Two Validated Spectrophotometric Methods for Quantitative Analysis of Amlodipine Besylate in Pharmaceutical Preparations by Redox Reaction

Abstract

This research aims to develop two spectrophotometric methods for the quantitative determination of amlodipine besylate (ADB) in its pure form and in pharmaceuticals. Both methods are characterized by simplicity, high accuracy, sensitivity, cost-effectiveness, and eco-friendliness. The underlying principle for both techniques is based on redox reactions. The first method (indirect) involves the reaction of ADB with a known excess of N-bromosuccinimide (NBS) in an acetic acid medium. The residual NBS is subsequently determined by its ability to bleaching the color of Orang G dye, with the remaining dye measured at λ max = 478 nm. The second method (direct) entails the reduction of potassium permanganate by ADB in an alkaline medium, resulting in the formation of a bluish- green manganate ion (MnO₄^2-) which exhibits maximum absorbance at λ max = 608 nm. Linearity for the two methods was observed in the ranges 1-35 and 1-70 µg. mL^-1, with determination coefficients (R²) of 0.9989 for each method. The molar absorptivity values were 2.166 ×10⁴ and 0.98 ×10⁴ L.mol^-1.cm^-1, while Sandell’s sensitivity index values were 0.0262 and 0.058 µg.cm^-2, respectively. The limit of detection (LOD) was found to be 0.196 and 0.567 µg.mL^-1, while the limit of quantification (LOQ) was 0.653 and 1.89 µg.mL^-1, respectively. The proposed methods were effectively applied to evaluate ADB  in pure forms and pharmaceutical preparations (tablets, capsules). The validity of these methods was confirmed through recovery studies using the standard addition method.