tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 71

Introduction to Modern Liquid Chromatography, Third Edition part 71. High-performance liquid chromatography (HPLC) is today the leading technique for chemical analysis and related applications, with an ability to separate, analyze, and/or purify virtually any sample. Snyder and Kirkland's Introduction to Modern Liquid Chromatography has long represented the premier reference to HPLC. This Third Edition, with John Dolan as added coauthor, addresses important improvements in columns and equipment, as well as major advances in our understanding of HPLC separation, our ability to solve problems that were troublesome in the past, and the application of HPLC for new kinds of samples. . | 656 BIOCHEMICAL AND SYNTHETIC POLYMER SEPARATIONS Chemical Composition as a Function of Molecular Size A copolymer typically exhibits both molecular-weight and chemical-composition distributions. Depending on polymerization conditions the chemical composition may or maynot vary with polymer molecular weight. To investigate the presence of such chemical heterogeneity we can couple SEC with a spectroscopic technique that yieldschemical-compositioninformation. Such a aombincdscchniquc provides the average compositional eachpoint in the SECchromatogram thatis for each molecutri-star. f oalyoneoOtwr monomers canbe retectot byUV ttir combinationora UV drtechor ang annthercsunentsahiontotogitivr detaugor refractive indsa RI eae niarmdplebr uaadhe trllnw the cancontrattanofrnch monomeriAddicionaSmformatiro eu broOenine0tcrm tombimiio SECwtthoithsr FTIR or Nh R rat oss c on- Althaugh iofoamationaboiit rdenucat comaocitionns afunationofmateablnr size can beveryvairebk aven tba tmelktefECteoetioneaancontem evaciatf et molecules dnai vary mbothchemicel nampneitinn stttb e olreerM waiVid Thaiis differences mchemicglcemnehetidnrenrrsultid mokctdetwitnUVerent moltciUar weights liaviHR the N h molecrlar rize in salutian as illustrated in Figure . A fraction obtAnodStomaUgh-reshiutionSEC iepnretinn rechuignSd Ore in Fig. whieontcinmolecgnet wtth the tomemotecularetzr geaetionraAgs Rg in sohltioT bTt witt Ciffrrentmolecuier weientSltt it retenfmoretaoeto anew the chemifal ompositiohUstributio itacner aiean oet thenveeoge chemicnlctm-position. Litewise die eunctionality-SrpeOettribution FnDi may bemutrimpaetant than the awnraa numr-t oefbnctionai oroopspermoktek. Ti lt wtii rtpecutOy true if the ahemicalcompotition or the numbenof Iiio-tiouil grrypsyar mokculris known or suspect ttevr . inoxample is eeactioe pre- ootymeat thetacentedm many formi iit t i s tae tralantt o Oefives sndeontings. MhiecutesoTthoutteaahve functiona groups wdt ut eoact mokehkrwith .

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