ionizationios10

1GasChromatography(GC;GLC;GSC)"BasicGasChromatography"byMcNair,Wiley,1997"ModernPractiseinGC"byGrob,pp.
900"GasChromatography"byWillett,pp.
250(Wiley)MartinandSynge1941idea;1952instrument1969NobelprizeManufacturersPerkinElmer,HewlettPackard,Shimadsu,Phillips,CarloErba,Varian,etcpriceinexpensive;manyperlaboratorySeparationtechnique—puren'simplepartitioningbetweentwophases2SchematicGCapparatusLiquidsampleofca.
0.
1mlvolumeinjectedviaasyringeintoheatedinjectorportwhereitisrapidlyvolatilisedandsweptbyastreamofflowing(carrier)gasthruacolumn&outviaadetector.
3Impuritiesinstyrene60mInnowax,2ml/minHe,1mlsplit80:1,80C(9min),5C/minto150C4SchematicgaschromatographCarriergas(highpurity,unreactive,cheap):N2,He,H2Flowcontrolconstant,reproducibleflowrateInjectionport(sampleinlet,microlitresyringe)Oven—thermostattedatconstantTorlinearrateColumnDetectorDataprocessingretentiontime(volume)peakarearecorder,integrator,microprocessor,computer,etc5Powerfulanalyticaltool—whyVerylargeseparatingpowerpara(138.
4°C),ortho(144.
4°C)&meta(139.
1°C)xyleneHighspeedofanalysisnosamplepre-treatmentusuallyQuantitativeanalysisexcellentHighsensitivity58ppmofphenylacetylene(#11)instyrenesampleQualitativeanalysistheAchillesheel!
Justbecausepeakat18minislabelleda-methylstyreneSimpletouseandoperateunskilled,automatic,lowcost6QualitativeanalysisIdentificationbasedonretentiontimes(volumes)NotconclusiveevenbycomparingtwoormoredifferentcolumnsIfanalytesknownthenreasonablesuppositionUnambiguousGC+MSorGC+IRMixtureofunknownalcoholsknownsn-amyl7Quantitativeanalysis5.
00mlofasolncontaininganinternalstandard,S,ofconcentration100mg/mlwereaddedtoasolnofunknown,X.
Chromatographyofthemixturegaveanarearatioof(AX/AS)=0.
81±0.
01.
Calibrationofknownweightratiomixesgave:weightratio,W=(WX/WS)0.
200.
400.
80arearatio,A=(AX/AS)0.
230.
460.
91CalculateweightofXinunknown.
Byleast-squares:A=1.
132W+0.
005soifA=0.
81thenW=0.
711butWS=500mg\WX=356mg8Detectors—keycomponentsFlameionizationfamilytheparentFID—workhorse,quasi-universal,reliableflamephotometricFPD—#6sulphur/phosphorusdetectoralkaliflameAFIDornitrogen/phosphorusNPDorTIDElectroncaptureECD—#5halothaneinbloodanalysisveryhighsensitivity,veryselectiveThermalconductivityTCDorHWDorkatharometerrobust,universal,lowsensitivityMassspectrometerMSD—expensivebutworthitexcellentforidentification9Flameionisationdetector(s)FID(basicdesign)mixH2andcarrier,burnincleandust-freeaircollectionsformedcurrentelutingcpdsAFID(N/Psensitive)surroundjetbyalkalisaltsurfacecatalysedreactionsFPD(collectphotonsemitted)Sulphurmode394nmPhosphorusmode526nm10FlameionizationdetectorMDQ—5picograms/secondResponse—quasi-universalLinearity—excellent(over106)Stability—flowandtemperatureinsensitiveTemperaturelimit—400CCarriergas—Nitrogen,heliumorhydrogenSummaryRuggednon-responsivetowaterandair("inorganics")destructiveandverywidelyused11FlamephotometricdetectorMDQ—1nanogramS(394nm);0.
1ngP(526nm)Response—effectivelyonlySandPcompoundsLinearity—moderate(104)Stability—goodTemperaturelimit—400CCarrier—nitrogenSummaryveryselectiveflameneedscleanhydrogen/airsupplyexpensivebutinvaluableforpesticideandairpollutionwork12FlamephotometricdetectorSulphurmode;394nmlargesolventpeaksmallhydrocarbonpeak(pentadecane)for4,000ngdodecanethiol(IS)20ngmethylparathion20ngPhosphorusmode;526nmtinysolventpeaktributylphosphate(IS)20ngmethylparathion20ngSamesampleinbothcases13HotWireDetector(TCD)Tungsten-rheniumfilamentsCurrentof0.
