The MS/MS spectra for the precursor ions m/z 242 and 228are shown in the insets in Fig. and (b) (CID 25%), respectively . At the higher ion source pressure of 30 Torr, TNT and TNB both produced adduct ions such as ([TNT+NO3-HNO2] -, m/z 242) and ([TNB+NO3-HNO2] -, m/z 228) as major ions. The MS/MS system has designated the ions that appear in the lower m/z area (see insets in Fig. ). The MS/MS spectrum for the m/z 242, [TNT+NO3-HNO2] -, ion showed that the ions at m/z 212/213, 195, and 182 originated from TNT; however, the MS/MS peak for m/z 225 did not appear in the TNT mass spectrum at 30 Torr (Fig. ) , m/z 228), appears as minor ions, but its intensity increases as the ion source pressure increases . It should be mentioned that practically all metal surfaces can adsorb hydrogen gas, with palladium metal adsorbing/absorbing hydrogen gas in a large way. The cathode in this work is stainless steel, therefore in the presence of high electron density, metastable species, and photons in the HCD plasma, the inner surface becomes reactive, assisting surface reactions. To explore the Birch type reduction processes of the nitroaromatic explosives in the HCD ion source, benzene, deuterated benzene, and toluene were used as model organic compounds shown in Figures ), (b) and (c) . At higher ion source pressures (5 and 30