The ratio of NOx such as NO2 and NO3 in air-excited plasma increases as the ion source pressure rises. The NO2 -and NO3 -ions generated in the HCD plasma then took part in proton abstraction processes, as described in Equs. 1 and 2 : However, the generation of m/z 212 and 213 ions was seen in the MS/MS spectra for the precursor ion with m/z 242. (inset in Fig. ) . Furthermore, when utilizing MS/MS mode, the intensity ratios for the m/z 212, 213, and 214 ions derived from the m/z 242 ion are completely different from those formed from TNB (Fig. ). As a result, the peaks in the TNT mass spectra at m/z 212 and 213 are thought to be from the ([TNT+NO3-HNO2] -, m/z 242) ion .