Although some nitroaromatic compounds can naturally occur in the environment, the vast majority of them come from anthropogenic sources. Indeed, nitroaromatic compounds such as 2,4,6-trinitrotoluene (TNT) and related-compounds are widely used as chemicals or synthetic intermediates in industrial manufacturing of explosives, dyes, pharmaceuticals, polyurethane foams and pesticides. [1] Considering the proven toxicity of nitroaromatic compounds on living organisms [2] , and their significance in the forensic sciences, much attention has been given to these compounds [3]. Thus, nitroaromatic compounds have been extensively studied by mass spectrometry (MS) coupled with different ionization sources. At first, classical vacuum ionization techniques such as Electron Ionization (EI) [4, 5] and Chemical Ionization (CI) [5-7] were widely used to examine nitroaromatic compounds. Upon the development of atmospheric pressure ionization (API) techniques, atmospheric pressure chemical ionization (APCI) [8] and electrospray ionization (ESI) [9] became established as preferred techniques to analyze nitroaromatic compounds [10]. In particular, ESI of TNT in the negative ion mode can produce competitive processes : (i) deprotonation [M-H]-and (ii) electrochemical reduction M •-. [11, 12] Afterwards, Collision-Induced-Dissociation (CID) has been extensively used for structural as well as quantitative information [13] TNT samples are commonly analyzed at low resolution by tandem mass spectrometry. Under CID conditions, these negatively charged molecular species dissociate by competitive losses of either OH • (implicating the "ortho effect", Scheme 1), or by loss of NO • (after NO 2 /ONO isomerization). In addition, NO 2  release was also observed. Scheme 1. Stepwise OH  release implicating the "ortho effect" promoted by the radical anion [M] •-(m/z 227) of TNT. In this study, we have used a standard solution (1 mg/mL in MeOH:ACN (1:1)) of 2,4,6-trinitrotoluene (TNT), obtained from AccuStandard Europe (Niederbipp, Switzerland). TNT was prepared by dilution at 1 µg mL-1 in H 2 O/MeOH (1:1), then infused at a flow rate of 5 µL min-1 into an LTQ-Orbitrap XL mass spectrometer (Thermo Fisher Scientific, Courtaboeuf, France) and ionized by ESI in the negative ion mode. The employed spray voltage was-2.5 kV giving mainly the deprotonated molecule [M-H]-at m/z 226 and the