SEPA
United States
Environmental Protection
Agency
Protocol for the Evaluation of Alternate Test
Procedures for Analyzing Radioactive Contaminants
in Drinking Water
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Office of Water (MS-140)
EPA 815-R-23-001
May 2023
Questions concerning this document should be addressed to:
William A. Adams, PhD
U.S. EPA, Office of Ground Water and Drinking Water, Standards and Risk Management Division,
Technical Support Branch,
26 W. Martin Luther King Dr. Cincinnati, OH 45268
Phone:(513)569-7656
adairns.willlliiairnPepa.gov
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Foreword
This document provides guidelines for the evaluation of radioactive contaminant analytical methods
under EPA's Drinking Water Alternate Test Procedure (ATP) Program. The Drinking Water ATP Program
only evaluates alternate methods for analytes regulated under the Safe Drinking Water Act (SDWA), the
program will not evaluate methods for unregulated or secondary contaminants. Additionally, devices
and equipment will only be evaluated as part of a complete method and not evaluated alone. This
drinking water ATP protocol provides guidance for the modification or development of drinking water
methods for compliance monitoring. It incorporates current recommendations for method validation
that have been developed by the Forum on Environmental Measurements. Under the Drinking Water
ATP Program, applicants are required to demonstrate that the alternate method being proposed is an
equally effective procedure, relative to an existing EPA-approved method. That demonstration then
provides basis for EPA's Office of Ground Water and Drinking Water to consider, independent of the ATP
evaluation, the approval a particular method.
This protocol provides basic information on the criteria the Agency generally uses in deciding whether a
method is suitable for evaluation under the Drinking Water ATP Program and the analyses that are
generally needed to demonstrate method equivalency. In this protocol, applicants are also directed to
demonstrate adequate ruggedness of the drinking water ATP through sufficient multi-laboratory
validation to support EPA's consideration of their use at a national level.
EPA anticipates that the standardized procedures described herein will expedite the processing of
drinking water ATP reviews, encourage the development of innovative technologies, and enhance the
overall utility of the EPA- approved methods for compliance monitoring under the National Primary
Drinking Water Regulations.
Disclaimer
The Office of Ground Water and Drinking Water reviewed and approved this document for publication.
Neither the U.S. government nor any of its employees, contractors, or their employees make any
warranty, expressed or implied, or assumes any legal responsibility for any third party's use of, or the
results of such use, of any information, apparatus, product, or process discussed in this protocol. The
mention of company names, trade names, or commercial products does not constitute an endorsement
or recommendation for use.
This document does not alter, substitute for, establish or affect legal obligations under Federal
regulations. This document is not a rule, is not legally enforceable, and does not confer legal rights or
impose legal obligations on any federal or state agency or on any member of the public. Interested
parties are welcome to suggest procedures that are different from what's recommended in this
document. EPA reserves the right to change this protocol without prior notice.
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Contents
Foreword ii
Disclaimer ii
1 Introduction 1
1.1 Background and Objectives 1
1.2 Scope of Radiochemical Drinking Water ATP Process 1
2 Overview of the Drinking Water ATP Process 1
2.1 Submission (initial application and subsequent documentation) 1
2.2 Application Information 2
2.2.1 Justification for Drinking Water ATP 2
2.3 Confidential Information in Applications 2
3 Method Development and Validation Study Plan 3
3.1 Introduction 3
3.2 Development of a Validation Study Plan 3
3.2.1 Background 3
3.2.2 Study Management 3
3.2.3 Technical Approach 4
3.2.4 Identification of Critical Steps and Plans for Addressing Critical Steps 4
3.2.5 Draft Candidate Method 4
3.2.6 Radiochemical Method Validation Study 4
3.3 Approval of Validation Study Plan 4
3.4 Method Validation Study Report 4
3.4.1 Background 5
3.4.2 Study Implementation 5
3.4.3 Demonstration Data 5
3.4.4 Calculations, Data Analysis and Discussion 5
3.4.5 Conclusions 5
3.4.6 Candidate Method 5
3.4.7 Validation Study Plan 5
4 EPA Review and Approval 6
4.1 EPA Review of Candidate Method 6
4.2 Approval Recommendation 6
4.3 Joint Drinking Water Wastewater Applications 6
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5 References 6
Appendix A: ATP Applicant Process: General Checklist A-l
Appendix B: Application and Document Submission Form B-l
Appendix C: Radiochemical Method Validation C-l
Appendix D: Standard EPA Method Format D-l
Appendix E: Validation Report Template E-l
Appendix F: Calculating Theoretical Detection Limits for Radiochemical Measurements F-l
Appendix G: Procedure for Preparing the Radiochemistry ATP Drinking Water Test Matrix G-l
Appendix H: Sample Calculations H-l
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uction
1.1 Backgroui tives
Pursuant to the Safe Drinking Water Act, EPA promulgates, via publication in the Federal Register, test
procedures (analytical methods) for data gathering and compliance monitoring under National Primary
Drinking Water Regulations.
Under the Agency's Drinking Water Alternate Test Procedure (ATP) Program, an organization may
request evaluation of a method as an alternate test procedure to a method already approved in the
drinking water regulations. These alternate drinking water methods, or ATPs, will be referred to as
"candidate" methods through the remainder of this document. Devices and equipment will only be
evaluated as part of a complete method and not evaluated alone. The organization or entity seeking the
candidate method evaluation is responsible for validating the candidate method. EPA evaluates test
methods used to measure regulated contaminants in drinking water for nationwide approval. This
requires EPA to assess any candidate method in such a manner that its interlaboratory range in
accuracy, precision and detection capability can be compared to EPA-approved test methods measuring
the same target analyte(s). To be considered for approval, the candidate method must be an equally
effective procedure as the approved method (see Safe Drinking Water Act §1401(1)); that is, a method's
performance characteristics in general must be equivalent to, or better than, those of existing approved
methods for the contaminant of interest. This allows EPA to ensure that data gathered under the Safe
Drinking Water Act are comparable on a nationwide basis. Those methods that demonstrate acceptable
performance through their ATP evaluation, become candidates for an EPA approval action.
1.2 Scope of Radiochemical Drinking Water ATP Process
The protocol design described in this document is consistent with candidate method validation
requirements in other areas of chemistry but has been modified to adjust for the technical differences
between chemical and radiochemical test methods. Radiochemical test methods differ from the other
areas of analytical chemistry in several ways, including: 1) the types of detection systems used, 2) the
chemical yields for sample preparation steps are generally measured and corrected for and 3) the
detection limits (DLs) for radiochemical test methods for finished drinking water analyses are specifically
defined by Federal regulation. This validation protocol is designed to address these differences with
special attention to the manner in which accuracy, precision and detection capability are assessed for
method approval.
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Agency staff reviews the application, including justification for the candidate method provided by the
applicant, and determine whether a drinking water ATP evaluation is warranted. If the candidate
method application is accepted for consideration, the applicant then develops a validation study plan in
consultation with EPA's drinking water ATP staff. Once the study plan is approved, the applicant
performs the validation study and submits a validation study report and candidate method to the
Drinking Water ATP Program. If EPA determines that the laboratory validation demonstrates
performance equivalent to or better than that obtained with an approved method, EPA Drinking Water
ATP Program representatives will generally recommend approval by EPA senior leadership using one of
two options: 1) approval through the conventional "notice and comment" rulemaking process, or 2)
approval through the expedited method approval process. Additional information on the expedited
method approval process can be found on miking water analytical methods web page. A general
checklist of the ATP process can be found in Appendix A.
2.1 Sub inn i s s i o in (i in i t i i II i | ¦ | ¦ II i cat i o in 11 ¦ I "" II - e q u e in t d o cume in t a t i o in)
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Applicants should submit drinking water ATP applications (see Appendix IB) to the Drinking Water ATP
Coordinator. Upon receipt and acknowledgment of the application, EPA staff will assign an identification
number or name to the application. The applicant should use the identification number or name and
Appendix IB as a cover sheet for all future communications and any supplemental documentation
concerning the application.
2.2 Applicatioin IIinformatioin
Information required on the drinking water ATP application includes: the name and address of the
applicant; the date of submission of the application; the title of the proposed candidate method
including a shortened method name or number to use in the regulation and for reference; the analyte(s)
for which the ATP is proposed; a brief summary of the proposed method and the justification for
proposing the ATP. The applicant should provide all required application information and any associated
attachments for the application to be considered complete.
2.2.1 Justification for Drinking Water ATP
The applicant should provide a brief justification for why the drinking water ATP is being proposed.
Because EPA review and evaluation of proposed ATPs can entail considerable effort, EPA does not
expect to entertain evaluation of impractical methods or method modifications that fall within the scope
of flexibility already allowed in an approved method or in EPA's "Technical Notes on Drinking Water
Methods" (EPA Document No. EPA-600-R-94-173, October 1994). Examples of appropriate justifications
include but are not limited to: the candidate method successfully overcomes some or all of the
interferences associated with the approved method; the candidate method reduces the amount of
hazardous wastes generated by the laboratory; the cost of analyses or the time required for analysis is
reduced; or, the quality of the data is improved. It is highly recommended that the method developer
consult with ATP staff concerning the proposed candidate method and its justification prior to extensive
method development.
2.3 Confident >rmation in Applications
When submitting information with the proposed drinking water ATP application, the applicant may
assert a business confidentiality claim covering part or all of the information. The method for submitting
a claim is described in the Code of Federal Regulations (CFR) at 40 CFR 2.203(b). EPA staff will handle
such information according to the regulations in subparts A and B of 40 CFR Part 2. Information covered
by such a claim will be disclosed by EPA only to the extent, and by means of the procedures, set forth in
40 CFR Part 2, Subpart B. If no such claim accompanies the information when it is received by EPA, it
may be made available to the public by EPA without further notice to the business.
