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Communicating Confidence of Per- and Polyfluoroalkyl Substance (PFAS) Identification via High Resolution Mass Spectrometry



Joseph Charbonnet, Carrie McDonough, Feng Xiao, Trever Schwichtenberg, Dunping Cao, Sarit Kaserzon, Kevin Thomas, Pradeep Dewapriya, Benjamin Place, Emma Schymanski, Jennifer Field, Damian Helbling, Christopher Higgins


Per- and polyfluoroalkyl substances (PFASs) are important environmental contaminants, yet relatively few analytical reference standards exist for this class. Nontarget analyses performed by means of high-resolution mass spectrometry (HRMS) are increasingly common for the discovery and identification of PFASs in environmental and biological samples. The certainty of PFAS identifications made via HRMS must be communicated through a reliable and harmonized approach. Here, we present a confidence scale along with identification criteria specific to suspect or nontarget analysis of PFASs by means of nontarget HRMS. Confidence levels range from level 1a—"Confirmed by Reference Standard," and level 1b—"Indistinguishable from Reference Standard," to level 5— "Exact Masses of Interest," which are identified by suspect screening or data filtering, two common forms of feature prioritization. This confidence scale is consistent with general criteria for communicating confidence in the identification of small organic molecules by HRMS (e.g., through a match to analytical reference standards, library MS/MS, and/or retention times), but incorporates the specific conventions and tools used in PFAS classification and analysis (e.g., the detection of homologous series and specific ranges of mass defects). Our scale clarifies the level of certainty in PFAS identification, and in doing so, facilitates more efficient identification.
Environmental Science and Technology Letters


per- and polyfluoroalkyl substances (PFASs), high-resolution mass spectrometry (HRMS), confidence scale, nontarget analysis (NTA), suspect screening, isomers


Charbonnet, J. , McDonough, C. , Xiao, F. , Schwichtenberg, T. , Cao, D. , Kaserzon, S. , Thomas, K. , Dewapriya, P. , Place, B. , Schymanski, E. , Field, J. , Helbling, D. and Higgins, C. (2022), Communicating Confidence of Per- and Polyfluoroalkyl Substance (PFAS) Identification via High Resolution Mass Spectrometry, Environmental Science and Technology Letters, [online],, (Accessed June 13, 2024)


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Created May 26, 2022, Updated November 29, 2022