Capillary electrophoretic separation of enantiomers using the single isomer heptakis-(2,3-dimethyl-6-sulfato)-β-cyclodextrin as chiral resolving agent in methanol-water background electrolytes

The utility of the sodium salt of the single isomer heptakis-(2,3-dimethyl-6-sulfato)-beta-cyclodextrin as chiral resolving agent in methanol-water background electrolytes was studied by capillary electrophoresis. The effective mobilities of neutral, weak acid and weak base enantiomers were measured as a function of the methanol concentration in the 0 to 50% (v/v) range, while the heptakis-(2,3-dimethyl-6-sulfato)-beta-cyclodextrin concentration was simultaneously varied in the 0 to 100 mM range. The addition of methanol improved the solubility and decreased the effective mobility of the analytes. The methanol-induced reduction in the extent of binding of the analytes to the charged cyclodextrin could be compensated for by increasing the concentration of the charged cyclodextrin in the background electrolyte. Separation selectivities closely followed the theoretical predictions of the charged resolving agent migration model of enantiomer separations. (C) 1998 Elsevier Science B.V. All rights reserved.