ASTM_D_6091_-_07_2014.pdf

Designation:D609107(Reapproved 2014)Standard Practice for99%95%Interlaboratory Detection Estimate(IDE)forAnalytical Methods with Negligible Calibration Error1This standard is issued under the fixed designation D6091;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice establishes a standard for computing a99%95%Interlaboratory Detection Estimate(IDE)and pro-vides guidance concerning the appropriate use and application.The calculations involved in this practice can be performedwith DQCALC,Microsoft Excel-based software availablefrom ASTM.21.2 The IDE is computed to be the lowest concentration atwhich there is 90%confidence that a single measurement froma laboratory selected from the population of qualified labora-tories represented in an interlaboratory study will have a truedetection probability of at least 95%and a true nondetectionprobability of at least 99%(when measuring a blank sample).1.3 The fundamental assumption of the collaborative studyis that the media tested,the concentrations tested,and theprotocol followed in the study provide a representative and fairevaluation of the scope and applicability of the test method aswritten.When properly applied,the IDE procedure ensures thatthe 99%95%IDE has the following properties:1.3.1 Routinely Achievable IDE ValueMost laboratoriesare able to attain the IDE detection performance in routineanalyses,using a standard measurement system,at reasonablecost.This property is needed for a detection limit to bepractically feasible.Representative laboratories must be in-cluded in the data to calculate the IDE.1.3.2 Routine Sources of Error Accounted ForThe IDEshould realistically include sources of bias and variation whichare common to the measurement process.These sourcesinclude,but are not limited to:intrinsic instrument noise,sometypical amount of carryover error,plus differences inlaboratories,analysts,sample preparation,and instruments.1.3.3 Avoidable Sources of Error ExcludedThe IDEshould realistically exclude avoidable sources of bias andvariation,that is,those which can reasonably be avoided inroutine field measurements.Avoidable sources would include,but are not limited to:modifications to the sample,measure-ment procedure,or measurement equipment of the validatedmethod,and gross and easily discernible transcription errors(provided there was a way to detect and either correct oreliminate them).1.3.4 Low Probability of False DetectionThe IDE is a trueconcentration consistent with a measured concentration thresh-old(critical measured value)that will provide a highprobability,99%,of true nondetection(a low probability offalse detection,=1%).Thus,when measuring a blanksample,the probability of not detecting the analyte would be99%.To be useful,this must be demonstrated for the particularmatrix being used,and not just for reagent water.1.3.5 Low Probability of False NondetectionThe IDEshould be a true concentration at which there is a highprobability,at least 95%,of true detection(a low probabilityof false nondetection,=5%,at the IDE),with a simultane-ous low probability of false detection(see 1.3.4).Thus,whenmeasuring a sample at the IDE,the probability of detectionwould be at least 95%.To be useful,this must be demonstratedfor the particular matrix being used,and not just for reagentwater.NOTE1The referenced probabilities,and,are key parameters forrisk-based assessment of a detection limit.1.4 The IDE applies to measurement methods for whichcalibration error is minor relative to other sources,such aswhen the dominant source of variation is one of the following(with comment):1.4.1 Sample Preparation,and calibration standards do nothave to go through sample preparation.1.4.2 Differences in Analysts,and analysts have little oppor-tunity to affect calibration results(such as with automatedcalibration).1.4.3 Differences in Laboratories,for whatever reasons,perhaps difficult to identify and eliminate.1.4.4 Differences in Instruments(measurement equipment),which could take the form of differences in manufacturer,model,hardware,electronics,sampling rate,chemical process-ing rate,integration time,software algorithms,internal signalprocessing and thresholds,effective sample volume,and con-tamination level.1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.02 on Quality Systems,Specification,and Statistics.Current edition approved Jan.15,2014.Published February 2014.Originallyapproved in 1997.Last previous edition approved in 2007 as D6091 07.DOI:10.1520/D6091-07R14.2Available fromASTM International Headquarters.OrderAdjunct No.ADJDQ-CALC.Original adjunct produced in 2007.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Co