium-137 beta
decays to stable barium-137 and metastable barium-137 (Ba-137m). Metastable barium-137 has a half-
life of about 150 seconds and further decays to stable barium-137 with emission of gamma rays and
conversion electrons. Analysts using cesium-137 as a beta calibrant need to correct for the effect of the
conversion electrons (which represent about 9.5% of cesium-137 emissions). If the primary beta emitter
in samples is expected to be cesium-137, then cesium-137 is the preferred calibrant.
4.7 Crosstalk
Crosstalk occurs when alpha decays are misclassified as beta counts and vice versa. It is affected by
nuclide characteristics (decay mode and energy), the physical configuration used for counting (i.e.,
composition and thickness of solids), and characteristics and capabilities of the detection system.
Crosstalk cannot be completely eliminated, but it can be minimized through appropriate adjustment of
the alpha and beta discriminators in the instrument set-up. Results are corrected for crosstalk based on
measurements of misclassification during calibration.
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.
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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 the 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 a concentric ring) with a raised wall to contain the sample
being evaporated.
NOTE: Always use the same type planchet for calibration and sample determinations in order to
maintain the same geometric configuration.
6.3 Electric hot plate
6.4 Drying oven/heat lamp
A drying oven capable of maintaining a temperature of 105 °C + 2 °C. Alternately, heat lamps may be
used if a drying oven is not available.
6.5 Desiccator
Beakers
Beakers of various sizes as appropriate for sample preparation.
6.7 Pipettes
Pipettes of various sizes.
6.8 Analytical balance
The analytical balance should have a readability of 0.1 mg.
7 I. • i us up-! -i j i ii •" if« -
Analytical reagent grade or better chemicals should be used. Commercial reagents are often not tested
for trace radioactivity. Therefore, analysts are cautioned 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.
7.1 Distilled/deic water
Distilled or deionized water having minimum resistivity of 10 MQ/cm at 25 °C.
7.2 Nitric Acid
Nitric acid, HN03, concentrated (16 M).
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7.3 Nitric Acid,, 1 M
Prepare by adding about 63 mL 16 M nitric acid to approximately 900 mL distilled/deionized water and
diluting to a 1000-mL volume.
7.4 Callii birants
National Institute of Standards and Technology (NIST)-traceable thorium-230 or natural uranium
solutions (for alpha calibrations), and strontium-90/yttrium-90 solution or cesium-137 (for beta
calibrations). See Section 4.6 for cautions regarding the use of natural uranium and cesium-137 as
calibrants. After preparing a working solution from a 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.
NOTE: Be cognizant of potential volatility losses if cesium-137 is used as a beta calibrant. If a laboratory
flames prepared samples to mitigate potential interference of hygroscopic salts, analyze for gross beta
activity before the flaming procedure is performed.
NOTE: Prepared standards and working solutions should be assigned unique identification numbers
traceable to the original standards and labeled with expiration dates.
3 ! -i i ,| ! ' • mi . 1! b i * 11 1 i 1111 ¦ '
Containers
Collect samples in glass or plastic containers. The gross alpha/beta analysis is a screening test and
subsequent analyses for Ra-226, Ra-228 and uranium may be required. Thus, 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. Sampling bottles must be contamination free. Consider
the possibility of radioactivity deposition on container and equipment surfaces. Thus, the laboratory
should have a standard operating procedure for cleaning sample containers before they are used.
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
radioactive-free 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 sample pH 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.
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8.4 I served 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: For states that require gross alpha testing within 48 hours of samples collection, samples need to
be received by the laboratory within 24 hours.
NOTE: Screen sample preservatives used by the laboratory (or by field samplers) for radioactive content
by lot number prior to use to verify that preservatives do not introduce radioactive contamination.
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 needs to have appropriate segregation procedures in place to prevent cross
contamination of samples.
9 Quality Control
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 Initial 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).
9.1,1,1 Demonstration of Low Contamination
Contamination due to sample processing is assessed by counting at least four LRBs (Section 3.7)
prepared in a blank solids matrix, preferably consisting of either tap water solids (TWS) or synthetic
water solids (SWS - See Section 15: SOP for the preparation of radiochemistry SWS matrix; also see
Section 11.3.3). For drinking water, the LRB volume needs to 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 required gross alpha particle activity detection limit of 3 pCi/L and
below the required gross beta detection limit of 4 pCi/L.
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9.1.1.2 Demonstration of Accuracy
Initial demonstration of accuracy is verified by counting at least four LFBs (Section 3.6) prepared in a
blank solids matrix, preferably consisting of either tap water solids (TWS) or synthetic water solids (SWS
-Section 15; see also Section 11.3.3). Fortify with Th-230 (or natural uranium) and Sr-90/Y-90 (or Cs-137)
standards at activity levels between the maximum contaminant levels (MCLs) and the required DLs. The
recommended fortification level is about 3 to 5 times the DL. LFBs are prepared and handled like
samples following the procedure described in Section 11. Calculate the average recovery for the LFBs to
demonstrate method accuracy. The average recovery must be within ± 30% of the known amount of
added radioanalyte.
