A method for the quantitation of the enantiomers of the non-steroidal anti-inflammatory drug (NSAID) ibuprofen (IB) in human plasma and urine was developed for pharmacokinetic studies of the individual optical antipodes. Plasma samples were acidified, extracted with organic solvents and analysed by HPLC using an alpha(1)-acid glycoprotein column and UV detection; elution was performed with a phosphate buffer and isopropanol gradient; RS-flurbiprofen (FL) was used as internal standard. Calibration curves were linear in the range 0.25 - 25 mu g/ml of each IB-enantiomer. Enantiomers and internal standards were baseline separated. Precision and accuracy was +/- 3-6%, the limit of detection 0.1 mu g /ml, and the analytical recoveries of IB and FL 93.7 +/- 5 % and 94.5 +/- 4 % resp.; endogenous substances, IB metabolites and other drugs did not interfere with the assay. Urine samples were extracted and analysed as for plasma to assay free, and after alkaline hydrolysis, total IB-enantiomers. The described assay is simple to perform, reproducible, accurate and selective for the quantitation of IB-enantiomers in plasma and urine without precolumn derivatisation. Other chiral NSAID drugs were baseline resolved under similar chromatographic conditions: FL, fenopfrofen and ketoprofen; the optical purities of these compounds may be determined with high sensitivity with this HPLC system.
