SummaryThe addition of 1-20% (v/v) of methanol or acetonitrile as organic modifier to the mobile phase in a micellar electrokinetic capillary chromatographic (MECC) system, containing sodium dodecyl sulfate and a buffer, is shown to extend the elution range and thus increase the peak capacity of a given system. Although thenet changein theelution rangeparameter, tO/tmc,is essentially the same for both modifiers, the acetonitrile-modified system exhibits much faster elution times for the polar and non-polar test solutes employed in this study. Retention, as measured by thecapacity factor, is generally decreased with the increaseof anorganic modifier, just as in conventional reversedphase chromatography. However, changes in selectivity as a function of the added modifiers are noted among polar and nonpolar solutes as well. The efficiency of these MECC systems is increased with the addition of either organic modifier.
Dynamically modified open tubular capillary columns were evaluated for separations of biological and clinical interest. Small diameter, dynamically modified columns were readily prepared by simple addition of cetyltrimethylammonium salts to the mobile phase. Separations similar to those obtained on conventional reversed-phase columns were observed for neutral solutes, and ion-pair reversed-phase separations were observed for charged solutes. Borosilicate and standard flint glasses were evaluated with respect to common etching procedures. A potential clinical application is presented in the separation of antitumor drugs.
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