Objective: To establish a method for simultaneously determining plasma concentration of five kinds of phenolic acids from Salvia miltiorrhiza extract in rat plasma by LC-MS/MS. Method: LC-MS/MS was adopted to determine contents of lithospermic acid

rosmarinic acid and salvianolic acid A

B

C with mobile phase of 0.1% aqueous formic acid-equal volume mixture of methanol and acetonitrile for gradient eluent

flow rate of 0.6 mL·min-1.Mass spectrum was operated by an electrospray ionization probe in the negative ion mode.Scan was in multiple reaction ion monitoring mode.Ion pairs for quantitative analysis of this five phenolic acids were m/z of 537.3/295.1

359.1/161.0

493.3/295.1

717.5/519.1

491.2/293.2.Determination of this five phenolic acids could be accomplished within 7 min. Result: Linear ranges of salvianolic acid A

B and lithospermic acid were 0.78-100 μg·L-1

linear ranges of rosmarinic acid and salvianolic acid C were 0.39-50 μg·L-1.Their inter-day and intra-day precisions represented by RSD were within 15%

their accuracies were between 92%-112%. Conclusion: A sensitive

accurate and easy LC-MS/MS method has been successfully developed

which can be applied to pharmacokinetic study of five phenolic acids from S. miltiorrhiza in rat plasma.