|Per- and polyfluoroalkyl substances (PFASs) are a group of anthropogenic organic fluorinated compounds. Recently, PFASs have been a growing concern about adverse effects on water environment and human health. However, it is difficult to understand the occurrence of unknown PFASs because a lot of various type of PFASs have been used and discharged in the environment. It has been needed to develop a new quick and simple method to understand how many unknown PFASs exist in environmental samples. In previous study, non-target analyses of PFASs based on insource fragmentation flagging in which fluoroalkyl group was recognized as common fragment ions was suggested to utilize for estimation of chemical formula1,2. Next, it is considered to be important to develop a procedure for non-target analyses by fragmentation flagging. To identify a specific precursor ion, an additional selection technique is necessary, as fragmentation flagging cannot refine the candidate ions enough. Main objective of this study is to suggest a procedure for identification of non-targeted PFASs based on fragmentation flagging by Liquid Chromatography-Ion Mobility-Quadrupole-Time of Flight Mass Spectrometry (LC/IM-QTOF).