ASTM D6091-03

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D 6091 – 03
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 D 6091; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope method, and gross and easily discernible transcription errors
(provided there was a way to detect and either correct or
1.1 This practice establishes a standard for computing a
eliminate them).
99%/95% Interlaboratory Detection Estimate (IDE) and pro-
1.3.4 Low Probability of False Detection—The IDE is a
videsguidanceconcerningtheappropriateuseandapplication.
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, a=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, b=5%, at the IDE), with a simulta-
written.Whenproperlyapplied,theIDEprocedureensuresthat
neouslowprobabilityoffalsedetection(see1.3.4).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
practically feasible. Representative laboratories must be in-
NOTE 1—The referenced probabilities, a and b, are key parameters for
cluded in the data to calculate the IDE. risk-based assessment of a detection limit.
1.3.2 Routine Sources of Error Accounted for—The IDE
1.4 The IDE applies to measurement methods for which
shouldrealisticallyincludesourcesofbiasandvariationwhich
calibration error is minor relative to other sources, such as
are common to the measurement process. These sources
when the dominant source of variation is one of the following
include,butarenotlimitedto:intrinsicinstrumentnoise,some
(with comment):
typical amount of carryover error, plus differences in labora-
1.4.1 Sample Preparation, and calibration standards do not
tories, analysts, sample preparation, and instruments.
have to go through sample preparation.
1.3.3 Avoidable Sources of Error Excluded—The IDE
1.4.2 Differences in Analysts,andanalystshavelittleoppor-
should realistically exclude avoidable sources of bias and
tunity to affect calibration results (such as with automated
variation, that is, those which can reasonably be avoided in
calibration).
routine field measurements.Avoidable sources would include,
1.4.3 Differences in Laboratories, for whatever reasons,
but are not limited to: modifications to the sample, measure-
perhaps difficult to identify and eliminate.
ment procedure, or measurement equipment of the validated
1.4.4 Differences in Instruments (measurementequipment),
which could take the form of differences in manufacturer,
model,hardware,electronics,samplingrate,chemicalprocess-
1
This practice is under the jurisdiction ofASTM Committee D19 on Water and
ing rate, integration time, software algorithms, internal signal
is the direct responsibility of Subcommittee D19.02 on General Specifications,
Technical Resources, and Statistical Methods.
processing and thresholds, effective sample volume, and con-
Current edition approvedAug. 10, 2003. Published September 2003. Originally
tamination level.
approved in 1997. Last previous edition approved in 1997 as D6091–97.
Copyright © ASTM International, 100 Barr Harbor Drive, PO
...