多维气相色谱图解.pdf

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1、MultidimensionalGasChromatographyExamplesofcomplexsamplesTobaccosmoke•TheuseoftwoormorecolumnstoOver1000peaksidentified-eachactuallycanresolveasample(orusingasinglecontaintwoormorecomponents.columninmorethanonedirection.PCBs•Currentcolumntechnologyisverynearthetheoretical

2、limit.207speciesbutonly~180resolved•However,it’sstillnotpossibletoCoffeeresolveallcomponentsinacomplexmixture.Over600componentsidentified.MultidimensionalGCMultidimensionalGCElementalspecificandmassdetectorsarehelpfulbutMethodreliesonpassingaportionofacolumnseffluentcan’tal

3、wayssolvetheproblem.toasecondcolumnusingflowswitching.injectiondetector1portExamplecolumn1switchingMScan’ttello-,m-,-psubstitutionorcisfromvalvetrans.detector2column2MultidimensionalGCcanassistinsomecasesandreliesonrelativelyinexpensivetechnology.MultidimensionalGCWhyboth

4、er?Basicassumptionisthatnosinglecolumncanresolveallcomponentsofinterest.column1PossiblechoicesBest-ifsinglecolumn/analysiscandothejob.heart-cutregionSecondbest-usetwoseparateassayswithdifferentconditionsorcolumns.column2Lastresort-multidimensionalGC.Whybother?ApproachesE

5、nrichmentSampleislimitedUsedtoincreaseamountsoftracecomponentsYouneedallofyourdatafromasinglerunHeart-cuttingTimeislimitedWhileamultidimensionalruncanbelongerthanaGrabsanunresolvedportionofasampleforsingleassay,itsstillshorterthantwoseparaterunsimprovedseparationEquipmen

6、tislimitedBackflushingOneGCsetupcandotheentireassayReversecolumnflowtodriveoffhighlyretainedcomponentsEnrichmentEnrichmentexamplePre-concentrationoftracecomponentsinitiallyonapackedcolumn.Moresamplecanbeplacedonapackedcolumnthanacapillary.Onlythetracecomponentsofinterestar

7、eenrichedregionpassedtothecapillarycolumn.assayedoncolumn2Resultsinmoresamplebeingintroduced.column1HeartcuttingHeart-cuttingexampleAlsocalled“cutandtransfer.”Nosinglecolumncanresolveallcomponentsofcolumn1interestoraverylargepeakmasksothercomponents.Passingtheunresolveda

8、reatoasecondcolumncanbeusedtofixtheproblem.column2Thesecondcolumncanalsobeadifferentpolarity.LatexBalloo