An innovative spectrofluorometric method was developed for the analysis of a recently FDA approved antihepatitis
C velpatasvir (VELP). The developed method was relied on dispersive solid phase extraction (dSPE)
using synergistic effect of reduced graphene oxide (RGO) and cobalt hydroxide nanoparticles (CHNPs) in
addition to cloud point extraction (CPE) using polyethylene glycol 6000 (PEG 6000) as non-ionic
surfactant. This method combines the merits of preconcentration and interferences elimination achieved
by dSPE and CPE, respectively. All relevant parameters such as surfactant concentration, ionic strength,
pH, incubation time and others were thoroughly investigated and optimized. Fluorometric detection of
VELP was carried out at excitation wavelength of 350 nm and emission wavelength of 415 nm. Under the
optimum conditions, a linear calibration curve was achieved in the range of 0.5–45 ng mL
1. Limits of
detection (LOD) and quantification (LOQ) based on three and ten times the standard deviation of the
blank were 0.040 and 0.112 ng mL
1, respectively. This method was successfully applied for
determination of VELP in real samples such as tablets, human plasma and urine samples with good
recoveries.