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. DL studies for gross alpha and
gross beta are performed to demonstrate that a laboratory is capable of meeting the regulatory DLs
over a range of solids. After calibrating the instrument as described in Section 10, prepare seven LFBs
using a blank matrix, preferably consisting of either tap water solids (TWS) or synthetic water solids
(SWS - Section 15; also see Section 11.3.3). Fortify with the gross alpha and gross beta radionuclide
standards at activity concentrations at or near the required detection limits defined at 40 CFR 141.25(c).
Prepare and analyze the LFBs as described in Section 11. Calculate the DLs as described in Section 12.6.
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 Excep tion for Experienced Analysts
If an analyst has at least one year of experience preparing and analyzing LRBs and LFBs for evaporative
gross alpha/beta analyses as described in Sections 9.1.1.1 - 9.1.1.2, and there have been no changes to
the instrumentation, previously documented data may be used to fulfill the IDC system background 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 in different
batches and counted on nonconsecutive days can be used to assess sample processing contamination
and the data for at least four LFBs in different batches and counted on nonconsecutive days can be used
to assess accuracy. The amount of the radionuclide standard added to the sample batch LFBs should
follow the guidance described in Section 9.1.1.2.
9,2 Ongoing QC Criteria
This section summarizes ongoing QC criteria that must be followed when processing and analyzing
drinking water compliance samples.
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9.2.1 Calibration and Background Checks
The calibration stability and background of each detector used to count analytical samples or QC
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 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 calibration stability, each day prior to sample counting, run alpha and beta QC check sources.
The check sources, alpha and beta-emitting radionuclides, do not have to be NIST-traceable but must
have well documented count rates. Count each check source long enough to obtain about 10,000 counts
(1% counting uncertainty). Record and monitor the counts on control charts.
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 counts for each detector via control charts.
9.2.1,3 Post-run Calibration Stability and Background Checks
After completion of a sample counting batch, run alpha and beta QC check sources 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 Co ir re ct i ve Act i o n
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 QC Options for Automated Systems
If a gas proportional counter measures samples sequentially with an automatic sample changer, it is
possible that the batch size combined with a lengthy count time will create a sample counting set that
requires several days to complete. In such cases, it is permissible to arrange the batch order so that a
batch QC sample fortified with a known activity (e.g., an LFB, Section 9.2.6) and a QC sample that is not
expected to have any measureable activity (e.g., an LRB, Section 9.2.5) are counted at the end of each
24-hour period. The LFB would thus substitute as the calibration stability check source and the LRB
would substitute as the instrument background check. If these QC samples meet their acceptance
criteria, then it may be assumed that little or no change in the calibration or background have occurred
while samples were being measured.
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9.2.5 Laboratory Reagent Blank (LRB)
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 uncertainty to the analytical
results. Ensure that LRB activities do not exceed regulatory DLs 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.
9.2.6 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. The activity level added to the LFB should be between
the MCL and required detection limit. Accuracy as percent recovery must be within ±30% of the amount
of activity added. If the LFB fails to meet the recovery criterion, reanalyze it. If the reanalysis fails,
prepare and analyze a new LFB. Record and monitor LFB recoveries on control charts.
9.2.7 Laboratory Fortified Sample Matrix (IUFSM)
Prepare one LFSM (Section 3.8) per preparation batch. Spike the LFSM with gross alpha and gross beta
standards at activities that are approximately 10 times the anticipated level in the samples or at least 10
times the DL (i.e., spike at least 30 pCi/L for gross alpha and 40 pCi/L for gross beta). Accuracy as percent
recovery must be within ±30% of the amount of activity added. If the LFSM fails to meet the recovery
criterion, reanalyze it. If the reanalysis fails, re-prepare the sample batch 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.
9.2.8 Duplicate (DUP) or Laboratory Fortified Sample Matrix Duplicate (LFSMD)
Batch precision is assessed through preparation of either a DUP (Section 3.4) or, if non-detects are
frequent, 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 12.7. A DUP or
LFSMD that fails the batch precision requirement needs to be reanalyzed. If the reanalysis fails, it may
indicate a lack of sample homogeneity. Re-prepare the sample batch provided sufficient volume is
available. Otherwise, a new set of samples should be collected. Record and monitor RPD and NAD on
control charts.
9.2.9 Field Blank (if needed)
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.
on
10.1 Iinstirumerit Setup
Establish voltage plateaus and appropriate operating conditions as recommended by the instrument
manufacturer with a focus on minimizing crosstalk. By minimizing beta-to-alpha crosstalk, an instrument
will provide more sensitive and reliable low-level measurements for gross alpha. Perform calibration and
QC checks as described in Section 9.2.1 initially, 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).
