Quantitation of diltiazem hydrochloride in commercial dosage forms by visible spectrophotometry

Abstract

A selective and sensitive visible spectrophotometric method has been described for the quantitation of diltiazem hydrochloride in commercial dosage forms. The method is based on the reaction of the tertiary amino group of the drug with sodium hypochlorite to form the chloro drug derivative, followed by the destruction of the excess hypochlorite by sodium nitrite and the subsequent development of blue color takes place by the reaction of chloro derivative of drug with starch and potassium iodide in sodium bicarbonate medium. The maximum absorbance of the resulting blue solution is read at 540 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 2.5-25.0 μgmL-1 with a linear regression equation of A = 9.85 × 10-4 + 4.90 × 10-2 C and coefficient of correlation, r = 0.9999. The molar absorptivity is found to be 2.26 × 104 L mol-1 cm-1. The limits of detection and quantitation of the proposed method are 0.12 and 0.37 μg mL-1, respectively. The proposed method has been successfully applied for the quantitation of diltiazem hydrochloride in commercial dosage forms. The results of the proposed method compared with those of Abdellatef's spectrophotometric method presented good mean recovery with acceptable true bias of all pharmaceutical samples within ± 2.0%.