Enantioselective reversed-phase and non-aqueous capillary electrochromatography using a teicoplanin chiral stationary phase

Enantiomeric separation of chiral pharmaceuticals is carried out in aqueous and non-aqueous packed capillary electrochromatography (CEC) using a teicoplanin chiral stationary phase (CSP). Capillaries were slurry packed with 5 μm 100-Å porous silica particles modified with teicoplanin and initially evaluated using a non-aqueous polar organic mode system suitability test for the separation of metoprolol enantiomers (Rs=2.3 and 53 000 plates m−1). A number of pharmaceutical drugs were subsequently screened with enantioselectivity obtained for 25 racemic solutes including examples of neutral, acidic and basic molecules such as coumachlor (Rs=3.0 and 86 000 plates m−1) and alprenolol (Rs=3.3 and 135 000 plates m−1) in reversed-phase and polar organic mode, respectively. A statistical experimental design was used to investigate the effects of non-aqueous polar organic mobile phase parameters on the CEC electroosmotic flow, resolution and peak efficiency for two model solutes. Results primarily indicated that higher efficiency and resolution values could be attained at higher methanol contents which is similar to findings obtained on this phase in liquid chromatography.