Colorimetric Method for Determination of some 1,4-Dihydropyridine Drugs in their Tablets and Capsules

A simple, accurate and selective colorimetric method was developed and validated for determination of five 1,4-dihydropyridine drugs (1,4-DHP) using Tetrabutylammonium hydroxide reagent (TBAH). The proposed method was based on addition of TBAH to the studied drugs then produced yellow colors were measured spectrophotometrically. Different variables affecting the reactions conditions carefully studied and optimized and under the optimum conditions, Beer's law was obeyed in the concentration range of 2.50-40.0 µg/mL and the limits of detection were ranged from 0.750-1.956 µg/mL. The proposed method was successfully extended to pharmaceutical preparations tablets or capsules and the results which obtained were comparable with that obtained by the reference methods.