Isomers of emerging per- and polyfluoroalkyl substances in water and sediment from the Cape Fear River, North Carolina, USA

Per- and polyfluoroalkyl substances (PFAS) have become ubiquitous environmental contaminants found in many parts of the globe and in all environmental compartments. The phase out of legacy C8 PFAS has led to an increase in functionality of the carbon backbone chain to include ether linkages and branching points. With the increased production of functionalized PFAS, there remains a paucity of information regarding the occurrence of constitutional isomers in the environment. In this study, a series of novel PFAS constitutional isomers were detected by high resolution mass spectrometry and characterized by MS/MS in river water collected weekly over 40 weeks. Constitutional isomers of C4H2F8O4S1 (-1.8 +/- 2.5 ppm) were detected for the first time in 83% of the samples analyzed and the MS/MS fragmentation patterns clearly indicated there were two coeluting isomers present. Two chromatographically resolved peaks with deprotonated molecular formula C7H1F14O5S1 (1.9 +/- 2.7 and 2.2 +/- 3.1 ppm) were detected in 85% of the samples measured. MS/MS fragmentation patterns and a standard provided by a fluorochemical manufacturer confirmed the two isomers. A series of novel chlorinated PFAS were detected (M-1: C11H1Cl1F20O5 0.9 +/- 2.7 ppm and C14H1Cl1F26O6 2.1 +/- 2.6 ppm) in 34% of the water samples analyzed. The exact structure is not confirmed. River sediment collected below the water sample location contained several of the compounds detected in the water column illustrating the connectivity between the environmental compartments. Results highlight the need for further studies on the occurrence of isomers and authentic standards to confirm structures. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Novel PFAS constitutional isomers were detected in river water samples, including two coeluting isomers of C4H2F8O4S1 in 83% of samples, and two chromatographically resolved peaks of C7H1F14O5S1 in 85% of samples. Additionally, novel chlorinated PFAS were detected in 34% of water samples. The study emphasizes the need for further research on the occurrence of isomers and the use of authentic standards to confirm structures.