Infrared thermal desorption (IRTD) was coupled with direct analysis in real time mass spectrometry (DART-MS) for the detection of both inorganic and organic explosives from wipe collected samples. This platform generated discrete and rapid heating rates that allowed volatile and semi-volatile organic explosives to thermally desorb at relatively lower temperatures, while still achieving elevated temperatures required to desorb non-volatile inorganic explosives. IRTD-DART-MS demonstrated the thermal desorption and detection of refractory potassium chlorate and potassium perchlorate oxidizers, compounds difficult to desorb with traditional moderate-temperature resistance-based thermal desorbers. Nanogram to sub-nanogram sensitivities were established for analysis of a range of organic and inorganic explosive compounds. Detailed investigations and high-speed visualization revealed conduction from the heated glass-mica base plate as the dominant process for heating of the wipe and analyte materials, resulting in thermal desorption through boiling, aerosolizing, and vaporization of samples. Optimization of the infrared emission interval duration identified limitations based on melting of the wipe material. Finally, desorbed ion distributions for organic and inorganic species were considered as a function of in-source collision induced dissociation (CID). The thermal desorption and ionization characteristics of the IRTD-DART technique resulted in optimal sensitivity for the formation of nitrate adducts with both organic and inorganic species. The IRTD-DART-MS coupling and IRTD in general offer unique explosive detection capabilities to the defense, security, and law enforcement arenas.
Infrared heating, Thermal desorption, Explosives detection, Direct analysis in real time, Mass spectrometry, Inorganic explosives