Estimation of Tenofovir Disproxil Fumarate in Bulk and Formulations by Visible Spectrophotometric Methods

Two direct, simple and sensitive visible spectrophotometric methods (A and B) have been developed for the determination of tenofovir disproxil fumarate in bulk and tablet dosage forms. The method A is based on the reaction of drug with aromatic aldehyde such as Para dimethyl amino cinnamaldehyde (PDAC) in the presence of sulphuric acid in non aqueous medium and formed purple red colored condensation products with an absorption maximum of 502nm. The method B is based on the reaction of the drug with nitrous acid for diazotization and followed by coupling with N-(1-Naphthyl) Ethylene Diamine dihydrochloride (NED) in acid medium to form colored species with wavelength maximum at 500nm. The Beer's law obeyed in the concentration range of 20-60 μg/ml, 8-24 μg/ml for methods A and B respectively. The proposed methods are applied to commercial available tablets and the results are statistically compared with those obtained by the reference UV method and validated by recovery studies.