HPLC resolution of thioridazine enantiomers from pharmaceutical dosage form using cyclodextrin-based chiral stationary phase

Resolution of racemic thioridazine obtained from Thioril® tablets (Cipla Ltd., Goa, India) into its enantiomers has been achieved by HPLC using a β-cyclodextrin (CD)-bonded stationary phase. Thioridazine was isolated from commercial formulations and was purified using preparative TLC. The purity was ascertained by RP-HPLC. For the resolution of rac-thioridazine using cyclodextrin based CSP and mobile phase of 0.05 M phosphate buffer (pH 6.5)–acetonitrile (50:50) was found to be successful. The optimum conditions of resolution were established by systematically studying the effect of organic modifier, concentration of buffer, pH and flow rate of mobile phase. The detection limit was found to be 10 μg (5 μg of each enantiomer). The enantiomeric purity of each of the resolved isomers was verified by optical rotation.