Designation:D7675−22StandardTestMethodforDeterminationofTotalHydrocarbonsinHydrogenbyFID-BasedTotalHydrocarbon(THC)Analyzer1ThisstandardisissuedunderthefixeddesignationD7675;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethoddescribesaprocedurefortotalhydro-carbons(THC’s)measurementinhydrogenintendedasafuelonamethane(C1)basis.ThedeterminationofTHConaC1basisisananalyticaltechniquewhereallthehydrocarbonsareassumedtohavethesameresponseasmethane(CH4).Sensi-tivityfrom0.1partspermillionbyvolume(ppm(v),µmol/mol)upto1000ppm(v)concentrationisachievable.Highercon-centrationscanbeanalyzedusingappropriatedilutiontech-niques.Thistestmethodcanbeappliedtoothergaseoussamplesrequiringanalysisoftraceconstituentsprovidedanassessmentofpotentialinterferenceshasbeenaccomplished.1.2ThistestmethodisaFlameIonizationDetector-based(FID-based)hydrocarbonanalysismethodwithouttheuseofseparationcolumns.Therefore,thismethoddoesnotprovidespeciationofindividualhydrocarbons.Severalvarietiesofinstrumentsaremanufacturedandcanbeusedforthismethod.1.2.1ThismethodprovidesameasureofTHC“asCH4,”becauseallhydrocarbonspeciesarequantifiedthesameasCH4response,whichisthesolespeciesusedforcalibration.MagnitudeoftheFIDresponsetoanatomofcarbonisdependentonthechemicalenvironmentofthisatominthemolecule.ThismethodprovidestheTHCresultasifallcarbonatomsarefromaliphatic,aromatic,olefinic,oracetyleniccompounds,wherethedetectorresponsecausedbytheseatomsisapproximatelyrelativetothenumberofcarbonatomspresentinthemolecule.Othertypesofmolecules,includingthosecontainingoxygenorchlorineatoms,willresponddifferentlyandusuallymuchlowerthanthecorrespondingaliphatichydrocarbon.Therefore,othermethods(TestMethodsD7653,D7892,orequivalent)mustbeutilizedtodeterminetheexactconstituentsoftheTHCresponsedetermi...
