Simultaneous determination of rufloxacin, fenbufen and felbinac in human plasma using high-performance liquid chromatography

A simple, specific and sensitive high-performance liquid chromatographic method has been developed for the simultaneous determination of rufloxacin, fenbufen and felbinac in human plasma. Plasma, spiked with internal standard, was vortex-mixed for 1 min with a mixture of dichloromethane-diethyl ether (80:20, v/v). The evaporated extract was dissolved in 0.02 M NaOH. Drugs were resolved at room temperature on a 5 mu m Zorbax SAX column (250X4.6 mm I.D.) equipped with a 20X4.6 mm anion-exchange Vydac AXGU (10 mu m particle size) precolumn. The mobile phase consisted of acetonitrile and phosphate buffer (pH 7.0): delivered at a flow-rate of 1.2 ml/min. Detection was made at 280 nm. 2-[4-(2'-Furoyl)phenyl]propionic acid was used as internal standard. The calibration curve was linear from 0.2 to 10 mu g/ml for rufloxacin, from 0.5 to 30 mu g/ml for fenbufen and from 0.2 to 10 mu g/ml for felbinac, respectively. The detection limit was 0.1 mu g/ml for rufloxacin, 0.3 mu g/ml for fenbufen and 0.1 mu g/ml for felbinac, respectively.