Significance and Use
4.1 The ASTM guidance manual, Form and Style for ASTM Standards,4 Section A21, requires a precision and bias statement in all ASTM test methods. Section A21.2.2 states:
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| Precision shall be estimated in accordance with the interlaboratory test program prescribed in Practice E691, Conducting an Interlaboratory Study to Determine the Precision of a Test Method, or by an interlaboratory test program that yields equivalent information, for example, a standard practice developed by an ASTM technical committee. |
4.2 Practice D2777, Section 1.1, states:
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| This practice establishes uniform standards for estimating and expressing the precision and bias of applicable test methods for Committee D19 on Water. Statements of precision and bias in test methods are required by the Form and Style for ASTM Standards, “Section A21. Precision and Bias (Mandatory).” In principle, all (ASTM Committee D19) test methods are covered by this practice. |
4.3 Practice D2777, Section 1.2, requires a task group proposing a new test method to carry out a collaborative study from which concentration limits, repeatability and reproducibility precision and bias statements are developed.
4.3.1 This guide describes options for developing and optimizing chemical test methods for Committee D19, not implementation of a test method by a laboratory. Refer to Guide E2857 for procedures used in validating existing test methods for your laboratory.
4.3.2 The collaborative study described in Practice D2777 is not the test method validation. The collaborative study verifies the new test method is reproducible among different laboratories, different instruments/apparatus, and different analysts.
4.3.3 Practice D2777, Section 6.1, assumes the test method has already been optimized prior to conducting the collaborative study.
4.4 Practice D2777, Section 4 (Summary of Practice), requires, a collaborative study only after the task group has assured itself that preliminary evaluation work is complete and the test method has been written in its final form.
4.5 Practice D2777, Section 5.2 (Significance and Use), requires the collaborative test corroborates the test method write up (preliminary evaluation) within the limits of the test design.
4.5.1 The assumption is that the collaborative study is a fair evaluation of the inter-laboratory variability when using the test method to analyze the matrices, and concentration ranges specified in the test method.
4.6 Practice D2777, Section 6 (Preliminary Studies), requires considerable pilot work on a test method should precede the determination of precision and bias (collaborative study). This pilot work evaluates such variables as:
4.6.1 Representative Sampling,
4.6.2 Suitability of containers,
4.6.3 Preservation requirements,
4.6.4 Identification of interferences,
4.6.5 Holding times (Practice D4841),
4.6.6 Concentration range,
4.6.7 Quantitation ranges,
4.6.8 Concentration and preparation of reagents,
4.6.9 Reagent standardization,
4.6.10 Shelf life of reagents,
4.6.11 Calibration,
4.6.12 QC, and
4.6.13 Sample size.
4.7 Potentially significant factors are investigated in advance and are controlled in the written test method that is distributed for the collaborative test.
4.8 Only after the proposed test method has been thoroughly tried and proved and reduced to unequivocal written form should a collaborative test be conducted.
4.9 The Committee D19 test method is written in two steps:
4.9.1 Step I—Single laboratory characterization or optimization (Practice D2777, Section 6.3.1.1).
4.9.2 Step II—Collaborative study (Practice D2777, Section 6.3.1.2).
4.10 This document is a guide to Committee D19 task groups developing chemical test methods.
Scope
1.1 This guide identifies procedures for use in developing and optimizing new or modified Subcommitees D19.05 and D19.06 test methods intended for regulatory compliance reporting in EPA drinking water and wastewater programs. This guide may also be useful for developing test methods for emerging contaminants that may not yet have regulatory requirements.
1.2 This guide also cites statistical procedures that are useful in the single laboratory characterization and optimization and in the inter-laboratory studies (ILSs).
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project’s many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