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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. Establish control charts to monitor background counts for
changes in instrument performance.
10 „ 2 „ 1 IB a c kg iro u n d S u bt ira ct i o in
For drinking water compliance samples, include a background subtraction measurement with each
batch of samples.
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, no sample changer, 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 based on the counting time determined for a source with the
maximum allowable solids (Section 10.4). 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 counts on the longer background control chart. If the short background counts are in
statistical control of the long background (i.e., within + 3 standard deviations of the mean long
background counts), then the weekly long background count can be used for background subtraction.
10.3 Geometry Considerations
For gross alpha and gross beta measurement using gas-flow proportional counters, initial calibration
involves preparation of solid self-absorption (sometimes alternately called mass-efficiency or mass-
attenuation) curves for alpha and beta and for the determination of crosstalk. The self-absorption
curves consist of points that are well distributed throughout a mass range. The geometry of the
calibration sources used for preparing the self-absorption/cross-talk curves needs to be the same as that
of the prepared sample and QC sample planchets (i.e., prepare and mount calibration sources in the
same manner as samples).
2ta Particle Self-Absorption (Mass Efficiency) Curves
Prepare separate alpha and beta particle self-absorption curves by plotting the efficiency of the
radionuclide standard (as net cpm/dpm) along the y-axis vs. the sample residue mass (in mg) along the
x-axis. In general, the laboratory's tap water can be used in preparing efficiency standards for drinking
water analyses. However, if the laboratory's tap water has a low solids content, or is not representative
of samples that will be analyzed, then the laboratory should establish a matrix that facilitates
intercomparison of results among laboratories. The SWS matrix described in Section 15 (also see Section
11.3.3) may be used as an alternative in place of tap water.
10.4.1 Dissolved Solids Ranges
Determine the dissolved solids (in mg/L) in the tap water or SWS matrix that will be used as the matrix
by adding a known quantity of the water in a tared test planchet and evaporating to dryness. Weigh the
test planchet and determine the final weight of dissolved solids residue. Use this value to determine the
volumes needed to obtain the residue weight ranges for preparing the alpha and beta self-absorption
11
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curves. As an example, if 5 mL of water yields 2.5 mg solid residue after evaporation, the volume of
water needed to provide a 100 mg residue would be 200 mL [(100 mg/2.5 mg) x (5 mL)].
NOTE: For an alpha self-absorption curve, Th-230 or natural uranium calibration standard is added to
varying size aliquots of tap water or SWS matrix, such that the evaporated residue weights vary between
0 and approximately 100 mg (appropriate masses for a 2-inch counting planchet).
NOTE: For a beta self-absorption curve, Sr-90/Y-90 or Cs-137 is added to varying size aliquots of tap
water or SWS matrix, such that the evaporated residue weights vary between 0 and approximately 200
mg (appropriate masses for a 2-inch counting planchet).
10.5 Preparation of Standards
Prepare each alpha and beta efficiency standard by adding calibration standard, the appropriate volume
of tap water or SWS matrix, and a few mL 16 M HN03 to a beaker and evaporate to near dryness on a
hot plate. Add about 10 mL 1 M HN03 (or higher concentration) to the beaker in 3-4 mL aliquots
(separately) and swirl to dissolve the residue. Transfer the solution in small portions to a tared counting
planchet, rinsing with a small volume of HN03 after each addition to ensure quantitative transfer.
Evaporate each portion in the planchet until only a residual amount of liquid remains before addition of
the next portion. Evaporate to dryness after all portions from the beaker have been added. Transfer the
planchet to an oven at 105 °C ± 2 °C and fully dry the residue for at least 1 hour (or alternately, dry
under a heat lamp). Remove from the oven, cool in a desiccator and weigh. Repeat the cycle of drying,
cooling and reweighing until a constant weight is obtained, or until the weight change is less than 4% of
the previously measured weight.
NOTE: In order to accurately correct for self-absorption during counting in the instrument, remove the
prepared standards from the desiccator prior to analysis, allow them to equilibrate at ambient
laboratory conditions, and re-weigh to verify that mass has not changed significantly.
10.6 Counting
The prepared efficiency standards should be alpha and/or beta counted 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. A single set of reference standards prepared in this way can be
used for each counting instrument and stored for re-verification when needed.
