Quantitative chiral analysis of carbinoxamine, doxylamine, and orphenadrine by capillary zone electrophoresis†

A simple capillary zone electrophoresis method is described for the simultaneous separation and quantitation of chiral carbinoxamine maleate, doxylamine succinate, and orphenadrine citrate using achiral diphenhydramine⋅HCl as an internal standard. The chiral analysis of these drugs was performed in a Tris buffer (100 mM; pH 4.60) with sulfated β-cyclodextrin (15 mg/mL) as a chiral selector. Several parameters affecting the separation were studied, including the pH of the buffer and the concentrations of buffer and chiral selector. Quantitation of the individual enantiomer (prepared from the related racemate) is attainable at 25–125 μM for carbinoxamine maleate, doxylamine succinate, or orphenadrine citrate. The migration order of the separated enantiomers is compared to that of a structurally related dexchlorpheniramine, an S-enantiomer of chlorpheniramine. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 366–370, 2000