Titrimetric, spectrophotometric and kinetic methods for the assay of atenolol using bromate-bromide and methyl orange

Three new methods have been developed for the determination of atenolol in bulk drug and in tablet formulation. The methods are based on the oxidation-bromination reaction of the drug by bromine, generated in situ by the action of acid on a bromate-bromide mixture. In the titrimetric method, the drug is treated with a known excess of bromate-bromide mixture in hydrochloric acid medium, followed by the determination of the unreacted bromine iodometrically. The spectrophotometric method involves the addition of a measured excess of bromate-bromide reagent in hydrochloric acid medium to atenolol, and after ensuring the reaction had gone to completion, the unreacted bromine is treated with a fixed amount of methyl orange, and absorbance measured at 520 nm. The absorbance was found to increase linearly with increasing concentration of atenolol. The kinetic method depends on the existence of a linear relationship between the concentration of the drug and the time of the oxidation-bromination reaction, as indicated by the bleaching of methyl orange acid colour. The working conditions were optimized. The tittimetric method is based on a 1: 1 reaction stoichiometry (atenolol:bromate) and is applicable over the 3-20 mg range. The spectrophotometric method permits micro determination of the drug (0.5-4.0 mu g ml(-1)) with an apparent molar absorptivity of 4.13 x 10(4) l mol(-1) cm(-1) and detection limit of 0.07 mu g ml(-1). The kinetic method is applicable in the concentration range 5-25 mu g ml(-1) with a detection limit of 3.72 mu g ml(-1). The proposed methods were successfully applied to the determination of atenolol in tablet preparations with mean recoveries of 97.63 to 101.78 %. The reliability of the assay was established by parallel determination by the reference method and by recovery studies using the standard addition technique.