It is worth noting that for the EIC of m/z 242 ([TNT+NO3-HNO2] -), all of the explosives yielded ion signals of varying intensities (Fig. ). TNT yielded a very strong ([TNT+NO3-HNO2] -, m/z 242) ion signal, which included the adduct ions for RDX, NG, and PETN with the NO3 -ion (Fig. ). The modified HCD ion source, as shown in Figure (b), has the potential to be used as a versatile ion source for real-time analysis of explosives at trace levels. The ion at m/z 228 is the result of TNT forming an adduct ion with the hydride ion (H -), ([TNT+H] -, m/z 228). The surfaces of the metals adsorb molecular hydrogen, making the surface-assisted reduction reaction (Birch reduction type reaction) easier . TNT reduction may be aided by the presence of photons and a high electron density in the HCD plasma. The mass spectrum for the EIC of the m/z 378 ion, [PETN+NO3] -, is shown in Figure (c), while RDX's adduct ion with the NO3 -, ([RDX+NO3] -, m/z 284) , revealed a very strong ion signal. TNT also produced the adduct ion ([TNT+NO3-HNO2] -, m/z 242), which included ions, for example, ([TNT+H] -, m/z 228) and ([TNT-H] -, m/z 226). The EIC of the m/z 378 ion, however, detected no ion signal from NG (Fig. ). This reprint has been approved by Elsevier .