SPECTROPHOTOMETRIC AND SPECTRODENSITOMETRIC DETERMINATION OF CARBIMAZOLE.

Two selective, sensitive and reproducible methods for the determination of carbimazole are described. The spectrophotometric determination of carbimazole was achieved through its reaction with a known excess of potassium bromate in bromide solution, then residual reagent was treated with sodium fluorescein in buffered medium at pH 5.5, where equivalent eosin is produced, which absorbed maximally at 517 nm. Stoichiometric study of the reaction showed that, carbimazole reacts with potassium bromate in the ratio of 1:1. The spectrophotometric method is linear over a range of 30–110 μg%. The spectrodensitometric analysis provides a rapid and precise method for the separation and quantitation of carbimazole. The method depends on the quantitative densitometric evaluation of thin layer chromatogram of carbimazole at 291 nm. It determines the drug in concentration range of 5–22.5 μg per spot. The two methods retained their accuracy and precision when applying the standard addition technique. The results obtained by applying the proposed methods were statistically analysed and compared with those obtained by the official B.P. method. [ABSTRACT FROM AUTHOR]