New simple spectrophotometric method for determination of the antiviral mixture of emtricitabine and tenofovir disoproxil fumarate

A new simple spectrophotometric method was recently developed for the determination of binary mixtures without prior separation. The method is based on generation of ratio spectra of compound X by using standard spectrum of compound Y as a divisor, then the peak to peak (or peak to trough) amplitudes between two selected wavelengths in the ratio spectra are found proportional to concentration of X without interference from compound Y. The method was applied for the determination of the antiviral mixture of emtricitabine (EMT) and tenofovir disoproxil fumarate (TEN). For the determination of EMT, a solution of 15 μg/mL TEN was used as divisor to generate the ratio spectra, and the peak to trough amplitudes between 228.5 and 260.5 nm were plotted against EMT concentration. Similarly by using 10 μg/mL EMT as divisor, the peak to trough amplitudes between 229 and 260 nm were found proportional to TEN concentration. The reliability and analytical performance of the proposed spectrophotometric procedure were statistically validated with respect to linearity, range, precision, accuracy, detection and quantification limits. Calibration curves were linear in the range of 2-40 μg/mL for both drugs with correlation coefficients >0.9997. The proposed method was successfully applied for the simultaneous determination of the two drugs in several laboratory prepared mixtures and in their combined tablet dosage form.