A direct enantioselective high-performance liquid chromatography was employed successfully for determination of the enantiomeric purity of levamisole. The elaborated method used S-naphthylethylcarbamoylated beta-cyclodextrin stationary phase in reversed-phase mode. The optimized mobile phase composition was acetonitrile-0.5% triethylammonium acetate buffer, pH 5.0 (2:8, v/v). Linearity, precision, accuracy, and the quantitation limit were determined. The method proved to be capable of determining 0.05% (w/w) of dexamisole (the enantiomeric impurity) contrary to the pharmacopoeial optical rotation measurement, in which only amounts of dexamisole higher than 2.2% (w/w) caused the test to fail. The enantiomeric purity of three different levamisole substances and levamisole tablets was assessed with the use of the method. The content of dexamisole impurity was found to be in the range 0.66-1.60% (w/w).

Department of Analytical Chemistry State Institute for Drug Control Srobárova 48 100 41 10 Prague Czech Republic

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