ENANTIOSPECIFIC DETERMINATION OF IBUPROFEN IN RAT PLASMA USING CHIRAL FLUORESCENCE DERIVATIZATION REAGENT, (-)-2-[4-(1-AMINOETHYL)-PHENYL]-6-METHOXYBENZOXAZOLE

A highly sensitive and reversed-phase high-performance liquid chromatographic method for the determination of the enantiomeric composition of ibuprofen in rat plasma is described. The method is based on the resolution of the diastereomeric amides formed on reaction of the ibuprofen enantiomers with (-)-2-[4-(1-aminoethyl)phenyl]-6-methoxybenzoxazole ((-)-APMB) in the presence of 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP) in dichloromethane. The reaction mixture was allowed to stand at room temperature for 5 min, and the reaction was completed by evaporation with a stream of nitrogen at 40 degrees C. The minimum quantifiable concentrations were 0.2 mu g/mL and 0.4 mu g/mL for S-ibuprofen and R-ibuprofen, respectively, in a 10 mu L injection volume. The method was applied to the determination of enantiomeric ibuprofen in plasma after oral administration to rats.