Development and Validation of Stability Indicating RP-HPLC and UV Method for Simultaneous Quantitation of Repaglinide and Sitagliptin Phosphate in Combination

The present work describes Stability indicating RP-HPLC and Simultaneous equation UV spectrophotometric method for the quantitative determination of Repaglinide and Sitagliptin phosphate. The parameters Specificity, linearity, accuracy, precision, detection limit, quantitation limit, Robustness and system suitability tests were studied and their results were complied to ICH guideline Q2 (R1).  Chromatography was carried out by reverse phase technique on an RP-18 with mobile phase composed of Acetonitrile: Phosphate buffer (65:35; % v/v) adjusted to pH 3.5 with 10% orthophosphoric acid) with flow rate 1 ml/min. Both drugs were eluted, isocratically using detection wavelength 228 nm. Simultaneous equation UV spectrophotometric method was performed and two wavelengths 240 nm (λmax of Repaglinide) and 267 nm (λmax of Sitagliptin phosphate) were selected for the formation of simultaneous equation. The A (1%, 1cm) was determined at both the wavelengths selected for each drug. A set of two simultaneous equations were formed as Cx and Cy. Methanol used as Solvent (diluent) for UV method. For proposed methods, the linearity for both methods were obtained in the concentration range of 0.5-2.5 μg/ml for Repaglinide and 50-250 μg/ml for Sitagliptin phosphate. Statistical analysis by student’s t-test showed no significance difference between the results obtained by these two methods. The suitability of method for the quantitative determination of Repaglinide and Sitagliptin phosphate was proved by validation. The proposed methods and its results had been successfully applied and validated statistically to the simultaneous estimation of Repaglinide and Sitagliptin phosphate in their combination for quality analysis.