Simultaneous determination of mycophenolic acid and valproic acid based on derivatization by high-performance liquid chromatography with fluorescence detection

A reliable and validated reversed‐phase high‐performance liquid chromatography (HPLC) method using fluorescence detection is reported for the simultaneous quantitation of mycophenolic acid (MPA) and valproic acid (VPA) in human plasma. The method is based on the pre‐column derivatization of valproic acid with 4‐bromomethyl‐6, 7‐dimethoxycoumarin (BrMMC) and online solvatochromism of MPA by pH adjustment. The linear calibration range was 0.50–30 µg/mL for MPA and 5.00–150 µg/mL for VPA. The relative standard deviations of the method of intra‐ and inter‐day analyses (n = 6) were below 6.5 and 6.7% for MPA, and 5.8 and 6.3% for VPA, respectively. Dichloromethane was used for the simultaneous extraction of MPA and VPA from acidified plasma. This reliable method can be applied in the analysis of MPA and VPA in human plasma using only a small volume (100 µL). Copyright © 2005 John Wiley & Sons, Ltd.