Application of ion mobility spectrometry to the identification of trace levels of explosives in the presence of complex matrices

Methods are described for the analysis of trace levels of explosives on materials collected at the scene of real detonations. The methods exploition mobility spectrometry (IMS) to confirm and enhance the results obtained by high performance liquid chromatography with an ultraviolet detector (HPLC‐UV). Solvent‐extracted samples contain many interfering substances and are cleaned up by solid‐phase extraction (SPE) prior to HPLC fractionation. Explosive‐containing HPLC fractions are analysed by IMS after removal of solvent by vacuum centrifuge. IMS detection limits for explosives, typically a few hundreds of picograms, are at least an order of magnitude lower than those for UV detection. SPE and HPLC fractionation also removes interfering substances that can otherwise suppress IMS detection. Explosives discussed are di‐ and trinitrotoluene, ethylene glycol dinitrate, nitroglycerin, pentaerythritol tetranitrate, hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine, octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetraazine, and N‐methyl‐N,2,4,6‐tetranitroaniline.