High-performance liquid chromatographic determination of ketoprofen in blood and urine

A rapid, simple determination was developed for ketoprofen in biological fluids using high-performance liquid chromatography. The method requires selective extraction of this antirheumatic medicament and an internal standard with ether from the previously acidified plasma and urine. After evaporation of the ether, the residue is taken up by methanol and analyzed by reversed-phase liquid chromatography with detection at 254 nm. A concentration as low as 0.1 microgram/ml can be determined with a 0.5-ml sample.