New Spectrophotometric Methods Development for the Determination of Oseltamivir Phosphate in Capsules Based on the Oxidation Reactions of the Olefenic Double Bond

Simple, sensitive and selective spectrophotometric methods (M₁ and M₂ ) for the assay of oseltamivir phosphate (OP) through the olefenic double bond are proposed. Method M 1 is based on the reaction of potassium permanganate to the olefenic double bond in OP and estimating the unreacted permanganate with fast green FCF (FGFCF). Method M₂ involves the treatment of the olefenic double bond in OP with a Lemieux reagent ( mixture of KMnO₄ and NaIO ₄ ) and estimating the aldehyde formed with 3 - methyl - 2 - benzothiazolinone hydrazone (MBTH). The color produced in M ₁ and M ₂ methods has maximum absorption at 620nm and 654nm respectively. Beer's law obeyed in the concentration range of 4 - 20μg/ml and 4 - 12 μg/ml for method M ₁ and M ₂ respectively. The precision and accuracy of the methods are checked by the reported UV reference method. No interference was observed from the usually existing additives in pharmaceutical formulations and the app licability of the methods was examined by analyzing NATFLUE capsules containing OP. The both methods are found to be suitable for the determination of oseltamivir phosphate.