Soft Chemical Ionization Mass Spectrometric Analyses of Hazardous Gases and Decomposition Products of Explosives in Air

The need for rapid and accurate measurement of trace concentrations of compounds present in ambient humid air has led to construction of specialised mass spectrometers based on the Selected Ion Flow Tube Mass Spectrometry, SIFT-MS, its drift-tube variant, SIFDT-MS, and Proton Transfer Mass Spectrometry, PTR-MS. It is currently possible to analyse vapours of volatile organic compounds, VOC, and other gases including ammonia, hydrogen sulphide and hydrogen cyanide present in concentrations even below a part per billion by volume, ppbv. The reagent ions are formed in electrical discharges and their ion-molecule reactions with sampled analyte molecules take place at pressures of 1–2 mbar. As an example of analytical use, SIFT-MS coupled with the Laser Induced Breakdown, LIB, technique was used to analyse stable gaseous products from the decomposition of pure explosive compounds HMX, RDX, PETN and TNT and from 38 types of commercial explosive and propellant mixtures. Decomposition products analysed included NH3, HCN, HCHO, NO, NO2, HONO, HNO3, C2H5OH, CH3CN, DMNB, C2H6CO, C2H2 and nitroglycerine. For four selected explosives, it was found that the end products of the microscopic LIB laboratory tests correspond well to the composition of fumes from realistic explosions of 0.5 kg charges.