Development of a sensitive liquid chromatography/tandem mass spectrometry method for the determination of fenofibric acid in rat plasma.

A rapid and sensitive LC-MS/MS method for the quantification of fenofibric acid in rat plasma was developed and validated. Plasma samples were prepared by liquid-liquid extraction with a mixture of N-hexane-dichloromethane-isopropanol (100:50:5, v/v/v). Isocratic chromatographic separation was performed on a reversed-phase Discovery C(18) column (2.1 × 50 mm, 5 µm). The mobile phase was methanol-water-formic (75:25:0.25, v/v/v). Detection of fenofibric acid and the internal standard (IS) diclofenac acid was achieved by ESI MS/MS in the negative ion mode using m/z 317 → m/z 213 and m/z 294 → m/z 250 transitions, respectively. The method was linear from 0.005 to 1.250 µg/mL when 100 μL plasma was analyzed. The lower limit of quantification was 0.005 µg/mL. The intra- and inter-day precision values were below 8.2%, and accuracy ranged from -0.9 to 2.1% in all quality control samples. The recovery was 90.3-94.7% and 83.3% for fenofibric acid and IS, respectively. Total run time for each sample analysis was 2.5 min. The validated method was successfully applied to a pharmacokinetic study in six rats after oral administration of fenofibrate, the ester prodrug of fenofibric acid (equivalent to fenofibric acid 5 mg/kg). The method permits laboratory scientists with access to the appropriate instrumentation to perform rapid fenofibric acid determination.