tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 35

Introduction to Modern Liquid Chromatography, Third Edition part 35. 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. . | 296 REVERS ED-PHASE CHROMATOGRAPHY FOR NEUTRAL SAMPLES L 150 mm mL min Rs P 1050 psi r 12 3 4 Time min L 250 mm 11 mL min I . 2 Rs 0 fl P 1750 psi a3 4aA5 0 2 4 6 c Time min L 250 mm mL min Rs P 990 psi 0 1 . 20 d Time mm 30 L 100 mm mL min Rs P 1580 psi A 2 Time min Figure Illustrations of a change in column conditions to either improve resolution or decrease run time. Sampte components non-ionized for these conditions 1 phthalic acid 2 2-nitrobenzoic acid 3 2-fluorobenzoicacid C 3-nitrobenzoic acid S 2-chlorobenzic acid 6 4-chloroaniline 7 3-fluorobenzic acid 8 2 6-dimethylbenzoic acid 9 2-chloroaniline 10 3 4-dichloroaniline. Conditions Cis columns 5- im with d. . e l. l ed Li .kLh. is30 A -bufferfom5 ib- . ACN-tatferforM and d 40 Cin a and 30 Cin c and i recreated fromdataog 0b. less polar B-solgenr organio the A-sotvrmwlll be ACNor MeOH while the B-solvent eon be THF merfiylene etloridr chlg3oeorm metiiythr-eutyl ether MTgE ge othorbesspolar organic solvents. Sample retention is controlled by varying B and or the polarity of the B-solvent which can be approximated by the value of P in Table of Appendix I. NARPlsr ttter erraec nn f nations cmreteoet Fig. in a mixtureolltdonaogs Fig. Odgl t mid it rnextrrcthrvmsomago Fig. hamplesnoie ofton insolub einaounohg rnlutions SPECIAL PROBLEMS 297 Figure Non-aqueous reversed-phase NARP separations of carotenes. Conditions 250 x Cis column 8 chloroform-ACN mobile phase mL min ambient temperature. Adapted from 75 . which can be another reason to use NARP for such samples. From a practical standpoint if NARP is chosenfor asepi hition aUwater num be washed from the HPLCsystern and columnprcorto switching totheoonaeueous mobile phase. Generally a30-minutrflushwithACN or MeOH is sufficient. SPECIALPROBLEMS One reasonwhyRPE is morepopular .

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