Per- and polyfluoroalkyl substances (PFAS) is a term that describes a class of thousands (millions by a European definition) of synthetic fluorinated organic chemicals that have been manufactured over the past 80 years. Within the last 15 years, the EPA has worked with environmental laboratories like Enthalpy Analytical (Enthalpy) to develop and promulgate highly precise PFAS analytical methods. These methods allow for the quantitation of target PFAS chemicals at very low concentrations, often in the parts-per-trillion range. Unfortunately, due to the lack of commercially available reference standards for PFAS chemicals, most labs can only quantify a handful of target analytes; the most recent EPA method, 1633, targets a list of only 40 compounds. As such, we need other tools to more broadly evaluate the concentrations of PFAS chemicals in environmental samples. One such tool is the EPA Method 1621 for analysis of Adsorbable Organic Fluorine by Combustion Ion Chromatography (AOF-CIC) in an aqueous matrix.

The Case for EPA 1621 in the Treatment Industry

In January 2024, the EPA finalized Method 1621 as well as EPA 1633. EPA 1621, considered a proxy method, provides a single result that represents a total PFAS concentration that can be captured through adsorption (aka soluble, non-polymeric PFAS). Through this landmark step, the EPA has provided the means to better understand potential total soluble, non-polymeric PFAS concentrations in water. In its Information Collection Request for 400 publicly owned treatment works (POTW) facilities, the EPA outlines the use of both EPA Methods 1621 and 1633 for evaluation of upstream treated industrial discharge. This approach casts a wide analytical net and will help inform where we see significantly impacted waterways as a result of industrial discharge containing soluble organic fluorine.

In its October 2021 PFAS Roadmap, the EPA indicated that it would leverage National Pollution Discharge Elimination System (NPDES) permit monitoring to test for PFAS chemicals in industrial and commercial treated effluent. To effectively remove PFAS during this process, the treatment systems used must be able to handle the PFAS load in their influent. This requires a better understanding of the total PFAS concentration; EPA 1621 will aid in this effort providing a complementary technology to targeted methods to help determine a broader more accurate level of PFAS and organofluorine contamination. By understanding the potential total soluble, non-polymeric PFAS concentration in the influent, treatment plants can design optimal and cost-effective treatment systems.

Enthalpy’s Experience with EPA 1621

While the EPA 1621 method allows us to capture more information about total soluble, non-polymeric PFAS concentrations in the environment, the method has limitations. The quantitation limits for this method are in the parts-per-billion range, which is orders of magnitude higher than the targeted methods for individual PFAS species; combustion ion chromatography is also a particularly challenging technique. Enthalpy has partnered with the instrument manufacturer Metrohm to help optimize the instrumentation and procedure used in the EPA 1621 analytical process. Enthalpy has since obtained NELAC accreditation for EPA 1621 and now routinely processes samples collected from all over the country.

How can Enthalpy Support my PFAS projects?

Enthalpy’s deep bench of technical experts has a long history in providing PFAS analytical services. Having performed PFAS testing on thousands of samples for compliance purposes, Enthalpy has developed unique analytical programs that ensure rapid, defensible, and reproducible PFAS data for a wide range of project types. This includes methods EPA 1621, EPA 1633, EPA 533, EPA 537.1, as well as custom targeted methods developed for PFAS not currently included in EPA methods. Contact our Technical Solutions team for more information on how we can help optimize analytical services for your next project.