Fig. 8
Blank plasma sample spiked with velpatasvir (1, 20 µg/mL) as an internal standard. The arrows show the absence of peaks at the retention times of nirmatrelvir (2) and ritonavir (3). Chromatographic conditions: Column: Thermo Hypersil ODS C8 column (250 × 4.6 mm, 5 μm) at 35 °C, Mobile phase: phosphate buffer (50 mM, pH = 3): acetonitrile (35:65, v/v), Elution: Isocratic, Detection: DAD at 210 nm, Flow rate: 1 mL/min, Injection volume: 5 µL