Objective: To develop a sensitive and reliable ultra performance liquid chromat-ography tandem mass sepctrometry(UPLC-MS-MS) method for simultaneous determination and pharmacokinetics of orientin

vitexin and quercitrin in rat plasma. Method: Following a protein precipitation with methanol for plasma samples after iv Compound Hongcao injection to rat. The analysis was achieved by BEH C18 column and the mobile phase was consisted of acetonitrile and water (0.1% formic acid included) follow step gradient elution. A TQD tandem mass spectrometry equipped with electrospray ionization source was used as detector and operated by multiple reaction monitoring (MRM) positive ion mode of the transitions 449.2-329.2

433.2-313.0

449.2-303.4 for orientin

vitexin and quercitrin

respectively. Result: Good linearity was achieved for the three flavonoids

the intra-and inter-day precisions were lower than 15.71%

and the accuracy were from 86.25% to 112.44%. The MRT of the three flavonoids were all blow 21 min in rats. Conclusion: The method was proved to be suitable for the pharmacokinetics of Compound Hongcao injection

which offers advantages of rapid

high sensitivity and selectivity.