ASTM D7783-21
(Practice)Standard Practice for Within-laboratory Quantitation Estimation (WQE)
Standard Practice for Within-laboratory Quantitation Estimation (WQE)
SIGNIFICANCE AND USE
5.1 Appropriate application of this practice should result in a WQE achievable by the laboratory in applying the tested method/matrix/analyte combination to routine sample analysis. That is, a laboratory should be capable of measuring concentrations greater than WQEZ %, with the associated RSD equal to Z % or less.
5.2 The WQE values may be used to compare the quantitation capability of different methods for analysis of the same analyte in the same matrix within the same laboratory.
5.3 The WQE procedure should be used to establish the within-laboratory quantitation capability for any application of a method in the laboratory where quantitation is important to data use. The intent of the WQE is not to impose reporting limits. The intent is to provide a reliable procedure for establishing the quantitative characteristics of the method (as implemented in the laboratory for the matrix and analyte) and thus to provide the laboratory with reliable information characterizing the uncertainty in any data produced. Then the laboratory can make informed decisions about censoring data and has the information necessary for providing reliable estimates of uncertainty with reported data.
SCOPE
1.1 This practice establishes a uniform standard for computing the within-laboratory quantitation estimate associated with Z % relative standard deviation (referred to herein as WQEZ %), and provides guidance concerning the appropriate use and application.
1.2 WQEZ % is computed to be the lowest concentration for which a single measurement from the laboratory will have an estimated Z % relative standard deviation (Z % RSD, based on within-laboratory standard deviation), where Z is typically an integer multiple of 10, such as 10, 20, or 30. Z can be less than 10 but not more than 30. The WQE10 % is consistent with the quantitation approaches of Currie (1)2 and Oppenheimer, et al. (2).
1.3 The fundamental assumption of the WQE is that the media tested, the concentrations tested, and the protocol followed in developing the study data provide a representative and fair evaluation of the scope and applicability of the test method, as written. Properly applied, the WQE procedure ensures that the WQE value has the following properties:
1.3.1 Routinely Achievable WQE Value—The laboratory should be able to attain the WQE in routine analyses, using the laboratory’s standard measurement system(s), at reasonable cost. This property is needed for a quantitation limit to be feasible in practical situations. Representative data must be used in the calculation of the WQE.
1.3.2 Accounting for Routine Sources of Error—The WQE should realistically include sources of bias and variation that are common to the measurement process and the measured materials. These sources include, but are not limited to intrinsic instrument noise, some typical amount of carryover error, bottling, preservation, sample handling and storage, analysts, sample preparation, instruments, and matrix.
1.3.3 Avoidable Sources of Error Excluded—The WQE should realistically exclude avoidable sources of bias and variation (that is, those sources that can reasonably be avoided in routine sample measurements). Avoidable sources include, but are not limited to, modifications to the sample, modifications to the measurement procedure, modifications to the measurement equipment of the validated method, and gross and easily discernible transcription errors (provided there is a way to detect and either correct or eliminate these errors in routine processing of samples).
1.4 The WQE applies to measurement methods for which instrument calibration error is minor relative to other sources, because this practice does not model or account for instrument calibration error, as is true of most quantitation estimates in general. Therefore, the WQE procedure is appropriate when the dominant source of variation is not instrument calibration, but is perhaps one or ...
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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.
Designation: D7783 − 21
Standard Practice for
1
Within-laboratory Quantitation Estimation (WQE)
This standard is issued under the fixed designation D7783; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope variation (that is, those sources that can reasonably be avoided
in routine sample measurements). Avoidable sources include,
1.1 This practice establishes a uniform standard for com-
but are not limited to, modifications to the sample, modifica-
puting the within-laboratory quantitation estimate associated
tions to the measurement procedure, modifications to the
with Z % relative standard deviation (referred to herein as
measurement equipment of the validated method, and gross
WQE ), and provides guidance concerning the appropriate
Z%
and easily discernible transcription errors (provided there is a
use and application.
way to detect and either correct or eliminate these errors in
1.2 WQE is computed to be the lowest concentration for
Z%
routine processing of samples).
which a single measurement from the laboratory will have an
estimated Z% relative standard deviation (Z% RSD, based on
1.4 The WQE applies to measurement methods for which
within-laboratory standard deviation), where Z is typically an
instrument calibration error is minor relative to other sources,
integer multiple of 10, such as 10, 20, or 30. Z can be less than
because this practice does not model or account for instrument
10 but not more than 30. The WQE is consistent with the
10 %
calibration error, as is true of most quantitation estimates in
2
quantitation approaches of Currie (1) and Oppenheimer, et al.
general. Therefore, the WQE procedure is appropriate when
(2).
the dominant source of variation is not instrument calibration,
but is perhaps one or more of the following:
1.3 The fundamental assumption of the WQE is that the
media tested, the concentrations tested, and the protocol
1.4.1 Sample Preparation, and especially when calibration
followed in developing the study data provide a representative
standards do not go through sample preparation.
and fair evaluation of the scope and applicability of the test
1.4.2 Differences in Analysts, and especially when analysts
method, as written. Properly applied, the WQE procedure
have little opportunity to affect instrument calibration results
ensures that the WQE value has the following properties:
(as is the case with automated calibration).
