Simultaneous determination of chlorzoxazone and ketoprofen in binary mixtures and in ternary mixtures containing the chlorzoxazone degradation product by reversed-phase liquid chromatography.

New, simple, rapid, and precise reversed-phase high-performance liquid chromatographic (LC) methods were developed for the simultaneous determination of chlorzoxazone (CH) and ketoprofen (KT) in binary mixtures and in ternary mixtures containing the CH degradation product, 2-amino-4-chlorophenol (CD). The analytes were separated by LC on a Lichrosphere 60 C18 column (250 x 4 mm, 5 microm). The mobile phases, methanol-water (40:60, v/v) at 1 mL/min and methanol-0.05% phosphoric acid (60:40, v/v, pH 2.81) at 1.5 mL/min, satisfactorily resolved the binary and ternary mixtures, respectively. The UV detector was operated at 280 nm for the determination of CH and at 254 nm for the determination of KT and CD. Linearity, accuracy, and precision were found to be acceptable over the concentration ranges of 20-240 and 5-60 microg/mL for CH and KT, respectively, in the binary mixtures and 50-300, 10-60, and 20-160 microg/mL for CH, KT, and CD, respectively, in the ternary mixtures. The optimized methods proved to be specific, robust, and accurate for the quality control of CH and KT in pharmaceutical preparations.