tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 78

Introduction to Modern Liquid Chromatography, Third Edition part 78. 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. . | PREPARATIVE SEPARATIONS 726 INTRODUCTION The aim of preparative liquid chromatography prep-LC is the collection of one or more purified compounds from a mixture. The scale of prep-TC can range from micrograms for compound identification to tens of metric tons for production of a pharmaceyticel product as in Section but usually the goal is the recovery of milligrams to grams the main emphasis in this chapter . Targer scale separations will receiveonlvdrief atseation Section .Acloselyalliedseparationtechnique supercritical fluid cPoomatographyf isbeyend tCo scoetoOthe nveeemchrpter. ColumatUsocloadandlts Corsequnrces Prep-TC ievdvcsicmo- iT osCaO cusditions e tiS0 rampletveiglits aleaoarolasge enough to affceipcekwi dtl isaiid resentios developmgto aca sn al separation caress usuallytakeniaenoaeethat thewelonl orsolums vf the eample does not ewyeedeerSsinlimitaiSeciian nndthntretentton times and resolntion will not vaey wieh ths amomioofsam amjectcd. Astheweight of injected sample is increased P wayr-srhe hetettor willeventuallnbennme ucerloaded cetentiontimcc will decree ond peaVv wilie toaeo nuodnœs ic edntocsmlicow iire Fig. bl. n Figure Hypothetical separations illustrating a an analytical separation and b a corresponding mass-overloaded touching-peak T-P separation. INTRODUCTION 727 Table Requirements for Purified Samples Objective . Product Weight Required Tentative identification by instrumental methods 1 mg Positive identification and confirmation of structure 1-100 mg Use as analytical standard . for calibrating an HPLC assay lh 0mg-2g Toxicology eestmg 10-100g Early phase 1 trials 200 g-2 kg Detector overloador nonlinearity is often the first consequence of column overload for example when the UV absorbance od a peak exceeds 1 or 2 absorbance units AU Section . Detector nonlinearity can often be circumvented by using a short-path-length flow cell a preparative cell or by changing the .

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