tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 19

Introduction to Modern Liquid Chromatography, Third Edition part 19. 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. . | 136 EQUIPMENT 15-i 90 10 10H E A C A D B C 0- 0 a B D 50 50 AU Figure Results of a gradient proportioning valve GPV test a Gradient proportioning valve test results b detail showing 2 allowed difference between plateaus. Baseline is generated by 50 50 A B the remaining plateaus are 90 10 A C A D B C and B D from left to right. Solvents A B water C D acetone in water. TypicalSystemPerfornnanceParameters for Parameter Test Typical Specification e Typical Acceptance Criteria Linearity 1 Visual linearity 5-95 B Dwell-volume Varies As measured Step-test accuracy 1 iO zt 1 0 GPM test Not specified 2 plateadrangefe Flow rate collect 10 ml at 1 mL min 1 2 12 sec on 10 mL at 1 mL min Pressure blcid-eim ii Urom 4000 psi Not specifieb 15 in 10 min Retention repeodevibiirty Not specifief min Area reprodTcibilten 10 pL injection 1 Gradient proportioning valve. Difference beleveanhigeestplatnauapd loorstplateau whee Cer De fc blendedwithA-or the acceptance critesion I hsctro 2 r since the cowbination of measuewment errors volumetric glassware andthe timing start stop errors will add somewhat to the overall measured error. Pressure Bleed-Down. Malfunctioning check valves and worn pump seals often show up aseevrotiobsm oxpecaed values of mixingoecueaoa gradieat hnepriryineP flow rate. Aa aPditionnitesrcf thcoutlue checdvvtcnt van bemnda witba prassere bleed-downenrti Fsethiitsse iiaeoutlet tubing from the pump is blocked by a union and a plug . The high-pressure shutoff limit for the pump is set near its maximum MAINTENANCE 137 value for example 5000 psi 350 bar for a system capable of 6000 psi 400 bar . The pump is then turned on and allowed to shut off at the upper pressure limit. The maximum pressure is recorded and 10 minutes later the pressure is recorded again. A pressure drop of 15 indicates that the check valves are working propcrly. A larger drop suggests that the outlet check valve s should be cleaned or replaced or .