Stereoselective determination of the major ibuprofen metabolites in human urine by off-line coupling solid-phase microextraction and high-performance liquid chromatography

A simple, rapid and sensitive off-line solid-phase microextraction method coupled to high-performance liquid chromatography was developed for the stereoselective analysis of the major ibuprofen metabolites in human urine samples. For this purpose, a carbowax/templated/resin coated fiber was used. Several parameters influencing the efficiency of the analyte extraction were explored. The chromatographic separation was achieved on a Chiralpak AS column using hexane:isopropanol (95:5 v/v) plus 0.05% trifluoroacetic acid as the mobile phase, at a flow-rate of 1.2 mL/min. Detection was carried out at 230 nm. The mean recoveries were between 1.4 and 1.6%, with R.S.D. values lower than 9.5 for both 2-OHIbu enantiomers, and between 3.7 and 5.7%, with R.S.D. values lower than 13.4 for all four COOHIbu stereoisomers. The method was linear over the 5-50 μg/mL concentration range and the quantification limit was 5 μg/mL for all metabolite stereoisomers. Within-day and between-day assay precision and accuracy for both metabolites were studied at three concentration levels of each stereoisomer (15, 30 and 45 μg/mL) and were lower than 15%.