Rapid detection of tert-butoxycarbonyl-methamphetamine by direct analysis in real time time-of-flight mass spectrometry

PURPOSE: Phenethylamines constitute the majority of drug-related arrests in Japan. Recently, the smuggling of tert-butoxycarbonyl (t-Boc)-protected phenethylamines has become of increasing concern, because of the difficult identification of these masked substances. METHODS: In this study, a rapid and accurate method for the detection of t-Boc-methamphetamine (t-Boc-MP) by direct analysis in real time–time-of-flight-mass spectrometry (DART–TOF-MS) was developed. The efficiency of the method was evaluated by comparison with conventional gas chromatography–MS (GC–MS) and liquid chromatography–TOF-MS (LC–TOF-MS) techniques. RESULTS: During GC–MS analysis of t-Boc-MP, MP was generated in the injection port, which can lead to an analytical error. In the LC–TOF-MS spectrum, fragment ions were detected, which were generated by McLafferty rearrangement in the ion source. On the other hand, in the DART–TOF-MS analysis of t-Boc-MP, pyrolysis could be suppressed by using a micro-syringe injection method, and the fragment ions generated by McLafferty rearrangement were still observed. Moreover, protonated t-Boc-MP could be detected. CONCLUSIONS: Hence, DART–TOF-MS provides a rapid and accurate method for the detection of t-Boc-MP, allowing suppression of the pyrolysis reaction and identification of both fragment ions and protonated t-Boc-MP. To our knowledge, this is the first report for detecting t-Boc-MP by MS techniques.