Automated flow injection spectrophotometric determination of some phenothiazines using iron perchlorate: applications in drug assays, content uniformity and dissolution studies

Abstract

An automated flow injection determination of some phenothiazine derivatives, based on their oxidation with iron(III) in a strongly acidic medium, is described. Chlorpromazine, promethazine, thioproperazine, promazine, levomepromazine, fluphenazine, trifluoperazine and thioridazine are determined in the range 10–250 µg ml^–1. The precision is better than 1% and a measurement rate of 120 per hour can be obtained. The method was evaluated by carrying out an interference study with common excipients and other drugs, a recovery study and by the analysis of commercial formulations, the results of which are compared with those obtained by the official method. The method was applied in content uniformity tests and for monitoring the dissolution of solid dosage forms.