BackgroundInformationontheProposedMDLRevisionThefollowingpresentationwascreatedbyRichardBurrowswhowasoneofthemembersofTheNELACInstitute(TNI)thattooktheleadonrevisingtheMethodDetectionLimit(MDL).ItoutlinestherationalefortheproposedrevisiontotheMDLandgivesbackgroundinformationonthetopic.TheMDLproposedbyTNIwentthroughseveralroundsofreviewfromitsdiversemembersandoutsidereviewers,includingfederalgovernmentagencies,stategovernments,municipalities,andcommerciallaboratoriesofallsizes.TheMDLproposedbyTNIwasthenreviewedbytheEPAworkgroupcomposedof14differentoffices(including8ofthe10EPAregions).TheEPAworkgroupmadesomeminorchangestotheMDLsubmittedbyTNI.BoththeversionsubmittedbyTNIandtheMDLrevisionintheProposedCleanWaterActMethodsUpdateRulefortheAnalysisofEffluentareavailableintheDocket.TheRevisedMDLintheproposedruledoesnotaddressquantitationlimits.Really– ArevisedMDLprocedureRichardBurrowsDawnoftheMDL1984USEPAtheMDLprocedureispromulgatedin40CFR,Part136,AppendixBforuseinthewastewaterprogramanddefinedas3.14timesthestandarddeviationofsevenlowlevelspikedblanks.TheMLisalsopromulgatedatthistime.MDLRising1999 USEPApublishedMethod1631BforanalysisofmercuryusingtheoldMDLapproachandmodifiedMLdefinition,whichprovidedanopportunityforalegalchallengeoftheMDLandML.2000 USEPAenteredintoasettlementagreementwiththeAllianceofAutomobileManufactures,ChemicalManufacturer’sAssociation,UtilityWaterActGroupandAFPA.Whatweretheobjections?MDLproceduremakestheassumptionthatblankresultsarecenteredaroundzeroIftheyarenot,thentheMDLwillbeanunderestimateandmanyfalsepositiveswillresultMDLmakestheassumptionthatshorttermvariance(7replicatesinonebatch)isthesameaslongtermvarianceIfitisnot,thentheMDLwillbeanunderestimateandmanyfalsepositiveswillresultSecondaryconcernsAssumptionofconstantvarianceatdifferentconcentrationsAssumptionofnormaldistributionLackofanyguaranteeofactualdetectabilityLackofuseofLDinCurrie’sclassicLC/LD/LQdescriptionofperformanceinthedetection–quantitationrangeTheclassicdefinitionof“Detected”isfromLloydCurrie.Hecalledthevaluewhereyouarealmostpositiveyourdetectionisnotbackgroundthe“CriticalLevelLC”.Whatdoesdetectedmean?TheMDLisequaltoLCPreviousattemptstoUpdateGuidelinesEstablishingTestProceduresfortheAnalysisofPollutants;ProceduresforDetectionandQuantitation68FR11770March12th2003ACILprocedure(2003‐2005)Consensusprocedure(2005‐2006)FACDQProcedure(2005‐2007)Reason#1thatweneedMDLsWeneedtomaketheQuantitationlimitmeaningfulAppliestoMRL,LLOQ,oranyquantitationlimit01234567891011012345678

