A micellar electrokinetic capillary chromatography method for monitoring mycophenolic acid in serum of transplant recipients

Mycophenolic acid (MPA), the active metabolite of the immunosuppressive agent mycophenolate mofetil (MMF), was for the first time quantified in the serum of transplant recipients using micellar electrokinetic capillary chromatography (MEKC). Sample preparation was carried out with solid phase extraction (SPE) using octadecyl-modified endcapped silica (C18 EC) as sorbent. Extremely varying recovery rates in preliminary experiments showed both the importance of pH monitoring during the single SPE steps and the necessity of an internal standard. MPA carboxy butyl ether (CBE), a specifically developed reference standard, was employed. Furthermore, optimisation of the MEKC parameters detection wavelength and injection time was of primary importance in order to enable the quantitation of therapeutic trough serum levels of MPA in the range lower than 5 μg · mL-1. Under optimised conditions, a limit of quantitation of 1.0 μg · mL-1 was achieved allowing the determination of MPA in the serum of patients.