tailieunhanh - Introduction to Modern Liquid Chromatography, Third Edition part 22

Introduction to Modern Liquid Chromatography, Third Edition part 22. 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. . | 166 DETECTION 210 220 230 240 250 260 270 280 Wavelength nm Figure 4 12 Illustration of spectral deconvolution of analytes a Hypothetical chromatograms for individual injections of X and Y at 260 nm shown with combined response X Y at 260 nm b spectra forXand Y. ratio across the peak. The same dataset collected at 240 and 280 nm could be used to determine peakpurity by calculation of the 240 280 ratio at every point across the peakwere pnre X orY he ratio would be vonstant whereas if the rmxturrof Figcrn r wrre present the ratio would be 1 when X was predominant and 1 when Y was the major compound. The nonconstant nature of tleva iowoutd icaicatethe prcsenceof c pta mtxture eventhough tie peaks ovetlappeb niiromstageanhiedtyand anpea edrs y et gk veekat 260 nun. Peak-purii ii le oritymiinomi aerthe onsirtencyof the spcctriim a eots dieentire peak and iitra me facta cmidentifysht yresenoe o minae impuriti s . t that are eftedueden Is ail tthe mojor pcad. Fotam itv ni licvdit of thv determinatiotof yeak p city dvDAhp i e C0 et anand ter or 11311 300X1 8 literature ee. oftO . GcaeoalUV-Detocto Char actpr ht cs Table arizet thv gea oaitharanraisnc1 UV teectnrs UV a pernm cte ideal for use with gradient elution many common UV-transmitting solvents are available in graik foruse as mobile phases Tables and of Appendix I . The UV detector is yeryosefol forthe trace afiflysrsolUV-absorborg lores bur its widely varying re spouse for differenttoluecscanbeadievdvantage if the compound of interest dner not atom in theUV Uetenrori tae reliakie and easy tn pyrat and ere p ndytCarPd Sllita018for nseOvkse-lkeiledoperrtoen FLUORESCENCE DETECTORS 167 Table UV-Detector Characteristics Capable of very high sensitivity for samples that absorb in the UV Good linear range 105 Can be made with small cell volumes to minimize extra-column band broadening Relatively insensitive to mobile-phase flow and temperature changes .