An on-site inspection system for explosives in a container using dust collection through a vent cover and ion mobility spectrometric detection†

Rapid and accurate cargo-inspection systems are required for shipping containers, because illegal and hazardous items, such as explosives and drugs, can be easily concealed in large containers. Dust in a container is suspended in the air and deposited in vent covers. The vapor and particulate matter of explosives can be adsorbed onto the dust. In this study, a model vent cover system was developed for a container and explosive-adsorbed dust specimens were modeled using organic [cotton fabric (CF) and sawdust (SD)] and inorganic substances [clay (CL) and silica (SL)]. The dust was placed in the inner part of the vent cover and collected through the vent holes, and the explosive components present in the dust were rapidly analyzed using ion mobility spectrometry (IMS). 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, namely poly(tetrafluoroethylene) (PTFE) and lens cleansing paper (LCP). The dust collection rate decreased when the dust was located away from the vent holes. The order of the dust collection rate was SD > CF > SL > CL. The limit of detection (LOD) of TNT was considerably lower than those of RDX and PETN. The LODs of the explosives when using the LCP collection filter were lower than those when using the PTFE filter. The LOD order was CF < SD < CL < SL for the PTFE collection filter and CL < SL < CF < SD for the LCP filter. The technique developed in this study can be employed as a rapid and accurate cargo inspection system for shipping containers.