Validated spectrophotometric and chromatographic methods for analysis of the recently approved hepatitis C antiviral combination ledipasvir and sofosbuvir.

This work describes five simple and reliable spectrophotometric and chromatographic methods for analysis of hepatitis C antiviral binary mixture of ledipasvir (LPV) and sofosbuvir (SBV). Method I is based on the use of A and derivative spectrophotometry with the zero-crossing technique where LPV was determined using its A and D amplitudes at 324 and 338nm respectively, while SBV was determined by measuring the D amplitudes at 276nm. Method II involves the application of the ratio spectra derivative spectrophotometry. For LPV, 12μg/mL SBV was used as divisor and the DD amplitudes at 239.8nm were plotted against LPV concentrations; while by using 10μg/mL LPV, the amplitudes at 279.2nm were found proportional to SBV concentrations. Method III depends on ratio-difference measurement where the peak to trough amplitudes between 229.2 and 268.4nm were measured and correlated to LPV concentration. Similarly, the amplitudes between 268.6 and 229.2nm in the SBV ratio spectra were recorded. For method IV, the two compounds were separated using HPTLC sheets of silica gel and a mobile phase composed of chloroform-methanol (94:6) followed by densitometric measurement of LPV and SBV spots at 331 and 267nm respectively. Method V depends on HPLC-DAD. Effective chromatographic separation was achieved using Thermohypersil C8 column (4.6×250mm, 5μm) with a mobile phase consisting of 0.01M sodium dihydrogen phosphate (pH 2.5) and methanol (20:80) at a flow rate 1.2mL/min and detection at 332 and 262nm for LPV and SBV respectively. Analytical performance of the developed methods was validated according to the ICH guidelines with respect to linearity, ranges, precision, accuracy, detection and quantification limits. The validated methods were successfully applied to the simultaneous analysis of LPV and SBV in mixtures of different proportions and their combined tablet dosage form.