Determination of Ibuprofen Enantiomers in Human Plasma by Derivatization and High Performance Liquid Chromatography with Fluorescence Detection

Abstract A sensitive and selective reverse phase high performance liquid chromatographic (HPLC) method was developed for the determination of the enantiomers of ibuprofen in human plasma. Ibuprofen and fenoprofen (internal standard, ISTD) are extracted from human plasma by n-butyl chloride, following acidification of plasma. The method is based on the separation of the diasteromers formed on reacting ibuprofen enantiomers and ISTD with S-(-)-1-(1-naphthyl)ethylamine. Separation is achieved by HPLC on an Inertsil ODS-2 column, with a mobile phase composed of water (pH 3.0):ACN (33.5:66.5). Detection is by fluorescence detection with excitation and emission at 280 and 320 nm, respectively. The mean retention times of S-(+)-ibuprofen, R-(-) -ibuprofen, S-fenoprofen and R-fenoprofen (ISTD) are approximately 11.3, 12.3, 7.7 and 8.5 minutes, respectively.