Spectrophotometric method for the determination of amlodipine besylate with ninhydrin in drug formulations

A spectrophotometric method has been developed for the determination of amlodipine besylate in pure form and in pharmaceutical preparations. The method is based on the reaction of the primary amino group of the drug with ninhydrin in N,N'-dimethylformamide (DMF) medium producing a coloured complex which absorbs maximally at 595 nm. Beer's law is obeyed in the concentration range of 10-60 mug ml(-1) with RSD of 0.66% and molar absorptivity of 6.52 x 10(3) 1 mol(-1) cm(-1). All variables were studied in order to optimize the reaction conditions. The proposed method has been applied successfully to the analysis of the bulk drug and its dosage forms. No interference was observed from common pharmaceutical adjuvants. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision. (C) 2001 Elsevier Science S.A. All rights reserved.