Specifically, in accordance with 40 CFR §2.203(b), a business may assert a business confidentiality claim
covering the information by placing on (or attaching to) the information at the time it is submitted to
EPA, a cover sheet, stamped or typed legend, or other suitable form of notice employing language such
as trade secret, proprietary, or company confidential. Confidential portions of otherwise non-
confidential documents should be clearly identified and may be submitted separately to facilitate
identification and handling by EPA. If confidential treatment is only required until a certain date, the
notice should state so accordingly. It should be noted, however, that any analytical method being
considered for approval in the Federal Register cannot itself be claimed as confidential business
information; the vendor must be prepared for the method to be published and made widely available.
If a claim of business confidentiality is later received after the information is initially conveyed as part of
an ATP application, EPA will make such efforts as are administratively practicable to associate the late
claim with copies of the previously submitted information in EPA files. However, EPA cannot ensure that
such efforts will be effective considering the possibility of prior disclosure or widespread prior
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dissemination of the information, See §2.203(c).
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3.1 Introduction
Method development and validation are the processes by which a laboratory substantiates the
performance of a method by demonstrating that the method can meet EPA's acceptance criteria and
that the method is rugged, that is, yields acceptable method performance and data quality over the
range of drinking water sample types and of laboratory conditions specified in the method. In order to
produce a method that is rugged and meets quality control acceptance criteria, the method developer
needs to have a firm understanding of the chemistry involved in the method. Because methods vary
widely in their chemistry and procedures, no definitive global guidance can be provided on how to
develop a rugged method. In general, though, all candidate methods should: (a) identify critical points of
each step in the procedure, (b) demonstrate that these critical points are satisfactorily addressed or
controlled in the method and (c) demonstrate that acceptable method performance is attained using all
procedural options specified in the method. Generally, there is an expectation that multiple,
independent laboratories or sites be used in the validation process to ensure method ruggedness.
Critical points of a method can take a variety of forms depending on the method. For example, certain
methods may require separation of an analyte at a specific pH or a narrow pH range. Thus, for the
method to be truly rugged, pH control may be required to ensure that other samples, laboratory
conditions, or chemists obtain satisfactory results using the method.
Once an application has been accepted by the Drinking Water ATP Program, the applicant should discuss
their plans to address method ruggedness with drinking water ATP staff prior to formulating the
validation study plan. Such consultation will help avoid both inadequate study plans (for example, not
enough analyses addressing critical points of the method) and study plans with unnecessary analyses.
The following sections summarize the major components of the validation study plan.
3.2 Development ion Study Plan
Prior to conducting the candidate method validation study, the applicant should prepare and submit a
detailed study plan for EPA approval. Guidelines describing the parameters that should be addressed in
a radiochemical method validation study are provided in Appendix C. Sections specific to radiochemical
methods are also identified.
3.2.1 Background
The Background section of the validation study plan should:
• Identify the candidate method.
• Include a summary of the candidate method.
• Describe the reasons for development, the logic behind the technical approach and the
advantages of the method in comparison to existing technology or methodology.
• List the analytes measured by the candidate method including corresponding Chemical Abstract
Services Registry Number (if applicable).
3.2.2 Study Management
The Study Management section of the validation study plan should:
• Identify the organization responsible for managing the study.
• Identify certified (if applicable), independent laboratories, facilities, and other organizations that
will participate in the study.
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• Delineate the study schedule following approval of the study plan.
3.2.3 Technical Approach
The Technical Approach section of the validation study plan should:
• Describe how participating laboratories will be selected.
• Explain who will prepare the test matrix and how it will be distributed.
• Specify the numbers and types of analyses to be performed by the participating laboratories in
accordance with this protocol.
• Identify specific reagents, materials, instrumentation or software required.
3.2.4 Identification of Critical Steps and Plans for Addressing Critical Steps
As mentioned previously, a properly developed and validated method recognizes and controls critical
steps in terms of the chemistry or ruggedness, or both, of the method. The applicant should identify
those parts of the procedures that could be vulnerable to technician expertise or result in poorer
performance with foreseeable departures from ideal conditions. The Plan should identify the steps that
will be taken to control these critical steps.
3.2.5 Draft Candidate Method
A draft of the candidate method should be included as a separate attachment to the validation study
plan. The draft details the step-by-step procedures of the candidate method. This includes all
equipment, reagents and materials required and data evaluation or calculation procedures. Unless the
applicant is a consensus standards organization or government organization that has their own method
format requirements, all applicants should submit the candidate method written in the standard EPA
method format (Appendix D). Applicants from organizations having their own format requirements
should compare their specific method format with the EPA method format to ensure that all sections of
the EPA method format are addressed. The 17 sections listed in Appenc of this document should be
included for all candidate methods. Recent drinking water methods published by EPA (for example,
Methods 150.3, 533, 546) may also be consulted for format and the level of detail required.
3.2.6 Radiochemical Method Validation Study
Radiochemical methods follow different procedures for validation than those methods analyzing for
organic and inorganic contaminants. Procedures specific to radiochemical methods can be found in
Appendix C.
3.3 Approval of Validati cly Plan
Once EPA is satisfied that the written method and the proposed study plan meet the criteria described
in this document, the applicant will be instructed to proceed with the method validation study.
;thod Validation Study Report
The applicant should document the results of the validation study in a formal validation study report
containing the elements described in this section. In all cases, a copy of all required validation data
should be maintained at the laboratory or other organization responsible for developing the method.
The information and supporting data in the validation study report must be sufficient to enable EPA to
determine whether the candidate method performs as well as or better than the approved reference
method.
The validation study report should contain background information and describe the study design. In
addition, the validation study report should detail the process and results of the study, provide an
analysis and discussion of the results, and present study conclusions. The approved validation study plan
should be appended to the validation study report and referenced as appropriate.
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The validation study report should identify and discuss any deviations from the validation study plan
that were made in implementing the study along with problems encountered and corrective actions. To
the extent possible, deviations should be discussed with EPA in advance of being implemented to ensure
that the deviations are appropriate.
See Appendix E for the validation study report template.
3.4.1 Background
The Background section of the validation study report describes the candidate method. The Background
section of the validation study report should:
• Include a method summary.
• Summarize the justification for the ATP evaluation and the proposed benefits the candidate
method offers to drinking water monitoring.
• List the analytes measured by the candidate method, including corresponding Chemical
Abstracts Service Registry identification.
3.4.2 Study Implementation
The Study Implementation section of the validation study report describes the methodology and
approach undertaken in the study. This section should:
• Identify the laboratories or other organizations or both that participated in the study.
• Delineate the study schedule that was followed.
• Explain how samples were collected and handled.
• Specify the numbers and types of analyses performed by the laboratory.
• Identify any problems encountered or deviations from the study plan and their resolution or
impact on study performance or results or both.
3.4.3 Demonstration Data
This section of the validation study report should include the demonstration data for the analyzed
samples. For each sample, the report should compare method performance data obtained with the
candidate method to the approved reference method performance data. Demonstration data should be
provided for samples using all procedural options specified in the method.
3.4.4 Calculations, Data Analysis and Discussion
This section of the validation study report should provide sufficient documentation of the data obtained
with the candidate method to permit an independent reviewer to verify the study results. Example
calculations are required as part of the results and should be included in the validation study report. The
test data and calculations should be electronically reported in a format compatible with Microsoft®
Office applications. The discussion should address any discrepancies between the results and the quality
control acceptance criteria.
3.4.5 Conclusions
The Conclusions section of the validation study report describes the conclusions drawn from the study
based on the data analysis discussion. The Conclusions section should contain a statement(s) regarding
achievement of the study objective(s).
3.4.6 Candidate Method
The candidate method should be appended to the validation study report. Format should follow that
specified in Appendix D.
3.4.7 Validation Study Plan
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The validation study plan should be appended to the validation study report.
4 I I i r I1"' / ! .J I I ! I
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EPA's Drinking Water ATP Program reviews the candidate methods and the validation data. If a
candidate method is determined to provide equivalent method performance relative to the reference
method, it becomes a candidate for approval by EPA senior leadership.
4.2 Appro ;oinn inn ein clatii oin
EPA will complete its review and notify the applicant of EPA's recommendation. If the candidate method
is recommended for approval, EPA will pursue formal approval using one of two options: 1) approval via
the conventional "notice and comment" rulemaking process or 2) approval via the expedited method
approval process. Find additional information on EPA's drinking water analytical methods web page .
4.3 Joint Drinking Water Wastewater Applications
Candidate methods can be submitted for ATP evaluation for both drinking water and wastewater
applications. However, the requirements for compliance monitoring under the National Primary
Drinking Water Regulations differ from those under the National Pollutant Discharge Elimination System
permit program. Review and evaluation of ATP candidate methods that are submitted for dual
applications are thus handled by both the Drinking Water ATP Program and the Wastewater ATP
Program.
5 References
1. The NELAC Institute, (n.d.). Radiochemistrv Performance Testing Scoring Criteria. Retrieved from The
NELAC Institute: http://www.nelac-institute.org/
2. International Organization for Standardization. (1995). Guide to the Expression of Uncertainty in
Measurement Geneva, Switzerland.
3. U.S. Department of Commerce. (1994). Guidelines for Evaluating and Expressing the Uncertainty of
National Institute of Standards and Technology Measurement Results. Technical Note 1297.
