Development and validation of new assay method for the simultaneous analysis of diltiazem, metformin, pioglitazone and rosiglitazone by RP-HPLC and its applications in pharmaceuticals and human serum.

Simple, sensitive, rapid, and accurate high-performance liquid chromatographic (HPLC) method is developed and validated for the simultaneous determination of diltiazem, metformin, pioglitazone, and rosiglitazone hydrochloride in raw materials, their pharmaceutical formulations, and human serum. In HPLC, all the above drugs were chromatographed using acetonitrile-methanol-water (30:20:50, v/v, pH 2.59 ± 0.02) as the mobile phase at a flow rate of 1.0 mL/min at ambient temperature. The separation is carried out on a Hiber, 250-4.6 RP-18 column, equipped with a UV-vis detector at 230 nm. All the antidiabetic drugs eluted at different retention time and each showed a good resolution from diltiazem. The method is successfully applied to pharmaceutical formulations because no chromatographic interferences from the tablet excipients are found. The method is found to be linear, accurate, and precise with apposite detection and quantification limit. Suitability of the method for the quantitative determination of the drugs is proven by validation in accordance with the requirements laid down by International Conference on Harmonization (ICH) guidelines. The validation results, together with statistical treatment of the data, demonstrated the reliability of this method.