Fragmentation studies of neutral per- and polyfluoroalkyl substances by atmospheric pressure ionization-multiple-stage mass spectrometry
The establishment of fragmentation pathways has a great interest in the identification of new or unknown related compounds present in complex samples. On that way, tentative fragmentation pathways for the ions generated by atmospheric pressure ionization of neutral per- and polyfluorinated alkyl substances (PFASs) have been proposed in this work. Electrospray (ESI), atmospheric pressure chemical ionization (APCI) and photoionization (APPI) were evaluated using mobile phases and source conditions that enhance the ionization efficiency of ions generated. A hybrid mass spectrometer consisting of a linear ion trap and an Orbitrap was used to combine the information of both multiple-stage mass spectrometry (MSn) and mass accuracy measurements to characterize and establish the genealogical relationship between the product ions observed. The ionization mechanisms to generate ions such as [M–H]−, [M]−•, and [M+O2]−• or the in-source collision-induced dissociation (CID) fragment ions in each API source are discussed in this study. In general, fluorotelomer olefins (FTOs) ionized in negative-ion APCI and APPI generated the molecular ion, while fluorotelomer alcohols (FTOHs) also provided the deprotonated molecule. Besides, fluorooctane sulfonamides (FOSAs) and sulfonamido-ethanols (FOSEs) led to the deprotonated molecule and in-source CID fragment ions, respectively. The fragmentation pathways from these precursor ions mainly involved initial α,β-eliminations of HF units and successive losses of CF2 units coming from the perfluorinated alkyl chain. Moreover, FTOHs and FOSEs showed a high tendency to generate adduct ions under negative-ion ESI and APPI conditions. The fragmentation study of these adduct ions has demonstrated a strong interaction with the attached moiety.
KeywordsFluorotelomer olefins Fluorotelomer alcohols Fluorooctane sulfonamides and sulfonamido-ethanols Atmospheric pressure ionization Multiple-stage mass spectrometry Fragmentation pathway
The authors acknowledge the financial support received from the Spanish Ministry of Economy and Competitiveness under the project CTQ2015-63968-C2-1-P and the financial support from the Spanish Ministry of Science, Innovation and Universities under the project PGC2018-095013-B-I00. The authors also thank the Generalitat of Catalonia for the research project 2018 SGR-310. Juan F. Ayala-Cabrera also thanks the Spanish Ministry of Education, Culture and Sports for the PhD FPU fellowship (FPU14/05539) and the Research Institute in Water (IdRA) of Barcelona for the PhD research financial assistance.
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Conflict of interest
The authors declare that they have no conflict of interest.
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