Retrieved from National Institute of Standards and Technology: http://www.nist.gov/
4. U.S. Environmental Protection Agency. (2004). Multi-Agency Radiological Laboratory Analytical
Protocols Manual. NUREG -1576, EPA402-B-04-001C.
5. U.S. Environmental Protection Agency. (2005). Chapter VI, Critical Elements for Radiochemistry. The
Manual for the Certification of Laboratories Analyzing Drinking Water. Washington, D.C. EPA815-R-
05-004.
6. U.S. Environmental Protection Agency. (2017). Procedure for Safe Drinking Water Act Program
Detection Limits for Radionuclides. EPA 815-B-17-003.
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Step 1: Initial Inquiry
Y
N
N/A
Notes
The application includes name, address, date, and title of the proposed
method.
The proposed method is for drinking water and the analysis of regulated
contaminants or water quality parameters.
The EPA has assigned a unique identifier to the submitted method.
The applicant has included method data with their request (optional).
The EPA has determined the request is allowed within the method-specified
flexibility.
The EPA has determined an evaluation of the proposed method as an ATP
candidate method is warranted.
Step 2: ATP Initial Application
Y
N
N/A
Notes
The applicant has provided the Application and Document Submission Form
with all requested information.
The application includes the analyte to be studied.
The application lists the approved EPA reference method(s) used for
comparison with the candidate method.
The applicant has submitted justification for the candidate method to the
Drinking Water ATP Coordinator.
The applicant is asserting a claim the candidate method contains confidential
business information (CBI).
The applicant has attached paperwork pursuant to 40 CFR 2.203(b) regarding
CBI.
The applicant has submitted and separated the CBI and indicated with an
appropriate coversheet marked "confidential."
The EPA has handled CBI pursuant to subparts A and B of 40 CFR Part 2.
Step 3: Submission of Study Plan
Y
N
N/A
Notes
The study plan cover sheet includes name, address, date, case number, and
title of the proposed method.
A draft of the candidate method has been provided.
The applicant has identified the critical points of the study proposal.
The applicant has discussed methods to control the critical points of the
proposal.
The applicant has included experiments to verify all procedural options
specified in the method.
The applicant has included in their validation study plan a discussion to
address method ruggedness.
The applicant has submitted a complete validation study plan to EPA for
review following the ATP protocol guidelines.
The background of the study plan includes a summary of the candidate
method.
The background of the validation study plan includes a list of the analytes
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Step 3: Submission of Study Plan
N/A
Notes
and corresponding Chemical Abstracts Service (CAS) Registry identifications.
The validation study plan identifies the organization responsible for
managing the study.
The validation study plan identifies the laboratories/organizations that will
participate in the study.
The validation study plan contains and assigns a study schedule to the
laboratories/organizations participating in the study.
The validation study plan uses the same holding times, extract holding times,
and preservation agents specified in the candidate method.
The validation study plan lists all the equipment that will be used in the
candidate method.
The validation study plan lists all the reagents that will be used in the
candidate method.
The validation study plan includes all 17 sections of the EPA method format.
The validation study plan identifies critical steps and the plan to monitor and
account for departures from method performance.
The validation study plan identifies interferences (chemical, physical) that
may affect the results and the plans to mitigate the interferences.
The validation study plan includes a method to determine precision and
accuracy using fortified reagent water.
The validation study plan includes a method to determine effectiveness
above and below the Maximum Contaminant Level (MCL).
The validation study plan includes a method to incorporate the preservative
agent(s) into fortified reagent water as identified in the method.
The validation study plan includes analysis of drinking water from a hard
water source. (Optional)
The validation study plan includes
that contains total organic carbon
analysis of drinking water from a source
> 2mg/L. (Optional)
The validation study plan includes analysis of artificial drinking water with a
high ionic strength. (Optional)
The validation study plan includes analysis of artificial drinking water with a
high organic content. (Optional)
The validation study plan includes analysis of artificial drinking water with a
high chloride content. (Optional)
The validation study plan includes analysis of artificial drinking water with a
disinfection byproduct. (Optional)
The validation study plan includes an analysis of the Quality Control Targets
used in the candidate method.
Step 4: Submission and Review of Method Validation Study Report (MVSR)
Y
N
N/A
Notes
The background of the MVSR contains a method summary, justification for
the ATP evaluation, and a list of the analytes.
The MVSR study implementation section identifies the
laboratories/organizations that participated in the study.
The MVSR implementation report lists the study schedule that was followed.
The MVSR study implementation section explains how the samples were
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Step 4: Submission and Review of Method Validation Study Report (MVSR)
Y
N
N/A
Notes
collected and handled.
The MVSR implementation section specifies the types and numbers of
analyses to be performed in the lab.
The MVSR implementation report identifies and describes any deviations or
problems that impacted the study performance.
The MVSR presents a sufficiently detailed version of the candidate method in
the correct EMMC format.
The MVSR contains sample calculations.
The test data is reported in a format compatible with Microsoft® Office
applications.
The MVSR contains a discussion of discrepancies between results and quality
control acceptance criteria.
The MVSR contains a conclusion section discussing achievement of the study
objective(s).
The MVSR contains the approved validation study plan in the appendix.
Developed in collaboration with EPA, the MVSR contains data from multiple
matrices to identify interferences or matrix effects.
Step 5: Data Review of MVSR by EPA
Y
N
N/A
Notes
Applicant has completed the Application and Document Submission Form.
The applicant has submitted evidence of instrument calibration.
The applicant has submitted a rigorous evaluation of bias in their analytical
method.
The applicant has submitted an evaluation of precision, using the extremes
of the quantitation range, regulatory levels, and multiple matrices.
The method blank meets the minimum reporting level (MRL) described in
the reference method (if applicable).
The results from the initial demonstration of capability (IDC) passes the
Quality Control Targets used in the candidate method.
The method demonstrates chemical and microbiological storage and
stability.
The method has utilized a minimum number of sites/laboratories for data
collection, as determined by the EPA.
Step 6: Final Evaluation by EPA
Y
N
N/A
Notes
The applicant has demonstrated through design, experiment, and data
collection that their candidate method is rugged.
The applicant has submitted any additional paperwork and data requested
by the EPA.
The EPA has satisfactorily protected the CBI of the applicant.
The EPA has determined the candidate method as ab ATP submission is
equally effective as the reference method.
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EPA Office of Ground Water and Drinking Water
Alternate Test Procedure Candidate Method
Application
~ Initial Application
~ Supplemental Documentation
~ Final Application
Applicant Information
Applicant Name:
Address:
State:
Zip Code:
Contact name:
Phone number:
Email address:
Submission Date:
Candidate method:
Analyte(s):
Candidate method title:
Reference method number or name or both:
Attachments
~ Justification for Candidate Method
~ Validation Study Plan
~ Validation Study Report
~ Raw Data Package (spreadsheets, calibrations, etc.)
~ Data Collection Certification
~ Other Documentation:
EPA use only Case number:
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Appendix C: Radiochemical Method Validation
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Method validation is the process by which a method developer substantiates the performance of a
candidate method. Candidate methods should be validated to demonstrate they have acceptable
performance characteristics such as accuracy, precision and detection capability for the measurement of
their target radioanalyte(s). Although this is generally achieved by comparing the performance of the
candidate method to that of existing approved methods, additional metrics such as robustness or
ruggedness may also warrant evaluation.
Recently, the NELAC Institute (TNI) published radiochemistry Performance Testing study acceptability
criteria that are based on the results of past radiochemistry Performance Testing studies
(Radiochemistry Performance Testing Scoring Criteria, ). These scoring criteria are not test method-
specific, but instead reflect the average performance of all test methods for a specific radioanalyte. EPA
may base the acceptability criteria for candidate methods validated using the procedures detailed in this
protocol on the current NELAC Performance Testing scoring criteria. This approach will provide limits for
performance characteristics that are representative of the current proficiency for all the test methods
currently in use.
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The candidate method validation study design described in this protocol is intended to provide sufficient
data to determine the performance characteristics of candidate methods and provide data to determine
whether constituents typically found in finished drinking water matrices will adversely affect method
performance. The study design will evaluate the candidate method's performance in obtaining
measurements for the test matrix and determine if the candidate method is comparable to test
methods already approved by EPA to measure the same target radioanalytes in drinking water. The
validation study is broken down into the Reagent Blank (RB) study, the Detection Limit (DL) study (see
Appendix IF for definition and discussion of the Safe Drinking Water Act DL) and the method
performance study.
Because the RB and DL studies assess the candidate method's performance independent of matrix
effects, these studies should employ water equivalent to or better in quality than ASTM Type II water.
The method performance study will gather data to assess the candidate method's performance in the
test matrix, which is representative of the types of samples that the method may be used to measure on
a routine basis. The method performance study's design is intended to provide sufficient data to
characterize the candidate method's intra-laboratory and inter-laboratory performance. Each study (RB,
DL and method performance) is discussed in more detail in App. C, Sect. 4.
Under the validation study, the sample test matrix (as identified) should be analyzed at four different
matrix and spike level combinations by three certified laboratories and their results employed in the
validation study report. The applicant may elect to employ more than three laboratories or more than
four matrix and spike level combinations. However, in such cases, the applicant is responsible for
adjusting the calculations for the study appropriately. The number of study samples and the total
number of samples in a three-lab study are listed below in Table 1.
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Table 1. Types and Numbers of Samples Required for the Candidate Method Validation Study
Study
Sample Type
Number of Samples
per Participating
Laboratory1
Total Number of
Samples in a Three Lab
Study2
Reagent Blank
RB
6
18
Detection Limit3
DL (replicates spiked at
or below the target
radioanalyte's required
DL)
7
21
Method performance
Reagent Water
Fortified at Maximum
Contaminant Level
7
21
Method performance
Test Matrix at Maximum
Contaminant
Level
7
21
Method performance
Test Matrix at V-i
Maximum Contaminant
Level
7
21
Method performance
Test Matrix at 2 x
Maximum Contaminant
Level
7
21
1The total number of samples required per participating laboratory is 41.
