Enantioseparation of uncharged compounds by capillary electrophoresis using mixtures of anionic and neutral β-cyclodextrin derivatives

The use of the polyanionic sulfobutyl-beta-cyclodextrin in combination with a neutral cyclodextrin derivative such as trimethyl-beta-cyclodextrin (TMCD) or dimethyl-beta-cyclodextrin (DMCD) in a pH 3 phosphoric acid-triethanolamine buffer has proved to be very suited to the enantioseparation of acidic compounds such as non-steroidal anti-inflammatory drugs. In this paper, the usefulness of such dual cyclodextrin systems was evaluated for the enantioseparation of weakly acidic and neutral compounds. Fairly good results with respect to chiral resolution were obtained at pH 3 for weak acids in these dual systems, However, no complete enantioseparation could be achieved under these conditions for the neutral drug chlormezanone. Another ionizable derivative, carboxymethyl-beta-cyclodextrin, was then investigated together with TMCD or DMCD at pH 3 and 5. After optimisation of the concentration of the neutral cyclodextrin derivative, high enantioresolution could be obtained at pH 5 for chlormezanone as well as for all the other compounds tested. (C) 1998 Elsevier Science B.V. All rights reserved.