Sensitive method for the determination of baclofen in plasma by means of solid-phase extraction and liquid chromatography–tandem mass spectrometry

A simple and sensitive method for the determination of baclofen in plasma is described. Baclofen and the internal standard, KM 08205, were isolated from plasma by solid-phase extraction using C 18 material. After separation by reversed-phase liquid chromatography, the analytes were detected with tandem mass spectrometry. The extraction procedure was optimised regarding the solid-phase extraction material, the pH in the conditioning solution and the washing volume. The method was proven to be selective and sensitive with an absolute recovery of about 95%, a relative standard deviation below 5% and a limit of quantification of 10 nmol/l.