ASTM D7783-21

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
...