An accurate, precise, simple, efficient and reproducible, isocratic Reversed Phase-High Performance Liquid Chromatography (RP-HPLC) method was developed and validated for the simultaneous estimation of Metformin and Nateglinide in bulk and combined pharmaceutical tablet dosage forms. Metformin and Nateglinide were separated by using a Symmetry ODS C18 (4.6mm×150mm) 5µm Particle Size, Waters Alliance e2695 HPLC system with 2998 PDA detector and the mobile phase contained a mixture of Methanol: 0.1% Orthophosphoric acid (64:36% v/v). The flow rate was set to 1ml/min with the responses measured at 224nm. The retention time of Metformin and Nateglinide was found to be 2.808min and 3.880min respectively with resolution of 5.68. Linearity was established for Metformin and Nateglinide in the range of 20-100µg/ml for Metformin and 60-140µg/ml for Nateglinide with correlation coefficient 0.999. The percentage recovery was found to be is 100.30% for Metformin and 100.21% for Nateglinide respectively. Validation parameters such as specificity, linearity, precision, accuracy and robustness, limit of detection (LOD) and limit of quantitation (LOQ) were evaluated for the method according to the International Conference on Harmonization (ICH) Q2 R1 guidelines. The developed method was successfully applied for the quantification of bulk and active pharmaceutical ingredient present and in combined tablet dosage form.

Keywords: Metformin and Nateglinide, RP-HPLC, Validation, Accuracy, Robustness.