2The grand total number of samples required in a three-lab study is 123.
3 In some cases the DL study may not be needed if the DL test is passed (see App. C, Sect. 4).
3 General Study
3.1 Selecting and Supporting the Participating Laboratories
A minimum of three laboratories should participate, in order to characterize inter-laboratory method
performance. The laboratories employed should be certified by EPA or a State to test for radioanalytes
in drinking water. If the applicant is a certified laboratory, the applicant should locate at least two other
certified radiochemistry laboratories to participate in the method validation study with them. If the
applicant is not a certified laboratory, the applicant should obtain the services of at least three certified
radiochemistry labs. The applicant should provide the participating laboratories with the candidate
method standard operating procedure, any technical assistance requested by them and with sufficient
volume of the test matrix to run the method performance study. The applicant should collect the
necessary data from the participating laboratories to produce a single validation study report and data
package for submission to EPA.
3.2 Validation Study Test Matrix
Finished drinking water matrices could potentially have levels of regulated and unregulated chemical
and radioactive constituents (that is, organics, solvents, cations, anions, metals, etc.) at concentration
levels by themselves or in summation with others that may interfere with the sample preparative steps
in a radiochemical test procedure. Since test methods used to monitor the compliance status of public
water systems are approved for nationwide use, any method validation study for candidate methods for
drinking water should be conducted using a test matrix that is representative of the diversity in both
unregulated and regulated constituents that may be found in finished drinking water.
A test matrix has been developed for use in the method performance study. This test matrix was tested
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by EPA, is within the bounds of the types of finished drinking water that are found nationally and is
reasonable to test the method performance of a high ionic strength water matrix. The matrix sample
components and directions for preparing the test matrix are identified in Appendix 6.
The applicant should provide EPA with documentation that the test matrix was preserved and stored
according to the approved procedures for the candidate method and that all analyses took place within
the required holding times. The applicant laboratory should ensure sufficient quantities of the test
matrix are available for all the test batches needed by all the participating laboratories.
3.3 Significant Figures, Rounding Data Results and Data Reporting Conventions
All measurement results should: (1) be reported directly as obtained with appropriate units, (2) be
reported even if it is negative, (3) be expressed in an appropriate number of significant figures and (4)
include an unambiguous statement of the uncertainty. The appropriate number of significant figures is
determined by the magnitude of uncertainty in the reported value.
The value, as measured (including zero and negative numbers) and the measurement uncertainty (either
expanded uncertainty or the combined standard uncertainty) should be reported in the same units. For
presentation of data in the method validation report the measurement uncertainty should be rounded
to two significant figures and both the value and uncertainty should be reported to the same number of
decimal places. For example, a value of 0.8961 pCi/L with an associated combined standard
measurement uncertainty of 0.0234 should be reported as 0.896 ± 0.023 pCi/L with a coverage factor of
one.
Note: Rounding should only be used in determining the final results.
3.4 Uncertainty Evaluation and Reporting
The submitted method should describe the equations or procedures used to evaluate the uncertainty of
each result. When describing uncertainties, the method should use the terminology and symbols of the
Guide to the Expression of Uncertainty in Measurement; International Standards Organization 1995 (2).
Each measurement result should be reported with its associated counting uncertainty in accordance
with the applicable regulations; however, EPA also encourages labs to perform a complete uncertainty
evaluation and report the overall measurement uncertainty of each result as well.
Since laboratories may calculate uncertainties using different methods and report them using different
coverage factors, uncertainties should be reported with an explanation of what they represent. In
particular, reports should clearly distinguish between counting uncertainties and total uncertainties.
Furthermore, any analytical report, even one consisting of only a table of results, should state whether
the uncertainty is a standard uncertainty ("one sigma") or an expanded uncertainty ("k sigma") and in
the latter case it should also state the coverage factor (k) and, if possible, the approximate coverage
probability. If the laboratory uses a shorthand format for the uncertainty, the report should include an
explanation of the format.
Additional information about the evaluation and expression of uncertainty can be found in National
Institute of Standards and Technology Technical Note 1297: Guidelines for Evaluating and Expressing the
Uncertainty of National Institute of Standards and Technology Measurement Results and the Multi-
Agency Radiological Laboratory Analytical Protocols Manual |4|.
4 Performing the Reagent Blank and Detection Limit Studies
Participant laboratories should initially produce RB and DL data quantifying their performance with the
candidate method that is independent of matrix interferences. These data assess laboratory baseline
proficiency with the candidate method prior to assessing matrix interferences with a candidate method
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performance study.
The data generated by these initial demonstrations of performance are designed to determine if the
laboratory can perform the candidate method and generate results comparable to those generated
using the approved test methods for a specific regulated radioactive contaminant or contaminants. The
candidate method's detection capability is assessed with a RB study and DL study.
In some cases, applicants may only need to do the RB study and forgo the DL study if the candidate
method can successfully pass the DL test in App. C. Sect. 4.2.1.
Figure 1. Reagent Blank Study Process
modification is necessary, the applicant should notify EPA of the modification before proceeding.
4.1 Reagent Blank Study
Each participating laboratory should demonstrate that it is capable of measuring the analyte at
sufficiently low levels to determine if the candidate method can meet the required DL for the target
radioanalyte(s). An RB analysis is performed to measure the effect of possible contamination of the
reagents and lab ware. The RB study should use deionized water that meets or exceeds the ASTM Type II
standard for reagent water. This sample should be free of matrix interferences and will allow an initial
assessment to be made for the candidate method's baseline performance as it is used by the
participating laboratories. Each participating laboratory should use the candidate method to prepare
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and measure two RBs on three non-consecutive days for a total of six RBs. The RBs should be assumed
to be a normal sample that is dispensed, prepared and processed with the reagents and procedures
specified in the candidate method for routine sample analysis. They should be measured using the
detection system specified in the candidate method using the count times calculated as necessary for
routine sample measurements in order to meet the required DLs. The average net activity for these RB
measurements should then be calculated. For each participating laboratory, the absolute value of the
average net activity found in the study's RBs should not exceed one-half of the required DL for each
radioactive contaminant measured using the candidate method as they are listed in Table B at 40 CFR
part 141.25(c)(1) and Table C at 40 CFR part 141.25(c)(2). If the absolute value of the average net activity
found in the study's RBs exceeds one-half of the required DL, the applicant may wish to modify the
method and have each participating laboratory repeat the RB study. If a method modification is
necessary, the applicant should notify EPA of the modification before proceeding.
4.2 Detection Limit Test and Detection Limit Study
The candidate method should be evaluated against the DL test criteria to determine if an additional DL
study should be done. If the candidate method can pass the DL test, applicants can forgo the DL study
and begin the method performance study.
4.2.1 Detection Limit 'Test
If the method always produces a result (positive, negative or zero) and if there are theoretically
defensible equations for calculating the DL, then the applicant may determine the DL by a documented
calculation without performing a DL study. For more information on calculating theoretical DLs for
radiochemical measurements see Appendix IF. In this case, the calculated DL must not exceed the
required DL. As an additional check, the results of the RB analyses will be evaluated statistically to test
whether the observed variability significantly exceeds the standard deviation expected at the required
DL, as shown below.
4.2.2. Statistical Evaluation of the Reagent Blanks
Let Bi, 62, ..., Bn denote the results of all the RB analyses (for example, n = 18 if there are three labs and
six blanks per lab). Calculate the following statistic 1/1/:
The critical value for 1/1/ is the 99th percentile of the chi-squared distribution with n degrees of freedom.
For example, if n = 18, the critical value is Wc = 34.81.
The candidate method should NOT be deemed to pass the DL test if 1/1/ > l/l/c and the applicant should
conduct a DL study. If EPA determines that the data appear suspect (for example, if all the blank results
are exactly zero) the applicant may be requested to perform a DL study.
4.2.3 Detection Limit Study
The DL study will verify that the method is capable of routinely achieving the required detection
(1)
i=1
Wc =Xo.99(n)
(2)
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capability for the method. Whenever practical, the first step of the DL study should be a theoretical
estimation of the Safe Drinking Water Act DL based on the definition in 40 CFR 141.25(c) and all relevant
data obtained in the method background study, such as instrument background levels, chemical yields,
etc. Appendix IF of this document describes how to calculate such a theoretical estimate in the simplest
cases. If the theoretical estimate of the DL does not exceed the required DL, an experimental DL study
should be performed as described below. However, if the theoretical estimate of the DL exceeds the
required DL, the performance of the method will be considered inadequate and there will be little value
in completing the experimental DL study. In this case, the applicant may wish to modify the method (for
example, increase counting time or increasing the sample volume) and repeat the calculation of the
theoretical estimate of the DL. If a method modification is necessary, the applicant should notify EPA of
the modification before proceeding. If a theoretical estimation of the DL is found to be impractical, the
experimental DL study is required.
The experimental DL study consists of seven replicate samples. Each sample should be made with ASTM
Type II reagent water, at a minimum, using the sample volume prescribed in the method. The sample
should be spiked with National Institute of Standards and Technology traceable source(s) of the method
target radionuclide(s) to an activity concentration at or below their required DL. The sample should be
mixed and then processed through sample preparation, processing and analysis per the candidate
method. The measurements of the DL study samples will then be assessed by calculating a precision
statistic. See App. C, Sect. 6.1 for further information.
