Moreover, expected cleavage reactions that take place in the gas phase between MPT plasma and tablets produce abundant MS fragment ions, which provide rich structural information and would become a powerful tool to figure out the structure exactly by using a simple mass spectrometer. To clarify this phenomenon, we took azithromycin as an example. The ions at m/z 592 ([M-C8H16O2N + H]+), m/z 574 ([M-C8H18O3N + H]+), and ions at m/z 434 ([M-C8H16O2N-C8H14O3 + H]+), m/z 416 ([M-C8H18O3N-C8H14O3 + H]+) in MPTDI-TOF full-scan mass spectrum of azithromycin (Figure 5a) correspond to the MS2 ions and MS3 ions (Supplementary Figure S-1a) in tandem mode obtained by LTQ mass spectrometer, respectively.