Utilization of bromination reactions for the determination of carbamazepine using bromate–bromide mixture as a green brominating agent

Abstract

One titrimetric and two spectrophotometric procedures have been developed for the assay of carbamazepine (CBZ) in bulk drug, formulations and spiked human urine. The methods are based on the bromination of CBZ by the bromine generated in situ by the action of the acid on the bromate–bromide mixture. The twin advantages of avoiding liquid bromine and analysis in a cost-effective manner are realized. In titrimetry, the drug was treated with a known excess of bromate–bromide mixture in hydrochloric acid medium followed by the determination of unreacted bromine iodometrically. Spectrophotometry involves the addition of a measured excess of bromate–bromide reagent in acid medium to CBZ, and after the reaction is ensured to be complete, the residual bromine was determined by reacting with a fixed amount of either methyl orange and measuring the absorbance at 510 nm (method A) or indigo carmine and measuring the absorbance at 610 nm (method B). Titrimetric procedure is applicable over the range of 1.00–7.50 mg CBZ, and the calculations are based on a 1:1 reaction stoichiometry (CBZ:KBrO3). In spectrophotometric methods, Beer’s law is valid within concentration ranges of 0.25–1.50 and 0.50–6.00 μg ml−1 CBZ for methods A and B, respectively. The proposed methods were successfully applied to the determination of CBZ in tablets and syrup, in addition to spiked human urine by the spectrophotometric methods, with mean recoveries of 95.50–104.0% and the results were statistically compared with those of an official method by applying Student’s t-test and F-test.

Keywords

• Carbamazepine
• Bromate–bromide
• Methyl orange
• Indigo carmine
• Pharmaceutical analysis