Developments in solid–liquid extraction approaches for direct liquid sampling of surfaces combined with mass spectrometry for explosives and narcotics detection have shown great promise. Solid–liquid extraction techniques are especially relevant to addressing some existing limitations by eliminating the need for thermal desorption to produce gas phase analyte molecules, extending the list of accessible and extractable analytes, i.e., inorganic salts and oxidizers.
Rapid screening for chemical traces of explosives and narcotics is widely used to support homeland security and law enforcement. These target compounds span a range of physicochemical properties from organic to inorganic, with preferential ionization pathways in both negative and positive mode operation. Nonvolatile inorganic oxidizers present in homemade fuel-oxidizer mixtures, pyrotechnics, and propellants create a unique challenge to traditional thermal desorption-based technologies. Developments in solid–liquid extraction techniques, specifically, open port sampling interface mass spectrometry (OPSI-MS) provide compelling capabilities to address these hurdles. We have investigated the trace detection of wipe-based (i.e., common swipe sampling collection method) explosives, oxidizers, and narcotics using an OPSI source and compact single quadrupole mass analyzer. The liquid dissolution and extraction capabilities of OPSI enabled detection of both traditional military-grade explosives and homemade explosive oxidizers. OPSI-MS sensitivities were on the order of several nanograms to sub-nanogram levels. The system demonstrated quick temporal responses, polarity switching capabilities, and rapid signal decay with minimal carryover, all critical to high throughput screening applications. Coupling traditional swipe sampling with OPSI-MS offers a promising tool for contraband screening applications.
"Open port sampling interface mass spectrometry of wipe-based explosives, oxidizers, and narcotics for trace contraband detection", Forbes, Thomas P. and Lawrence, Jeffrey and Hao, Changtong and Gillen, Greg, Anal. Methods, (2021) 13, 3453-3460. http://dx.doi.org/10.1039/D1AY01038G.