EPA Method 18

1048METHOD18-MEASUREMENTOFGASEOUSORGANICCOMPOUNDEMISSIONSBYGASCHROMATOGRAPHYNOTE:Thismethodisnotinclusivewithrespecttospecifications(e.g.,equipmentandsupplies)andprocedures(e.g.,samplingandanalytical)essentialtoitsperformance.Somematerialisincorporatedbyreferencefromothermethodsinthispart.Therefore,toobtainreliableresults,personsusingthismethodshouldhaveathoroughknowledgeofatleastthefollowingadditionaltestmethods:Method1,Method2,Method3.NOTE:Thismethodshouldnotbeattemptedbypersonsunfamiliarwiththeperformancecharacteristicsofgaschromatography,norbythosepersonswhoareunfamiliarwithsourcesampling.Particularcareshouldbeexercisedintheareaofsafetyconcerningchoiceofequipmentandoperationinpotentiallyexplosiveatmospheres.1.0ScopeandApplication.1.1Analyte.Totalgaseousorganiccompounds.1.2Applicability.1.2.1Thismethodisdesignedtomeasuregaseousorganicsemittedfromanindustrialsource.Whiledesignedforppmlevelsources,somedetectorsarequitecapableofdetectingcompoundsatambientlevels,e.g.,ECD,ELCD,andheliumionizationdetectors.Someothertypesofdetectors1049areevolvingsuchthatthesensitivityandapplicabilitymaywellbeintheppbrangeinonlyafewyears.1.2.2Thismethodwillnotdeterminecompoundsthat(1)arepolymeric(highmolecularweight),(2)canpolymerizebeforeanalysis,or(3)haveverylowvaporpressuresatstackorinstrumentconditions.1.3Range.Thelowerrangeofthismethodisdeterminedbythesamplingsystem;adsorbentsmaybeusedtoconcentratethesample,thusloweringthelimitofdetectionbelowthe1partpermillion(ppm)typicallyachievablewithdirectinterfaceorbagsampling.TheupperlimitisgovernedbyGCdetectorsaturationorcolumnoverloading;theupperrangecanbeextendedbydilutionofsamplewithaninertgasorbyusingsmallervolumegassamplingloops.Theupperlimitcanalsobegovernedbycondensationofhigherboilingcompounds.1.4Sensitivity.Thesensitivitylimitforacompoundisdefinedastheminimumdetectableconcentrationofthatcompound,ortheconcentrationthatproducesasignal-to-noiseratioofthreetoone.Theminimumdetectableconcentrationisdeterminedduringthepresurveycalibrationforeachcompound.2.0SummaryofMethod.1050Themajororganiccomponentsofagasmixtureareseparatedbygaschromatography(GC)andindividuallyquantifiedbyflameionization,photoionization,electroncapture,orotherappropriatedetectionprinciples.Theretentiontimesofeachseparatedcomponentarecomparedwiththoseofknowncompoundsunderidenticalconditions.Therefore,theanalystconfirmstheidentityandapproximateconcentrationsoftheorganicemissioncomponentsbeforehand.Withthisinformation,theanalystthenpreparesorpurchasescommerciallyavailablestandardmixturestocalibratetheGCunderconditionsidenticaltothoseofthesamples.Theanalystalsodeterminestheneedforsampledilutiontoavoiddetectorsaturation,gasstreamfiltrationtoeliminateparticulatematter,andpreventionofmoisturecondensation.3.0Definitions.[Reserved]4.0Interferences.4.1ResolutioninterferencesthatmayoccurcanbeeliminatedbyappropriateGCcolumnanddetectorchoiceorbyshiftingtheretentiontimesthroughchangesinthecolumnflowrateandtheuseoftemperatureprogramming.4.2Theanalyticalsystemisdemonstratedtobeessentiallyfreefromcontaminantsbyperiodicallyanalyzingblanksthatconsistofhydrocarbon-freeairornitrogen.10514.3Samplecross-contaminationthatoccurswhenhigh-levelandlow-levelsamplesorstandardsareanalyzedalternatelyisbestdealtwithbythoroughpurgingoftheGCsampleloopbetweensamples.4.4Toassureconsistentdetectorresponse,calibrationgasesarecontainedindryair.Toadjustgaseousorganicconcentrationswhenwatervaporispresentinthesample,watervaporconcentrationsaredeterminedforthosesamples,andacorrectionfactorisapplied.4.5Thegaschromatographruntimemustbesufficienttoclearallelutingpeaksfromthecolumnbeforeproceedingtothenextrun(inordertopreventsamplecarryover).5.0Safety.5.1Disclaimer.Thismethodmayinvolvehazardousmaterials,operations,andequipment.Thistestmethodmaynotaddressallofthesafetyproblemsassociatedwithitsuse.Itistheresponsibilityoftheuserofthistestmethodtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortoperformingthistestmethod.Theanalyzerusersmanualshouldbeconsultedforspecificprecautionstobetakenwithregardtotheanalyticalprocedure.6.0EquipmentandSupplies.10526.1EquipmentneededforthepresurveysamplingprocedurecanbefoundinSection16.1.1.6.2EquipmentneededfortheintegratedbagsamplingandanalysisprocedurecanbefoundinSection8.2.1.1.1.6.3EquipmentneededfordirectinterfacesamplingandanalysiscanbefoundinSection8.2.2.1.6.4EquipmentneededforthedilutioninterfacesamplingandanalysiscanbefoundinSection8.2.3.1.6.5EquipmentneededforadsorbenttubesamplingandanalysiscanbefoundinSection8.2.4.1.7.0ReagentsandStandards.7.1ReagentsneededforthepresurveysamplingprocedurecanbefoundinSection16.1.2.7.2QualityAssuranceAuditSamples.Whenmakingcompliancedeterminations,anduponavailability,anauditsamplemaybeobtainedfromtheappropriateEPARegionalOfficeorfromtheresponsibleenforcementauthority.NOTE:Theresponsibleenforcementautorityshouldbenotifiedatleast30dayspriortothetestdatetoallowsufficienttimeforsampledelivery.8.0SampleCollection,Preservation,Storage,andTr