Enantiomeric separations of cationic and neutral compounds by capillary electrochromatography with monolithic chiral stationary phases of beta-cyclodextrin-bonded negatively charged polyacrylamide gels

Enantiomeric separation by capillary electrochromatography with beta-cyclod extrin-bonded negatively charged polyacrylamide gels was examined. The colu mns used are capillaries filled with a negatively charged polyacrylamide ge l, a so-called monolithic stationary phase, to which allyl carbamoylated be ta-CD (AC-beta-CD) derivatives covalently bind. The capillary wall is activ ated first with a bifunctional reagent to make the resulting gel bind coval ently to the inner surface of the fused-silica tubing. Enantiomeric separat ions of 15 cationic compounds were achieved using the above-mentioned colum ns and mobile phases of 200 mmol l(-1) Tris-300 mmol l(-1) boric acid buffe r (pH 7.0 or 9.0) or 200 mmol l(-1) Tris-300 mmol l(-1) boric acid buffer ( pH 7.0) containing an achiral crown ether (18-crown-6). Enantiomeric separa tions of two neutral compounds were also achieved using 200 mmol l(-1) Tris -300 mmol l(-1) boric acid buffer (pH 9.0) as a mobile phase. High efficien cies of up to 150 000 plates m(-1) were obtained. Both the within- and betw een-run reproducibilities of retention time and separation factor were good . The reproducibilities of retention time and separation factor for three d ifferent columns prepared from a different batch of monomers were acceptabl e. The gel-filled capillaries were stable for at least 3 months with interm ittent use, utilizing the mobile phase of 200 mmol l(-1) Tris-300 mmol l(-1 ) boric acid buffer (pH 9.0). (C) 2000 Elsevier Science B.V. All rights res erved.