1 The Study of Thermal Decomposition of RDX by Corona Discharge- Ion Mobility Spectrometry-Mass Spectrometry Zuzana Lichvanová a , Martin Sabo a , and Štefan Matej čík a a Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina, F2 842 48, Bratislava, Slovakia, matejcik@fmph.uniba.sk In this study we have examined the formation of ions from hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) sample evaporated at 473 K in reactions with reactant ions (RI) produced in negative corona discharge (CD). The ions have been analysed and detected by ion mobility spectrometry coupled to orthogonal acceleration time of flight spectrometer (IMS-oaTOF). The chemical ionisation was carried out by O 2 - , O 2 - (H 2 O), N 2 O 2 - , N 2 O 3 - and N 2 O 3 - (H 2 O) RI formed in CD operated in zero air in the reverse gas flow mode at elevated temperatures 438 K and by Cl - (H 2 O) n (n=0,1,2) at 332 K. In case of 332 K, the RI were prepared by admixture of carbon tetrachloride (CCl 4 – dopant gas) in order to enhance sensitivity of RDX. Keywords: corona discharge, negative ions, ion mobility spectrometry, mass spectrometry, thermal decomposition, RDX 1. Introduction The detection of trace amounts of explosives is an important security issue. There exists a growing demand to deploy detection devices in controlled environments such as the airports, mass transit stations, military checkpoints and densely crowded places. Over the past three decades, progress has been made in research focused on understanding of chemical and physical properties of explosives, particularly well-known hexahydro- 1,3,5-trinitro-1,3,5-triazine (RDX) (Najarro et al. 2012; Gapeev et al. 2003). RDX is an explosive nitroamine compound which is widely used as an ingredient of solid propellants in military and in industrial applications. It has been also developed as a more powerful explosive than TNT. It is stable in storage and considered as one of the most brisant military explosives. Therefore, many studies have been dedicated to its ignition, decomposition and combustion behaviour (Liebman et al. 1987). Several techniques have been used for a research of RDX explosive focused on its thermal decomposition. RDX has been examined over selected thermal ranges using a pyrolysis technique interfaced to an atmospheric pressure chemical ionization tandem mass spectrometer MS-MS system by Liebman et al.(1987). Another research of RDX has been focused on using pyrolysis-gas chromatography (PGC) and pyrogenic products of this explosive were identified by pyrolysis capillary gas chromatography-mass spectrometry (PCGC-MS) (Huwei and Ruonong 1989). In addition to experimental studies of RDX, theoretical calculations dealing with the mechanism of the gas phase unimolecular decomposition of RDX using the principles of gradient-corrected density functional theory have been developed (Wu and Fried 1997). Among the methods and techniques reported for the detection of explosives so far, an IMS has proved to be one of the best methods for detection trace amounts of explosives. The IMS systems are based on separation of the ions according to their mobility as they drift through gas under the influence of an applied electric field (Eiceman et al. 2003). The conventional ionization source used in IMS devices is a radioactive 63 Ni foil which emits high energy electrons (Crawford and Hill 2013). Several alternative ionization sources have been