Development and validation of a liquid chromatographic method for the determination of related substances in verapamil hydrochloride.

The development of a reversed-phase liquid chromatographic method for the determination of related substances in verapamil hydrochloride is described. The method is based on the use of a simple mobile phase on a specialty base-deactivated reversed-phase column. It enables the resolution of 13 related compounds from the parent drug and from each other. Validation of the method showed it to be reproducible, selective, accurate and linear over the concentration range of analysis with a limit of detection of 0.5 microgram ml-1. The developed method proved to be a real improvement compared with the LC test for chromatographic purity described in the USP monograph for verapamil hydrochloride.