10.7 Crosstalk
Alpha-to-beta crosstalk occurs when alpha decays are misclassified as beta counts and beta-to-alpha
crosstalk occurs when beta decays are misclassified as alpha counts. Minimizing crosstalk during
instrument set-up will help minimize the corrections that need to be applied to samples and optimize
the accuracy and uncertainty of the measurement. Determination of crosstalk is instrument-dependent
and needs to be performed along with preparation of self-absorption curves.
erification
Annual verification of self-absorption (mass-efficiency) calibration and determination of crosstalk are
required. The accuracy of each curve is re-verified by measuring at least three of the prepared solids
standards (Section 10.5) that were used to generate the original curve. The standards should span the
range of weights that were used to prepare the curve. For the re-verification measurement to be
acceptable, the original measurement of a solids standard must lie within the range defined by the
uncertainty of the re-verified solids standard's measurement calculated at the 95% confidence level.
12
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NOTE: Evaluate alpha and beta check source standards after instrument repair and after gas bottle
changes. If check source results indicate 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 by preparing new self-absorption curves. Preparation of the new curves can
be performed using the stored solids standards.
11 Pre
11.1 Vei aparation and Counting Requirements
Verify sample preparation and counting requirements for the gross alpha determination as discussed in
Section 1.7.
11.1.1 Short-lived Radionuclides
If the contribution of radium-224 and other short-lived radionuclides to the gross alpha activity is
desired, prepare and analyze samples within 48 hours after the samples have been collected.
11.1.2 Radium-226
If radium-226 gross alpha (without contribution of radon ingrowth) is desired, hold the samples for 2-3
weeks (allowing for radium-224 decay), then prepare and count as soon as possible.
NOTE: Keep in mind that drinking water compliance with the gross alpha 15 pCi/L regulation excludes
alpha activity contributed by radon and uranium, thus the need to count samples as soon as possible
after preparation.
11.2 Sample Volume
The sample volume used for the gross alpha and gross beta analysis may be limited by the solids in the
sample. The sample size should be adjusted so that the solid residue on the planchet is < 100 mg (for
alpha only, or alpha and beta determination) or < 200 mg (for beta only determination). The analyst
should verify by calculation that the required DLs can still be achieved. All samples must be counted for
sufficient time to ensure the DLs can be met.
NOTE: It is recommended that the analyst evaporate an aliquot of preserved sample, transfer it to a
tared planchet, dry it and weigh the solids to obtain an estimate of the dry residue that will be present.
11.3 Evaporation Procedure
Shake the preserved sample to suspend any solids and ensure that a representative aliquot will be used.
11.3.1 Aliquot
Measure the appropriate volume required into a beaker that has sufficient capacity to prevent loss of
sample due to spattering as it dries.
11.3.2 Evaporate
Evaporate the aliquot to near dryness, but do not allow the sample to go completely dry. During the
evaporation process, rinse the walls of the container with 2-3 mL of 1 M HN03 at least twice to ensure
no residue is left on the container walls.
NOTE: Alternate concentration levels of HN03 are permissible.
11.3.3 Mitigate Chloride Salts
Chlorides will attack stainless steel and increase the sample solids and no correction can be made for
those added solids. The SWS matrix that may be used to prepare QC samples and efficiency calibration
13
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standards contains some chloride salts. Chloride salts can be converted to nitrate salts by acidifying the
samples to pH < 2 using 16 M HN03.
11.4 Transfer to Planchet
Add about 10 mL 1 M HN03, or preferably HN03 at a higher concentration (see Note below), to the
beaker in 3-4 mL aliquots (separately) and swirl to dissolve any residue. Transfer the solution in small
portions to a tared planchet, rinsing with a small volume of HN03 after each addition to ensure
quantitative transfer. Evaporate each portion so that a residual amount of liquid remains before
addition of the next solution. This helps to ensure that the final deposition of solids will be uniform.
Evaporate to dryness on the planchet after all portions from the beaker have been added.
NOTE: 1 M HN03 may not be sufficient to solubilize the solid residue; therefore, the analyst is
encouraged to use a more concentrated nitric acid solution to enhance solubility if needed.
11.5 Dry to Constant Weight
Dry the sample residue in a drying oven at 105 °C ± 2 °C for at least 1 hour (or alternately, dry under a
heat lamp), cool in a desiccator, and weigh. Repeat the cycle of drying, cooling and reweighing until the
weight change is less than about 4% of the previously measured weight. As noted in Section 10.5, in
order to accurately correct for self-absorption during counting, remove the prepared samples from the
desiccator prior to analysis, allow them to equilibrate at ambient laboratory conditions, and re-weigh to
verify that the mass has not changed significantly.
NOTE: If constant weight cannot be obtained due to the presence of hygroscopic salts, flame the
planchet to a dull red color. If hygroscopic salts are an issue, and to minimize the loss of volatile beta-
emitting radionuclides, the beta activity may be determined after the prepared samples are dried at 105
°C for 2 hours. Samples can then be flamed and counted for alpha activity.
