Confirmation of amphetamine, methamphetamine, MDA and MDMA in urine samples using disk solid-phase extraction and gas chromatography–mass spectrometry after immunoassay screening

A method using mixed phase disk solid-phase extraction (SPE) and gas chromatography–mass spectrometry (GC–MS) was developed for confirmation of amphetamine (AMP), methamphetamine (MET), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) in urine samples after immunoassay screening. Disk SPE provided hydrophobic (C18) and strong cation-exchange (SCX) interactions. The analytes were retained on SCX functional groups in the disk and eluted with ammoniated ethyl acetate after washed with methanol. Confirmation and quantitation was exercised by selected ion monitoring using nikethamide as chromatographic standard. Recoveries of the amphetamines were between 73.0 and 104.6% with RSDs in range of 2.1–6.4% (n=3). The limits of detection were 2 ng/ml for AMP, MET and MDMA, and 4 ng/ml for MDA. Five real urine samples were tested with the method after immunoassay screening, and the results were comparable to those of traditional liquid–liquid extraction (LLE). The method was solvent-saved, simple, rapid and reliable, and the extract was cleaner than that of LLE.