5 f !!'¦ !! !!.¦!! !! 11,. 11 t' \ ! t
The method performance assessment study is to be performed by three laboratories, each analyzing
seven replicates at four different matrix and spike level combinations, as listed below:
1) Reagent water, spiked at the Maximum Contaminant Level.
2) The test matrix, spiked at the Maximum Contaminant Level.
3) The test matrix, spiked at Vz the Maximum Contaminant Level.
4) The test matrix, spiked at 2 times the Maximum Contaminant Level.
The results of the bias and precision evaluations are subject to the criteria as described in App. C, Sect.
6.3 and App. C, Sect. 6.4, respectively, at each matrix and spike level for the study to be acceptable.
Therefore, it is recommended that the analyses be performed in reagent water first, then in the order of
increasing concentration in the matrix. There is no need to complete all four sets of analyses if one has
failed.
If either the results of the bias or precision evaluations fails the criteria for any spike level or matrix,
then the applicant should investigate why the method failed the criteria and possibly modify the method
and repeat the calculation. If a method modification is necessary, the applicant should notify EPA of the
modification before proceeding.
6 Acceptability Criteria for Radiochemical Study Results
The NELAC Institute has published and maintained a table of radiochemical Performance Testing study
acceptability criteria [1|. The calculations discussed in this section were developed to account for the
presence of variability between multiple laboratories. The precision evaluation in App. C, Sect. 6.4 is
based on the single-laboratory standard deviations (presented in Table 2) that were used to develop the
NELAC performance testing criteria. Assessing method performance using these criteria will help ensure
compliance monitoring measurements for regulated contaminants that meet or exceed a minimum
acceptable level of performance for laboratories nationally.
6.1 Experimental Detection Limit Studies
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The assessment of the replicate results for one analyte at all of the participating laboratories uses a chi-
square statistic to test whether the pooled relative standard deviation of the results exceeds the
maximum value allowed at the required DL.
Calculate the mean, X, and a chi-square statistic, x2 f°r each of the participating laboratories,
mixl.xl.-Xm)-
and
1.96
Xi
7=1
IL
(3)
7 = 1
Where:
m is the number of laboratories (three or more).
n is the number of replicate measurements (n = 7).
ju is the spike concentration (not to exceed the required DL).
X/yis the result of the jth replicate measurement (j = 1, 2, ..., n) at the ith laboratory (/' = 1,2,..., m).
Then calculate the overall chi-square statistic:
X'
ill
-I
Xt
i=i
(4)
To be deemed acceptable, the value of %2 should be less than or equal to the 99th percentile of the
distribution with m x (n-1) degrees of freedom. When n = 7 and m = 3, the value of this percentile is
34.81.
Note: Refer to Appendix IH - Sample Calculations Section 1.0 for an example calculation.
6.2 Method Performance Study Criteria
App. C. .Sect. 6.3 and App. C, .Sect. 6.4 present the step-by-step processes by which the bias and
precision of the method performance study data should be assessed. In the event that the NELAC
Institute updates their performance testing acceptability criteria in the future, the updated table should
be used to reference these limits until an addendum to or revision of this document is published.
Table 2. Means and Standard Deviations (from NELAC Performance Testing Criteria)
Analyte
Spike Level Range (i*1)
Standard Deviation (oNELAC)
Gross Alpha
7 to 75
(0.1610 n) +1.1366
Gross Beta
8 to 75
(0.0571 n) + 2.9372
Barium-133
10 to 100
(0.0503 n) + 1.0737
Cesium-134
10 to 100
(0.0482 n) + 0.9306
Cesium-137
20 to 240
(0.0347 n) + 1.5185
Cobalt-60
10 to 120
(0.0335 n) + 1.3315
lodine-131
3 to 30
(0.0624 n) + 0.6455
Radium-226
1 to 20
(0.0942 n) + 0.0988
Radium-228
2 to 20
(0.1105 n) +0.3788
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Analyte
Spike Level Range (n1)
Standard Deviation (oNELAC)
Strontium-89
10 to 70
(0.0379 n) + 2.6203
Strontium-90
3 to 45
(0.0902 n) +0.5390
Tritium
1000 to 24000
(0.0532 n) +38.8382
Natural Uranium
2 to 70
(0.0700 n) + 0.2490
Uranium (mass)
3 to 104 ng/L
(0.0700 n) +0.3700
Zinc-65
30 to 360
(0.0530 n) + 1.8271
1 n = spike level (pCi/L or ng/L)
Based on an EPA study using the test matrix, the following spike levels should be used for Barium-133
and Cesium-134:
Barium-133 - 50 pCi/L equivalent to slightly greater than 1/2 the Maximum Contaminant Level of
Barium-140 (90 pCi/L).
Cesium-134 - 40 pCi/L equivalent to 1/2 the actual determined Maximum Contaminant Level.
6.3 Bias Evaluation for the Method Performance Study
In order to assess whether the average concentration of the replicates for a given spike level and matrix
is significantly different from the spike level, it is first necessary to calculate r, the ratio of the between-
laboratory standard deviation to the within-laboratory standard deviation.
The within-laboratory standard deviation (sw) and the between-laboratory standard deviation (s/>) are
calculated as follows:
a
i=i
(5)
Where:
st is the standard deviation of the 7 replicate results for laboratory /'.
Sb
(=i
(6)
Where:
Xi is the mean of the 7 results for laboratory /'.
X is the grand mean of the 21 results over all three laboratories.
Note: If the radicand is negative, sb should be set to zero.
Calculate the ratio r:
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r =
Sb
(7)
Using oNELAC (Table 2), calculate the acceptable combined standard deviation for lab averages,
°c. ~ aNELAC x
2 , 1
r/ + y
r2 + 1
(8)
Note: The appropriate value of oNELAC may differ for different spike levels.
For the method to be acceptable, the grand mean, X, should be within the following range:
oc x 2.58
"±-^- 191
Where:
H is the spike level.
2.58 is the 99.5th percentile of a standard normal deviation distribution.
Refer to Appendix IH - Sample Calculations (App. IHL .Sect. 2.1) for an example calculation.
6.4 Precision Evaluation for the Method Performance Study
Calculate a statistic for total precision using the equation below.
3 7
1
x2 = - > > (Xtj-Xf (10)
Own at
NELAC1=1J=1
Where:
°nelac's determined from Table 2.
X is the grand mean of the 21 tests over three laboratories for the given spike level and matrix.
For the method to be acceptable %2 should be below the 99th percentile of the chi-square distribution
with 20 degrees of freedom (37.57). Refer to Appeini' - Sample Calculations (App. IH., .Sect. 2.2) for an
example calculation.
7 ACC'l'ii ¦
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Radiochemistry, in The Manual for the Certification of Laboratories Analyzing Drinking Water for the
required instrument stability checks and preparation batch quality control samples, their frequencies
and acceptability limits.
8 Quality Control
Laboratories measuring radiochemical compliance monitoring samples in support of the Safe Drinking
Water Act should follow the requirements found in Chapter VI, Critical Elements for Radiochemistry, in
The Manual for the Certification of Laboratories Analyzing Drinking Water . Section 7.4 in Chapter VI
of this manual requires laboratories to participate in at least one Performance Testing study per year for
each regulated radioactive contaminant using a specific method for certification. Section 7.7 in the same
chapter specifies quality control tests and their acceptance criteria to assess sample preparation batch
accuracy, precision, detection capability and interferences. Section 7.7 also requires instrument quality
control checks be made in order to monitor their stability. Instrument specific calibration requirements
and stability checks are described in Section 3.1. Section 7.8 in Chapter VI states that laboratories should
collect quality control data and order them by quality control test in a control chart in order to
document each method's performance and the stability of counting instrumentation. In order to ensure
data consistency and reliability nationally, the requirements found in Chapter VI should be followed
along with any quality control requirements found in currently approved methods.
The contents of the quality control section (Section 9) in candidate method standard operating
procedures should be consistent with the requirements found in Chapter VI. The candidate method
standard operating procedure should specify either the sample preparation batch quality control tests,
the instrument stability checks and their acceptance criteria as they are found in Chapter VI or explicitly
reference where the quality control test requirements appropriate to the candidate method may be
found in Chapter VI.
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Appendix D: .Standard EPA Method Format
[Note: Each method should be a free-standing document, providing all information necessary for the
method user to perform the analysis. References within a method should be restricted to associated or
source material. Procedural steps or instructions should not be referenced as being found elsewhere but
should be included in totality within the method. The following section numbering scheme is typical
with the Environmental Monitoring Management Council (EMMC) format.]
1 Scope ..ik! }.1 ih11"1.¦ < 11¦ "¦! i
[This section outlines the purpose, range, limitations, and intended use of the method and identifies
target analytes.]
2 d
[This section provides an overview of the method procedure and quality assurance.]
3 1
[This section includes definitions of terms, acronyms and abbreviations used in the method. If preferred,
definitions may be provided in a glossary at the end of the method or manual. In this case, the
definitions section should still appear in the method, with a notation that definitions are provided in a
glossary (refer to the specific section number of the glossary) at the end of the method.]
4 Interferences
[This section identifies known or potential interferences that may occur during use of the method and
describes ways to reduce or eliminate these interferences.]
5 Safety
[This section describes special precautions needed to ensure personnel safety during the performance
of the method. Procedures described here should be limited to those which are above and beyond good
laboratory practices. The section should contain information regarding specific toxicity of analytes or
reagents.]
6 Equipment and Supplies
[This section lists and describes all non-consumable supplies and equipment needed to perform the
method.]
