[Determination of azathiopurine and 6-mercaptopurine in serum by reversed-phase high performance liquid chromatography].

A method for simultaneous determination of azathiopurine(AZP) and its metabolite 6-mercaptopurine (6-MP) concentration in serum has been developed. Reversed-phase high performance liquid chromatography with gradient elution and dual wavelength detection was employed. After protein precipitation with acetonitrile, the serum sample was evaporated to dryness with a gentle N2 stream at 37 degrees C and 100 microL of the mobile phase were added to dissolve the residue. After centrifugation, 20 microL of the supernatant was injected directly into the HPLC. The detection wavelength was set at 278 nm (AZP) and 325 nm (6-MP). The internal standard was metronidazole. The minimum detectable mass concentration for both AZP and 6-MP in serum was 5 mg/L. The average recoveries were (100.6 +/- 4.2)% for AZP and (102.4 +/- 4.5)% for 6-MP.