1492Ch27

Manahan,StanleyE.ANALYSISOFBIOLOGICALMATERIALSANDXENOBIOTICSEnvironmentalChemistryBocaRaton:CRCPressLLC,200027ANALYSISOFBIOLOGICALMATERIALSANDXENOBIOTICS____________________________________________________27.1.INTRODUCTIONAsdefinedinChapter22axenobioticspeciesisonethatisforeigntolivingsystems.Commonexamplesincludeheavymetals,suchaslead,whichservenophysiologicfunction,andsyntheticorganiccompoundsthatarenotmadeinnature.Exposureoforganismstoxenobioticmaterialsisaveryimportantconsiderationinenvironmentalandtoxicologicalchemistry.Therefore,thedeterminationofexposurebyvariousanalyticaltechniquesisoneofthemorecrucialaspectsofenvironmentalchemistry.Thischapterdealswiththedeterminationofxenobioticsubstancesinbiologicalmaterials.Althoughsuchsubstancescanbemeasuredinavarietyoftissues,thegreatestconcernistheirpresenceinhumantissuesandothersamplesofhumanorigin.Therefore,themethodsdescribedinthischapterapplyprimarilytoexposedhumansubjects.Theyareessentiallyidenticaltomethodsusedonotheranimalsand,infact,mostweredevelopedthroughanimalstudies.Significantlydifferenttech-niquesmayberequiredforplantormicrobiologicalsamples.Themeasurementofxenobioticsubstancesandtheirmetabolitesinblood,urine,breath,andothersamplesofbiologicalorigintodetermineexposuretotoxicsubstancesiscalledbiologicalmonitoring.Comparisonofthelevelsofanalytesmeasuredwiththedegreeandtypeofexposuretoforeignsubstancesisacrucialaspectoftoxicologicalchemistry.Itisanareainwhichrapidadvancesarebeingmade.Forcurrentinformationregardingthisarea,thereaderisreferredtoexcellentreviewsofthetopic,1,2andseveralbooksonbiologicalmonitoringsuchasthosebyAngerer,Draper,Baselt,andKneipandcoauthorsaslistedinthebackofthischapterunder“SupplementaryReferences,”areavailableaswell.Thetwomainapproachestoworkplacemonitoringoftoxicchemicalsareworkplacemonitoring,usingsamplersthatsamplexenobioticsubstancesfromworkplaceair,andbiologicalmonitoring.Althoughtheanalysesaregenerallymuchmoredifficult,biologicalmonitoringisamuchbetterindicatorofexposurebecause©2000CRCPressLLCitmeasuresexposuretoallroutes—oralanddermalaswellasinhalation—anditgivesanintegratedvalueofexposure.Furthermore,biologicalmonitoringisveryusefulindeterminingtheeffectivenessofmeasurestakentopreventexposure,suchasprotectiveclothingandhygienicmeasures.27.2.INDICATORSOFEXPOSURETOXENOBIOTICSThetwomajorconsiderationsindeterminingexposuretoxenobioticsarethetypeofsampleandthetypeofanalyte.Bothoftheseareinfluencedbywhathappenstoaxenobioticmaterialwhenitgetsintothebody.Forsomeexposures,theentrysitecomposesthesample.Thisisthecase,forexample,inexposuretoasbestosfibersintheair,whichismanifestedbylesionstothelung.Morecommonly,theanalytemayappearatsomedistancefromthesiteofexposure,suchasleadinbonethatwasoriginallytakeninbytherespiratoryroute.Inothercasestheoriginalxenobioticisnotevenpresentintheanalyte.Anexampleofthisismethemoglobininblood,theresultofexposuretoanilineabsorbedthroughtheskin.Thetwomajorkindsofsamplesanalyzedforxenobioticsexposurearebloodandurine.Bothofthesekindsofsamplesareanalyzedforsystemicxenobiotics,whicharethosethataretransportedinthebodyandmetabolizedinvarioustissues.Xeno-bioticsubstances,theirmetabolites,andtheiradductsareabsorbedintothebodyandtransportedthroughitinthebloodstream.Therefore,bloodisofuniqueimportanceasasampleforbiologicalmonitoring.Bloodisnotasimplesampletoprocess,andsubjectsoftenobjecttotheprocessoftakingit.Uponcollection,bloodmaybetreatedwithananticoagulant,usuallyasaltofethylenediaminetetraaceticacid(EDTA),andprocessedforanalysisaswholeblood.Itmayalsobeallowedtoclotandbecentrifugedtoremovesolids;theliquidremainingisbloodserum.RecallfromChapter22thatastheresultofPhase1andPhase2reactions,xenobioticstendtobeconvertedtomorepolarandwatersolublemetabolites.Theseareeliminatedwiththeurine,makingurineagoodsampletoanalyzeasevidenceofexposuretoxenobioticsubstances.Urinehastheadvantageofbeingasimplermatrixthanbloodandonethatsubjectsmorereadilygiveforanalysis.Otherkindsofsamplesthatmaybeanalyzedincludebreath(forvolatilexenobioticsandvolatilemetabolites),airornails(fortraceelements,suchasselenium),adiposetissue(fat),andmilk(obviouslylimitedtolactatingfemales).Variouskindsoforgantissuecanbeanalyzedincadavers,whichcanbeusefulintryingtodeterminecauseofdeathbypoisoning.Thechoiceoftheanalyteactuallymeasuredvarieswiththexenobioticsubstancetowhichthesubjecthasbeenexposed.Therefore,itisconvenienttodividexenobioticanalysisonthebasisofthetypeofchemicalspeciesdetermined.Themoststraightforwardanalyteis,ofcourse,thexenobioticitself.Thisappliestoelementalxenobiotics,especiallymetals,whicharealmostalwaysdeterminedintheelementalform.Inafewcasesorganicxenobioticscanalsobedeterminedastheparentcompound.However,organicxenobioticsarecommonlymetabolizedtootherproductsbyPhase1andPhase2reactions.Commonly,thePhase1reactionproductismeasured,oftenafteritishydrolyzedfromthePhase2conjugate,usingenzymesoracidhydrolysisprocedures.Thus,forexample,trans,trans-muconicacidcanbemeasuredasevidenceofexposuretotheparentcompoundbenzene.Inothercasesa©2000CRC