C. Willis et al., Quantification of free mycophenolic acid by high-performance liquid chromatography-atmospheric pressure chemical ionisation tandem mass spectrometry, J CHROMAT B, 748(1), 2000, pp. 151-156
To facilitate the investigation of free mycophenolic acid concentrations we
developed a high-performance liquid chromatography tandem mass spectrometr
y method using indomethacin as an internal standard. Free drug was isolated
from plasma samples (500 mul) using ultrafiltration, The analytes were ext
racted from the ultrafiltrate (200 mul) using C-18 solid-phase extraction.
Detection was by selected reactant monitoring of mycophenolic acid (m/z 318
.9-->190.9) and the internal standard (m/z 356.0-->297.1) with an atmospher
ic pressure chemical ionisation interface. The total chromatographic analys
is time was 12 min. The method was found to be linear over the range invest
igated, 2.5-200 mug/l (r>0.990, n=6). The relative recovery of the method f
or the control samples studied (7.5, 40.0 and 150 mug/l) ranged from 95 to
104%. The imprecision of the method, expressed in terms of intra- and inter
-day coefficients of variation, was <8 and <9%, respectively. Further, anal
ysis of pooled patient plasma produced an intra-day imprecision of 6.6%. Th
e signal-to-noise ratio at the limit of quantification (2.5 mug/l) was appr
oximately 5:1. The mean absolute recovery (n=6) of mycophenolic acid and th
e internal standard were 76.0+/-13.5% and 86.0+/-9.1%, respectively. The me
thod reported provides an accurate and precise quantification of free mycop
henolic acid over a wide analytical range and thus can be used for routine
monitoring and pharmacokinetic studies. (C) 2000 Elsevier Science B.V. All
rights reserved.