仪器分析英文原版教案(6)

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1、AtomicEmissionSpectroscopy(Chapter9/10):IdentificationofelementsbutnotcompoundsExcitationandAtomization:Traditionallybasedon¥flamebut¥arcandspark¥plasmaexcitationoffers(i)increasedatomization/excitation(ii)widerrangeofelements(iii)emissionfrommultiplespeciessimultaneously(iv)widedynamicrangeCEM3

2、33page8.1FlameExcitationSources:(Fig9-3)PrimaryCombustionZoneInterzonalRegionSecondaryCombustionZoneFlameTemperatures:FuelOxidantTemperatureGasAir~1800¡CH2O2~2600¡CAcetyleneO2~3000¡CCEM333page8.2LaminarFlowBurner:(Fig9-5)¥Cheap¥Simple¥Flamestability¥LowtemperatureCEM333page8.3ArcandSparkExcitati

3、onSources:¥Limitedtosemiquantitative/qualitativeanalysis(arcflicker)¥Usuallyperformedonsolids¥Largelydisplacedbyplasma-AESElectriccurrentflowingbetweentwoCelectrodes(Fig10-16)SamplepressedintoelectrodeormixedwithCupowderandpressed-briquettingCyanogenbands(CN)350-420nmoccurwithCelectrodesinair-He

4、,AratmosphereCEM333page8.4Arc/sparkunstable-eachlinemeasured>20s(needsmultichanneldetection)photographicfilm:¥Cheap¥Longintegrationtimes¥Difficulttodevelop/analyze¥Non-linearityofline"darkness"Fig10-17CEM333page8.5Fig10-18multichannelPMTinstruments:¥forrapiddeterminations(<20lines)butnotversatil

5、e¥routineanalysisofsolids-metals,alloys,ores,rocks,soils¥portableinstrumentsCEM333page8.6PlasmaExcitationSources:gascontaininghighproportionofcationsandelectrons(1)InductivelyCoupledPlasma(ICP)Fig10-1¥Torchupto1"diameter¥Arcoolsoutertube,definesplasmashape¥Radio-frequency(RF)upto2kW¥Arflowupto20

6、L/minCEM333page8.7PlasmaStructure:(Fig.10-4)¥Brilliantwhitecore-Arcontinuumandlines¥Flame-liketailupto2cm¥Transparentregion-measurementsmade¥Hotterthanflame(10,000K)-morecompleteatomization/excitation¥Atomizedin"inert"atmosphere¥Littleionization-toomanyelectronsinplasmaCEM333page8.8(2)DirectCurr

7、ent(DC)Plasma(Fig10-5)¥DCcurrent(10-15A)flowsbetweenCanodesandWcathode¥Plasmacoreat10,000K,viewingregionat~5,000K¥Simpler,lessArthanICP-lessexpensiveCEM333page8.9AtomicEmissionSpectrometers:Maybe>1,000visiblelines(<1)onconti