Chromatography - Indiana University 1 Chromatography Chromatography • Major types...

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Transcript of Chromatography - Indiana University 1 Chromatography Chromatography • Major types...

  • 9/8/2014

    1

    Chromatography

    Chromatography

    Majortypesofchromatography LiquidChromatography ThinLayerChromatography GasChromatography

    Majorpurposes Purification Characterization

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    ChromatographyBasics Separation! Basedondifferentaffinities(IMF)forstationaryandmobilephases

    Stationaryphase:silicagelparticles,polymerparticles

    Mobilephase:flowinggas,flowingorganicliquid

    CharacterizationofPurifiedSubstance

    Bigquestionsinorganicchemistrylab:

    Wasitpurified?Whatwaspurified?

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    TLC

    Thinlayerchromatography

    Stationaryphase Mobilephase

    SeparationANDCharacterization

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    PolarityandIMF

    Silicagel:polar,watercoveredsurface Compound(s)

    Polar:_______affinityforplate,travels_______ Nonpolar:_______affinityforplate,travels______

    Developingsolvent Polar:higheraffinityforplate,travelsslower,displacescompoundmore(compoundtravels__________)

    Nonpolar:loweraffinityforplate,travelsfaster,displacescompoundless(compoundtravels________)

    TestyourUnderstanding

    Whichspotrepresentsamorepolarcompound?

    Whatwouldhappentoeachspotifalesspolarsolventwereused?

    WhyshouldyouALWAYSreportyourdevelopingsolventwithanyTLCdata?

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    QuantitativeCharacterization

    Retentionfactor Distancetraveled/solventfrontdistance

    Unitless ForsilicagelTLC,basedonpolarityofthecompound(s) Mustreportsolvent!

    SolventeffectonRf Polarsolventsoutcompetecompounds,drivethemupplate

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    ChoosingaDevelopingSolvent

    AdjustsolventtogiveRf valuesaround0.4

    Commonmixtures Ether/Hex EtOAc/Hex CH2Cl2/methanol

    Determinedexperimentally

    Visualization

    MostcompoundsareinvisibleonTLC

    UVlamp Stains Iodinechamber

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    ApplicationofTLC

    Purity Identity ReactionProgress

    Whatcanwedetermineabouttheidentityoftheunknown?

    Column1isyourtargetcompound;column2isanexpectedimpurity.Whatcanyoudetermineaboutyourreaction(column3)?

    CommonProblems

    Overspotting Underspotting Wrongsolvent

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    ColumnChromatography

    SimilartoTLCinseparation Preparativeprocess

    0.1gto5gscale Purifysmallquantitiesofliquids/solids(advantageoverrecrystallization?)

    Notforcharacterization!

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    Mobilephase:eluentsimilartoTLC

    Stationaryphase:silicagelsimilartoTLC

    ColumnisupsidedownfromTLC,soalargerRf foracompoundmeansitcomesout____

    PracticalConsiderations

    Preparingthecolumn Loadingthesample Choosingthesolvent Separationcapacity

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    PracticalConsiderations

    Preparingthecolumn Loadingthesample Choosingthesolvent Separationcapacity

    PracticalConsiderations

    Preparingthecolumn Loadingthesample Choosingthesolvent Separationcapacity

    Mostcommon:Hexane/ethylacetateCH2Cl2/methanol

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    PracticalConsiderations

    Preparingthecolumn Loadingthesample Choosingthesolvent Separationcapacity

    Effectofdiameter Effectoflength EffectofSilicagelgrade

    FlashChromatography

    Fasterseparation Tighterseparations

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    HPLC

    GasChromatography

    Chromatography TLC(analytical) Column(preparative) GC(analytical)

    WhydoweneedGC? StrengthsofTLC WeaknessesofTLC

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    GCBasics

    GasPhaseSeparation

    Partitioningbetweenmobilegasandstationarycolumn

    Highlyeffectiveseparations

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    GC

    Injection Column Detector Chromatogram

    GC

    Injection

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    GC

    Column

    ColumnMaterial

    Nonpolar Fornonpolarmaterial

    vDW Followsbp

    Polar Forpolarmaterial

    Followspolarity

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    GC

    Detector FID TCD

    GC

    Chromatogram Retentiontime Areaunderpeak

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    GCParametersandRetentionTime

    Lengthofcolumn Typeofcolumn Temperatureprofile Gasflowrate

    ImportantGCQuestions

    Whatiseachpeak?(identity) Characterization DeterminationofUnknown

    Howmuchofeachcompound?(Quantity) Absolutequantity Relativequantity(productdistribution)

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    Identity

    RetentiontimecorrespondstoRf

    Spikewithauthenticsample

    GasChromatography/MassSpec

    Identifyingcomponentsinmixtures

    Separationthenidentification

    GCMS

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    Quantitation Areaunderpeakcorrespondstoamountofcompoundcausingsignal

    Usestandardplottodetermineabsoluteconcentration

    Usepercentoftotalareatodetermineproductdistribution Assumessameresponsefactor

    ReviewofTechniques Purification

    Extraction Recrystallization Distillation Columnchromatography

    Identification MS IR NMR mp,bp GC TLC

    Purityanalysis Elementalanalysis Mp,bp GC TLC ProtonNMR