tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 45

Introduction to Modern Liquid Chromatography, Third Edition part 45. 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. . | 396 NORMAL-PHASE CHROMATOGRAPHY a 40 H2O ACN 20 30 b 30 H2O ACN I----------------11--------------------------------- 0 10 20 30 c 20 H2O ACN 5 6 7 I 0 10 20 30 Time min . Figure Separation of a mixture of derivatized oligosaccharides by HILIC with mobile phases of varying -water. Conditions 200 x PolyHydroxyethyl A column 5-pm particles mobile phases are water-acetonitrile as indicated in the figure 2 mL min. Values of n in the figure for each peak refer to the number of saccharide units in the corresponding oligosaccharide. The chromatograms are recreated fromthe data of 38 . RetentionMechanism Although the cetention mechamam for HILtChas record considorable. attenoioit in the literature ahis topics asthe subject has very limited practical application the reader may wish to skip this section. Retenno in 1SIL1C s beLeesUrai lee a pardoning of the lute a water layen that isformidon Resurface of the column packing 38 39 42 44 . For silica ascolunui packingand HILICconditions it h c s beenshown I42- theti h e column dncdpolumeSUo coctinues lodeceease is themebilo-phasewctee iuireuses from 0 to .eeTo shie has beenahtributedto lhe boitgun od aSayeeoSwater cn eLi silica surface. The oCsercationthat HILKSseparotionoreouira at lerst2-Oe 0watra in the moSiiephase chefirmeenetmposhanro inHOLIhsaoihatioe af Chswatsr layer whicoPrrsumablo ocmpaisef she sirtinnary aTcre. hrs altopLttiCleoisS the stationary olose mJirleesome orgamc sclvent acetonitrile ftomthe mehiirpSnse with furtheocontributioas th tolnte retcntlonhrom boththesilioa oerlaan siloeols and any columnligiads ihrt 3 winthohitrmoleciCrs. A di s ttioa sen Pt mato betwesh srsaOitiOiton antl hrt tanei l c Le stationary phese asmihecaiL ofRSC Itchon . atisheUeved oyoonLe investigatositoctiheatlwo ctocrttes car OedissmguishednaacompIrison otvalaos of k as a SrncLon t ttaovolume-Sraatioo lU oftCeB-iotvcns watte rn ahitoaiel. In RPC wCkeio loruncl tomoolve c1hl Clr

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