NOTE: Volatile radionuclides (e.g., tritium, iodine, carbon, technetium) may be lost at the elevated
temperatures required to mitigate hygroscopic salts. As such, the flaming procedure should be
considered an option of last resort for gross alpha/beta determination.
i I •; iib "I .lions
Modern detector systems offer multiple counting options such as counting on separate plateaus and
simultaneous alpha-beta counting on the beta plateau. There are advantages and disadvantages
associated with the various options. The following equations provide general guidance for calculating
results.
12.1 Count Rate
The net count rate, Rx, for any single count (sample, background, standard) is generically calculated as
R
x ts tB
where
Rx = Net count rate (x = a or (B) 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
14
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u(fix) —
M
Nx Bx
TT + TT
s lB
2,
The square of the standard uncertainty is denoted by u (Rx).
Nx , Bx
u\Rx) = -$; + -i
s lB
12.2 Efficiency
Calculate the individual efficiencies of the Th-230 (or natural uranium) and Sr-90/Y-90 (or Cs-137):
Rx
£xm a
•"Std(*)
where
x = Alpha (a) or beta ((B)
£xm = Efficiency for x determined for mass m
Rx = Net count rate of the respective standard (a or (B) in counts per minute
^std(x) = Activity of the standard at the time of count, disintegrations per minute
12.3 Crosstalk
Crosstalk is a misclassification of alpha- and beta-produced counts. Crosstalk is mass-dependent and
thus, crosstalk correction factors need to be determined at the same time the self-absorption/mass
efficiency curves are prepared. Following the guidance in MARLAP (see Section 14, Reference 3) chapter
16:
v _ fiam
X-am ~ ~
aam "r Pam
where
Xam= alpha-into-beta crosstalk factor, determined by obtaining the counts in the alpha channel and
beta channel for a pure alpha-emitting source at a given mass, m
aam = Recorded net alpha count rate
Pam = Recorded net beta count rate due to crosstalk from the alpha-emitting source
_ af3m
(;
¦f3m Pf}r
Xpm= beta-into-alpha crosstalk factor, determined by obtaining the counts in the alpha channel and
beta channel for a pure beta-emitting source at a given mass, m
apm = Recorded net alpha count rate due to crosstalk from the beta-emitting source
Ppm = Recorded net beta count rate
Prepare separate calibration curves with the sample residue mass (in mg) along the x-axis and the mass-
dependent parameter (alpha efficiency, beta efficiency, alpha-into-beta crosstalk, beta-into-alpha
crosstalk) along the y-axis. Determine the best fit curve for interpolating efficiency/crosstalk data for
unknown samples based on their residue masses.
When the equations above are used for the crosstalk factors, the alpha and beta counting efficiencies are
determined during calibration from the combined counts in both the alpha and beta channels. Be aware
that there are alternative definitions of crosstalk factors in other published methods that require each
efficiency to be determined from only the counts in its own channel.
15
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12.4 Gross Alpha Actiiviit illations
Calculate the gross alpha activity concentration for each sample.
12.4.1 Sa implle Counted only at the Alpha Voltage Plateau
_ R
-------
l(l-Xp)2u2(Ra) + X2u2(Rp)
u(cAa) = , 7Y" and U95% = 1.96 x u(cAa)
Z.ZZ X £a X V X — Aa — ApJ
where
u(.cAa) = Gross alpha standard counting uncertainty ("one-sigma") in pCi/L
U95o/0 = Gross alpha expanded counting uncertainty (95 % confidence) in pCi/L
Xp = Beta-into-alpha crosstalk factor (for a given mass)
u2(Ra) = Square of the standard uncertainty of Ra, calculated as in Section 12.1
u2(Rp) = Square of the standard uncertainty of Rp, calculated as in Section 12.1
Xa = Alpha-into-beta crosstalk factor (for a given mass)
2.22 = Conversion factor from dpm to pCi
sa = Alpha efficiency (for a given mass), determined from graph of efficiency versus solids residue mass
per cm2 of planchet area, (cpm/dpm)
V = Volume of sample aliquot, in liters
1.96 = Coverage factor for 95 % level of confidence
12.5 Gross Beta Activity Calculations
Calculate the gross beta activity concentration for each sample.
12.5.1 Sa iinplle Counted on Beta Voltage Plateau
If alpha activity is less than the detection limit when a sample is counted at the beta voltage plateau, the
gross beta activity concentration can be determined from the following equation:
Ap SpXVx 2.22
where
Cap = Gross beta activity concentration in pCi/L
Rp = Net count rate at the beta voltage plateau
Sp = Beta efficiency, determined from graph of efficiency versus solids residue mass per cm2 of planchet
area, (cpm/dpm)
V = Volume of sample aliquot, in liters
2.22 = Conversion factor from dpm to pCi
The gross beta standard counting uncertainty and expanded counting uncertainty (95 % confidence) are
calculated as:
u(Rp)
u{.CaP) = £f}XVx 2 22 Und U95% = 1,96 X U(^
where
u(cAp) = Gross beta standard counting uncertainty ("one-sigma") in pCi/L
U95o/0 = Gross beta expanded counting uncertainty (95 % confidence) in pCi/L
u(Rp) = Standard uncertainty of Rp, calculated as in Section 12.1
Sp = Beta efficiency, determined from graph of efficiency versus solids residue mass per cm2 of planchet
area, (cpm/dpm)
V = Volume of sample aliquot, in liters
2.22 = Conversion factor from dpm to pCi
17
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1.96 = Coverage factor for 95 % level of confidence
NOTE: If prepared QC samples (e.g. LFBs, LFMSs) contain an alpha-emitting standard, crosstalk may
occur. Adjust gross beta activity and uncertainty calculations accordingly to account for crosstalk. Where
possible, minimize beta-to-alpha crosstalk to levels that provide sensitive and reliable low-level
measurements for gross alpha (e.g. ~0.1%).
