Analysis of Explosives by Liquid Chromatography/Thermospray/Mass Spectrometry

Abstract

Abstract We have investigated the application of liquid chromatography/thermospray/mass spectrometry (LC/TSP/MS) to the separation and identification of commercial and military explosives. The LC was performed using a reverse phase column with an isocratic mobile phase and a flow rate of 1.5 mL/min. These conditions resulted in retention times of less than 3 min for common explosives, permitting rapid analysis. The TSP was operated in the filamenton ionization mode which yielded unique spectra for the following explosive compounds: 1,3,5-trinitrotriazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,4,7-tetraazacyclooctane (HMX), trinitrotoluene (TNT), dinitrotoluene (DNT), pentaerythritoltetranitrate (PETN), nitroglycerin (NG), diphenylamine (DPA), and monomethylaminenitrate (MMAN). The majority of explosives yielded only negative ion thermospray mass spectra, which exhibited a strong [M + CH3COO]−; however, components of double-based smokeless powders also yielded positive ion spectra. An important forensic science application of this work is the identification of commercial and military explosives. Spectra which were obtained from the residues of improvised explosive devices of military C4 and a double-based smokeless powder allowed identification of the pure explosive compounds, LC/TSP(filament-on)/MS provided limits of detection less than 2.5 picograms for PETN.