Environmental Fate of Cl-PFPECAs: Predicting the Formation of PFAS Transformation Products in New Jersey Soils

Abstract

Although next-generation per- and polyfluorinated substances (PFAS) were designed and implemented as safer and environmentally degradable alternatives to "forever" legacy PFAS, there is little evidence to support the actual transformation of these compounds and less evidence of the safety of transformed products in the environment. Multiple congeners of one such PFAS alternative, the chloro-perfluoropolyether carboxylates (Cl-PFPECAs), have been found in New Jersey soils surrounding a manufacturing facility. These compounds are ideal candidates for investigating environmental transformation due to the existence of potential reaction centers including a chlorinated carbon and ether linkages. Transformation products of the chemical structures of this class of compounds were predicted based on analogous PFAS transformation pathways documented in peer-reviewed literature. Potential reaction products were used as the basis for high-resolution mass-spectrometric suspect screening of the soils. Suspected transformation products of multiple congeners, the Cl-PFPECAs, including H-PFPECAs, epox-PFPECAs, and diOH-PFPECAs, were tentatively observed in these screenings. Although ether linkages have been hypothesized as potential reaction centers under environmental conditions, to date, no documentation of ether scission has been identified. Despite exhaustive scrutiny of the high-resolution data for our Cl-PFPECA-laden soils, we found no evidence of ether scission.

Keywords: PFAS alternatives; environmental transformation; high-resolution mass spectrometry; next-generation chemicals; polyfluorinated alkyl substances.

Figure 1

HR LC–MS/MS QToF mass chromatograms and spectra of the precursor/fragments for the observed transformation products of the (0,1) Cl-PFPECA congener (A, 460.9262 Da), (0,1) H-PFPECA (B, 426.9657 Da), (0,1) epox-PFPECA (C, 422.9544 Da), and (0,1) diOH-PFPECA (D, 440.9649 Da). Within each panel, two spectra were recorded at low (top) and high (bottom) collision energies. Note that elution times increase with the increase in molecular mass. Spectra acquired for the sample at site 1 (see Table S1).

Figure 2

Log X-PFPECA soil concentration vs distance from Solvay facility, where X is Cl or H for the (0,1) congener (A). Log H-PFPECA vs log Cl-PFPECA detected in soils for (0,1) (B).

Figure 3.

(A) Hydro-Eve structure (InChIKey = VCWDSNIRAAZWFY-UHFFFAOYSA-N). (B) (0,1) H-product structure (InChIKey = PRHHPWLHMYCAEB-UHFFFAOYNA-N), (C) HR LC–MS mass chromatogram of the Hydro-Eve industrial sample for the expected mass of Hydro-Eve (426.9651) and (D) HR LC–MS spectra of the anion mass 426.9651 from the Hydro-Eve industrial sample, and (E) HR LC–MS mass chromatogram of the Hydro-Eve industrial sample for the mass 332.978, corresponding to the mass of the −ESI in-source fragment of (0,1) H-product. (F) HR LC–MS spectra of the anion mass 332.978 from the Hydro-Eve industrial sample. Note, extracted mass chromatograms for the Hydro-Eve industrial sample with expected extracted mass of Hydro-Eve (C, 426.9651) and the 332.978 (E) anion mass on bottom reveal retention time elution differences.

Scheme 1.

Predicted Transformation Pathway of the (0,1) Cl-PFPECA Congener Containing a Single Propyl Unit, which is Oriented for Consistency with the Fragmentation Patterns Reported Herein^{a a}The transformation pathway with the previously reported propyl carbon orientation (14) can be found in Scheme S1. References used to predict each step are depicted in brackets.