12 „ 5 „ 2 S i in u II t a in e o u s C o u in t i n g
For simultaneous counting, incorporating crosstalk, the gross beta activity concentration (in pCi/L) is
calculated using the crosstalk factors described in Section 12.3:
(1 -Xa)Rp-XaRa
Cap 2.22 x £p x V x (1 - Xa - Xp)
where
cAp = Crosstalk-adjusted gross beta activity concentration, in pCi/L
Xa = Alpha-into-beta crosstalk factor (for a given mass)
Rp = Net count rate recorded in the beta channel, in counts per minute
Ra = Net count rate recorded in the alpha channel, in counts per minute
Xp = Beta-into-alpha crosstalk factor (for a given mass)
2.22 = Conversion factor from dpm to pCi
£p = Beta efficiency (for a given mass), determined from graph of efficiency versus solids residue mass
per cm2 of planchet area, (cpm/dpm)
V = Volume of sample aliquot, in liters
Calculate the gross beta standard counting uncertainty and expanded counting uncertainty (95 %
confidence) as follows:
l(l-Xa)2u2(Rp) + X2u2(Ra)
= 2.22xefxVx(l-Xa-Xf) """ = ^
where
u(cAp) = Gross beta standard counting uncertainty ("one-sigma") in pCi/L
U95o/0 = Gross beta expanded counting uncertainty (95 % confidence) in pCi/L
Xa = Alpha-into-beta crosstalk factor (for a given mass)
u2(Ra) = Square of the standard uncertainty of Ra, calculated as in Section 12.1
u2(Rp) = Square of the standard uncertainty of Rp, calculated as in Section 12.1
Xp = Beta-into-alpha crosstalk factor (for a given mass)
2.22 = Conversion factor from dpm to pCi
£p = Beta efficiency (for a given mass), determined from graph of efficiency versus solids residue mass
per cm2 of planchet area, (cpm/dpm)
V = Volume of sample aliquot, in liters
1.96 = Coverage factor for 95 % level of confidence
12.6 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 9.1.1.3. From the definition, the
equation in Section 12.6.1 can be derived (see reference 9 in Section 14).
18
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12.6.1 IDIL Equation
The single sample drinking water detection limit is calculated as:
1.962
x
DL =
sxV x 2.22
where
ts = Sample count time, in minutes
tB = Background count time, in minutes
B = Number of background counts
s = Efficiency, determined from graph of efficiency versus solids residue mass per cm2 of planchet area
(cpm/dpm)
V = Volume of sample aliquot, in liters
2.22 = conversion factor from dpm to pCi
Determine sample detection limits for both gross alpha and gross beta to confirm compliance relative to
the required detection limits.
12.6.2 DL Study
The DL study described in Section 9.1.1.3 consists of seven replicate fortified tap water (or synthetic
water solids) samples 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:
And
Xi =—T2
_ 1
j=i
„ n
1.96
£(*« -*.)2
j=i
Where
n = Number of replicate measurements
= Activity fortified in sample replicates
To be deemed acceptable, the value of x2 should be less than or equal to the 99th percentile of the^2
distribution with (n-1) degrees of freedom.
12.7 Relative Percent Difference Calculation
As described in Section 9.2.8, relative percent difference (RPD) is used to evaluate precision of duplicate
measurements. The RPD is calculated as
RPD = )As~Adup}, X 100 %
(As+Adupy
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
19
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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
u2(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, prepare a new sample and
duplicate.
13 Pollution Prevention
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
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. Friedlander, G., Kennedy, J.W., and Miller, J. Nuclear and Radiochemistry, John Wiley and Sons,
Inc., New York, New York (1964).
5. Youden, W.J. and Steiner, E.H. Statistical Manual of the Association of Official Analytical
Chemists (1975).
6. Dixon, W.J. and Massey, F.J. Introduction to Statistical Analysis, 3rd Edition. McGraw-Hill (1969).
7. Harley, J.H., Hallden, N.A., and Fisenne, I.M. "Beta Scintillation Counting with Thin Plastic
Phosphors," Nucleonics, 10:59 (1961).
