Acetaminophen (MW 151.16), also named paracetamol, is a commonly used noninflammatory and antipyretic analgesic, and is the main component of many common cold medicines. The protonated molecular ion m/z 152 and fragment ions at m/z 110, and 93 of acetaminophen can be found in the full-scan mass spectrum of MPTDI-TOF MS (Supplementary Figure S-3g), which is consistent with the result obtained by MPT-LTQ MS. However, the peak at m/z 121 is observed due to hydrolysis reaction that occurred and acetic acid molecules that is produced. Then, acetic acid dimer molecules formed in MPT ion source, and strong peak at m/z 121 is observed. The ion at m/z 110 might be produced by losing the group of CH2CO from the protonated acetaminophen (Supplementary Figure S-2g). The protonated acetaminophen lost an acetamide molecule CH3CONH2 to form the fragment ion at m/z 93. Comparing the mass spectral data of Supplementary Figure S-3g with Supplementary Figure S-1g, it can be acknowledged that MPT ionization source coupled with a simple mass spectrometer can achieve the same effects as with a tandem mass spectrometer in the aspect of qualitative analysis.