Test method for vapor collection and ion mobility detection of explosives with low vapor pressure

Abstract

Rationale: IMS has been widely used for the on-site detection of explosives. Air sampling method is applicable only when the concentration of explosive vapor is considerably high in the air, but vapor pressures of common explosives such as TNT, RDX, and PETN are very low. A test method for analyzing the vapor detection efficiency of explosives with low vapor pressure via IMS was developed using artificial vapor and collection matrices. Methods: Artificial explosive vapor was produced by spraying an explosive solution in acetone. Fifteen collection matrices of various materials with woven or nonwoven structure were tested. Two arrangements of horizontal and vertical positions of the collection matrices were employed. Explosive vapor collected in the matrix was analyzed through IMS. Results: Only three collection matrices of stainless steel mesh (SSM), polytetrafluoroethylene sheet (PFS), and lens cleansing paper (LCP) showed the TNT and/or RDX ion peaks at explosive vapor concentration of 49 ng/L. There was no collection matrix to detect PETN vapor at lower than 49 ng/L. For the PFS, TNT and RDX were detected at 49 ng/L vapor concentration. For the LCP, TNT and RDX were detected at vapor concentrations of 14 and 49 ng/L, irrespectively. Conclusions: The difference in the explosive vapor detection efficiencies could be explained by the adsorption and desorption capabilities of the collection matrices. The proposed method can be used for evaluating the vapor detection efficiency of hazardous materials with low vapor pressure.