8. Hallden, N.A., and Harley, J.H. "An Improved Alpha-Counting Technique," Analytical Chemistry,
32:1860 (1960).
9. Procedure for Safe Drinking Water Act Program Detection Limits for Radionuclides, USEPA 815-B-
17-003. April 2017.
NAD =
Ms Adup
20
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i '. 'I ' !f« >i I 'i .. | • 1 'ii> 'i i ' >! !' ''"Ji: ill i.l i . ' , . I Si >!¦' >! « VS)
Matrix
15.1 Puirpo :)pe
This SOP describes the preparation of a synthetic water solids (SWS) matrix used as an alternate to tap
water in developing self-absorption curves for gross alpha and gross beta analysis.
15.2 Summairy of Method
Salts are added to deionized water conforming to ASTM Type I or II requirements. The prepared SWS
matrix is allowed to equilibrate for at least 16 hours. The result is a 1-liter sample of approximately 240
ppm of total dissolved solids.
15.3 Health and Safety
Appropriate laboratory safety procedures for handling reagents and chemicals should be followed.
15.4 Definitions
15.4.1 ppm
Parts per million is equivalent to mg/L
15..4.2 SWS
Synthetic Water Solids
15..4.3 IDS
Total Dissolved Solids
15.5 IE q u i p inn e in t a in d Suppl i e s
15.5.1 IB a II a nee
Top-loading balance, maximum allowed mass at least 10,000 g with readability to 0.01 g (10 mg)
15.5.2 Mass Calibration Weights
ASTM Class 2 or equivalent calibration weight set with masses of at least 1 g and up to 50 g
15,.5,.3 Pipettes
Pipettes - volumetric, to deliver, 1-mL and 4-mL
15.5.4 Spatula
15.5.5 Magnetic Stir Plate
15.5.6 Magnetic Stir Bars
15 „ 5 „ 7 ¥o I u m etric IF II a s Iks
250-mL, 1.0-L, and 4.0-L volumetric flasks, glass or plastic, calibrated 'to contain' (TC), Class A
15.5.8 Containers
1-L and 4-L containers, glass or plastic, to store prepared SWS matrix solutions
15.5.9 Weigh Boat
Weighing boats or dishes, polystyrene (40 x 40 x 8 mm), or equivalent
21
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15.5.10 IF i II t e r i n g IE q u i p irri e n t
15.5.11 Filters
0.45 nm pore diameter membrane filters, or equivalent.
15.6 Reagents
15.6.1 Purity
All reagents should be ACS grade or better.
NOTE: The following reagents may be substituted with equivalent salts of varying states of hydration.
For example: anhydrous barium chloride may be substituted for barium chloride dihydrate, provided the
proper conversion has been made to adjust the water content of the salt for the elements of interest.
The ppm content of each of the salts is shown in Section 16, Table 1.
CAUTION: ONLY the hydration state of the salts may be varied.
15.6.2 Alluiminuirn
Aluminum Chloride Hexahydrate
15.6.3 Barium
Barium Chloride Dihydrate
15.6.4 Calcium
Calcium Nitrate Tetrahydrate
15.6.5 Iron
Iron (III) Chloride
15.6.6 Magnesium
Magnesium Sulfate Heptahydrate
15.6.7 Phosphate
Sodium Phosphate Dibasic
15.6.3 Bicarbonate
Sodium Bicarbonate
15.6.9 Sulfate
Sodium Sulfate, Anhydrous
15.6.10 Water
Reagent Water - ASTM Type I or Type II
15.7 Interferences
None.
atiioins
Ensure balance is calibrated and that daily/monthly performance checks are performed as specified by
the laboratory's SOP(s) using acceptable weights for the masses to be measured (1 - 25 g).
15.9 Sampll Preservation
Once prepared, let the solution stand for at least 16 hours prior to filtration.
22
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15.10 Procedure
15.10.1 Stock Standard Preparations
Prepare each of the following stock standard reagents separately using reagent water and 250-mLTC
volumetric flasks.
NOTE: The masses identified need to be adhered to as closely as practical with no more than 10%
variance in the mass of the salt added. Therefore, a 1.0 g addition may be allowed a tolerance from 0.9
to 1.1 g. The determined total dissolved solids of the solution and the concentration of the contaminant
will change accordingly. Document all weights used.
