Development of Spectrophotometric Procedures for the Simultaneous Determination of Voxilaprevir, Sofosbuvir and Velpatasvir in Pure Form and in Tablets Ion-Association Complex Method

Abstract

Two spectrophotometric procedures are developed for the estimation of three antihepatitic drugs namely Voxilaprevir (VOXL), Sofosbuvir (SOFOS) and Velpatasvir (VELP) in pure form and in different pharmaceutical formulations. The first method is based on the oxidation of velpatasvir and sofosbuvir with potassium iodate in an acidic medium followed by extracting the liberated iodine with cyclohexane and measurement at λ= 525 nm. Beer’s law is valid in the concentration ranges from 10–400 and 5–400 µg/ml for velpatasvir and sofosbuvir, respectively. The apparent molar absorptivity of the resulting-colored complex was found to be 1.34 × 10 for velpatasvir and sofosbuvir, respectively. The second method is based on the interaction of the antithepatatis drugs, Voxilaprevir, Velpatasvir and sofosbuvir in 1,2-dichloroethane with bromophenol blue (BPB), bromocresol green (BCG) and bromocresol purple (BCP) in the same solvent to produce stable colored ion pairs with maximum absorbance at 385–405 nm. Regression analysis of Beer’s plots showed good correlation in the concentration ranges 10–60, 10–60 and 5–40 µg/mL for voxilaprevir and 1.64 × 103 l.mol−1.cm−1 for velpatasvir, 10–150, 10–150 and 10–60 µg/mL−for sofosbuvir with BPB, BCG and BCP reagents, respectively. The limit of detection is 0.46–7.69 µgml11 for sofosbuvir and 10–250, 10–150 and 10–100 µgml−1 and limits of quantitation range between 1.52–8.53 µgml1. The optimum assay conditions were investigated and the recovery of the drugs from their dosage forms ranged from 99.33% to 100.5%. Intraday relative standard deviations (RSD) were 0.029–1.397% and the correlation coefficients ranged from 0.9992 to 1. The two methods can be applied successfully for the determination of these drugs in tablets. The results of analysis were validated statistically through recovery studies.