Application of a SPME-IMS detection system for explosives detection

The detection of illicit explosives in a large room, container, or cargo hold is problematic due to the current limitations in sampling and detection of explosives and to the size and time constraints of the search. Solid Phase MicroExtraction (SPME) can be used to rapidly extract volatile and semi-volatile compounds from the headspace of an explosive and ion mobility spectrometry (IMS) is a rapid presumptive organic detection technique that has already found widespread use in the detection of hidden explosives. SPME has recently been coupled to IMS as a sample pre-concentration device in order to improve the detection of explosives concealed in open areas. Detection limits have been determined for the following taggants: 2-nitrotoluene (2-NT), 4-nitrotoluene (4-NT), 2,3-dimethyl-2,3-dinitro butane (DMNB) and the following volatile explosive compounds: 2,4-dinitrotoluene, (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), and 2,4,6-trinitrotoluene (2,4,6-TNT). Nitrocellulose (NC) is also capable of being detected by the SPME-IMS system on a reliable basis. Results from these experiments point towards the usefulness of this technique as a potential screening tool for explosive compounds. Mass transport experiments are being conducted to determine the compound concentration in a flow of air for detection to occur. Further work will also be conducted using explosive odor signature compounds as potential illicit explosive detection compounds.