Enantioseparations in nonaqueous and aqueous capillary electrochromatography using helically chiral poly(diphenyl-2-pyridylmethylmethacrylate) as chiral stationary phase

Capillary electrochromatographic (CEC) enantioseparations were performed in nonaqueous and aqueous-organic background electrolytes (BGE) using fused-silica capillaries packed with native and aminopropyl silica coated with helically chiral poly(diphenyl-2-pyridylmethyl methacrylate) (PDPM) as chiral stationary phase (CSP). The contribution of the aminopropyl groups of the silica gel and the pyridyl groups of the chiral selector to the anodic electroosmotic flow (EOF) generated in these capillaries was evaluated. Furthermore, different nonaqueous BGEs (methanol, acetonitrile) were tested; the influence of the ammonium acetate concentration, the apparent pH (pH*) of the BGE, and the composition of the aqueous-organic BGE were investigated with regard to the EOF and basic chromatographic parameters. The effect of the contributions of a pressure-driven and electrokinetically driven flows and mass transfer characteristics of the stationary phase on the plate heights and enantioseparations was evaluated.