Use of Electron Activated Dissociation (EAD) On the ZenoTOF 7600 System to Elucidate PFAS Structures

Polyfluoroalkyl Substances (PFAS) in the Environment (Session 2)
Oral Presentation

Prepared by C. Butt, K. Oetjen, M. Shimizu, D. Tran
SCIEX, 500 Old Connecticut Path, Framingham, MA, 01701, United States

Contact Information: [email protected]; 508-383-7416


Poly- and perfluoroalkyl substances (PFAS) are well-known environmental contaminants and are widely detected in humans and wildlife, water, soil and air. Even though there are an estimated 5,000 unique PFAS industrially manufactured, most monitoring efforts are focused on only 20-30 compounds. Non-target acquisition using high resolution accurate mass spectrometry is beneficial for elucidating unknown compound structures, such as PFAS. However, traditional fragmentation methods using collision-induced dissociation (CID) can be too aggressive to form diagnostic MS/MS spectra. Alternatively, electron activated dissociation (EAD) has shown potential as a form of fragmentation. Standard solutions of 5 PFAS compounds (5:3 FTB, 5:1:2 FTB, AmPr-FHxSA, TAmPR-FHxSA, 6:2 FTSA-PrB), were infused on the ZenoTOF 7600 system using both CID and EAD fragmentation modes. Preliminary data showed that EAD generated a more comprehensive MS/MS fragmentation spectrum compared to CID, which resulted in additional structural information for improved compound elucidation. Initial experiments were focused on the 5:1:2 fluorotelomer betaine in positive electrospray ionization mode. Using CID fragmentation, the only fragment formed was the [C3H8N]+ ion at m/z 58.065 Da. The SCIEX Fluorochemical HR-MS/MS Spectral Library 2.0 contains the fragmentation spectra for several fluorotelomer betaines and confirms that the m/z 58.065 Da ion is the only significant fragment formed with CID. In contrast, the EAD fragmentation spectrum showed many fragment ions that corresponded to the unzipping of the carbon backbone of the molecule. For example, sequential losses of CF2 were observed. The presence of additional fragment ions in the more comprehensive MS/MS spectrum generated by EAD is more diagnostic of the unique fluorotelomer betaine compounds and therefore can provide more structural information.