Comparison of capillary zone electrophoresis and isotachophoresis determination of dimethindene enantiomers in pharmaceuticals using charged carboxyethyl-beta-cyclodextrin as a chiral selector.

Charged cyclodextrin-mediated capillary electrophoretic methods (capillary zone electrophoresis [CZE] and isotachophoresis [ITP]) in a hydrodynamically closed separation system with suppressed electroosmotic flow and UV absorbance photometric detection (for CZE) or conductivity detection (for ITP) were developed for a highly effective separation and quantitation of dimethindene enantiomers in various pharmaceutical formulations (solution, gel, capsules). Optimized electrolyte systems were based on low-mobility buffer constituents (epsilon-aminocaproic acid, beta-alanine, potassium acetate, acetic acid), negatively charged (at pH > 4.5) carboxyethyl-beta-cyclodextrin (CE-beta-CD), serving as chiral selector, and methylhydroxyethylcellulose, serving as an electroosmotic flow suppressor. Complete enantioseparations of dimethindene in the presence of low concentrations of CE-beta-CD (2.5 mg/ml in CZE, 6.0 mg/ml in ITP) clearly indicated a role of charge of this chiral selector in enantioresolution. It also outlined the potential of charged CD-derivatives as chiral selectors for various CE techniques. The proposed methods were successfully validated, appraising parameters of sensitivity, linearity, precision, accuracy/recovery, and robustness, and then, they were applied to pharmaceutical samples. Consistent results obtained by both CE methods indicate their usefulness for routine use.