QUANTIFICATION OF KETOPROFEN ENANTIOMERS - IN HUMAN PLASMA BASED ON SOLID-PHASE EXTRACTION AND ENANTIOSELECTIVE COLUMN CHROMATOGRAPHY

An HPLC method for the quantification of ketoprofen enantiomers in hum an plasma is described. Following extraction with a disposable C-18 so lid-phase extraction column, separation of ketoprofen enantiomers and I.S. (3,4-dimethoxy benzoic acid) was achieved using a chiral column [ Chirex 3005; (R)-1-naphthylglycine 3,5-dinitrobenzoic acid] with the m obile phase, 0.02 M ammonium acetate in methanol, set at a flow-rate o f 1.2 ml/min. Baseline separation of ketoprofen enantiomers and I.S., free from interferences, was achieved in less than 20 min. The calibra tion curves (n=14) were linear over the concentration range of 0.16 to 5.00 mu g/ml per enantiomer [mean r(2) of 0.999 for both enantiomers, root mean square error were 0.015 for R(-) and 0.013 for S(+)]. The i nter-day coefficient of variation for duplicate analysis of spiked sam ples was less than 7% and the accuracy was more than 93% over the over the concentration range of 0.2 to 4.0 mu g/ml for individual enantiom er using 1 ml of plasma sample. This method has been applied to a phar macokinetic study from healthy human volunteers following the administ ration of a ketoprofen extended release product (200 mg). This method is simple, fast and should find wide application in monitoring pharmac okinetic studies of ketoprofen.