Designation:D3598−89(Reapproved2016)StandardTestMethodforCitrateinSyntheticDetergents1ThisstandardisissuedunderthefixeddesignationD3598;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoverstheenzymaticdeterminationofcitrateinbothliquidandsolidsyntheticdetergents.Thetestmethodisapplicabletomostdetergentscontainingcitrateataminimumconcentrationofapproximately5%(1-8).21.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.MaterialSafetyDataSheetsareavailableforreagentsandmaterials.Reviewthemforhazardspriortousage.2.ReferencedDocuments2.1ASTMStandards:3D501TestMethodsofSamplingandChemicalAnalysisofAlkalineDetergentsD1193SpecificationforReagentWater3.SummaryofTestMethod3.1Thistestmethodemploysanenzymesystemthatisbasedupontheselectivecleavageofcitratebycitratelyase(citrateoxaloacetate-lyase;EC4.1.3.6)(1).Oneoftheproducts,oxaloacetate,isreducedtomalatebymalicdehydro-genase(L-malate:NADoxidoreductase;EC1.1.1.37)withthesimultaneousoxidationofreducedβ-nicotinamideadeninedinucleotidetoβ-nicotinamideadeninedinucleotide,oxidizedform.Thecourseofthereactionismeasuredspectrophoto-metrically.Thedecreaseinabsorbanceat340nmcausedbytheformationofβ-nicotinamideadeninedinucleotide,oxidizedform,isdirectlyproportionaltotheconcentrationofcitrate.4.Interferences4.1Thetestmethodishighlyspecificforcitrate.Otherorganicacids,forexample,cisandtrans-aconitic,d,l-isocitric,α-ketoglutaric,oxalic,succinic,ortartaricacids,donotinter-fere.4.2Althoughlowlevelsofzincormagnesium,orb...
