RESUMO
Three rapid, selective and sensitive spectrophotometric methods have been proposed for the quantitative determination of atenolol (ATN) in pure form as well as in its pharmaceutical formulation. The methods are based on charge transfer complexation reaction of ATN as n-electron donor with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (picric acid; PA) as pi-acceptors to give highly colored radical anion species. The colored products were quantified spectrophotometrically at 590 nm with DDQ (method A) and at 420 nm with both DNP (method B) and PA (method C). Under the optimized experimental conditions, Beer's law is obeyed over the concentration ranges of 3-48, 2-24 and 1.5-18 µg/mL ATN for method A, method B and method C, respectively. The molar absorptivity, Sandell sensitivity, limits of detection and quantification are also reported. The effects of reaction medium, reaction time and reagent concentration on the sensitivity and stability of the complexes formed have been examined. The proposed methods were successfully applied to the determination of ATN in pure form and commercial tablets with good accuracy and precision. Statistical comparison of the results was performed using Student's t-test and F-ratio at 95% confidence level and the results showed no significant difference between the reference and proposed methods with regard to accuracy and precision. Further, the accuracy and reliability of the methods were confirmed by recovery studies via standard addition technique.
