tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 79

Introduction to Modern Liquid Chromatography, Third Edition part 79. 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. . | 736 PREPARATIVE SEPARATIONS phase is no longer a minor issue. The major difficulty is the elimination of water which has a higher boiling point and higher heat of vaporization than typical organic solvents resulting in long evaporation times. This not only limits the quantity of material that can be isolated in a given time but also exposes the product to a higher temperature during prolonged evaporation this can lead to degradation of the these reasons manychromato aphers routinely select nonaqueous NPC Section tor prcptLC. Fos NPC sarriedout ohtissoSventsshat bcihbelcw 80oC see otApnsnSxSd tOerrsovrey aPpurifke aroSecy is relaXvely simple. NPC it sisooftrhfavoran boa noSedtiaUy laroervaSueottCr oeparation factor a whichceoracoonnsoo Inrges clSnwedie ihtfieexamplooS Figure tfl-s isseprctallyttueSoratoseinrsSatedsoiatst such as isomers Section . RPCis notruled out forprcp-TC teparation nothete cin- sevrrctxpXent for the recoreroofp Ni nei r urodosO drprwdingontha wahtreoisite prodcot. AdditixnaSSyany reqcircd nufteesaraddisivet canbrrdrchaPCoomaiist ht valctilo to avridthenfcessitc oSsohormoyatfrom thrpredocs. Many cxmnrcnesatros-at vrly resoluble in water especially at a pH where they are not ionized for excmpkia ttroxgiyauidic pHfor anneth iyanaie Oioc pH Oora base see Un01ec7iO v lursasa funcXon otcrmpnund molecular rtrueStlseIlTheappronolaaeadJ usrmextoS oeehH of o o rt uc fei iita followed rnpenralevaoornnonoetlln SoacXocinooeertoel minote mostnP the organic solveee - P nn sxprectpisaSomottofOta ervSuct ondahow ts ercovcry by filtratien. An alteruntioeaporoash ortae continuecs rntsa ti ox nt she psi-tSo aqueous fraotien vSOi a watef-imhetcibfe organic oo-vem. TOe prxduei istnui partitixnePinoran erganicoolvent weschsstoenrasilyeemovco -c evasoration. Either of stasr vpprxaches siso lecnss ane iuollooStlSreimoegntXabutfaa ehto p the .

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