Development of a liquid chromatographic method for the control of related substances in chlorprothixene hydrochloride

The development of a reversed-phase liquid chromatographic method, using a mobile phase containing a mixture of anion and cation ion-pairing agents and a base-deactivated octyldecylsilyl column as stationary phase, is described for the control of all known impurities in (Z)-chlorprothixene hydrochloride (bulk drug). Validation of the method showed it to be reproducible, selective for both (Z) chlorprothixene hydrochloride and its E-isomer, accurate and linear over the concentration range of analysis with a limit of detection of 0.3 microgram ml-1.