Simultaneous Determination of Fenproporex, Diethylpropione and Methylphenidate in Oral Fluid by LC-MS/MS

A liquid chromatography–tandem mass spectrometry method has been developed and validated for confirmation and quantification of three amphetamine-type stimulants (ATS) in oral fluid (OF), namely fenproporex (FEN), diethylpropione (DIE) and methylphenidate (MPH), which are misused by some Brazilian drivers and have potentially dangerous consequences in road traffic. In this method, the OF was extracted by a simple and fast liquid–liquid extraction using acetonitrile. Calibration curves were linear throughout the concentration range from 2.5 to 90 ng mL−1 in OF, using internal standard. The lower limit of quantification and the limit of detection were 2.5 and 0.5 ng mL−1, respectively, for all ATS. Intra- and inter-assay precision and accuracy values were within regulatory limits. The analyte extraction presented poor recoveries, but was considered appropriated for analyses of ATS in OF due to the low limits of detection. Matrix effects and carry over were not detected. All analytes were stable during the whole analytical procedure. The present analytical method was considered simple and sensitive for simultaneous determination of FEN, DIE, and MPH in OF and suitable for clinical and forensic toxicology.