ASTM D6091-07

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6091 − 07 AnAmerican National Standard
Standard Practice for
99 %/95 % Interlaboratory Detection Estimate (IDE) for
1
Analytical Methods with Negligible Calibration Error
This standard is issued under the fixed designation D6091; 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 routine field measurements. Avoidable sources would include,
but are not limited to: modifications to the sample, measure-
1.1 This practice establishes a standard for computing a
ment procedure, or measurement equipment of the validated
99%/95% Interlaboratory Detection Estimate (IDE) and pro-
method, and gross and easily discernible transcription errors
videsguidanceconcerningtheappropriateuseandapplication.
(provided there was a way to detect and either correct or
The calculations involved in this practice can be performed
eliminate them).
with DQCALC, Microsoft Excel-based software available
2
1.3.4 Low Probability of False Detection —The IDE is a
from ASTM.
true concentration consistent with a measured concentration
1.2 The IDE is computed to be the lowest concentration at
threshold (critical measured value) that will provide a high
whichthereis90%confidencethatasinglemeasurementfrom
probability, 99%, of true nondetection (a low probability of
a laboratory selected from the population of qualified labora-
false detection, α=1%). Thus, when measuring a blank
tories represented in an interlaboratory study will have a true
sample, the probability of not detecting the analyte would be
detection probability of at least 95% and a true nondetection
99%.Tobeuseful,thismustbedemonstratedfortheparticular
probability of at least 99% (when measuring a blank sample).
matrix being used, and not just for reagent water.
1.3 The fundamental assumption of the collaborative study
1.3.5 Low Probability of False Nondetection—The IDE
is that the media tested, the concentrations tested, and the
should be a true concentration at which there is a high
protocolfollowedinthestudyprovidearepresentativeandfair
probability, at least 95%, of true detection (a low probability
evaluation of the scope and applicability of the test method as of false nondetection, β=5%, at the IDE), with a simultane-
written.Whenproperlyapplied,theIDEprocedureensuresthat
ous low probability of false detection (see 1.3.4). Thus, when
the 99%/95% IDE has the following properties: measuring a sample at the IDE, the probability of detection
1.3.1 Routinely Achievable IDE Value —Most laboratories
wouldbeatleast95%.Tobeuseful,thismustbedemonstrated
are able to attain the IDE detection performance in routine
for the particular matrix being used, and not just for reagent
analyses, using a standard measurement system, at reasonable
water.
cost. This property is needed for a detection limit to be
NOTE 1—The referenced probabilities, α and β, are key parameters for
practically feasible. Representative laboratories must be in-
risk-based assessment of a detection limit.
cluded in the data to calculate the IDE.
1.4 The IDE applies to measurement methods for which
1.3.2 Routine Sources of Error Accounted for—The IDE
calibration error is minor relative to other sources, such as
shouldrealisticallyincludesourcesofbiasandvariationwhich
when the dominant source of variation is one of the following
are common to the measurement process. These sources
(with comment):
include,butarenotlimitedto:intrinsicinstrumentnoise,some
1.4.1 Sample Preparation, and calibration standards do not
typical amount of carryover error, plus differences in
have to go through sample preparation.
laboratories, analysts, sample preparation, and instruments.
1.4.2 Differences in Analysts,andanalystshavelittleoppor-
1.3.3 Avoidable Sources of Error Excluded—The IDE
tunity to affect calibration results (such as with automated
should realistically exclude avoidable sources of bias and
calibration).
variation, that is, those which can reasonably be avoided in
1.4.3 Differences in Laboratories , for whatever reasons,
perhaps difficult to identify and eliminate.
1
This practice is under the jurisdiction ofASTM Committee D19 on Water and
1.4.4 Differences in Instruments (measurement equipment),
is the direct responsibility of Subcommittee D19.02 on Quality Systems,
which could take the form of differences in manufacturer,
Specification, and Statistics.
Current edition approved March 1, 2007. Published April 2007. Originally
model,hardware,electronics,samplingrate,chemicalprocess-
approved in 1997. Last previous edition approved in 2003 as D6091–03. DOI:
ing rate, integration time, software algorithms, interna
...