ASTM E2857-22

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Designation: E2857 − 21 E2857 − 22
Standard Guide for
Validating Analytical Methods
This standard is issued under the fixed designation E2857; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide describes procedures for the validation of chemical and spectrochemical analytical test methods that are used by
a metals, ores, and related materials analysis laboratory.
1.2 This guide may be applied to the validation of laboratory developed (in-house) methods, addition of analytes to an existing
standard test method, variation or scope expansion of an existing standard method, or the use of new or different laboratory
equipment.
1.3 The suggested approaches in this guide may also be used to validate the implementation of standard test methods used
routinely by laboratories of the mining, ore processing, and metals industry.
1.4 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.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
E135 Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
E1601 Practice for Conducting an Interlaboratory Study to Evaluate the Performance of an Analytical Method
E1763 Guide for Interpretation and Use of Results from Interlaboratory Testing of Chemical Analysis Methods (Withdrawn
2015)
2.2 ISO Standard:
ISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories
3. Terminology
3.1 Definitions—For definitions of terms used in this guide, refer to Terminology E135.
This guide is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials and is the direct responsibility of
Subcommittee E01.22 on Laboratory Quality.
Current edition approved Dec. 1, 2021April 1, 2022. Published April 2022. Originally approved in 2011. Last previous edition approved in 2021 as
ε1
E2857 – 11E2857 – 21.(2021) . DOI: 10.1520/E2857-21.10.1520/E2857-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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3.2 Definitions of Terms Specific to This Standard:
3.2.1 validation (of an analytical method), n—confirmation, by the provision of objective evidence and examination, that a method
meets performance requirements and is suitable for its intended use.
4. Significance and Use
4.1 Method validation is a process of demonstrating that the method meets the required performance capabilities. International
standards such as ISO/IEC 17025, certifying bodies, and regulatory agencies require evidence that analytical methods are capable
of producing valid results. This applies to laboratories using published standard test methods, modified standard test methods, and
in-house test methods.
4.2 Although a collaborative study is part of this guide, this guide may be used by a single laboratory for method validation when
a formal collaboration study is not practical. This guide may also be applied before a full collaboration study to predict the
reliability of the method.
4.3 The use of multiple validation techniques described in this guide increases confidence in the validity or application of the
method.
4.4 It is beyond the scope of this guide to describe fully the fundamental considerations in Section 5. For a more descriptive
definition of these concepts, refer to the International Union of Pure and Applied Chemistry (IUPAC) technical report,
“Harmonized Guidelines for Single Laboratory Validation of Methods of Analysis” (1), the IUPAC Compendium of Analytical
Nomenclature (Orange Book) (2), and the Eurachem publication, The Fitness for Purpose of Analytical Methods, A Laboratory
Guide to Method Validation and Related Topics (3).
5. Fundamental Considerations
5.1 During the process of method validation, the user of an analytical method should apply a number of fundamental tenets of
analytical chemistry as they relate to the development and implementation of test methods. It is important to make the distinction
between the validation of a test method by a standards-developing organization and the implementation of that test method by a
laboratory. Whether the test method was developed by a committee of experts or by one individual in a company laboratory, the
laboratory shall implement the method in the laboratory and shall demonstrate that the method is being performed sufficiently well
and that the results meet the goals for data quality. That is, they should ascertain that the measurement process provides sufficient
levels of performance fit for the purpose of testing the materials at hand. It is advisable to determine and document performance
characteristics of the method including repeatability precision, limit of detection, limit of quantification, and perhaps other
parameters. The laboratory is advised to evaluate the method for bias and for susceptibility to introduction of bias (namely,
ruggedness). A number of important considerations are discussed in 5.1.1-5.1.7, but specific procedures for determination and
calculation are beyond the scope of this guide.
NOTE 1—In the following discussion, the term measurement process means the entire process by which a laboratory performs a test including specimen
preparation, measurements, and calculation of results either manually or by the software.
5.1.1 Precision—The first step in development and implementation of an analytical method is demonstration that measurements
can be made with sufficient repeatability for the purpose of quantitative analysis. Precision is defined as the degree of agreement
among a set of values. Precision under repeatability conditions is measured by having a single analyst in a single laboratory use
a single set of equipment to prepare and analyze portions of a material with low heterogeneity. Precision under reproducibility
conditions is measured by having a number of different analysts at different laboratories prepare and analyze portions of a
homogeneous material. Any number of conditions intermediate between repeatability conditions and reproducibility conditions
may be used if the data serves a useful purpose. A good example is having multiple analysts in a single laboratory perform the
analyses, perhaps on multiple days. In the terminology of Committee E01, repeatability is the same as within-laboratory standard
deviation, S , which is defined as the standard deviation of results collected on the same material in the same laboratory on different
r
days. In contrast, reproducibility is synonymous with between-laboratory standard deviation, S , which is defined as the standard
R
deviation of results obtained on the same material in different laboratories.
5.1.1.1 The most common estimators of precision are standard deviation, relative standard deviation, and variance. Equations and
examples are available in many texts on statistics.
