Validated spectrophotometric methods for the determination of amlodipine besylate in drug formulations using 2,3-dichloro 5,6-dicyano 1,4-benzoquinone and ascorbic acid

Two simple and sensitive spectrophotometric methods have been proposed for the determination of amlodipine besylate either in pure form or in pharmaceutical formulations. The first method is based on the charge transfer complexation reaction of the drug with 2,3-dichloro 5,6-dicyano 1,4-benzoquinone (DDQ) to give coloured product having maximum absorbance at 580 nm. The second procedure depends on the measurement of purple red colour produced by the interaction of drug with ascorbic acid in N,N-dimethylformamide medium (DMF) which absorbed maximally at 530 nm. Under the optimized experimental conditions, Beer's law was obeyed in the concentration ranges of 1-125 and 10-140 μg ml^-1 with DDQ and ascorbic acid, respectively. Both the methods were applied successfully for the analysis of amlodipine besylate in dosage forms. Results of analyses were validated statistically and through recovery studies.