A validated method for the analysis of diltiazem in raw materials and pharmaceutical formulations by rp-HPLC.

A simple, selective and rapid reversed phase high performance liquid chromatographic (HPLC) method for the analysis of diltiazem (DTZ) in bulk material and pharmaceutical formulations has been developed and validated. Sample was resolved on a Hypersil, ODS, C-18(150x4.6 mm, 5 micron) column. The mobile phase consisted of methanol-water (80:20 v/v, pH 3.1 adjusted with phosphoric acid) was delivered at a flow rate of 0.5 ml/min at ambient temperature and the retention time was about 2.6 minutes with symmetrical peaks. Studies were performed on an HPLC system equipped with a UV/visible detector at 236 nm. Flurbiprofen (FLR) was used as an internal standard. The developed method gave good resolution between diltiazem and internal standard. The method is specific to DTZ and able to resolve the drug peak from formulation excepients. The calibration curve was linear over the concentration range of 0.195-50 mg/ml (R2=0.999). The proposed method is accurate (the accuracy results were 94.1-99.39 for diltiazem recoveries), precise (The intraday and interday precision CVs were 0.035-2.2 %) and linear within the desired range. The lower limits of detection for DTZ was found to be 0.0184 microg/ml and the quantitation limit was about 0.056 microg/ml and therefore could be employed as a more convenient and efficient option for the analysis of diltiazem and its related compounds in drug substance and formulations.