tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 73

Introduction to Modern Liquid Chromatography, Third Edition part 73. 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. . | 676 ENANTIOMER SEPARATIONS a Retention of enantiomer R -X fî -X m R -CS m R -X - R -CS m Mobile phase Xd R -X- R -CS phl2nary - s R -CS s x 1 x R -X - R -CS s Retention of enantiomer S -X S -X m R -CS m a S -X S -XJ- R -CSD Mobile phase KdCS m d. S -X R -CS phlTena K s Kfl -CSh 1 X S -X - R -CS s Figure Equilibria for the retention of R- and S- enantiomers chiral-mobile-phase additive CMPA mode. Subscripts m and s refer to corresponding species in mobile and stationary phases Ka and Kj represent association and distribution constants respectively. distribution of the complexed solutes X CS between the mobile and stationary phaseswithdistributionconstants K .Rj-xq -C0 and f t sj-j qRp-t Additionalludhe uiicomplcxcdaiialytd i Xsancomp-ex drrsctiy withthe CMPA in the stationary phase via processes i and j in Fig. . The same equilibria have be considered for eheS-msniiourer obaetded solarer-tet t is then a weighted average of values of k for free and complexed X. If the CMPA is very strongly re-aiyyo itmdy saturate-oei-ationrsyylsese leadmg ton tisuarion similar to tWat oiadynamisaliy cotted CSP-column mo yshrsimilarsitnatioa foe ion-pairing . The eontequencto at Figute summaaizrd to tollowaiWithout the addition of tie segu-tc Khan an septsation of thtecaatiomerstR d anU S -X can ogtur Ora i o nty 5 iX. CUheu thy CM0A is ptcbtnt in tie mobile phon- joid ifits interarsion wit. Ot analyte it imaihareit and enamids-elective tksi Cso setemion is of theiwo enantiomers should differ hopefully leading to theiachromatoptantiic teoonation. In addieion mste tssociatioaof the two s- Smt nus 1 km eeswitii lte CMPA with ditltrsai retentioncS Stee odd complexed ooluteh stereosebet ivist may om Mtt from dTtweu t ratention ofit e diastereomerie tstocidtes as -we-i as nonequal as-lsorltnc formation ssaysthwaa i or . Stertneeltct-aity uaht1ibhSioas from eUtseiadiviCyainrodesset mac eitOer enhance orcstsnuete eacO .

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