Development and validation of an LC/MS/MS assay for mycophenolic acid in human peripheral blood mononuclear cells

The aim was to develop a LC/MS/MS method able to quantify mycophenolic acid (MPA) in the peripheral blood mononuclear cells (PBMCs) of transplanted patients. PBMCs were isolated from blood by a density gradient separation. The chromatographic separation was carried out on a Zorbax Stable Bond CN, 150 mm x 2.1 mm, and MS/MS detection was performed after positive electrospray ionisation of the protonated parent ion. The calibration range was from 0.25 to 100ng/sample. Extraction from the cells and ionisation recoveries reached 73.5 and 37.9%, respectively. Inaccuracy was always < 10% with CVs < 15%. MPA was stable at room temperature in the autosampler over 48 h and at -20 degrees C over 1.5 months. Application to clinical samples taken from patients treated with mycophenolate mofetil indicated that the method is suitable for measuring intracellular MPA. (c) 2007 Elsevier B.V. All rights reserved.