7 I 1 IS >!. I " '!!. I .!! J!
[This section lists and describes all reagents and standards required to perform the method and provides
preparation instructions or suggested suppliers or both as appropriate.]
8 Sample Collection, Preservation and Storage
[This section provides requirements and instructions for collecting, preserving and storing samples.]
9 Quality Control
[This section cites the procedures and analyses required to fully document the quality of data generated
by the method. The required components of the laboratory's quality assurance program and specific
quality control analyses appropriate to the method are described in this section. It should reference
Chapter VI, Critical Elements for Radiochemistry in The Manual for the Certification of Laboratories
Analyzing Drinking Water |5j for the required quality control tests and the specific quality control
acceptance criteria for each of them.]
D-l
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10 Calibration and .Standardization
[This section describes the method or instrument calibration and standardization process and the
required calibration verification. Corrective actions are described for cases when performance
specifications are not met.]
I I I !! ¦> edi i!! .~
[This section describes the sample processing and instrumental analysis steps of the method and
provides detailed instructions to analysts.]
I | '.»!.» / nJr , ! ,,|k! ¦ J. nl til""!!
[This section provides instructions for analyzing data, equations, and definitions of constants used to
calculate final sample analysis results and their uncertainties.]
I ' f i 1! i ! I I I I I > ! i
[This section provides method performance criteria for the method, including precision or bias
statements regarding detection limits and sources or limitations of data produced using the method.]
14 Pollution Prevention
[This section describes aspects of the method that minimize or prevent pollution known to be or
potentially attributable to the method.]
I ' ^ I i 1 1
[This section describes minimization and proper disposal of waste and samples.]
16 References
[This section lists references for source documents and publications that contain ancillary information.]
11 I i •! il "! !! !!' I !! !! > ! I \ k.| I ' Jl
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Appendix E: Validation Report Template
Microsoft® Word
This template is to be used to prepare final validation study reports for ATPs. The template sets up the
primary validation study report sections along with brief instructions for each section. The template is
prepared using an Adobe®-supported font for proper .pdf conversion. Please do not make any changes
to fonts or styles. The following section numbering scheme is typical with the EMMC format.
If the alternate test method demonstrates equivalency to an approved method, EPA may subsequently
approve the method for compliance monitoring through either conventional notice-and-comment
rulemaking or through the expedited methods approval process. In either case, this validation report will
be incorporated in the public docket associated with the approval action.
If typing the validation study report directly into the template, replace the text of the template and
begin typing the report (that is, select the Title section and replace it with the method title). This page of
instructions can be deleted upon completion of the validation study report.
Insert graphics within the text in TIFF, JPEG or Microsoft® Office compatible file format (*.wmf or
*.emf).
Save the file with the graphics in place as a document file (.doc).
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Alternate Test Procedure (ATP) Validation Study Report
Title
[The title should clearly and concisely specify the name of the method
(for example, "measurement of turbidity", "nitrate analysis", etc.) and
applicable). The title should also include a shortened method name or
and for reference]
Date
Name and address of organization
Author name(s)
[Include individual(s) with responsibility for overseeing development of the alternate test method and
verifying accuracy of the data presented in the validation study report. Designate the appropriate point
of contact in the event questions arise after review of the report.]
Phone number and email address
[Author or point of contact phone number and email address.]
, the scope of the measurement
the instrumentation (if
number to use in the regulation
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1 Bac"
[Provide a method summary discussing the experimental technique.]
1.1 M et Ih o d J u st i fi c a t i o in
[Specifically cite the approved method that the candidate method is being compared to, the
organization where the approved method originated (for example, ASTM, Standard Methods, EPA, etc.),
and the method number. Summarize justification for the candidate method and describe the advantages
relative to the approved method, especially in terms of improved sample throughput, reduction of
hazardous waste, cost reduction, elimination of interferences, etc.]
1.2 Method Equivalency
[Summarize the quality control acceptance criteria as defined in the approved method and describe how
the candidate method meets these specifications. Clearly indicate in the final sentence whether the
candidate method is "equally effective" in meeting quality acceptance criteria as the approved method.]
1.3 Ana llytes
[Identify the analytes that are determined using the candidate method and list the corresponding
Chemical Abstracts Service registry numbers.]
2 Study Implementation
[Clearly identify the managing organization responsible for development of the candidate method
validation study plan and all of the laboratories participating in the study. Explain why specific
laboratories were selected to participate and address any potential for conflict of interest.]
2.1 Study Schedule
[Delineate the study schedule.]
2.2 Sample Collection
[Describe how samples were collected and handled. Specify whether required holding times were met.]
2.3 Types of Analyses Performed
[Describe the number and types of analyses performed by each laboratory (for example, specify how
many replicate analytical runs were performed to evaluate precision and accuracy in each drinking
water matrix, incorporation of blanks, etc.]
2.4 Study Plan Deviations
[Fully describe any problems encountered or deviations from the study plan and the resolution or
impact of these issues on the study plan performance results.]
3 Method Procedure and Data
[The candidate method should be prepared in standard EPA EMMC-method format and submitted with
the initial validation study plan. In this final validation report, the method should be attached as an
addendum and referenced as such in this section. Compare and contrast procedural differences
between the candidate method and the approved method.]
3,1 Validation Study Demonstration Data
[Submit complete demonstration data for both reagent water and drinking water matrix analyses in
tables, graphs or figures, as appropriate. The data should clearly present the candidate method data in
comparison with the required reference method quality control criteria. Address the items in the
following subsections, as appropriate.]
3,1,1 Calibration
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[Demonstrate acceptable calibration performance as defined in the validation study plan. Include
calibration verification through incorporation of calibration checks.]
3.1.2 Initial Demonstration of Capability
[Demonstrate acceptable low system background, precision and accuracy and detection limit or
minimum reporting level confirmation (as specified in the validation study plan).]
3.1.3 Quality Controls
[Include verification of method performance using blanks, fortified blanks, matrix spikes, and other
quality controls as specified in the validation study plan.]
3.1.4 Precision and Accuracy
[Include all precision and accuracy data for reagent water and drinking water matrix samples.]
3.2 Holding Time or Storage Stability
[If specified in the validation study plan, submit storage stability data. Otherwise, indicate that a holding
time study was not required.]
4 Data Analyji il -i ¦¦ii-'.-m.-h
[Provide a comparison of the candidate method data to the approved method to confirm equivalency of
performance. Discuss in detail any discrepancies between the results and quality control acceptance
criteria. Discuss method ruggedness based on overall performance as specified in the validation study
plan (for example, multi-laboratory studies, analyses performed on multiple instruments, assessments
of various drinking water matrices, etc.)]
5 Conclusions
[Discuss achievement of validation study objectives.]
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ilj II ! i " I ! I I I ?!! i"! > , ' ,. 11J .ll.Mi I",! I ii ,|i
[Append the approved validation study plan.]
E-5
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iij ii ! i > i ! i i i fihJi! > I. • "Mb ! si!, il 11 .1 .
Raw Data
[Submit raw data in an excel spreadsheet. Identify instruments used and operating conditions,
detectors, and separation procedures.]
Example Calculations
[Provide sample calculations to verify that the laboratory has used the raw data to correctly arrive at the
final results.]
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11. ! I ! ! . I I ! ! ! 1 [ N III, ! I li I. '»!!!!. ¦! !
It is the expectation of the ATP program that all data will be collected as outlined in the validation study
plan. Applicants must attest on the application that the data collection was performed as outlined in the
validation study plan.
The applicant hereby certifies that the data included with this application were collected as outlined in
the validation study plan.
Applicant (print name)
Applicant (signature) and (Date)
[Questions, comments, or applications should be directed to:
William A. Adams, PhD.
U.S. EPA, OGWDW, TSC
26 W. Martin Luther King Dr. Cincinnati, OH 45268
Phone:(513)569-7656
adams.william@epa.gov
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Mb"!~! 'v'1 ' I ' 1 s "I 11"! i'' I i«.\ 'I -Ml' al il \M-~- (l! ¦"!! ii I i ,, J«!. i..
ii i "!! !!, ",{ (m'I
1 Definition of the Detection Limit for the .Safe Drinking Water Act
i s .II. .. ii Ii!!- s.| iix ih~ ¦ -H| > ~! 1! > ~!! i ,
The detection capability of radiochemical measurements used for the Safe Drinking Water Act drinking
water compliance monitoring is specifically defined at 40 CFR part 141.25(c) as a DL. It further defines a
DL with the following conditions:
"The DL shall be that concentration which can be counted with a precision of plus or minus 100 percent
at the 95 percent confidence level (1.96a where a is the standard deviation of the net counting rate of
the sample)."
The Safe Drinking Water Act DL according to this definition differs from other "detection limits/' such as
the method detection limit or DL, (defined in 40 CFR part 136, Appendix B) and the minimum detectable
activity or Minimum Detectable Activity, which is commonly used by radiochemists. Required DLs for the
Safe Drinking Water Act drinking water compliance monitoring for radioactivity concentrations are
expressed in terms of the definition given in 40 CFR 141.25(c).
For measurements involving simple nuclear counting with Poisson counting statistics, the procedure
given in Section 2.0 below may be used to obtain a preliminary estimate of the Safe Drinking Water Act
DL.
Note: Many radiochemical measurements involve simple Poisson counting. However, since it is possible
that a submitted candidate method may involve measurement techniques with different statistics (for
example, gamma-ray spectrometry), laboratories should contact EPA before submitting their study plan
to determine if the equations in this appendix may be used to calculate the DL for the candidate method
they wish to propose for approval.
