Rapid detection of explosives in collected dust using ion mobility spectrometry

Vapor and particulate matter from explosives can be adsorbed onto dust, enabling their detection in security and military applications. In this study, model explosive-adsorbed dust specimens were prepared using four types of dust from two inorganic substances [silica (SL) and clay (CL)] and two organic materials [sawdust (SD) and cotton fabric (CF)]. Three explosives, namely 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and pentaerythritol tetranitrate (PETN), were investigated, along with two different collection filters of poly(tetrafluoroethylene) (PTFE) and lens cleansing paper (LCP). The dust was sprayed in a hood and collected using a cyclone collector. The explosive components present in the dust were rapidly detected using ion mobility spectrometry (IMS). The adsorption efficiencies of TNT, RDX, and PETN onto dust were 36 - 97, 45 - 76, and 37 - 90 %, respectively, and the values of the inorganic dusts were higher than those of the organic dusts. The dust collection rate ranged from 5 to 15 %, and decreased in the order of CL > CF > SL = SD. The factors influencing rapid explosive detection were the intrinsic vapor pressure of the explosive, interactions between the dust and the explosive, thermal conductivities of the dusts and collection filters, and structure of the collection filter. Due to the low vapor pressure of RDX, this explosive was detected later than TNT and PETN. In most cases, detection was more rapid when using the LCP than when using the PTFE because of the thicker and woven structure of the PTFE filter. The detection limits achieved using the LCP (0.049 - 1.17 mu g) were lower than those of the PTFE (0.67 - 10.05 mu g). When the PTFE was used, the detection limits for the organic dusts were lower than those for the inorganic dusts. Notably, the detection limits of the explosives adsorbed onto dust were significantly higher than those of the pure explosives.