Enantiomer separations by nonaqueous capillary electrophoresis using octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin

The newest member of the single-isomer isomer sulfated cyclodextrin family, octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin (ODAS-gamma-CD) was use d for the first time as a resolving agent for the nonaqueous capillary elec trophoretic separation of the enantiomers of 26 weak base pharmaceuticals i n an acidic methanol background electrolyte. The solubility limit of ODAS-g amma-CD at room temperature proved to be 55 mM in this background electroly te, which afforded good, fast enantiomer separations for most of the basic drugs tested. For all the bases studied, the effective mobilities and separ ation selectivities were found to follow the predictions of the charged res olving agent migration model of electrophoretic enantiomer separations. The effective mobilities of the weakly binding weak bases remained cationic th roughout the entire 0 to 45 mM ODAS-gamma-CD concentration range; separatio n selectivities increased as the ODAS-gamma-CD concentration was increased. The effective mobilities of the moderately binding weak bases became anion ic in the 2.5 to 45 mM ODAS-gamma-CD concentration range; separation select ivities first increased as the effective mobilities approached zero, then d ecreased again as the ODAS-gamma-CD concentration was increased further. Th e effective mobilities of the strongly binding weak bases became anionic in the 0 to 2.5 mM ODAS-gamma-CD concentration range; separation selectivitie s decreased as the ODAS-gamma-CD concentration was increased above 2.5 mM. (C) 2000 Elsevier Science B.V. All rights reserved.