Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7a. Advances in the Analysis of Non-Target Per- and Polyfluorinated Alkyl Substances (PFAS)

Formatted Title:

Forensic Fingerprinting of the Unseen: Revealing the Dark Secrets of PFAS with High-Resolution Ion Mobility

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS), synthetic organic compounds known for their remarkable chemical stability, have become a widespread global contaminant. Owing to their extensive industrial usage over decades, these 'forever chemicals' permeate various environmental settings, raising significant public health alarms. The current analytical tools often miss a segment of PFAS compounds, referred to as PFAS 'dark matter'. The objective of this study was to explore the use of novel analytical tools for PFAS forensic fingerprint analysis, specifically high-resolution ion mobility (HRIM) coupled to high resolution mass spectrometry (HRMS), to delve deeper into this 'dark matter' to illustrate an unparalleled combination of analytical techniques for understanding PFAS distribution, impact, and possible mitigation.

Approach/Activities:

We incorporated the MOBIE HRIM System (MOBILion Systems, Chadds Ford, PA) with existing liquid chromatography (LC) and HRMS methods, aiming to reveal the hidden aspects of PFAS. By analyzing a technical perfluorooctanoic acid standard, we employed HRIM to identify and fully resolve eleven isomers and interrogate an authentic aqueous film forming foam (AFFF) sample. The ability of HRIM to convert arrival times to unique molecular identifiers, collision cross section (CCS), was also harnessed. This gave rise to a two-dimensional plot, the "confirmational space map", depicting the relative size and mass of each compound, as well as three-dimensional representations of chromatographic retention time, CCS, and m/z for a comprehensive fingerprint of each sample.

Results/Lessons Learned:

HRIM analysis showcased multiple advantages, including the separation of branched isomers and the addition of CCS as a complementary identifier to mass spectra. The confirmational space map served as a visual guide, facilitating the prioritization and annotation of unknown compounds by highlighting their structural characteristics. Overall, the combined use of LC, HRIM, and HRMS emerges as a potent toolset, capable of unveiling the broader spectrum of PFAS in the environment aimed at identifying and attributing sources of PFAS.

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