Cyclodextrins as buffer additives for the enantiomeric separation of pinacidil in capillary zone electrophoresis

The enantiomeric separation of pinacidil was studied using alpha-cyclodextrin (alpha-CD), beta-CD, heptakis (2,6-di-O-methyl)-beta-CD (DM-beta-CD), hydroxypropyl-beta-CD (HP-beta-CD) and gamma-CD as buffer additives at acidic pH in capillary zone electrophoresis. beta-CD, HP-beta-CD and gamma-CD all showed chiral recognition on the compound, with HP-beta-CD giving the highest chiral selectivity. Buffer concentration and HP-beta-CD concentration were optimized for the separation. The separation was improved by the addition of hydroxypropyl cellulose (HPC) to the buffer. A complete separation of pinacidil enantiomers was achieved by using 100 mM Tris-H3PO4 buffer (pH 2.3) containing 9 mM HP-beta-CD and 0.05% HPC.