Enantioseparations in normal- and reversed-phase nano-high-performance liquid chromatography and capillary electrochromatography using polyacrylamide and polysaccharide derivatives as chiral stationary phases

Enantioseparations of chiral compounds with different structures (beta-blockers, benzodiazepines, diuretica, etc.) were performed in fused-silica capillaries packed with silica gel which was modified by covalent attachment of poly-N-acryloyl-L-phenylalanineethylester (Chiraspher(R)) or by coating with cellulose tris(3,5-dimethylphenylcarbamate). Three different separation modes, normal- and reversed-phase nano-HPLC and capillary electrochromatography (CEC) with and without pressure-assistance were performed in these capillaries using essentially the same experimental set-up. This allows a more reliable comparison of the different techniques. Nano-HPLC separations in the normal-phase mode gave relatively high peak efficiency compared to HPLC in regular size columns. However, under the experimental conditions of this study no significant gain in separation efficiency could be obtained by changing from pressure-driven to electrically-driven migration of the solutes. (C) 1999 Elsevier Science B.V. All rights reserved.