2 .Simple Pois
The definition of the Safe Drinking Water Act DL may be expressed mathematically as follows:
RDl — 1-96 X aDL (11)
Where:
Rdl is the mean net count rate for a sample with concentration at the DL.
ODListhe standard deviation of the net count rate.
The relationship for the standard deviation of a radiochemical measurement is centered around the fact
the gross rate has a background rate subtracted from it to derive a net count rate.
Rdl — Rg Rb (12)
Where:
F-l
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Rg is the mean gross count rate for a sample (with concentration at the DL).
Rb is the mean background count rate for a sample measurement.
However, each count rate is a calculated quantity, as specified below.
and
(13)
Where:
Rg is the mean gross count rate for a sample (with concentration at the DL).
Rb is the mean background count rate for a sample measurement.
Cg is the mean total (gross) sample count.
Cb is the mean total background count.
£g is the time of the measurement used to accumulate the sample count.
£b is the time of the measurement used to accumulate the background count.
The standard deviation of a count rate is inversely proportional to the square root of the mean of a
measurement. Assuming Poisson counting statistics, the standard deviation of RG and RB are given by:
ctg is the standard deviation of the gross count rate.
ob is the standard deviation of the background count rate.
Since the net count rate, Rdl, is the difference between Rg and Rb, its standard deviation is given by:
(14)
Where:
(15)
Where:
CTDListhe standard deviation of the net count rate.
Combine equation 14 and 15.
(16)
When this expression for aous substituted into equation 11.
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RDl — 1-96 x
RG j Rb
t-G t-B
(17)
Equation 12 may now be used to eliminate the variable /?Gfrom the equation. Since Rg = Rdl+ Rb,
equation 17 may be rewritten as:
RDl — 1-96 X
Rql + Rb
t-G tB
(18)
Equation 18 may now be solved algebraically for the value of Rdl. First rewrite the radicand.
Rdl = 1-96 X
Rdl /II
1- fig x ( 1
tG \tG tB
(19)
Square each side of the equation.
1.96
RDl — 7 x Rdl + 1-96 RB x [- I- —
1 1
—I—
(20)
Collect all terms on the left-hand side to put the equation in standard quadratic form.
7 L96
R2dl-^— XRDL- 1.962RBX (- + -) = 0
1 1
1
tG £b
(21)
The quadratic formula gives two solutions to equation 21, one of which is positive and one of which is
negative. The positive solution is required, and it is given by the following equation.
Rdl ~
1.96
2 tr
X
1 +
4 tl /II
1 + X Rd X I 1- —
1.962 B \tG tB
(22)
Equation (22) provides a reasonable estimate of the count rate at the DL for the net activity that is based
on counting statistics alone. This count rate should then be divided by the product of the experimental
factors, H, which can include the following items: the method of detection's counting efficiency, the
sample volume, gravimetric or tracer recoveries, conversion factors to picocuries, etc. The result can be
F-3
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used to derive a specific DL of the radioanalyte of interest for a radiochemical method of analysis that is
used for the Safe Drinking Water Act compliance monitoring.
DL =
R
DL
H
(23)
Where:
H is the product of the experimental factors.
DL is the Safe Drinking Water Act Detection Limit.
This DL is equivalent to the DL specified in 40 CFR part 141.25(c). It is expected that the experimental
factors will vary with each specific method.
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Appendix G: Procedure for Preparing the Radiochemistry ATP Drinking
Water Test Matrix
1 Purpo .cope
This standard operating procedure details the requirements for the preparation of the Test Matrix for
use in performing tests associated with the development of candidate radiochemistry methods for
application as an EPA ATP for Radiochemistry.
The Test Matrix applies only for use in developing Radiochemistry ATPs and should not be used as a
basis for assessment of other drinking water procedures.
2 d
Prescribed salt solutions are added to deionized water conforming to ASTM Type I or II requirements.
The prepared Test Matrix is allowed to equilibrate for at least 16 hours. The result is a 1 L sample of
approximately 350 ppm of total dissolved solids.
The Test Matrix is spiked as needed for the applicant's tests and acidified based on the radioanalyte of
interest per the requirements for sampling preservation cited in The Manual for the Certification of
Laboratories Analyzing Drinking Water |5|.
3 Health and Safety Warnings
Laboratory safety procedures for handling reagents and chemicals are to be followed.
4 [
None
5 Equipment and Supplies
• l-L and 4-L containers to meet sample container requirements for specified drinking water
analysis, glass or plastic.
• Top loading balance, maximum allowed mass at least 10,000 grams readability to 0.01 g (10 mg).
• ASTM Class 2 or equivalent calibration weight set with masses of 1, 2, 5, 10, 20 and 50 g.
• Pipette - volumetric, to deliver, lmL and 4 mL.
• Spatula.
• Stir plate - magnetic.
• Stir bar - 40 mm magnetic.
• 250 mL volumetric flask, glass or plastic, to contain, Class A.
• Weighing dish, polystyrene, minimal 40 x 40 x 8 mm.
6 Reagents
All reagents used are to be American Chemical Society grade or better.
Note: The following reagents may be substituted with equivalent salts of varying hydrated state. By
example: Barium chloride anhydrous 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 determined ppm content of each of the salts is presented in Table 3 (see Section 15).
Caution: ONLY the hydration state of the salts may be varied.
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• Aluminum Chloride Hexahydrate - American Chemical Society Grade.
• Barium Chloride Dihydrate - American Chemical Society Grade.
• Calcium Nitrate Tetrahydrate - American Chemical Society Grade.
• Iron (III) Chloride - American Chemical Society Grade.
• Magnesium Sulfate Heptahydrate - American Chemical Society Grade.
• Potassium Chloride - American Chemical Society Grade.
• Sodium Phosphate Dibasic - American Chemical Society Grade.
• Sodium Bicarbonate - American Chemical Society Grade.
• Sodium Sulfate, Anhydrous - American Chemical Society Grade.
• Reagent Water - ASTM Type I or Type II.
7 Interferences
None
8 Calibrations
Ensure balance is calibrated and that daily or monthly performance checks are performed as required by
the lab's standard operating procedures using acceptable weights for the masses to be measured (1 - 25
g)-
9 Sample Handling and Preservation
Once prepared let the solution stand for at least 16 hours prior to filtration. The solution is not to be
preserved until it has been spiked.
I i * I i >. ,vi iJ
a. Prepare each of the following stock standard reagents separately using reagent water and a 250
mL TC volumetric flask.
Note: The masses identified should 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 in 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. All weights used are to be documented.
i. Aluminum Chloride Hexahydrate 4 mg/mL: Dissolve 1.0 g of AICI3*6H20, dilute to 250 mL
with reagent water.
ii. Barium Chloride Dihydrate 4 mg/mL: Dissolve 1.0 g of BaCI2*2H20, dilute to 250 mL with
reagent water.
iii. Calcium Nitrate Tetrahydrate, 40 mg/mL: Dissolve 10 g of Ca(N03)2*4H20, dilute to 250 mL
with reagent water.
iv. Iron (III) Chloride, 4 mg/mL: Dissolve 1.0 g of FeCI3, dilute to 250 mL with water.
v. Magnesium Sulfate Heptahydrate, 100.0 mg/mL: Dissolve 25 g of MgS04*7H20, dilute to
250 mL with reagent water.
vi. Potassium Chloride, 60 mg/mL: Dissolve 15 g of KCI, dilute to 250 mL with reagent water.
vii. Sodium Bicarbonate 80 mg/mL: Dissolve 20 g of NaHC03, dilute to 250 mL with reagent
water.
viii. Sodium Phosphate Dibasic Anhydrous, 14 mg/mL: Dissolve 3.5 g of Na2HP04, dilute to 250
mL with reagent water.
ix. Sodium Sulfate Anhydrous, 60 mg/mL: Dissolve 15 g of NaS04, dilute to 250 mL with
reagent water.
b. To constitute 1 L of test matrix, add 1 mL of each reagent to a 1 L glass or plastic TC volumetric
flask and dilute with reagent water to 1 Liter, swirling or stirring to mix.
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c. To constitute 4 L of test matrix, add 4 mL of each reagent to a 4 L glass or plastic TC volumetric
flask and dilute with reagent water to 4 Liters, swirling or stirring to mix.
d. Transfer to an appropriate glass or plastic container with label for storage.
e. Allow solution to stand for at least 16 hours, then filter.
f. Determine the Total Dissolved Solids of the sample using an appropriate procedure.
g. Record the results of the Total Dissolved Solids analysis for submittal with the ATP application
package.
h. Spike the Test Matrix with a known concentration of the radioisotope of interest as required
based on proposed ATP protocol. Swirl to mix.
i. Record the date, time and spike isotope(s) and level(s).
j. Preserve the Test Matrix with acid as required based on proposed ATP requirements. Test and
adjust the pH of the Test Matrix to ensure that it meets drinking water sample requirements of
less than 2.0. Swirl to mix.
k. Record the preservative used, concentration, amount added and pH of the Test Matrix.
I. Allow the Test Matrix to stand for at least 16 hours prior to sample analysis.
I I I / ¦ 1 s.l' "I | ¦ ,| , i ,\Ii'f {!! ¦"!! i r ; ¦"!! 111"!! i i
All required recorded results of the preparation of the Test Matrix solution are to be reviewed and
submitted with the ATP application package.
12 Quality Control
Quality control is to be maintained in accordance with testing laboratory's quality assurance project
plan. Test Matrix Total Dissolved Solids should be within ±20 ppm of the target value of 300 ppm.
I ' > I i ! I i 1,1 ! i J I !!1 11 I ! i I ! !! 11! !! ¦
The Test Matrix in an unspiked and unpreserved state contains no materials that are considered wastes
of a regulatory concern for disposal.
