CHROMATOGRAPHIC MASS-SPECTROMETRIC DETERMINATION OF IBUPROFEN ENANTIOMERS IN HUMAN PLASMA USING R(-)-2,2,2-TRIFLUORO-1-(9-ANTHRYL)ETHANOL AS DERIVATIZING REAGENT

A relatively rapid, inexpensive, sensitive and stereospecific gas chro matographic-mass spectrometric method was developed for the quantifica tion of S(+) and R(-)-ibuprofen in human plasma. This method uses a co mmercially available internal standard and has no interference from en dogenous substances nor metabolites. The method involves derivatizatio n of ibuprofen enantiomers with optically active R(-)-2,2,2-trifluoro- 1-(9-anthryl)ethanol using oxalyl chloride as the coupling reagent. Th e subsequently formed diastereoisomers are separated by gas chromatogr aphy and analysed by mass spectrometry using selected-ion monitoring. The assay is successfully applied to a pharmacokinetic study. The simp licity, sensitivity and precision of the method make it convenient for the quantification of ibuprofen enantiomers in biological samples.