Objective: To develop a HPLC method to determine the concentration of vancomycin (VAN) in human plasma and study the stability of vancomycin in different condition. Method: The metonidazole was used as inter standard (I.S.) The analytical column was a Kromasil C18 column connected with the Agilent 1100 HPLC system. The isocratic mobile phase was the acetonitrile and buffer of KH2PO4 (0.01 mol·L-1) with the rate of (7 ∶93). The detective UV wavelength was 236 nm and the column temperature was 30 ℃. The plasma samples

added metonidazole as internal standard

were deposited down the protein with 30% ZnSO4 and 20 μL of the upper phase was injected into the sampler.The stability of the samples in different conditon were studied. Result: The chromatography was good and not interfered by the components of the plasma. The linear equation was Y=-1.94×10-2X+0.653(r=0.999 3). The recovery of vancomycin in different concention were all >78%. The samples were stability in 4 ℃ for a week

the standard solution of vancomycin were stablity for a half year. Conclusion: This is a accurate

sensitive and conventient method for the dertermination of VAN in the therapeutic drug monitoring.