Sensitive determination of atenolol in tablets using chloramine-T and two dyes

Three methods, one titrimetric and two spectrophotometric, using chloramine-T (CAT) and two dyes, metanil yellow and indigocarmine have been developed for the determination of atenolol (ATN) in bulk drug and in tablets. The titrimetric method (Method A) involves the oxidation of the drug by a measured excess of CAT in acid medium followed by the determination of the residual oxidant by iodometric back titration. In spectrophotometric methods, ATN is oxidised by a known excess of CAT in acid medium followed by the determination of unreacted oxidant by reacting with a fixed amount of either metanil yellow (Method B) or indigo carmine (Method C) and measuring the increase in absorbance at 530 or 610 nm. Titrimetry is applicable in 3-20 mg range whereas in spectrophotometry, Beer's law is obeyed over the concentration ranges, 1-12 mug mL(-1) (Method B) and 2.5 - 20.0 mug mL(-1) (Method C). Molar absorptivity values as calculated from Beer's law data are found to be 1.19X10(4) L mol(-1) cm(-1) (Method B) and 6.65x10(3) L mol(-1) cm(-1) (Method C) and the corresponding Sandell sensitivity values are 0.022 and 0.040 mug cm(-2). The choice of experimental conditions, which provide the maximum accuracy, precision and sensitivity, is discussed. The common excipients and additives found in tablet preparations did not interfere. The proposed methods were successfully applied to the determination of the drug in tablets. Recoveries ranged from 96.43 to 103.74%. The utility and accuracy of the methods were further established by parallel determination by the official Indian Pharmacopoeial method and by recovery studies.