Aqueous film-forming foams (AFFFs) used to extinguish fires have been a major contributor to per- and polyfluoroalkyl substances (PFAS) concentrations at sites throughout the United States. Methods are needed to comprehensively capture both the known PFAS and PFAS that are not routinely measured or not yet discovered in complex matrices such as AFFF. This project will develop a rugged and reliable total organic fluorine (TOF) method for quantifying PFAS in PFAS-free firefighting formulations at high recovery, precision, accuracy, and low limits of detection. This project will optimize and validate two new TOF methods using adsorbable organic fluorine (AOF) and extractable organic fluorine (EOF) for comprehensive measurement of total PFAS in PFAS-free firefighting formulations, achieving limits of quantification < 1 parts-per-billion (ppb).

This project will build upon two new sensitive TOF methods developed at the University of South Carolina that utilize combustion ion chromatography (CIC) with two extraction techniques: (1) AOF (using activated carbon sorption) and (2) EOF (using solid phase extraction cartridges) to efficiently extract PFAS. Previous AOF and EOF methods were developed to measure total PFAS in industrial wastewater, river water, and air and can achieve 0.5 and 0.2 ppb detection, respectively. Optimization for measurement in firefighting formulations will utilize mixtures of a large number of PFAS (42) that include PFAS reported in conventional AFFFs and will include the following factors:

• type of activated carbon or SPE cartridge;
• sample volume and pH;
• rinsing solution composition and volume (for AOF);
• elution solvent and conditioning (for EOF);
• time and temperature of combustion;
• receiving solution composition, pH, and volume; and
• ion chromatography eluent composition, gradient, and type of column.

Recovery, accuracy, precision, limits of detection (LODs), and limits of quantification (LOQs) will be optimized and validated using PFAS-free firefighting formulations. It is anticipated that the new methods developed will be able to achieve <1 ppb levels. This method will also eliminate inorganic fluorine from total PFAS quantification, reduce the impact of other constituents on total PFAS measurement, minimize the potential for exclusion of PFAS (including short-chain PFAS) from the total measurement, and will be implementable in a production laboratory environment.

This project will develop two rugged and reliable TOF methods to determine whether firefighting formulations marketed as “PFAS free” contain levels above 1 ppb and will enable informed decisions regarding which firefighting formulations minimize PFAS. These highly sensitive TOF methods should also encourage PFAS-free formulations that can be adopted for conventional fire-fighting. Finally, the optimization of both AOF and EOF extraction methods will provide different options, as these methods will likely involve different sample volumes, analysis time, and cost. (Anticipated Project Completion - 2024)