Emerging Contaminants and the Shifting PFAS Landscape

The panel shifts focus to the evolving per- and polyfluoroalkyl substances (PFAS) landscape, taking on the ultrashort-chain compounds now drawing regulatory attention. Bryan Vining notes that early PFAS concern centered on eight-carbon compounds like perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), but trifluoroacetic acid (TFA) and other ultrashort-chain PFAS are now flagged as high concern because they show up in the environment at far higher levels than the legacy compounds. He points out that perfluoropropionic acid (PFPrA), a three-carbon acid, is increasingly common because many replacement chemicals now used in place of PFOA and PFOS produce it as a byproduct, and asks the panel what makes these ultrashort chains particularly difficult to analyze.

David Megson explains that the sheer number of potential precursors makes ultrashort-chain PFAS hard to pin down, and that emerging toxicological evidence on TFA is prompting different jurisdictions to introduce regulatory limits, a shift from earlier assumptions that its persistence alone wasn't cause for alarm. He notes that the refrigerant and pharmaceutical industries, both heavy users of CF3-based chemistry, are significant contributors, and that wastewater treatment can convert precursor compounds into these ultrashort forms. Having largely developed methods for longer-chain PFAS in water, Megson says the field is now grappling with more volatile compounds that behave differently in sample vials and require revisiting older techniques developed for chlorinated, gas chromatography (GC)-amenable compounds.

Pasquale Avino adds an analytical chemistry perspective, explaining that new or emerging PFAS compounds often lack reference standards altogether, forcing labs to rely on internal standards and retention time comparisons as a starting point. He frames this as a fundamental, almost foundational, challenge: building confidence in new methods before comparative data even exists. Vining connects this back to his own early experience using TFA as a mobile phase additive, noting it lingers in instruments indefinitely, a detail that leads directly into the panel's next topic: background contamination.screening and the question of what routine per- and polyfluoroalkyl substances (PFAS) methods leave undetected. David Megson acknowledges his own bias toward non-targeted analysis, but stresses it isn't feasible to run on every sample given the cost and labor involved. Instead, he advocates screening smarter: pairing targeted analysis with a broader "total" method, such as total organic fluorine, chosen to fit the matrix and investigation at hand, then performing mass balance to see how much of that total the targeted method actually captures.