Spcctrophotometric Micro Determination of Promrthazine Hydrochloride in Pharmaceutical Preparations Via Oxidative Coupling Reaction with Sulphanilamide and in the Presence of Ferric Chloride

A simple, accurate and sensitive spectrophotometry method for the determination of promethazine hydrochloride is described, this method is based on the oxidative coupling reaction of promethazine hydoehloride with sulphanilamide in the presence of ferric chloride and hydrochloric acid to form a green-water-soluble dye, which become more intense and stable al a temperature of 60,C^o ar d has a maximum absorption at 600 mn. A graph of absorbans versus concentration shows that Beer s law is obeyed over the concentration range of 25-900 ug of promethazine hydrochloric! in a final volume of 25 ml (i.e., 1-36 p.p.m) with a molar ubsorpilivily of 1.74x^10 Lit.mor ^-1.cm^-1, a Sandall sensitivity of . 018 ug . cm ^-2 , a relative error of (-2.16— 0.62%) and a relative standard deviation of less than 0.515% depending on the concentration. The optimum conditions for full colour development are described and the proposed method was applied satisfactorily to pharmaceutical preparations containing promethazine hydrochloride.