15.10.1.1 Aluminum Chloride Hexahydrate, 4 mg/mL
Dissolve 1.0 g of AICI3-6H20 in a small volume of reagent water, then dilute to 250 mL with reagent
water
15.10.1.2 Barium Chloride Dihydrate, 4 mg/mL
Dissolve 1.0 g of BaCI2-2H20 in a small volume of reagent water, then dilute to 250 mL with reagent
water
15.10.1.3 Calcium Nitrate Tetrahydrate, 40 mg/mL
Dissolve 10 g of Ca(N03)2-4H20 in a small volume of reagent water, then dilute to 250 mL with reagent
water
15.10.1.4 Iron (III) Chloride, 4 mg/mL
Dissolve 1.0 g. of FeCI3 in a small volume of reagent water, then dilute to 250 mL with reagent water
15.10.1.5 Magnesium Sulfate Heptahydrate, 100 mg/mL
Dissolve 25 g of MgS04-7H20 in a small volume of reagent water, then dilute to 250 mL with reagent
water
15.10.1.6Sodium Bicarbonate, 30 mg/mL
Dissolve 20 g of NaHC03 in a small volume of reagent water, then dilute to 250 mL with reagent water
15.10,1, /"Sodium Phosphate Dibasic Anhydrous, 14 mg/mL
Dissolve 3.5 g of Na2HP04 in a small volume of reagent water, then dilute to 250 mL with reagent water
15.10.1.8Sodium Sulfate Anhydrous, 60 mg/mL
Dissolve 15 g of NaS04 in a small volume of reagent water, then dilute to 250 mL with reagent water
15.10.2 Prepare SWS Matrix (1-L Volume Option)
To constitute 1 L of SWS matrix, add 1 mL of each stock standard reagent prepared in Sections 15.10.1.1
- 15.10.1.8 to a 1-L glass or plastic TC volumetric flask and dilute with reagent water to 1 L, swirling or
stirring to mix.
15.10.3 Prepare SWS Matrix (4-L Volume Option)
To constitute 4 L of SWS matrix, add 4 mL of each stock standard reagent prepared in Sections 15.10.1.1
- 15.10.1.8 to a 4-L glass or plastic TC volumetric flask and dilute with reagent water to 4 L, swirling or
stirring to mix.
15.10.4 Settle and Filter
Allow prepared solution to stand for at least 16 hours, then filter. Transfer filtered solution to an
appropriate 1-L or 4-L glass or plastic container.
23
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15.10.5 Determine IDS
Determine the total dissolved solids (TDS) of the prepared solution and label the container.
15.11 Data Acquisition, Calculations and Data Reduction
Record preparation of the SWS matrix solution and document the TDS level as specified in the
laboratory's SOP(s).
15.12 Quality Control
15.12.1 Quality Assurance
Maintain Quality control in accordance with the requirements in the laboratory's Quality Assurance
program.
15.12.2 IDS Target
The SWS matrix TDS level should be within + 20 ppm of the target value of 239 ppm.
15.13 Waste Management and Pollution Prevention
The SWS matrix contains no materials that are considered wastes of regulatory concern for disposal.
Dispose of SWS stock standard reagents in accordance with the testing laboratory's procedures and
state regulatory requirements.
15.14 Records Management
All records generated by this procedure should be in accordance with the laboratory's Quality Assurance
program. Maintain records developed in the preparation of the SWS matrix for inspection.
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16 Tables
Reagent
Analyte
Analyte/Compound
Mass Ratio
Mass of
Compound, g
ppm of
Reagent in
SWS Matrix
ppm of
Analyte in
SWS
AICI3-6H20
Aluminum
0.11
1
4.00
0.45
AICI3-6H20
Chloride
0.44
1
1.76
BaCI2-2H20
Barium
0.56
1
4.00
2.25
BaCI2-2H20
Chloride
0.17
1
0.68
Ca(N03)2-4H20
Calcium
0.17
10
40.00
6.79
Ca(N03)2-4H20
Nitrate
0.53
10
21.03
Na2HP04
Sodium
0.32
3.5
14.00
4.53
Na2HP04
Ortho-
phosphate
0.67
3.5
9.37
FeCI3
Iron
0.34
1
4.00
1.38
FeCI3
Chloride
0.66
1
2.62
MgS04-7H20
Magnesium
0.10
25
100.00
9.86
MgS04-7H20
Sulfate
0.39
25
38.97
NaHC03
Sodium
0.27
20
80.00
21.89
NaHC03
Carbonate
0.71
20
57.14
NaS04
Sodium
0.32
15
60.00
19.42
NaS04
Sulfate
0.68
15
40.58
Total Dissolved
Solids
238.71
17 References
1. 40 CFR 141. National Primary Drinking Water Regulations
2. Protocol for the Approval of Alternate Test Procedures for Analyzing Radioactive Contaminants
in Drinking Water, USEPA 815-R-15-008. February 2015.
3. ASTM D1193-99. Standard Specifications for Reagent Water. ASTM International.
Conshohocken, Pennsylvania. March 1999 (editorial change October 2001).
4. Manual for the Certification of Laboratories Analyzing Drinking Water, Criteria and Procedures
Quality Assurance, 5th Ed., USEPA 815-R-05-004, January 2005.
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