Designation:D2685−11StandardTestMethodforAirandCarbonTetrafluorideinSulfurHexafluoridebyGasChromatography1ThisstandardisissuedunderthefixeddesignationD2685;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversthedeterminationofair(Note1)andcarbontetrafluorideasimpuritiesinsulfurhexafluoride.NOTE1—Nitrogen,oxygen,oranyoftheirmixturesisconsideredtobeair.Commercialgradeairornitrogenisusedforstandardization.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D2472SpecificationforSulfurHexafluorideE260PracticeforPackedColumnGasChromatographyE355PracticeforGasChromatographyTermsandRelation-ships3.SummaryofTestMethod3.1Airandcarbontetrafluorideareseparatedphysicallybygaschromatographyandcomparedtocorrespondingcompo-nentsseparatedundersimilarconditionsfromareferencestandardmixtureofknowncomposition.Theindividualcom-poundsofairarenotseparated.Thecompositionofthesampleiscalculatedfromitschromatogrambycomparingtheareaofthepeakofeachcomponentwiththeareaofthepeakofthecorrespondingcomponentonthereferencestandardchromato-gram.4.SignificanceandUse4.1Airandcarbontetrafluoride(CF4)aretwocontaminantsofinterestinsulfurhexafluoride(SF6).Bothofthesecontami-nantsadverselyaffecttheperformanceofSF6whenusedasanelectricalinsulatinggas.SpecificationformaximumlevelsofthesecontaminantsaregiveninSpecificationD2472.4.2Gaschromatographyisusedtoseparatethesecontami-nantsfromasampleofSF6andtodeterminetheirconcentra-tion.5.Apparatus5.1GasCh...
