Detection and identification of explosives compounds using laser ionization time‐of‐flight techniques

Resonance‐enhanced multiphoton ionization has been used to detect the presence of vapour‐phase explosive‐type samples in a linear time‐of‐flight (TOF) mass spectrometer. In particular, nitrobenzene, 2‐nitrotoluene, 2,4‐dinitrotoluene, 2,4,6‐trinitrotoluene, ethylene glycol dinitrate, pentaerythritol tetranitrate (PETN), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX) and SEMTEX (PETN plus RDX plus plasticizer) have been analysed at a laser wavelength of 226.3 nm corresponding to a strong resonant transition of the neutral NO molecule. TOF mass spectra have been recorded and the intensity of the NO + ion monitored as a function of temperature for comparison with the temperature dependence of the various vapour pressures.