Quantitative analysis of trimethobenzamide hydrochloride by ion-pair column chromatography and semiquantitative analysis of 3,4,5-trimethoxybenzoic acid by thin-layer chromatography.

An ion-pair column chromatographic/UV spectrophotometric method for assaying trimethobenzamide hydrochloride in capsules and injections is presented, as well as a method for the detection of 3,4,5- trimethoxybenzoic acid in trimethobenzamide hydrochloride bulk drug and dosage forms. Results obtained by the USP XX, Pharmacopeial Forum, and ion-pair column assay procedures are compared, and results of a collaborative study of the proposed assay and impurity detection methods are presented.