Development and Validation of a Stability-Indicating RP-HPLC Method for the Determination of Sitagliptin Phosphate and Simvastatin in the Presence of their Degradation Products in Bulk and Binary Mixture

A simple, selective, and precise stability-indicating reversed-phase liquid chromatographic method has been developed and validated for the determination of sitagliptin phosphate monohydrate (STG); and simvastatin (SIM) in the presence of acid and alkali degradation products of STG, and the hydrolytic degradation product of SIM. The method was based on gradient elution on a reversed phase C18 column (150 mm × 4.6 mm, 5 μm)—Cosmosil using a mobile phase consisting of acetonitrile and 10mM potassium dihydrogen orthophosphate (pH 3.0; 0.01M) (85:15% v/v) and flow rate 1.0ml/min. Quantitation was achieved using UV detection at 225 nm for SIT and SIM and their degradation product was achieved. Linearity, accuracy, and precision were found tobe acceptable over the concentration ranges of 20-100 μg mL−1 and 0.4–20 μg mL−1 for STG and SIM, respectively. Limits of detection and quantitation for SIT were found to be 5.65 ng and 17.12 ng, respectively, while for SIM were found to be 2.72 ng and 8.25 ng, respectively. The proposed method was validated as per ICH guideline.