Mycophenolic acid （MPA）, an immunosuppressive drug, was determined in human plasma by a simple capillary zone electrophoresis （CZE） method. A bare fused-silica capillary with an internal diameter （i.d.） of 75/am and an effective length of 50 cm was used for the separation. A 200 }aL plasma sample was deproteinized with 400 μL acetonitrile, and the supematant was directly injected into the capillary after a water plug at a pressure of 0.5 psi for 10 s. Boric acid （H3BO3, 200 mmol/L） solution adjusted to a pH of 8.60 with 1 mol/L sodium hydroxide （NaOH） solution was selected as the background electrolyte （BGE） through a uniform design. Calibration curve established on each day was linear over the MPA concentration range of 0.625-30.0 Bg/mL in human plasma with the correlation coefficient （r） larger than 0.9997. The limit of detection （LOD） was 0.200 ~tg/mL. Intra- and inter-day precisions at three concentrations within the calibration range were less than 4.45%. Plasma samples collected from 14 renal transplant recipients treated with the prodrug mycophenolate mofetil （MMF） were analyzed successfully by both the developed CZE technique and a validated high-performance liquid chromatography-tandem mass spectrometry （HPLC-MS/MS） technique. The mean absolute and relative differences between the concentrations measured by the two methods were -0.17 and -0.20%, respectively. In conclusion, the CZE method described here was validated to be accurate, precise, and economical for the clinical quantification of MPA.
