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

A simple capillary zone electrophoresis method is described for the simulta neous separation and quantitation of chiral carbinoxamine maleate, doxylami ne succinate, and orphenadrine citrate using achiral diphenhydramine HCI as an internal standard. The chiral analysis of these drugs was performed in a Tris buffer (100 mM; pH 4.60) with sulfated beta-cyclodextrin (15 mg/mL) as a chiral selector. Several parameters affecting the separation were stud ied, including the pH of the buffer and the concentrations of buffer and ch iral selector. Quantitation of the individual enantiomer (prepared from the related racemate) is attainable at 25-125 mu M for carbinoxamine maleate, doxylamine succinate, or orphenadrine citrate. The migration order of the s eparated enantiomers is compared to that of a structurally related dexchlor pheniramine, an S-enantiomer of chlorpheniramine. (C) 2000 John Wiley & Son s, Inc.