Abstract
An ionization technique, direct analysis in real time (DART) has recently been developed for the ambient ionization of a variety samples. The DART coupled with time-of-flight mass spectrometry (TOFMS) would be useful as a simple and rapid screening for the targeted compounds in various samples, because it provides the molecular information of these compounds without time-consuming extraction. In this study, we investigated rapid screening methods of illicit drugs and their metabolites, such as methamphetamine (MA), 3,4-methylenedioxymethamphetamine (MDMA), amphetamine (AP) and 3,4-methylenedioxyamphetamine (MDA) in human urine using DART-TOFMS. As serious matrix effects caused by urea in urine samples and ionizations of the targeted compounds were greatly suppressed in the DART-TOFMS analyses, simple pretreatment methods to remove the urea from the samples were investigated. When a pipette tip-type solid-phase extraction with a dichloromethane and isopropanol mixed solution as an eluent was used for the pretreatment, the limits of detection (LODs) of 4 compounds added to control urine samples were 0.25 μg/ml. On the other hand, the LODs of these compounds were 0.5 μg/ml by a liquid-liquid extraction using a dichloromethane and hexane mixed solution. In both extractions, the recoveries of 4 compounds from urine samples were over 70% and these extraction methods showed good linearity in the range of 0.5-5 μg/ml by GC-MS analyses. In conclusion, our proposed method using DART-TOFMS could simultaneously detect MA, MDMA and their metabolites in urine at 0.5 μg/ml without time-consuming pretreatment steps. Therefore it would be useful for screening drugs in urine with the molecular information.
