tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 93

Introduction to Modern Liquid Chromatography, Third Edition part 93. 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. . | 876 TROUBLESHOOTING Table Continued Failed Test Symptom Symptom Possible Source Solution Gradient step-test failure Gradient proportioning valve GPV test failure Dwell-volume differences between systemt Flow-rate check failure Pressure bleed-down failure Retention time reproducibility failure Peak area reproducibility failure Gradient distortion Fig. Steps in gradient step-test are of uneven hdglu and or are distorted GPV test steps 5 Changes in retention yndfor selectivity tatween systems Flow rate 2 from set value l eif 1 my im. iy 10 mm min for standard test more than normal method performanct 1 imprecision in standard test more than normal inceliod performancn Gradient mixing volume too large relative to gradient volume Bubble check-valve fail lire or keel o edtt trit restricted solvent suppby tubing bad proportioning dteii ied Nnnmal for differences in dwell-volumc Bubble bad chock valve or pump seal leak wrong som essibihty sei Ca k valve oe jrnmp-seal failure leak Bubbles leaks check-valve or pump-seal failure 1 pump or mixing failuhe Autosampler - . i t uetaeot Use shallower gradient reduce mixing volume Degas mobile phase clean or replace check valve fix leak blocked reservoir frit badproporrioiiing vafoe Replaœfnt clear or replace tubing replace proportionmgmvpifoH Ad tmetlwdto compensate for dwell-volumedifferencas De as mobile phase clean or replace check valve replace pump seal adjust compressfodhyfor nore Clean or replace check valve rc cce pnmpsevl fxleak eeefas entSfVxieae s clean or replace check valve replace pump seal rpn gradientperfoemance edsl iddlscd davd ed Clean or replace needle ceplace sen see eutosamplec manpel REFERENCES 1. J. W. Dolan and L. R. Snyder Troubleshooting LC Systems Humana Press Springer Clifton NJ 1989. 2. V. R. Meyer Pitfalls and Errors of HPLC in Pictures Wiley-VCH Weinheim 2006. 3. J. W. Dolan LC Troubleshooting in LCGC a monthly column 1983-present . 4. http . REFERENCES 877 5. .