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5.1.1.2 The concept of maintenance of the repeatability over a period of time is known as statistical control. The laboratory can
implement tools such as control charts to demonstrate statistical control.
5.1.2 Limit of Detection (L )—The limit of detection is defined as the lowest amount of analyte that can be distinguished from
D
background by an analytical method. It is important to demonstrate that the measurement process has the capability to detect a
significantly lower amount (concentration or mass fraction) of the analyte than the laboratory must quantify. For additional
information, consult the IUPAC Orange Book and the Currie paper (4).
5.1.3 Limit of Quantification (L )—The limit of quantification is defined as the amount of analyte above which the estimated
Q
relative standard deviation (RSD) is ≤10 %. It is important to demonstrate and document that the measurement process has the
capability to quantify amounts less than or equal to those found in materials to which the test method is applied. For additional
information, consult the IUPAC Orange Book and the Currie paper (4).
5.1.4 Bias—Bias is the difference between the obtained result for a measurand and the true value of the measurand. An analytical
method may be subject to a known amount of bias that was estimated when the standard test method was developed and validated
by a committee. In an analogous manner, a laboratory developing a new test method or implementing a published standard test
method shall perform tests to estimate bias and demonstrate the method’s resistance to introduction of additional bias, that is,
ruggedness. Documentation of this performance enables the laboratory to elucidate the scope of the method and defend the results
obtained using the method.
NOTE 2—Accuracy is a concept related to both bias and precision. It is the combination of knowledge of both the precision obtainable under various
conditions and the amount of bias inherent in a given result. The concept of accuracy is often used in discussions of the fitness for purpose and the
reliability of results from a test method. In a published standard test method, the statements of precision and bias taken together provide the basis for
judgments of the accuracy of the test method.
5.1.5 Selectivity—The selectivity of a method is its ability to produce a result that is not subject to change in the presence of
interfering constituents. The selectivity of a method can be investigated by introducing or varying amounts of substances and
evaluating the results for changes. By understanding the principal of measurement, the analyst may be able to define a short list
of suspected interferences and, thereby, limit the amount of effort needed to establish the significant interference effects.
5.1.6 Calibration Model—Relative methods require calibration using measurements of suitable reference materials and
mathematical fitting of the measured responses to an algorithm, that is, an equation thought to describe adequately the relationship
between the amount of analyte and the measured response. Algorithms are almost always an approximation of the real world, and
as such, their ability to fit the data has limits that can be tested by a variety of means including, but not limited to, analyses of
certified or other reference materials and statistical evaluation of confidence intervals bracketing the calibration curve and
extrapolating performance predictions beyond the range of the calibration.
5.1.6.1 Working Range—The term working range is a name given to the concept of a portion of a calibration that provides valid
results as opposed to portions that are not fit for purpose. The range in which the method is considered to be valid can be
characterized using a number of approaches. The preferred methods are those that use objective data for the purpose of illustrating
under which circumstances a calibration model is fit for purpose.
5.1.6.2 Calibration Performance—There are statistical methods for measuring how well the chosen calibration algorithm, often
a line, fits the data, for the calibrants, consisting of known amounts of analyte and measured responses from the analytical
instrument for the calibrants. For every calibrant, one may calculate the difference between known and calculated amounts. This
information can be used to describe the performance of all or part of the calibration. Many things can be done with the information,
including calculating the standard deviation of the differences described in the previous section, constructing confidence intervals
around all ofor part of the range of amounts, plotting the difference as a function of the amount to look for trends, and spotting
any individual calibrant that clearly performs more poorly than the rest. Documenting behaviors like these, seeking the causes, and
taking corrective actions are suggested means to validate a test method.
NOTE 3—The applications of statistical tools, for example, confidence intervals around a calibration, need not be restricted to the region bounded by the
calibration lowest and highest calibrants or the values of thelowest and highest validation reference materials measured using the method and a particular
calibration. These tools can be extrapolated and still provide valid estimates of method performance. Laboratories may refer to Ref (5).
5.1.7 Ruggedness—Considered in its classical sense, ruggedness of an analytical method is the resistance of the results to change
caused by variations in the operational aspects of a test method. Operations characteristics may include substitution of machines
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used to prepare a specimen, substitution of sources of reagents and ingredients, changes to environmental conditions, and even
changes of personnel. A task group of a standard development committee will perform ruggedness testing at an early stage in the
validation process and at a small number of laboratories before a larger set of laboratories are asked to invest in an interlaboratory
study. The laboratory implementing a test method is advised to perform their own ruggedness tests at any time during
implementation and regular use of the method to identify and document effects of changes of these types.
6. Means of Method Validation
6.1 Once method development following the considerations of Section 5 has been completed, evidence validating method is
required. have been completed, laboratories may use the techniques of Section 6 to validate analytical methods. Validation may
be performed by using a single method; however, multiple validation techniques increase the confidence that the method
performance is acceptable for meeting measurement quality objectives. Acceptable validation methods are described in the
following sections.technique, but the use of multiple techniques provides a higher level of confidence in the performance of the
method.
6.2 Analysis of Reference Materia
...