A simple, accurate, sensitive and economical procedure for the estimation of amlodipine besylate and felodipine, both in pure form and in formulations has been developed. The method is based on the reduction of iron(III) by the studied drugs in acid medium and subsequent interaction of iron(II) with ferricyanide to form Prussian blue. The product exhibits absorption maximum at 760 nm in both cases. Beer's law is obeyed in the concentration ranges 5.0-15.0 and 1.5-5.0 μg/ml, for amlodipine and felodipine, respectively. The molar absorptivities are 1.76×104and 4.24×104l/mol cm. The corresponding Sandell sensitivities are 23.18 and 9.06 ng/cm2. The limits of detection as well as quantification are reported. Seven replicate analyses of solutions containing three different concentrations of each drug were carried out and the percent error and the RSD values have been reported. The proposed method was applied to the determination of these drugs in pharmaceutical formulations and the results demonstrate that the method is equally accurate and precise as the official methods as found from the t- and F-values. The reliability of the method was established by recovery studies using standard-addition technique. © 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.
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