CAPILLARY ELECTROCHROMATOGRAPHY - OPERATING CHARACTERISTICS AND ENANTIOMERIC SEPARATIONS

Some fundamental aspects of capillary electrochromatography (CEC) (ele ctroosmotic flow, capacity factor, plate height) were studied by carry ing out the separation of some neutral compounds with capillaries pack ed with octadecylsilica particles (ODS). No loss of efficiency up to a linear electroosmotic velocity of 1.3 mm/s was observed for retained analytes (capacity factors varying from 0.7 to 2.5). The extra-column dispersions caused by the frit and the unpacked section separating the frit from the detection window were estimated. Chiral separations of the neutral enantiomers of chlorthalidone by packed capillary electroc hromatography was successfully achieved using two approaches: (a) use of the chiral age nt, hydroxypropyl-beta-cyclodextrin (HP beta CD) dir ectly in the mobile phase with an achiral stationary phase (3 mu m ODS ); (b) use of a chiral stationary phase (5 mu m HP beta CD-bonded sili ca particles) with an achiral mobile phase. As with liquid chromatogra phy, the second method achieves higher selectivity and resolution in a shorter analysis time.