Enantioseparation of Tröger's base derivatives by capillary electrophoresis using cyclodextrins as chiral selectors

The enantioseparation of seven Tröger's base derivatives (TBs) was carried out by capillary electrophoresis using α-, β-, and γ-cyclodextrins as chiral selectors and phosphate at 20 mmol/l concentration, pH 2.5, as background electrolyte. The method was optimized with respect to the concentration of chosen chiral selectors (0-50 mmol/l) and the amount of organic solvent (acetonitrile, 0-25 % (v/v)) in the electrolyte. The results indicate that all the studied variables, i.e., type of chiral selector, its concentration, and the amount of the added organic solvent, have a significant impact on the enantioseparation of the studied TBs. The best results for the majority of the separated TBs were obtained utilizing β-cyclodextrin at 5 mmol/l concentration and with various amounts of acetonitrile added ranging from 5 to 15% (v/v) in the background electrolyte. For the two smallest studied TBs, γ-cyclodextrin with 10% (v/v) acetonitrile also provided good resolution.