2.4 Sample Preparation
50 μL of blank plasma samples were transferred to a 1.5 mL centrifuge tube, and then 50 μL of imatinib calibration standard solutions or QC solutions at different concentrations and 600 μL of precipitation agent were added successively. The mixture was vortex-mixed for 3 min, and centrifuged for 10 min at 15000×g. 50 μL of the supernatant and 300 μL of 50% methanol were mixed and vortexed for 1 min. Subsequently, the mixture was centrifuged for 3 min under the same centrifugal condition and 3 μL were injected into UPLC system.