Sample preparation
The protein precipitation was the preferred choice of seperation because of the minimized steps in extraction of drug from matrix. Aliquots of 100 µL plasma samples and 50 µL of IS (10 µg/mL) was added into 10 mL centrifuge tube and vortexed for 5 s. The mixture was precipitated with 500 µL acetonitrile. After vortexing for 30 s, the samples were centrifuged at 5500 rpm for 10 min. An aliquot of 5 µL of the supernatant was injected into the LC–MS/MS system for analysis.