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Introduction to Modern Liquid Chromatography, Third Edition part 69

Introduction to Modern Liquid Chromatography, Third Edition part 69. 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. . | 636 BIOCHEMICAL AND SYNTHETIC POLYMER SEPARATIONS The porosity of an SEC column can be characterized by its phase ratio V Vo as in Figure 13.39a. Other factors equal resolution increases for a larger phase ratio. Soft-gel SEC packings have high porosities with phase ratios of 1.5 to 2.4 136 while high-performance SEC packings have more modest phase ratios of 0.5 to 1.5 137 . However the disadvantage of lower phase ratios for high-performance SEC columns is morethan offset bytheir higherefficienciesand faster analysis times. As particlepf refdhfimete rand poetfbyiamt inhrease thu mcchanicaltbrnnythoffhe support dhcreadts. 13.8.2.3 earticleOiameter As in tacnrsyemodao a. - c t a rodigmto tapmcdd1 yit rnecfryn SEC tmproves column effictency. Column packtngs wtth particle dtameters of 10 to 12 im are availabfe forltysdemanding applications such as preparative separations while SEC packings with particle diameters of 4 to 5 im can be used for applications demanding higher resolution as for molecular-weight analysis or analytical separationsof proteinnumteneeii 13.8.2.4 lneryar rngR olubion Resolution n SEC scyntdoilf d tn atsy w silW a elsonng naolumo ch a flatte0 slope of log M versus retention time which effectively increases selectivity or values of a andksUybyiinrcitsi i thecolurnn plate number N. Higher values of N can be achieved by the use of smaller particle columns lower flow rates or an increase in column length. High-pcrformanccSEC columns are usually operated at flow rates of 1 ml mmorkoc for en mhmi.0. 101 .7 8111 11 eHfus hSfL dHhnsh ts Dm for proteintamOoOier bioaorymers or synthetie holrmerf meansthat N usuafia increases sobmiKflmli lvbcnlk ss mm ss redusodl Scction2.3.e . 13.8.3 fCoOile PhnodsCorGolFilroat ho In conttaro w S . o yC ohesmatyosayhs etp n-y oa is an active pat c thf1Sdeateno 1nn cfsr thfi tSaoCm SEC IS simply a carrier that transports solute molecules through the column. The mobile phase is selected Pampin tainthe ooloteinnoloti andynthe .