Formatted Title
Application of Multiple Chemical Analytical Techniques for Forensic Analysis of PFAS Sources to Fingerprint PFAS and Identify their Plumes
Background/Objectives
As many products containing proprietary PFAS, such as fluorinated firefighting foams, identification of these polyfluoroalkyl compounds can be key to relating PFAS sources to their plumes. The use of isomer profiles and analyte ratios obtained from chemical analysis of targeted PFAS analysis alone provides a very limited view of the presence of PFAS which does not clearly differentiate or identify different sources. Analysis of PFAS using using liquid chromatograph coupled to a quadrupole time-of-flight mass spectrometer (QToF/MS) with gas or liquid chromatography can provide a much more comprehensive signature of the PFAS present in samples, with varying degrees of certainty relating to the identification of specific PFAS and resulting Schymanski confidence levels. Further chemical analytical techniques such as use of the total oxidizable precursor (TOP) assay can be applied to augment QToF-MS, while forms of combustion ion chromatography (CIC) can assist with estimating the organofluorine mass in samples. However, lesser applied techniques such as nuclear magnetic resonance (NMR) and fourier transform infrared spectroscopy (FTIR) can also be applied to confirm results produced by QtoF-MS. We describe application of a combination of these techniques to identify PFAS and generate multiple lines of evidence to differentiate differing PFAS sources from their plumes.
Approach/Activities
The use of multiple chemical analytical tools from separate projects with distinct objectives will be described. Combinations of targeted and non-target approaches for PFAS chemical analysis on the same samples will be described, using USEPA 1633, TOP assay (with ultrashort PFAS), NMR, FTIR, and QToF-MS. The newly developed NMR protocols which achieve detection limits in the single digit ppt range will be described. The impact of additional analytical techniques to augment Schymanski confidence levels from use of QToF-MS will be described.
Results/Lessons Learned
The results from using multiple complementary analytical chemistry techniques to identify PFAS will be described aligning to the objectives of each project. Definitive, multiple lines-of-evidence approaches were developed to support unequivocal identification of specific PFAS, not included using targeted analytical approaches. The impact of isomeric profiles, manufacturing, age of release, fate and transport, and biotransformation products on the identification of sources of contamination will be described. Approaches for more definitive forensic identification of differing PFAS using a combination of analytical tools will be critically reviewed.