ASTM D6512-03
(Practice)Standard Practice for Interlaboratory Quantitation Estimate
Standard Practice for Interlaboratory Quantitation Estimate
SCOPE
1.1 This practice establishes a uniform standard for computing the interlaboratory quantitation estimate associated with Z % relative standard deviation (referred to herein as IQEZ %), and provides guidance concerning the appropriate use and application.
1.2 IQEZ % is computed to be the lowest concentration for which a single measurement from a laboratory selected from the population of qualified laboratories represented in an interlaboratory study will have an estimated Z % relative standard deviation (Z % RSD, based on interlaboratory standard deviation), where Z is typically an integer multiple of 10, such as 10, 20, or 30, but Z can be less than 10. The IQE10 % is consistent with the quantitation approaches of Currie (1) and Oppenheimer, et al (2).
1.3 The fundamental assumption of the collaborative study is that the media tested, the concentrations tested, and the protocol followed in the study provide a representative and fair evaluation of the scope and applicability of the test method as written. Properly applied, the IQE procedure ensures that the IQE has the following properties:
1.3.1 Routinely Achievable IQE Value—Most laboratories are able to attain the IQE quantitation performance in routine analyses, using a standard measurement system, at reasonable cost. This property is needed for a quantitation limit to be feasible in practical situations. Representative laboratories must be included in the data to calculate the IQE.
1.3.2 Accounting for Routine Sources of Error—The IQE should realistically include sources of bias and variation that are common to the measurement process. These sources include, but are not limited to: intrinsic instrument noise, some "typical" amount of carryover error; plus differences in laboratories, analysts, sample preparation, and instruments.
1.3.3 Avoidable Sources of Error Excluded—The IQE should realistically exclude avoidable sources of bias and variation; that is, those sources that can reasonably be avoided in routine field 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 was a way to detect and either correct or eliminate them.
1.4 The IQE applies to measurement methods for which calibration error is minor relative to other sources, such as when the dominant source of variation is one of the following:
1.4.1 Sample Preparationand calibration standards do not have to go through sample preparation.
1.4.2 Differences in Analystsand analysts have little opportunity to affect calibration results (as is the case with automated calibration).
1.4.3 Differences in Laboratories(for whatever reasons), perhaps difficult to identify and eliminate.
1.4.4 Differences in Instruments(measurement equipment), such as differences in manufacturer, model, hardware, electronics, sampling rate, chemical processing rate, integration time, software algorithms, internal signal processing and thresholds, effective sample volume, and contamination level.
1.5 Data Quality Objectives—Typically, one would compute the lowest % RSD possible for any given dataset for a particular method. Thus, if possible, IQE10 % would be computed. If the data indicated that the method was too noisy, one might have to compute instead IQE20 %, or possibly IQE 30 %. In any case, an IQE with a higher % RSD level (such as IQE50 %) would not be considered, though an IQE with RSD 10 % (such as IQE1 %) would be acceptable. The appropriate level of % RSD may depend on the intended use of the IQE.
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Designation: D 6512 – 03
Standard Practice for
1
Interlaboratory Quantitation Estimate
This standard is issued under the fixed designation D6512; 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 clude, but are not limited to: modifications to the sample;
modifications to the measurement procedure; modifications to
1.1 This practice establishes a uniform standard for com-
themeasurementequipmentofthevalidatedmethod,andgross
putingtheinterlaboratoryquantitationestimateassociatedwith
and easily discernible transcription errors, provided there was
Z% relative standard deviation (referred to herein as IQE ),
Z%
a way to detect and either correct or eliminate them.
and provides guidance concerning the appropriate use and
1.4 The IQE applies to measurement methods for which
application.
calibration error is minor relative to other sources, such as
1.2 IQE is computed to be the lowest concentration for
Z%
when the dominant source of variation is one of the following:
which a single measurement from a laboratory selected from
1.4.1 Sample Preparation, and calibration standards do not
the population of qualified laboratories represented in an
have to go through sample preparation.
interlaboratory study will have an estimated Z% relative
1.4.2 Differences inAnalysts,andanalystshavelittleoppor-
standard deviation (Z% RSD, based on interlaboratory stan-
tunitytoaffectcalibrationresults(asisthecasewithautomated
dard deviation), where Z is typically an integer multiple of 10,
calibration).
such as 10, 20, or 30, but Z can be less than 10. The IQE
10%
2 1.4.3 Differences in Laboratories (for whatever reasons),
is consistent with the quantitation approaches of Currie (1)
perhaps difficult to identify and eliminate.
and Oppenheimer, et al (2).
1.4.4 Differences in Instruments (measurementequipment),
1.3 The fundamental assumption of the collaborative study
suchasdifferencesinmanufacturer,model,hardware,electron-
is that the media tested, the concentrations tested, and the
ics, sampling rate, chemical processing rate, integration time,
protocolfollowedinthestudyprovidearepresentativeandfair
software algorithms, internal signal processing and thresholds,
evaluation of the scope and applicability of the test method as
effective sample volume, and contamination level.
written. Properly applied, the IQE procedure ensures that the
1.5 Data Quality Objectives—Typically, one would com-
IQE has the following properties:
pute the lowest % RSD possible for any given dataset for a
1.3.1 Routinely Achievable IQE Value—Most laboratories
particular method. Thus, if possible, IQE would be com-
10%
are able to attain the IQE quantitation performance in routine
puted. If the data indicated that the method was too noisy, one
analyses, using a standard measurement system, at reasonable
might have to compute instead IQE , or possibly IQE .
cost. This property is needed for a quantitation limit to be 20% 30%
In any case, an IQE with a higher % RSD level (such as
feasible in practical situations. Representative laboratories
IQE ) would not be considered, though an IQE with RSD
must be included in the data to calculate the IQE. 50%
<10% (such as IQE ) would be acceptable. The appropriate
1%
1.3.2 Accounting for Routine Sources of Error—The IQE
level of % RSD may depend on the intended use of the IQE.
should realistically include sources of bias and variation that
are common to the measurement process. These sources
2. Referenced Documents
include,butarenotlimitedto:intrinsicinstrumentnoise,some
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2.1 ASTM Standards:
“typical” amount of carryover error; plus differences in labo-
D2777 Practice for Determination of Precision and Bias of
ratories, analysts, sample preparation, and instruments.
Applicable Test Methods of Committee D19 on Water
1.3.3 Avoidable Sources of Error Excluded—The IQE
D6091 Practice for 99%/95% Interlaboratory Detection
should realistically exclude avoidable sources of bias and
Estimate (IDE) for Analytical Methods with Negligible
variation; that is, those sources that can reasonably be avoided
Calibration Error
in routine field measurements. Avoidable sources would in-
E1763 Guide for Interpretation and Use of Results from
Interlaboratory Testing of Chemical Analysis Methods
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This practice is under the jurisdiction of ASTM Committee D19 onWater and
is the direct responsibility of Subcommittee D19.02 on General Specifications,
Technical Resources, and Statistical Methods.
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Current edition approved March 10, 2003. Published May 2003. Originally For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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