Detection of odor signatures of smokeless powders using solid phase microextraction coupled to an ion mobility spectrometer

Abstract

The detection of hidden explosives through their odors is of great importance to law enforcement agencies and trained canines have traditionally been used for this purpose. This paper reports the extraction of odor signature compounds characteristic of smokeless powders, followed by their detection by ion mobility spectrometers (IMS). Such a method enables the detection of odor compounds, complementing canine detection and allows for mass calibration of IMS instruments. The smokeless powder additives reported include diphenylamine (DPA), ethyl centralite, 2-ethyl 1-hexanol and 2,4-dinitrotoluene. The pre-concentration of these volatile odor chemicals from different commercial smokeless powders onto a solid phase microextraction (SPME) device followed by IMS analysis is demonstrated in this paper. Five samples of smokeless powder samples representing double-based and single-based powders from three popular commercial brands were chosen for this study. Diphenylamine was found to be a common additive among all the powders tested. The mass of the analytes in the headspace available for detection was determined from response curves of the corresponding standards. The response curves were generated by printing precise amounts of standards onto substrates and analyzing them. The absolute detection limits were also determined from these response curves and the values ranged from 0.12 to 1.2 ng for the standards. Typical extraction times ranged between 5 and 40 min and the mass of diphenylamine and ethyl centralite extracted at the lowest extraction times was found to be greater than the LOD of the compounds.