HPLC method development for the simultaneous determination and validation of Diltiazem hydrochloride and its major metabolite desacetyl Diltiazem hydrochloride

A stability-indicating liquid chromatographic method has been developed and validated for the determination of Diltiazem Hydrochloride and its major metabolite desacetyl Diltiazem Hydrochloride. The concentration range was 25% to 250% and the flow rate was 1.0 mL/min. The mobile phase was 650:350 v:v acetate buffer and acetonitrile, respectively. The method was proved to be linear for the determination of Diltiazem Hydrochloride and the metabolite in the range of 25% to 250% of the specified limit i.e. 0.5%; the correlation coefficient met the acceptance criteria (≥ 0.998). The smaller point in the calibration curve was optimal for low concentration samples. The limit of detection and quantification were found to be 0.0633 and 0.450 μg/mL, respectively for desacetyl Diltiazem hydrochloride and 0.0408 μg/mL and 0.2668 μg/mL, respectively for Diltiazem hydrochloride. The degradation reaction of desacetyl Diltiazem hydrochloride by stress conditions was found to be faster and more intensive than Diltiazem hydrochloride.