High-performance liquid chromatographic method for the determination of fenofibric acid and reduced fenofibric acid in human blood, plasma and urine

In this study, a very reliable HPLC method was developed for the determination of fenofibric acid and reduced fenofibric acid in the biological samples described as follows. After addition of the internal standard solution and 0.5 M HCl to the biological sample, fenofibric acid, reduced fenofibric acid and the internal standard were extracted with a mixed solvent of n-hexane and ethyl acetate (90 : 10) from the mixture. The acids were back-extracted from the organic phase with 0.1 M Na2HPO4 and then re-extracted from the aqueous phase with a mixed solution of n-hexane and ethyl acetate (95 : 5) after addition of 0.5 M HCl. The organic phase was evaporated to dryness under the vacuum. The residue was dissolved in MeOH and diluted with distilled water. An aliquot of the resulting solution was injected on to the HPLC. High reproducibility was observed in this HPLC method (C.V.% less than 4%). Moreover it was confirmed that the conjugates in the urine could be hydroIyzed by incubation at 37 degrees C for 18 h after addition of 400 IU of beta-glucuronidase.