Reported ConcentrationReplicateNumber9Meanrecovery90%recovery,9%RSDSpike#1 #2 #3 #4 #5 #6 #7Mean MDL109 8.3 9.8 9.3 8.1 8.6 10.09.0 2.29SpikeTrueValue=LLOQCalculatedMDLMDL=2.29Reportedresults(withoutMDL)ND ND ND ND ND ND 10Reason#2thatweneedMDLsMDLsareneededinriskassessmentHandlingnon‐detectsSubstituteavaluesuchas1⁄2detectionlimitordetectionlimitMoresophisticatedmethodssuchasMaximumLikelihoodestimationandRegressiononOrderstatisticsThesestillbenefitfromadetectionlimitaslowaspossibleIfwedonothaveadetectionlimit,theQuantitationlimitwillbecomethenewDetectionlimitWhatareouroptions?ReplacetheMDLDQFACprocedureASTMIDE/WDEStopreportingbelowthequantitationlimitLeavetheMDLaloneImprovethingsforTNIlabsatleast,throughdevelopmentofastandardbytheEMMECModifytheMDLBasedonprinciplesfromtheDQFACandlearningfromthePilotsFromNEMC2012ProposedMDLrevision(2012‐2014)HassimilaritiestoACIL,ConsensusandFACDQ,butsimplifiedandlessdifferentfromthecurrentMDLOneprocedureratherthantwo,startwith7spikesand7blanksMDLS=tSs(StdDevofspikes)MDLB=X+tSb(Std Dev ofblanks)UsewhicheverishighestastheMDLRequiresongoingspikesProposedMDLrevisionRequiresspreadingtheinitial7replicatesacrossatleast3batchesIncludesinstructionsformultipleinstrumentswiththesameassignedMDLRequiresthatspikeresultsmeetqualitativeIDcriteriaRequiresongoing(quarterly)spikesRecalculate(butdonotredo)everyyearIncludesinstructionsfordeterminationofaMDLinaspecificmatrixRun 7 spikes at orbelow desiredLOQ (recommend1⁄2 LOQ)Run 7 methodblanksDoresultsmeetqual ID?Calculate MDLsCalculate MDLbSet higher ofMDLs and MDLbas MDLSet LOQ at spikelevelSet LOQ at 3xMDLFix problem orraise spike leveland repeatNoYesNoYesINITIAL DETERMINATION OF LOQ AND LODIs the spike level>3X MDL?Run 7 spikes at orbelow desiredLOQ (recommend1⁄2 LOQ)Run 7 methodblanksDoresultsmeetqual ID?Calculate MDLsCalculate MDLbSet higher ofMDLs and MDLbas MDLSet LOQ at spikelevelSet LOQ at 3xMDLFix problem orraise spike leveland repeatNoYesNoYesINITIAL DETERMINATION OF LOQ AND LODIs the spike level>3X MDL?INITIALDETERMINATIONOFLOQANDLOD...Run7spik.e.satorbelowdesired...LOQ(recommend%LOQ)Run7methodblanksRun 7 spikes at orbelow desiredLOQ (recommend1⁄2 LOQ)Run 7 methodblanksDoresultsmeetqual ID?Calculate MDLsCalculate MDLbSet higher ofMDLs and MDLbas MDLSet LOQ at spikelevelSet LOQ at 3xMDLFix problem orraise spike leveland repeatNoYesNoYesINITIAL DETERMINATION OF LOQ AND LODIs the spike level>3X MDL?lilI0FixproblemorraisespikelevelandrepeatRun7spik.esatorbelowdesiredLOQ(recommendLOQ}DoresultsmeetquaiiD?YesIRun 7 spikes at orbelow desiredLOQ (recommend1⁄2 LOQ)Run 7 methodblanksDoresultsmeetqual ID?Calculate MDLsCalculate MDLbSet higher ofMDLs and MDLbas MDLSet LOQ at spikelevelSet LOQ at 3xMDLFix problem orraise spike leveland repeatNoYesNoYesINITIAL DETERMINATION OF LOQ AND LODIs the spike level>3X MDL?0YesCalculateMDLs,,CalculateMDLbRun 7 spikes at orbelow desiredLOQ (recommend1⁄2 LOQ)Run 7 methodblanksDoresultsmeetqual ID?Calculate MDLsCalculate MDLbSet higher ofMDLs and MDLbas MDLSet LOQ at spikelevelSet LOQ at 3xMDLFix problem orraise spike leveland repeatNoYesNoYesINITIAL DETERMINATION OF LOQ AND LODIs the spike level>3X MDL?Run 7 spikes at orbelow desiredLOQ (recommend1⁄2 LOQ)Run 7 methodblanksDoresultsmeetqual ID?Calculate MDLsCalculate MDLbSet higher ofMDLs and MDLbas MDLSet LOQ at spikelevelSet LOQ at 3xMDLFix problem orraise spike leveland repeatNoYesNoYesINITIAL DETERMINATION OF LOQ AND LODIs the spike level>3X MDL?Doestherevisedprocedureaddresstheproblemsandconcerns?BlankdistributionnotcenteredaroundzeroThisisthemostimportantcauseoffailureofthecurrentMDLprocedureformethodssuchasICP,ICPMS,andmostWetChemistryprocedures,andresultsinhighfalsepositiveratesSituationisgettingworsebecauseinstrumentsensitivityisincreasinganddetectionlimitsarepushedlower.FullyaddressedintherevisedprocedureLeadinParticulateMatter0501001502002503003501234567UltrasonicextractionQuartzfilterblanksBlankresultMDL(S)X+tsDoestherevisedprocedureaddresstheproblemsandconcerns?Shorttermvariance(onebatch)isnotequaltolongtermvarianceInitialreplicatesspreadacrossbatchesandinstrumentsOngoingdatacollectionquarterlyDoestherevisedprocedureaddresstheproblemsandconcerns?AssumptionofconstantvarianceandnormaldistributionNowayaroundthisissuewithoutcollectionofverylargeamountsofdataVerificationstepscheckforandcorrectproblemsduetovery“non‐normal”datadistributionsDoestherevisedprocedureaddresstheproblemsandconcerns?LackofguaranteeofactualdetectabilityNotreasonabletoexpectthatspikesattheMDLwillreliablyreturndetectableresultsSpikesusedtogeneratetheMDLmustbereturndetectableresultsandmaytypicallybeusedtosettheLOQIfspikesattheMDLreturndetectableresults,thenthoseresultscanbeusedtocalculatealowerMDL!Doestherevisedprocedureaddresstheproblemsandconcerns?LackofuseofLDinCurrie’sclassicLC/LD/LQdescriptionofperformanceinthedetection–quantitationrangeDoestherevisedprocedureaddresstheproblemsandconcerns?LackofuseofLDinCurrie’sclassicLC/LD/LQdescriptionofperformanceinthedetection–quantitationrangeAccuratedeterminationofLDisverydifficultTypicallyquiteclosetotheLOQInstead,ensurethattheLOQhasallthepropertiesofLODReturnsresultsabovetheMDLCompatibilitywithQuantitationLimitconceptsSpikesusedtoverifyLLOQ(SW‐846)orMRL(DrinkingWater)willusuallybesuitableforcalculatingMDLs.

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Number of Method Blank ResultsMDL(b)= .13699% = .174MDL(s)= .325Fits normal distribution, S-W p=.082Mercury (ng/L) by 1631-0.02-.010.010.02MDL(s)99%.015MDL(b)LOQ(0.438)

N um ber of M ethod B lank R esultsDoes not fit normal distribution, S-W p=.005MDL(s)= .09699% = .098MDL(b)= .146TP (mg P/L) by 365.1-0.000200.0002MDL(s)MDL(b)99%LOQ(0.003)0246810121416

N um ber of M ethod B lank R esultsMDL(s)= .000821MDL(b)= .00095799% = .001Fits normal distribution, S-W p=.822NH3(mg N/L)-0.000200.0002.0013MDL(s)99%MDL(b).0040LOQ(0.0043)024681012

N um ber of M ethod B lank R esultsMDL(s)= .00111999% = .0014MDL(b)= .001422Fits normal distribution, S-W p=.251Questions?