SEPARATION OF PLANT PIGMENTS USING CHROMATOGRAPHY用色谱法分离植物色素

separation of plant pigments using chro__tographyBackground:Why are most plants green?  Why do the l

separationofplantpigmentsusingchro__tography Background: Whyaremostplantsgreen?Whydothele__esofsometreesturnfromgreentoorangeoryellowinautumn? Thisexperimentwillhelpshedsomelightonthissu__ect.Althoughmostplantle__esappeargreentoour eyes,severalpigmentsofdifferentcolorareusuallypresentinthechloroplasts.Apigmentisdefinedasany coloring__tterpresentinanorgani__fromthecolorofhairtothecolorofrosepetals.Thegreenpigment chlorophyll presentinplantsis.Thefunctionofchlorophyllistoabsorbsunlightfortheplanttoconvertcarbon dioxideandwatertosugarsthattheplant__yuseasitsenergysour__.Thispro__ssisknownas ab photosynthesischlorophylls .Inthefloweringplants,andprovidethegreencolorandabsorbthelight energyneededforphotosynthesis.So,howdoesthisgreenchlorophyllbecomethemyriadofcolorsthatis enjoyedbyso__ny?Whentheweathergetscooleranddaysgetshorter,aplantrecognizesthatitiswasting valuableenergyinproducingchlorophyll.Photosynthesisslowsdownduetothelowertemperaturesthat affectchemicalreactions.Also,lesswateris__ailableduringthesefreezingmonthsfortheplanttofunction nor__lly.Thechlorophyllslowlydisappears,revealingotherpigmentsthatarealreadypresentinthele__es. carotenoid,xanthophyll Otherac__ssorypigmentscommonlyfoundinle__esofplants,including,and anthocyanin arealsopresentinthechloroplastsandcollectadditionallightenergyforphotosynthesis. Purpose : identify Thepurposeofthisexperimentistoplantpigmentsbyseparationandisolationofthepigmentsusing thinlayerpaperchro__tography. : Technique Paperchro__tographyisausefultechniqueintheseparationandidentificationofdifferentplantpigments.In thistechnique,thepigmentstobeseparatedarefirstappliedbyrubbingthepigmentfromtheleafontothe paper,thenasaspotoralineonthepaperabout1.5cmfromthebottomedgeofthepaper.Thepaperis thenpla__dinacontainerwiththetipofthepapertouchingthesolvent.Solventisabsorbedbythe chro__tographicpaperandmovedupthepaperbycapillaryaction.Asthesolventcrossestheareacontaining plantpigmentextract,thepigmentsdissolveinandmovewiththesolvent.Thesolventcarriesthedissolved pigmentsasitmovesupthepaper.Thepigmentsarecarriedalongatdifferentratesbecausetheyarenot lesssolubleslower equallysoluble.Therefore,thepigmentswillmoveupthepaperthanthemoresoluble pigments.Alsoafactorinthemovementofpigmentsistheirmolecularweights.Pigmentswith__aller molecularweightswillmovefartherandfasteracrossthepaper.Pigmentswithlarger molecularweightsmoveslowerandthereforetr__ellessdistan__.Thisis SolventFront chro__togram knownasdevelopinga.(Seethepicturetotheright.) Thedistan__tr__eledbyaparticularcompoundcanbeusedtoidentifythe compound.Theratioofthedistan__tr__eledbyacompoundtothatofthe solventfrontisknownastheRvalue;unknowncompounds__ybeidentifiedbycomparing f theirR'stotheR'sofknownstandards. ff Pigment#2 Pigment#1 Origin