The overall goal of this proof-of-concept project is to develop a novel and low-cost method for measuring total organic fluorine (TOF) content in water, soil, and concentrates containing non-polymeric per- and polyfluoroalkyl substances (PFAS). Leveraging findings from a project that has demonstrated near complete defluorination of PFAS in AFFF and AFFF-impacted water and soil samples (SERDP Project ER18-1501), this project plans to use hydrothermal alkaline treatment (HALT) with readily available laboratory equipment to measure TOF as an alternative to costly combustion ion chromatography (CIC) instrumentation. As such, the project team plans a series of tasks to develop and validate the HALT-TOF method and compare results with alternative methods to TOF analysis, including CIC, 19F-nuclear magnetic resonance (NMR) spectroscopy, and high-resolution mass spectrometry (HRMS) with suspect library screening and semi-quantitative analysis. Results will provide the wider PFAS research community with a method for TOF analysis that can be adopted in most laboratories with minimal specialized equipment.

Recent work from the laboratory on HALT suggests that HALT may be leveraged to convert organic fluorine in diverse samples into F- for subsequent analysis with fluoride ion selective electrode or ion chromatography analysis methods that are routinely available in water quality analysis laboratories. Initial experiments will be conducted to optimize HALT conditions to defluorinate all PFAS in PFAS-spiked water samples. Based on the optimal conditions, a water sample protocol of HALT-TOF will be developed by using the mildest conditions possible (lowest temperature and alkali concentration) and more commercially available and accessible experimental devices (e.g., screw-top hydrothermal batch reactors and muffle furnaces). Then, the water sample analysis protocol will be modified to measure TOF in PFAS-spiked soil samples. Finally, the optimized HALT-TOF measurement protocol will be validated by comparison with CIC, 19F-NMR, and HRMS analysis of dilute and concentrated aqueous solutions and soil samples from AFFF-impacted sites.

Successful completion of this project will provide the Department of Defense, PFAS researchers, and site managers with an alternative to costly and specialized CIC methods for analyzing TOF in non-polymeric PFAS-containing samples, which is important for rapidly screening and evaluating PFAS treatment performance. Growing requests for rapid measurement of TOF in unknown samples have increased interest in the availability of methods like HALT-TOF that could be readily adopted by most water chemistry laboratories with minimal specialized equipment. (Anticipated Project Completion - 2025)