Plasma sample analysis was processed by the modified method [26]. A 100 μL of plasma was alkalinized with 20 μL of 5.0M NaOH, and vortexed. An equal amount of dichloromethane-diethyl ether (1:1 v/v) was used for one-step single extraction, and then vortexed. After centrifugation at 3500 rpm for 3 min, the organic layer was transferred and then evaporated under a stream of nitrogen at 35 °C until dryness and reconstituted in 50 μL of the mobile phase. An aliquot of 20μL was injected into HPLC for analysis.