Sensitive titrimetric and spectrophotometric assay methods for chlorpromazine with bromate-bromide mixture and two dyes

摘要

Three new methods using titrimetry and spectrophotometry are described for the determination of chlorpromazine hydrochloride with bromate-bromide mixture as the oxidimetric-brominating agent and two dyes,methyl orange and indigo carmine.In titrimetry (method A),the drug is treated with a measured excess of bromate-bromide reagent in acid medium,and the residual bromine is determined iodometrically.The two spectrophotometric methods involve the addition of a measured excess of bromate-bromide mixture to drug solution in acidic conditions followed by estimation of the unreacted bromine by treating with a fixed amount of methyl orange (method B) or indigo carmine (method C) and measuring the absorbance at 520 nm (method B) or 610 nm (method C).Titrimetric procedure is applicable over 1-10 mg range and the reaction stoichiometry is found to be 1:1 (drug:bromate).In spectrophotometric methods,the systems obey Beer's law over 1.0-6.0mug mL~(-1) and 2.5-15.0mug mL~(-1),for methods B and C,respectively.The molar absorptivity and Sandell sensitivity values and the limits of detection and quantification are reported for both spectrophotometric methods.The proposed methods were applied to the determination of chlorpromazine hydrochloride in tablets and injections with the assay results in the range of 98.63 to 101.88% of label claim.The reliability of the methods was assessed by parallel determination by the official method and by recovery studies.