13-paper-Traceability of surface chemical analysis

1TraceabilityofsurfacechemicalanalysisinironandsteelindustryK.KakitaNipponSteelTechnoresearchCorporation,KSP-A101,3-2-1Sakado,Takatsu-ku,Kawasaki,213-0012,JapanABSTRACT:Chemicalanalysisofironandsteelhas“not”directtraceabilitytoSIunitorprimarystandardspecifiedinISO/IEC170251).Itisbelievedtraditionallythatspecifiedanalysismethodsshouldhaveametrologicaltraceabilitytoprimarymethodthroughreferencematerials.REMCOrecentlydefinedCRMfollowingtothistraditionalconcept.ThispaperdescribestheresultsofworksrelatingISOsub-committees,ICASI(InternationalCommitteeofAnalysisinSteelandIronIndustry)andinternationalproficiencytestprogrammeswhichwerecarriedoutinordertoestablishmetrologicaltraceabilityinchemicalanalysisinironandsteelindustry.1INTRODUCTIONISO/IEC17025specifiesthatmeasurementsmadebythelaboratoryaretraceabletotheInternationalSystemofUnits(SI),howeverifitisnotpossible,thesamerequirementsfortraceabilitytocertifiedreferencematerial(CRM)s,agreedmethodsand/orconsensusstandardsarerequired.Inthefieldofchemicalanalysisofironandsteel,wegenerallyanalysesamplesusingconsensusstandardsandCRMs.ConsensusstandardsaregenerallydevelopedbyInternationalOrganizationforStandardizationandnationalbodies.CRMsareproducedbyseveralkindsoforganization.AsaguideforproducingandcertifyingRMs,wecanreferISOGuide352)developedbyREMCO.ThisguiderecentlyrevisedthedefinitionofCRMasfollows;CRMisreferencematerial,characterizedbyametrologicallyvalidprocedureforoneormorespecifiedproperties,accompaniedbyacertificatethatprovidesthevalueofthespecifiedproperty,itsassociateduncertainty,andastatementofmetrologicaltraceability.ThemeaningofmetrologyisdescribedalsointheISOGuide343)and35.TraceabilityofcalibrationtoprimarystandardsofSI(suchaslength,voltageormassitself)isatypicalconceptofmetrologicaltraceability.Inchemicalanalysis,conceptoftraceabilityisdifferentfromtheabove.TheGuidesdistinguishesbetweenfourbasicapproachestothecharacterisationofCRMs.a)measurementbyasingle(primary)methodinasinglelaboratoryb)measurementbytwoormoreindependentreference(relative)methodsinonelaboratoryc)measurementbyanetworkoflaboratoriesusingoneormoremethodsofdemonstrableaccuracyd)amethod-specificapproachgivingonlymethod-specificassessedpropertyvalues,usinganetworkoflaboratories.Themetrologicaltraceabilityinchemicalanalysismeansthatreference(relative)methodshaveatraceabilitytoprimarymethods.Referencemethodsorconsensusstandardsshouldbetraceabletoprimarymethod.ThefirstpriorityofISO/TC17/SC1(subcommitteeforchemicalanalysismethodsofironandsteel)isto2developconsensusstandardwhichisprimarymethoditself,ifpossible,ortraceabletoit.SomeexamplesofmetrologicaltraceabilityinInternationalStandardsareshowninFig1.Anarrow→meansadirectionofstandarddevelopment.Inthecaseofdeterminationofcarbon;Gravimetry(ISO437)→InfraredabsorptionmethodaftercombustionusingpuresubstanceRM(ISO9556andISO15349)→InfraredabsorptionmethodaftercombustionusingironandsteelCRM(ISO15350)→SparkOESroutinemethod.StandardizationofsparkdischargeOESwastriedinISO/TC17/SC1,howeveritisnotyetdeveloped(currentlydeactivated).Carboncontentsinmassfraction%0.0054.5Primarymethods0.00030.0034.5Relativemethods0.0055.0Relativemethods5.5RelativemethodsMethodsdevelopmentformetrologicaltraceability0.001RefereemethodsRoutinemethods1100.10.00010.0010.010.1CoulometryISO/TR4830GravimetryISO437HF-IRISO9556HF-IRISO15349HF-IRISO15350SparkdischargeAESISO17056(notstandardized)Fig1MetrologicaltraceabilityofthemethodsfordeterminationofcarboninironandsteelAnanalyticalprocedurerequiresacalibrationgraphusingCRMs,RMs,orpuremetal/chemicalcompounds.Bythesemethodsmassofelementisindirectlymeasuredandcalledrelativemethods.ExamplesincludeICP-MS,ICP-AES,FAAS,MAS(spectrophotometry)andHF(RH)-IR(Infraredabsorptionmethodaftercombustioninaninduction/resistancefurnace).Itisrecommendedtovalidatethesemethodsbyprimarymethods.CCQMproposestoclassifytwokindofprimarymethods4);aprimarydirectmethodistomeasurethevalueofanunknownsamplewithoutreferencetoastandardofthesamequantity(eg.gravimetryandtitrimetry),andaprimaryratiomethodtomeasuresthevalueofanunknownsamplebyreferencetoastandardofthesamequantity.Itsoperationmustbecompletelydescribedbyameasurementequationthatwillincludereferencetoaprimarystandardofthesamequanty(eg.ID-ICP-MSandCP-AA).Fig2showsamapofapplicationrangesofanalyticalmethodsforchemicalelementsinironandsteel.Therangesofprimarymethodsandthoseofrelative(reference)methodsareshownseparately.Wecanseethatprimarymethodsarepreparedforsomeelementsbutnotfortheotherelemnts.FinanciallysupportedbytheScienceandTechnologyAgencyofJapan,severalkindsofprimarymethodswerestudiedtovalidaterelativemethodsfordeterminationoflowcontentrangeofsomeelements.Fig32alsoshowstheelementsandrangeofcontentsofprimarymethodsstudied.validationby;relativemethodsprimarymethodsID-ICP-MS(Gravimetry,titrimetry)NAA,ICP-MSCPAAVacuumfusionvolumetryInertgasfusionmethod0.000010.00010.0010.010.1110100CSiMnPSNiCrMoCuWVCoTiAlAsSnBNPbMgCaZnZrBiSeTeSbTaNbCdHgCeLaPrNdNaFeHO0200mass%Fig1Applicationrangeofchemicalanalysismethods(ISOandJIS)foriro