Simultaneous Determination of Emtricitabine and Tenofovir Desoproxil Fumerate in Truvada by Derivative Spectrophotometry

Abstract

In present investigation, the first and second order derivative spectrophotometric methods for simultaneous estimation of emtricitabine and tenofovir desoproxil fumerate in pure and tablet dosage forms are developed. The absorption spectrum, first order and second order derivative spectra of combination of emtricitabine and tenofovir desoproxil fumerate standard/sample were recorded against reagent blank. Two peaks at 265 and 215 nm and one valley at 235 nm with absorbance values 0.639, 0.420 and 0.164, respectively were observed in absorption spectrum. In first order derivative spectrum three peaks at 380, 325 and 260 nm with positive amplitude and three valleys at 355, 280 and 225 nm with negative amplitude were found and peak at 260 nm and valley at 280 nm have maximum positive/negative amplitude, respectively than other peaks/valleys. Three peaks at 365, 290 and 250 nm with maximum positive amplitude at 250 nm and three valleys at 350, 265 and 215 nm with maximum negative amplitude at 215 nm were observed in second order derivative spectrum. Positive amplitude observed at 282.4 nm and negative amplitude at 258.7 nm in combined first derivative spectrum was taken for method validation of tenofovir desoproxil fumerate and emtricitabine, respectively. In case of second derivative method, amplitude of second derivative sharp peak at 282.4 nm was directly taken for validation of emtricitabine and since emtricitabine interferes with the measurements of tenofovir desoproxil fumerate at 258.7 nm, the difference of amplitudes was taken for method validation of tenofovir desoproxil fumerate. The % RSD of system precision and method precision were found to be within the acceptable limits. The mean percent of recovery in accuracy studies at three spiked levels were found to be in between 99.4-100.48. The developed method was found to be linear in the limits of 4-24 and 6-30 μg/mL for emtricitabine and tenofovir desoproxil fumerate, respectively. Limit of detection and limit of quantitation were found to be 0.652 & 0.232 and 2.080 & 0.773 μg/mL for emtricitabine and tenofovir desoproxil fumerate, respectively. The developed methods were applied for the determination of assay of Truvada and the percent of assay was found to be in the range of 100.75 ± 0.534 and 99.46 ± 0.671 for emtricitabine and tenofovir desoproxil fumerate, respectively. The stability of the drugs under different degradation conditions was found to be in the range of 81.04-90.13 %.