Impact of Adsorption on the Vapor Availability of Contained Explosives and Drugs

Abstract

AbstractDetection canines are used to locate explosives, drugs, and other contraband based on the presence of volatile organic compounds (VOCs) associated with the target items, even when attempts have been made to contain them in layers of packaging. It is important to understand the extent to which different materials impact vapor availability through adsorption or absorption and therefore the ability of canines to detect target materials. This study considered how the attenuation of vapor components associated with explosives and drugs (hexamethylene triperoxide diamine (HMTD), trinitrotoluene (TNT), triacetone triperoxide (TATP), and cocaine) by commonly used concealment and storage materials (metal, glass, plastic, and cardboard). Adsorption/desorption affinity was measured using a quartz crystal microbalance which can measure nanogram level mass changes as vapor from an analyte is flowed over and interacts with a sensor coated in a material of interest. Headspace analysis using solid phase microextraction (SPME) with gas chromatography/mass spectrometry or electron capture detector (GC/MS or ECD) measured the VOCs over time as each analyte of interest was exposed to either 50 cm2 or 100 cm2 of each material. Overall, the results demonstrated that the amount of sorption and vapor suppression varies based on the material, with the greatest attenuation of analyte vapor by cardboard, followed by polystyrene, and then glass. Furthermore, it also depends on the analyte, as demonstrated by minimal sorption of TATP, particularly to polystyrene, and the compounds in HMTD having different affinities resulting in an altered vapor profile.