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Clinical Chemistry, Vol 34, 493-496, Copyright © 1988 by American Association for Clinical Chemistry
R Mehvar, F Jamali and FM Pasutto
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.
This stereospecific "high-performance" liquid-chromatographic (HPLC) assay is suitable for pharmacokinetic studies of ibuprofen (IB). Very efficient extraction of the drug and internal standard, (+/-)-2-(4- benzoylphenyl)butyric acid, from plasma with isooctane/isopropanol (95/5, by vol) is followed by sequential reaction of the enantiomers with ethyl chloroformate and (S)-(-)-1-(1-naphthyl)ethylamine. The reactions take place at ambient temperature in less than 4 min. The naphthylethylamide derivatives of IB enantiomers and internal standard are then extracted into chloroform. After the organic layer is evaporated, the reconstituted residue is chromatographed at ambient temperature on a C18 reversed-phase column with a mobile phase of acetonitrile/water/acetic acid/triethylamine (55/45/0.1/0.02 by vol) at a flow rate of 1 mL/min. The IB diastereoisomers, detected at 232 nm, are free of interfering peaks and have a resolution factor of 2.2. Within the examined enantiomer concentration range of 0.1 to 20 mg/L in plasma, the peak-area ratios varied linearly with the corresponding IB concentrations. We used the assay to study the pharmacokinetics of IB enantiomers in plasma of a subject who took a single 600-mg dose of racemic drug.
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