Spiked or spiked and preserved Test Matrix solutions and Stock Standard Solutions are to be disposed of
in accordance with the testing laboratory's procedures and State regulatory requirements.
I il I ,vO! i.!'- ii ih!,u;V! Mil
All records are to be reviewed and approved in accordance with laboratory approved procedures and
the laboratory's quality assurance project plan.
Copies of the records developed in the preparation and quality control of the Test Matrix are to be
provided with the records for supplied to EPA for the ATP application.
G-3
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I " i >'\ In I I I«!!!!'~! Hi I I.^W C i is.I 1 J
Table 3. Test Matrix Solution Composition Chart
Chemical Compound
Analyte of Interest
Analyte to
Mass Added of
ppm of Chemical
ppm of Analyte in
Utilized
Compound Mass
Ratio
Compound in grams
Compound Utilized
in Test Matrix
Test Matrix1
Aluminum Chloride
Aluminum
0.11
4.00
0.45
Hexahydrate
Aluminum Chloride
Chloride
0.44
Not applicable
1.76
Hexahydrate
Barium Chloride
Barium
0.56
4.00
2.25
Dihydrate
Barium Chloride
Chloride
0.17
Not applicable
0.68
Dihydrate
Calcium Nitrate
Calcium
0.17
10
40.00
6.79
Tetrahydrate
Calcium Nitrate
Nitrate
0.53
10
Not applicable
21.03
Tetrahydrate
Disodium Phosphate
Sodium
0.32
3.5
Not applicable
4.53
Anhydrous
Disodium Phosphate
Ortho Phosphate
0.67
3.5
14.00
9.37
Anhydrous
Iron (III) Chloride
Iron
0.34
1
4.00
1.38
Iron (III) Chloride
Chloride
0.66
1
Not applicable
2.62
Magnesium Sulfate
Magnesium
0.10
25
100.00
9.86
Heptahydrate
Magnesium Sulfate
Sulfate
0.39
25
Not applicable
38.97
Heptahydrate
Potassium Chloride
Potassium
0.52
15
60.00
31.47
Potassium Chloride
Chloride
0.48
15
Not applicable
28.52
Sodium Bicarbonate
Sodium
0.27
20
Not applicable
21.89
Sodium Bicarbonate
Carbonate
0.71
20
80.00
57.14
Sodium Sulfate
Sodium
0.32
15
60.00
19.42
Anhydrous
G-4
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Sodium Sulfate
Sulfate
0.68
15
Not applicable
40.58
Anhydrous
^otal Dissolved Solids is 298.70.
G-5
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16 References
40 CFR 141 National Primary Drinking Water Regulations Protocol for the Approval of ATPs for
Radiochemical Analytes
ASTM D1193-99el; Standard Specifications for Reagent Water; American Society for Testing and
Materials, March 1999 with editorial change made in October 2001
The Manual for the Certification of Laboratories Analyzing Drinking Water (EPA 815-R-05-004)
http://water.epa.gov/scitech/drinkingwater/labcert/methods_index.cfm.
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Appendix HI: Sc
The following section provides examples in performing the necessary calculations for the determination
of sample data to meet the acceptance criteria established for the method.
1 il « jll !pi|!" I 4'" I "! M .1 il 11 I II 'I" I I!1 II r\!
The instructions for performing the calculation in an experimental DL study are given in Aipip. C. Sect. 6.1.
The following example illustrates how the evaluation criteria should be applied.
Suppose three laboratories participate in the DL study and that 21 artificially spiked samples at the same
concentration (/u) are analyzed, seven per laboratory, as suggested in App. C. Sect. 4.2.3 (These are the
minimum numbers of laboratories and samples permitted.). Assume that the required DL is 2.5 pCi/L and
the 21 samples are spiked at 2.5 pCi/L. Then:
m = 3.
n = 7.
H = 2.5 pCi/L.
In Table 4 the analysis results for the DL study from the three laboratories have been compiled and the
mean results determined.
Table 4. Example Detection Limit Study Results Spiked at 2.5 pCi/L
Lab (/)
1
2
3
4
5
6
7
Xi
1
1.06
3.04
1.63
2.97
1.90
3.62
2.49
2.3871
2
1.77
0.419
2.22
2.65
0.878
5.93
3.03
2.4139
3
2.37
-1.12
2.56
2.12
2.35
2.08
2.71
1.8671
Sample (/') Results in pCi/L
The last column in the table shows the arithmetic mean of the seven results for each of the three
laboratories, which is calculated using equation (3). For example, the arithmetic mean for the first
laboratory is:
if 1.06 + 3.04+ 1.63 + 2.97 + 1.90 + 3.62 + 2.49 16.71
xi = yljxij = 7 = j = 2.3871 (24)
j=i
Similar calculations are performed for the other two rows of the table.
After the three means are calculated a chi-square statistic is calculated for each laboratory using the
second part of equation three, as shown below.
9 7
1 96 \ 1
xl = Ysr}jXiJ - 2-3781)2 = 2-9924 (2S)
j=1
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(26)
j=i
(27)
7 = 1
Each of the individual chi-square statistics is presumed to have the %2 distribution with six degrees of
freedom.
Next equation (4) is used to calculate the overall chi-square statistic.
3
X2=} Xi = 2.9924 + 12.0406 + 6.5822 = 21.6151
(28)
i=l
This statistic has 18 degrees of freedom (three times six). So, the critical value for the statistic is the 99th
percentile of the ^-distribution with 18 degrees of freedom, which equals 34.81. Since the calculated
value of 21.6151 does not exceed 34.81, the method passes the experimental DL study.
2 Example - Method Performance Assessment Study
2.1 Bias
The instructions for performing the Method Performance Assessment study are given in Aipip. C. Sect. 5.
The evaluation criteria for the results are described in Aipip. C. Sect. 6.2 through Aipip. C. Sect. 6.4. The
following example illustrates how the evaluation criteria should be applied.
Suppose that a method for the determination of Cesium-137 is being evaluated. For the method
performance study, three laboratories each analyze seven replicates at four different matrix and spike
level combinations, as listed below:
1) Reagent water, spiked at the Maximum Contaminant Level.
2) The test matrix, spiked at the Maximum Contaminant Level.
3) The test matrix, spiked at Vz the Maximum Contaminant Level.
4) The test matrix, spiked at 2 times the Maximum Contaminant Level.
The following example reflects the first set of data, reagent water spiked at the Maximum Contaminant
Level. For Cesium-137, the Maximum Contaminant Level is 200 pCi/L. Therefore, 21 artificially spiked
samples at 200 pCi/L of Cesium-137 are analyzed, seven per laboratory, as suggested in Aipip. C, Sect. 5.
(These are the minimum numbers of laboratories and samples permitted.). Therefore, m = 3, n = 7, jU =
200 pCi/L.
From Table 2 (Section 4.6.2), onelac equals 1.5185 + (0.0347 * 200) = 8.46 pCi/L.
Table 5 shows the analysis results of the method performance assessment study for the reagent water
samples spiked at the Maximum Contaminant Level, including the mean and standard deviation
determined for each laboratory.
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Table 5. Example Method Performance Assessment Study Results Spiked at 200 pCi/L
Lab (/)
1
2
3
4
5
6
7
Xi
si
1
188.80
203.00
204.22
202.55
200.13
220.62
203.19
203.2160
9.3233
2
180.85
201.05
177.59
191.61
202.28
192.29
198.92
192.0841
9.7281
3
203.47
195.37
182.03
193.51
191.07
210.22
173.07
192.6760
12.4678
Sample (/') Results in pCi/L
The pooled within-laboratory standard deviation, Sw, is calculated as:
—
— (9.3 2 3 32 + 9.72812 + 12.46782) = V112.3360 = 10.5989
(29)
The grand mean, X, equals.
= 1
X = -(203.2160 + 192.0841 + 192.6760) = 195.9921
(30)
The between-laboratory standard deviation, sb is then calculated as:
Sb =
1 10.59892 /D1v
- x [(203.2160 - 195.9921)2 + (192.0841 - 195.9921)2 + (192.6760 - 195.9921)2] - = 4.8145 (31)
The ratio of between-laboratory to within-laboratory standard deviation, then equals:
4.8145
r = = 0.4542
10.5989
(32)
The combined standard deviation equals.
ac = 8.46 X
0.45422 + tj
0.45422 + 1
= 4.5509
(33)
acceptance limits are calculated as:
H-3
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4.5509 x 2.58 11.7412
200 + = 200 + = 200 + 6.7788 = 193.22 <-> 206.78 (34)
VT ~ 1.7321
Therefore, the grand mean, X, should fall between 193.22 and 206.78. Because the grand mean,
195.99 pCi/L falls between the lower acceptance limit, 193.22 and the higher acceptance limit, 206.78,
the average concentration at the Maximum Contaminant Level for this method is acceptable.
2.2 Precision
The X statistic for total precision is calculated below:
3 7 3 7
*2 = - 195-9921)2 = 35-94 (35)
retire (=17=1 (=17=1
Because 35.94 is less than the 99th percentile of the chi-square distribution with 20 degrees of freedom
(37.57), the precision for this method at the Maximum Contaminant Level is acceptable.
Because both the bias and precision passed for the reagent water samples spiked at the Maximum
Contaminant Level, separate analyses would then be performed in the test matrix, with each sample
spiked at the Maximum Contaminant Level, %*Maximum Contaminant Level and 2*Maximum
Contaminant Level. The bias and precision at each of these concentrations would then be assessed and
if both tests pass at each spike level, the method would pass the method performance assessment
study.
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