1.3.1 Routinely Achievable WQE Value—The laboratory
1.4.3 Differences in Instruments (measurement equipment),
shouldbeabletoattaintheWQEinroutineanalyses,usingthe
such as differences in manufacturer, model, hardware,
laboratory’s standard measurement system(s), at reasonable
electronics, sampling rate, chemical-processing rate, integra-
cost. This property is needed for a quantitation limit to be
tion time, software algorithms, internal signal processing and
feasible in practical situations. Representative data must be
thresholds, effective sample volume, and contamination level.
used in the calculation of the WQE.
1.3.2 Accounting for Routine Sources of Error—The WQE
1.5 Data Quality Objectives—For a given method, one
should realistically include sources of bias and variation that
typically would compute the WQE for the lowest RSD for
are common to the measurement process and the measured
which the data set produces a reliable estimate. Thus, if
materials.Thesesourcesinclude,butarenotlimitedtointrinsic
possible, WQE would be computed. If the data indicated
10%
instrument noise, some typical amount of carryover error,
that the method was too noisy, so that WQE could not be
10%
bottling, preservation, sample handling and storage, analysts,
computed reliably, one might have to compute instead
sample preparation, instruments, and matrix.
WQE , or possibly WQE . In any case, a WQE with a
20% 30%
1.3.3 Avoidable Sources of Error Excluded—The WQE
higherRSDlevel(suchasWQE )wouldnotbeconsidered,
50%
should realistically exclude avoidable sources of bias and
though a WQE with RSD < 10% (such as WQE ) could be
5%
acceptable. The appropriate level of RSD is based on the data
1
quality objective(s) for a particular use or uses. This practice
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.02 on Quality Systems,
allows for calculation of WQEs with user selected RSDs less
Specification, and Statistics.
than 30%.
Current edition ap
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7783 − 13 D7783 − 21
Standard Practice for
1
Within-laboratory Quantitation Estimation (WQE)
This standard is issued under the fixed designation D7783; 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.
Note—Balloted information was included and the year date changed on March 28, 2013.
1. Scope
1.1 This practice establishes a uniform standard for computing the within-laboratory quantitation estimate associated with Z %
relative standard deviation (referred to herein as WQE ), and provides guidance concerning the appropriate use and
Z %Z %
application.
1.2 WQE is computed to be the lowest concentration for which a single measurement from the laboratory will have an
Z% %
estimated Z %Z % relative standard deviation (Z %(Z % RSD, based on within-laboratory standard deviation), where Z is typically
an integer multiple of 10, such as 10, 20, or 30. Z can be less than 10 but not more than 30. The WQE is consistent with the
10 %
2
quantitation approaches of Currie (1) and Oppenheimer, et a.lal. (2).
1.3 The fundamental assumption of the WQE is that the media tested, the concentrations tested, and the protocol followed in the
developing the study data provide a representative and fair evaluation of the scope and applicability of the test method, as written.
Properly applied, the WQE procedure ensures that the WQE value has the following properties:
1.3.1 Routinely Achievable WQE Value—The laboratory should be able to attain the WQE in routine analyses, using the
laboratory‘slaboratory’s standard measurement system(s), at reasonable cost. This property is needed for a quantitation limit to be
feasible in practical situations. Representative data must be used in the calculation of the WQE.
1.3.2 Accounting for Routine Sources of Error—The WQE should realistically include sources of bias and variation that are
common to the measurement process and the measured materials. These sources include, but are not limited to intrinsic instrument
noise, some typical amount of carryover error, bottling, preservation, sample handling and storage, analysts, sample preparation,
instruments, and matrix.
1.3.3 Avoidable Sources of Error Excluded—The WQE should realistically exclude avoidable sources of bias and variation (that
is, those sources that can reasonably be avoided in routine sample measurements). Avoidable sources would include, but are not
limited to, modifications to the sample, modifications to the measurement procedure, modifications to the measurement equipment
of the validated method, and gross and easily discernible transcription errors (provided there wasis a way to detect and either
correct or eliminate these errors in routine processing of samples).
1.4 The WQE applies to measurement methods for which instrument calibration error is minor relative to other sources, because
1
This practice is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.02 on Quality Systems, Specification,
and Statistics.
Current edition approved March 28, 2013Nov. 15, 2021. Published April 2013March 2022. Originally approved in 2012. Last previous edition approved in 20122013 as
D7783 – 12.D7783 – 13. DOI: 10.1520/D7783-13.10.1520/D7783-21.
2
The boldface numbers in parentheses refer to athe list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D7783 − 21
this practice does not model or account for instrument calibration error, as is true of quantiation most quantitation estimates in
general. Therefore, the WQE procedure is appropriate when the dominant source of variation is not instrument calibration, but is
perhaps one or more of the following:
1.4.1 Sample Preparation, and especially when calibration standards do not go through sample preparation.
1.4.2 Differences in Analysts, and especially when analysts have little opportunity to affect instrument calibration results (as is the
case with automated calibration).
1.4.3 Differences in Instruments (measurement equipment), such as differences in manufacturer, model, hardware, electronics,
sampling rate, chemical-processing rate, integration time, software algorithms, internal
...
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