AbstractA simple, economic, selective, and precise RP-HPLC method has been developed and validated for the estimation of related impurities of Atazanavir and Cobicistat in combined dosage form. Chromatographic separation has been achieved by using LC-20 AT C18 (250mm x 4.6mm, 5μm) column and using mobile phase buffer (potassium dihydrogen phosphate, pH 3.0): acetonitrile (60:40), 1mL/min was a flow rate. Samples were scanned at a wavelength of 224 nm. As per the ICH guidelines the method is validated. Retention time of Cobicistat and Atazanavir were found to be 5.247 and 3.513 respectively and the retention time of Atazanavir impurity and Cobicistat impurity were found to be 2.747 minute and 4.370 minute respectively. Validation of the method was successfully established by performing various validation parameters such as specificity, precision, linearity, accuracy, LOD, LOQ, robustness, ruggedness according to ICH guidelines. The linearity was observed in the range of 2.5-7.5 μg/mL for related impurities of Atazanavir and 2.5-7.5 μg/mL for related impurities of Cobicistat. The LOD value was found 0.206 μg/mL and 0.342 μg/mL for Atazanavir impurity and Cobicistat impurity respectively. The proposed method was found to be specific, linear, sensitive, precise, accurate and robust in nature.KeywordsAtazanavir, Cobicistat, related impurities RP-HPLC Method, Validation.