Method 1621: Determination of Adsorbable Organic Fluorine in Aqueous Matrices by Combustion Ion Chromatography

Innovative Solutions for Water Testing
Oral Presentation

Prepared by S. Burket1, H. McCarty2, A. Hanley1, M. Alzipar1
1 - USEPA OST, 1200 Pennsylvania Avenue NW, Washington, DC, 20004, United States
2 - General Dynamics Information Technology, 3170 Fairview Park Drive, Falls Church, VA, 23310, United States


Contact Information: [email protected]; 202-566-2539

ABSTRACT

As a second part of its response to EPA’s PFAS Strategic Roadmap to address the “forever chemicals,” the EPA Office of Water published Method 1621 on January 31, 2024. Unlike EPA Method 1633 that targets 40 specific PFAS compounds, Method 1621 measures the aggregate concentration of organofluorines in wastewater by adsorbing them onto granular activated carbon, which is then combusted to release and trap any organofluorines as fluoride, and analyze it by ion chromatography. As such, adsorbable organic fluorine (AOF) is a method-defined parameter, where the results are wholly dependent on the manner in which the measurement is made. Although Method 1621 does not quantify all of the organofluorine it captures with the same accuracy and does not identify specific PFAS, the results demonstrate when organofluorines are present in the sample. The strength of the method is that it can broadly screen for thousands of PFAS compounds at the part-per-billion level in aqueous samples. In 2021 and 2022, the Office of Water led two single-laboratory validation studies of a draft ASTM standard in collaboration with the Office of Research and Development and Pace Analytical’s Minneapolis Laboratory. Building on the success of those two studies, in 2023, the Office of Water organized a multi-laboratory validation study that involved eleven commercial, state, and vendor laboratories, and tested nine real-world wastewater matrices. Although only nine laboratories completed the entire study, the Office of Water collected sufficient data to demonstrate that the procedure can reliably measure AOF in wastewater samples at low ppb levels, and to develop formal QC acceptance criteria for the method. The results also were used in conjunction with comments from the study participants to refine the final version of the method, including combusting both of the carbon columns together for routine analyses.