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June 2022 – US EPA Posts Method 1621

The US EPA Posts Method 1621 – A Possible Proxy for Total PFAS?!?!

During April 2022, The US EPA Office of Water solicited comments on its document, “Screening Method for the Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion Ion Chromatography (CIC).” The document was posted on the US EPA website. The published version of the method on the US EPA website was based on a single-laboratory method validation document, which was also posted on the US EPA website.

It is noteworthy that a (total) adsorbable fluorine method is being published, as one could easily predict, this method is being construed as proxy for “Total per- and polyfluoroalkyl substances (PFAS),” the implications of which will be challenging for toxicologists tasked with developing health-based guidelines, and worse yet standards. The document ultimately needs to be proposed as a draft method as part of formal rulemaking. Thankfully, unlike the posting of Method 1633, the posting of this method is clear in stating that, “This method is not approved for Clean Water Act compliance monitoring until it has been proposed and promulgated through rulemaking.”

Simply stated, Method 1621 is a screening method to estimate the concentration of adsorbable organic fluorine (AOF) in aqueous matrices. The method measures organofluorine compounds from PFAS and non-PFAS fluorinated compounds such as pesticides and pharmaceuticals. The result is reported as the concentration of fluoride in the sample.

The US EPA has categorized AOF as a “method-defined parameter,” which is a parameter defined solely by the method used to determine the analyte. In the case of Method 1621, the AOF value provides an estimated concentration of organofluorine compounds that are retained on the activated carbon sorbent with detection sensitivity claimed to be in low part-per-billion levels and an upper limit of 140 mg/L. Strict cleaning protocols are needed as the method can be subject to significant blank contamination.

A single-laboratory validation report in support of this method was posted, and it was stated that the US EPA expects to begin a multi-laboratory validation study of the procedure before the end of 2022. Once the multi-laboratory validation study is completed, the US EPA will finalize the method and include performance criteria. 

With respect to technical merits and potential shortcomings of Draft Method 1621, within the “Notice” section of the online document, the US EPA stated, “Laboratories, regulatory authorities, and other interested parties are encouraged to review the method, and where appropriate, utilize it for their own purposes, with the explicit understanding that this is a draft method, subject to revision.”

Directly responding to that request, Environmental Standards’ Principal and Senior Consulting Chemists were engaged by a number of industry advocacy groups and other industrial parties to review and comment on the draft document. On behalf of those interested parties, Environmental Standards is currently preparing formal comments for US EPA consideration. Other parties interesting in sponsoring review of this draft document should contact Rock J. Vitale, CEAC, at 610 935-5577, ext. 400.

Rock Vitale, CEAC

Technical Director of Chemistry