A sensitive, stability-indicating gradient reverse phase high performance liquid chromatographic (RP-HPLC) method was developed for the quantitative determination of impurities of linezolid in active pharmaceutical ingredient (API) and pharmaceutical formulations. Efficient chromatographic separation was achieved on X Bridge C18, 150 × 4.6 mm, 3.5 µm column with mobile phase containing a gradient mixture of solvents A and B. The flow rate of the mobile phase was 1.0 mL.min-1 with column temperature of 45 °C. The relative response factor values of N Oxide and Impurities A, B, C, D, E, F, G, H & I were 0.40, 1.03, 0.79, 0.99, 0.83, 0.91, 1.07, 1.03, 0.79 and 0.96, respectively. The linezolid formulation sample was subjected to stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Linezolid was found to degrade significantly in base and peroxide stress conditions. The degradation products were well resolved from linezolid and its impurities. The peak purity test results confirmed that the linezolid peak was homogeneous and pure in all stress samples and the mass balance was found to be more than 98%, thus proving the stability-indicating power of the method. The developed method was validated according to International Conference on Harmonisation (ICH) guidelines with respect to specificity, linearity, limits of detection and quantification, accuracy, precision and robustness.
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