Abstract: 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 µm and an effective length of 50 cm was used for the separation. A 200 μL plasma sample was deproteinized with 400 μL acetonitrile, and the supernatant 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 μg/mL in human plasma with the correlation coefficient (r) larger than 0.9997. The limit of detection (LOD) was 0.200 μg/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.

Key words: Mycophenolic acid, Capillary zone electrophoresis, Uniform design