3Aat16VTemperatureoffilament350CbutdependsonthermalconductivityofgasflowingoverhotwireResistanceofwirechangesasTchangesPre&postcolumndetection14ThermalconductivitydetectorMDQ—10nanograms(about50ppm)Response—universal(allexceptthecarrier)Linearity—moderate(104)Stability—flowandtemperaturesensitiveCarrier—hydrogenorheliumTemperaturelimit—400CSummarynon-destructiveandsimpletooperate(portable)moderatestabilityandsensitivyusedforfixedgasanalysis,eg,H2,N2,O2,CO2,Ar,etc15ElectroncapturedetectorRadioactivesourceemitsb-particles(fastelectrons)whichareconvertedintoslowelectronsbycollisionwithN2carriergasThesearecapturedbymoleculestoformaslowermovinganionsReductionincurrentascompoundflowsthroughdetector16ECD:organohalogenpesticidesColumnDB-210+15mx0.
53mmid;film1.
0mmHecarrier;100°-220°Cat3°C/min.
600pgeach2-lindane;4-aldrin;9-dieldrin;13-DDT17ElectroncapturedetectorMDQ—veryhighsensitivity(picogramrange)Response—veryselective(halogenatedcompoundsonly)Linearity—Poor(500to104)Stability—fairTemperaturelimit—220C(3H)or350C(Ni)Carrier—nitrogenorargon+10%methaneSummaryeasilycontaminated,carriermustbedrynon-destructiverequireslicenseforradioactivesource18ECD;biphenylsat30ppbeachMDQ:10fglindanein2mlinjection19ThecolumnTwokindscapillary(WCOT:0.
2to5mmfilmthickness,PLOT)0.
3mmid50m300,000plates0.
01ml2ml/minpacked3mmid2m3,000plates10ml40ml/minLiquidphaselowvapourpressureoveroperatingrange&thermallystablechemicallyinerttosolutesgoodsolventforsolutesusedandlowviscosityTemperatureisothermalprogrammed(linear,reproducible)20Packedcolumns(SS,glass)or"od;coiled,U-shapedSolidsupportuniformporediameter(10mmorless)largeinertsurfacearea(AW,treatedwithDMCS)regularlyshaped,uniformlysized(meshnos.
)egChromosorbW/AW/DMCS100-120meshPreparation(5%XonY):slurry5gliquidphaseXwith100gsolidsupportYinsmallquantityofsuitablesolventRotovapoffsolvent,packcolumnLeaveovernightathighestsafetemperatureinovenwithflowofcarrier21EffectofcolumntemperatureIncreasingthecolumntemperaturereducesretentiontimesbiggesteffectonlongesttimesConflict:analysistimeversusresolutionTemperatureprogrammingsidestepsprobleminitial,final,rateofclimbandtimings22SoluteclassesBasedonH-bondingcapabilityWeakbondIPolyalcohols,aminoalcohols,etcIIAlcoholsIIIEthers,ketonesIVAromatics,olefins,halocarbonsVSaturatedhydrocarbons23"Liquid"phase—theheartoftheGC'Polarity'Squalane—thestandardphasewithzeropolaritySiliconegumSE30/OV-1100-300C220Dexsil30050-400C470Di-nonylphthalate0-150C790OV-210silicone20-275C1500Polyethyleneglycol(CarboWax)60-225C2300OV-275silicone100-275C420024RTX-200(trifluoropropylmethylpolysiloxane)25Stabilwax(CarbowaxPEG20M)26SpecialisedapplicationsPyrolysisbrakeliningdustHeadspaceanalysisblackpeppercornsorcolacanMulticolumntechniquesdualback-flushingheart-cuttingHyphenatedGC+MSGC/FTIRPreparativeGCPyrogram27Headspaceanalysisof0.
1%cpdinwater28Multi-columntechniquesBackflushingtoventspeedingupanalysisofA,BbynotbotheringwithC,DHeart-cuttinganalyseforBinthepresenceoflargeamountsofinterferingADualcolumnfordifficultseparations1stcolumncanseparateA&BbutnotC&D;2ndcolvice-versa