Determination Of Ibuprofen Enantiomers In Human Plasma By Derivatization And High Performance Liquid Chromatography With Fluorescence Detection

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 lnertsil 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) art: approximately 11.3, 12.3, 7.7 and 8.5 minutes, respectively.The assay is linear in concentration ranges of 100 to 20,000 ng/mL. The analysis of pooled quality controls (400, 2,000, and 16,000 ng/mL) demonstrates excellent precision with relative standard deviations (RSD) (n=18) range from 3.6% to 8.8%. The method is accurate with all intraday (n=6) and overall (n=18) mean values for the quality control samples being less than 7.0% from theoretical.