Determination of mycophenolic acid and its glucuronide conjugate in human plasma by capillary electrophoresis

In clinical transplantation mycophenolate mofetil (MMF) has become an attra ctive immunosuppressive agent. To quantify mycophenolic acid (MPA) and its main metabolite mycophenolic acid glucuronide (MPAG) from small plasma volu mes, a capillary electrophoresis method has been developed, Separation of M MF and its metabolites MPA and MPAG was carried out in a 37 cm x 50 mum-l. D., fused silica capillary with an extended light path at the detection win dow (bubble-cell) and a TRIS buffer, pH 5.37 Detection was by UV at 214 nm. Sample preparation was by protein precipitation with acetonitrile and conc entration of the supernatant. Naproxen was used as internal standard. Separ ation of MMF, MPA and MPAG was in less than 6 min. The method is reproducib le and accurate, with lower limits of quantification of 0.5 mg L-1 for MPA and 2 mg L-1 for MPAG.