Development of a validated liquid chromatographic method for the determination of related substances and assay of tenofovir disoproxil fumarateThe present study describes the development and validation of a selective liquid chromatographic (LC) method for the analysis of tenofovir disoproxil fumarate (TDF) and its related substances. The gradient method uses a base deactivated C18 column (Hypersil BDS column; 25 cm  4.6 mm I.D.) maintained at a temperature of 301C. The mobile phases consist of acetonitrile, tetrabutylammonium/phosphate buffer pH 6.0 and water: (A; 2:20:78 v/v/v) and (B; 65:20:15 v/v/v). The flow rate is 1.0 mL/min and UV detection is performed at 260 nm. Good separation of TDF and 21 impurities was achieved. A system suitability test (SST) to check the quality of separation is also specified. The developed method was further validated with respect to robustness, precision, sensitivity and linearity. The method is proved to be robust, precise, sensitive and linear between 0.1 mg/mL and 0.15 mg/mL. The limit of detection and limit of quantification are 0.03 and 0.1 mg/ mL, respectively. The method was successfully applied to the quantification of related substances and assay of commercial TDF samples (bulk substances and tablets).