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A stability indicating LC method for oseltamivir phosphate

P.Raghuram, I.V.Soma Raju, Ratnakar Reddy, J.Sriramulu

An Isocratic reverse phase liquid chromatographic (RP-LC) assay method was developed for the quantitative determination of Oseltamivir Phosphate in bulk drug and in pharmaceutical dosage form, used to treat Antiviral (Influenza). The developed method is also applicable for the related substances determination .The chromatographic separation was achieved on Oyster-RP18e, 250mm4.6mm, 5mcolumn. TheLCmethod employs Solution A as mobile phase. The Solution A contains a mixture of phosphate buffer pH3.0:Methanol :Acetonitrile (60:25:15, v/v). The flowratewas 1.0 ml min-1and the detection wavelength was 207 nm. In the developed HPLC method the resolution between Oseltamivir Phosphate and its potential impurities, namely Imp-1, Imp-2 and Imp-3was found to be greater than 2.0. The drug was subjected to stress conditions of hydrolysis, Acid , Alkaline ,oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in Thermal, Photolysis,alkaline medium,Acid medium, and Oxidative stress conditions.Major degradation product formed during Photolysis was found to be Imp-1, Acid hydrolysis , Base and oxidation hydrolysis was found to be un specified impurities. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.6%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.