Spectrophotometric and spectrodensitometric determination of carbimazole

Two selective, sensitive and reproducible methods for the determination of carbimazole are described. The spectrophotometric determination of carbimaz ole was achieved through its reaction with a known excess of potassium brom ate in bromide solution, then residual reagent was treated with sodium fluo rescein in buffered medium at pH 5.5, where equivalent eosin is produced, w hich absorbed maximally at 517 nm. Stoichiometric study of the reaction sho wed that, carbimazole reacts with potassium bromate in the ratio of 1:1,The spectrophotometric method is linear over a range of 30-110 mug% The spectrodensitometric analysis provides a rapid and precise method for t he separation and quantitation of carbimazole. The method depends on the qu antitative densitometric evaluation of thin layer chromatogram of carbimazo le at 291 nm. It determines the drug in concentration range of 5-22.5 mug p er spot. The two methods retained their accuracy and precision when applying the sta ndard addition technique. The results obtained by applying the proposed met hods were statistically analysed and compared with those obtained by the of ficial B.P. method.