A negatively charged cyclodextrin, sulfated -cyclodextrin -CD-Ž y .
x SO , was used as a chiral selector for capillary electrophoresis separations of 4 4 basic pharmaceutical enantiomers. The charges of the basic enantiomers were controlled by adjusting the buffer pH. At pH 2.5, basic compounds are positively charged and interact stronger with the negatively charged CD than with neutral CDs, owing to the extra electrostatic interaction. This additional interaction is very useful for chiral separations of the enantiomers that interact weakly with the neutral CDs. For example, chiral separations of acebutolol, metanephrine, normetanephrine, nafronyl, labetalol, and nadolol were achieved at this pH. For labetalol and nadolol that have two chiral centers, three of the four isomers were Ž . separated. The capillary surface was dynamically coated with poly vinyl alcohol Ž . PVA to reduce the possible interactions between solutes and the capillary wall, to Ž . improve efficiency and reduce the electroosmotic flow EOF for enhancing resolution. PVA reduced the interactions between the analytes and the chiral selector; nevertheless, peak tailing was observed owing to the electrodispersion for the compounds that interact too strongly with the anionic CD. At pH 11.6, most of Ž . the basic test compounds except those having phenol groups are neutral and have weaker interactions with the negatively charged CD. The separation efficiency increased dramatically for all analytes at higher pH owing to the absence of electrodispersion. The existence of the neutral PVA polymer in the buffer solution increased the solubility of the neutral hydrophobic amines and reduced the solute᎐CD complexation. Chiral separations of a large number of compounds were achieved at a single concentration of the charged cyclodextrin.