Spectrophotometric Determination of some Phenothiazines Using N-Chlorosuccinimide

A simple and sensitive spectrophotometric method has been developed for the determination of some phenothiazine derivatives as pure and in dosage form. The method is based on oxidation of phenothiazines by N-chlorosuccinimide in hydrochloric acid medium to give red coloured species having maximum absorptions in the range 516.5-534.5nm. Beers law is obeyed over the concentration ranges 2-28, 2-32 and 4-40g.ml-1 with apparent molar absorptivity of 6.1610, 5.8910 and 5.3410 l.mol-1.cm-1 for phenothiazine, promethazine hydrochloride and chlorpromazine hydrochloride respectively. Additives and excipients normally found in dosage forms do not interfere.