仪器分析英文原版教案(15)

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1、Electrophoresis(Chapter30):Separationofchargedspecies(ions)basedontheirmigrationrateinelectricfieldSlaborplanarelectrophoresisporouslayer2-10cmlong-paper,celluloseacetate,polymergelsoakedinelectrolytebufferslowsimplebutdifficulttoautomatepoorquantitationlargequantit

2、ies(mL)CEM333page17.1Capillaryelectrophoresisnarrow(25-75mmdiameter)silicacapillarytube40-100cmlongfilledwithelectrolytebufferfastcomplexbuteasytoautomatequantitativesmallquantities(nL)Fig30-1CEM333page17.2Migrationratedependsonmovementinelectricfield¥molecularweigh

3、t¥charge-small/highly-chargedspeciesmigraterapidly-affectedbypH+-HA«H+A-affectedbyionicstrength122m=([A]×ZA+[B]×ZB...)2lowm,fewcounter-ions,lowchargeshieldinghighm,manycounter-ions,highchargeshieldingCEM333page17.3MigrationRate:Vv=m×E=mLmigrationrate(cmás-1)electric

4、field(Vácm-1)electrophoreticmobility(-veforanions)(cm2áVás)Electrophoreticmobilitydependsonnetchargeandfrictionalforces(size/molecularweightofanalyte)¥OnlyionsseparatedPlateHeightandNumber:m×VL2D×LN=H==2DNm×Vdiffusioncoefficient(cm2ás-1)Increasenumberofplates(better

5、resolution)byincreasingVCEM333page17.4¥Slabelectrophoresislargecross-sectionalarea,shortlengthlowelectricalresistance,highcurrentsSampleheatingVmax=500VN=100-1000lowresolution¥Capillaryelectrophoresissmallcross-sectionalarea,longlengthhighresistance,lowcurrentsVmax=

6、20-100kVN=100,000-10,000,000highresolution(HPLCN=1,000-20,000)Zonebroadening?¥Singlephase(mobilephase)-nopartitioningInchromatographythreezonebroadeningphenomena(i)longitudinaldiffusion(ii)transportto/fromstationaryphase(iii)multipath¥InplanarEPnostationaryphase¥Inc

7、apillaryEPnostationaryphaseormultipathCEM333page17.5TransportProcessesinElectrophoresis:Electromigrationionsmigratinginelectricfieldcations®cathode(-ve)anions®anode(+ve)Electroosmosismovementofentirefluidnearwallofcapillaryinonedirection!anode(+ve)®cathode(-ve)(A)An

8、alytedissolvedinbackgroundelectrolyteandpHbuffer(B)Silicacapillarywallcoatedwithsilanol(Si-OH)andSi-O-(C)Wallattractscations-double-layerf