Validated LC Method, with a Chiral Mobile Phase, for Separation of the Isomers of Fexofenadine Hydrochloride

Abstract

A high-performance liquid chromatographic method has been developed for resolution of the structural isomers of fexofenadine hydrochloride in the bulk drug. The isomers were resolved to baseline on a reversed-phase ODS column with pH 3 aqueous buffer–acetonitrile 60:40 containing 5 g L⁻¹ β-cyclodextrin as mobile phase additive. The aqueous buffer was prepared by dissolving 6.8 g KH₂PO₄ in 1,000 mL water and adjusting to the pH 3.0 with orthophosphoric acid. Resolution for the structural isomers was not less than 3.0. The method was extensively validated and proved to be accurate and precise. The calibration plot was indicative of an excellent linear relationship between response and concentration over the range 0.025–3.750 ppm for the meta isomer. The limits of detection and quantification for the meta isomer were 0.003 and 0.009 ppm, respectively, for an injection volume of 20 μL. Recovery of the meta isomer from bulk drug samples of fexofenadine HCl was 98.43, 96.52, and 97.72% for addition of 0.5, 0.6, and 0.7%, respectively. The analytical solution was stable for 48 h. The method was found to be accurate, and suitable for quantitative determination of the meta isomer in the bulk drug; it can also be used as a stability-indicating method for assay of fexofenadine.