A Kinetic spectrophotometric method for determination of amlodipine and Nifedipine in pharmaceutical preparations

A simple, accurate, sensitive and economical procedure for the estimation of amlodipine besylate and nifedipine, both in pure and dosage forms, has been developed. The method is based on the reduction of iron(III) by the studied drugs and subsequent interaction of iron(II) with ferricyanide to form Prussian blue. The reaction develops through a slow kinetics and completes in about 10 min. Both initial slope and fixed time methods were used to derive calibration graphs. The resulted calibration equations were linear in the concentration ranges of 1.0-20.0 and 3.0-19.0 μg ml^-1 for AML and NIF, and the detection limits were 0.10 and 0.19 μg ml^-1, respectively. Seven replicate analyses of solutions containing three different levels of each drug resulted in very low relative error of prediction (less than 1.6%) and relative standard deviation (less than 4%) confirming accuracy and precision of the proposed method. The proposed method was applied to the determination of these drugs in pharmaceutical formulations and excellent recoveries were obtained.