Determination of amphetamine-type stimulants in oral fluid by solid-phase microextraction and gas chromatography-mass spectrometry

► Propylchloroformate derivatization of amphetamine-type stimulants in oral fluid. ► Direct immersion solid-phase microextraction/gas chromatography-mass spectrometry. ► Linear range 2(4)-256 ng mL−1, detection limits 0.5-2 ng mL−1. ► Accuracy 98-112%, precision <15% of RSD, recovery 77-112%. ► Importance of residual evaluation in checking model goodness-of-fit.