Targeted PFAS methods remain central to routine analysis, but they capture only a small portion of a much larger fluorinated chemical landscape. That gap sits at the heart of Sarah Ortbal’s research at The University of Alabama, which combines targeted PFAS analysis with adsorbable organic fluorine (AOF) to show how much conventional workflows can miss in complex water and wastewater samples. In this Q&A, she discusses where targeted methods fall short, what AOF adds, and how laboratories can begin to incorporate broader fluorine measurements into existing PFAS workflows.
Where do traditional targeted PFAS methods fall short when applied to real-world water and wastewater samples?
Traditional targeted PFAS methods capture only a limited number of compounds. EPA Method 1633, for example, targets 40 PFAS analytes, while the broader PFAS universe includes many thousands of compounds. In real-world samples, that creates a clear mismatch between what may be present and what laboratories actually measure.
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That limitation becomes even more important when treatment or destruction is involved. If partial degradation occurs, a targeted method can make it look like a compound has been removed, when it may have simply transformed into something else. That is where broader fluorine measurements can help fill in the gaps.
What does adsorbable organic fluorine (AOF) reveal that targeted analysis cannot, and how should labs interpret that additional signal?
AOF measures overall organic fluorine load. Rather than focusing on a defined list of analytes, it captures compounds that contain carbon-fluorine bonds, including PFAS as well as some fluorinated pharmaceuticals and pesticides.
That broader view gives labs a more complete picture, but it also creates interpretation challenges. AOF does not identify each individual compound, so it cannot assign toxicity in the same way targeted analysis can. There is no clear toxicity threshold for a bulk organic fluorine measurement, because the signal can reflect many different compounds with different toxicological profiles.
Even so, the approach has clear value. If targeted PFAS concentrations are low but organic fluorine is high, that can point labs toward other contamination sources. In surface waters affected by runoff, for example, that extra signal could suggest fluorinated pesticides. In wastewater, fluorinated pharmaceuticals may contribute to the overall load. AOF works best as a tool for broadening the picture and helping trace where contamination may be coming from.
Your work shows up to 25× more fluorinated organics detected with AOF. What does that mean for how we currently assess PFAS risk and regulatory compliance?
That finding highlights how narrow much of the current regulatory focus still is. Many regulations remain centered on legacy compounds such as PFOA and PFOS, even though the larger universe of PFAS and related fluorinated organics is far broader.
Targeted methods still matter, especially for drinking water, where very low detection limits for specific compounds are critical. But for wastewater and other more complex matrices, broader screening approaches can offer a more useful overview. In those settings, AOF can help laboratories and regulators look beyond a small list of known analytes and assess fluorinated contamination more holistically.
Surface water work in Alabama also showed that context matters. Wastewater treatment plants did not appear to have a major effect on surface water PFAS and organic fluorine levels because rainfall and dilution were so significant. That means the most appropriate monitoring or regulatory approach may differ depending on the matrix and the environmental setting.
How can laboratories realistically integrate AOF or non-target approaches into existing PFAS workflows without disrupting throughput or robustness?
AOF requires a different sample preparation workflow than most targeted PFAS methods. AOF involves adsorbing the sample onto activated carbon and then combusting it for analysis, while targeted PFAS methods often rely on solid-phase extraction.
A practical bridge is extractable organic fluorine. This approach is similar in intent, but it uses a sample preparation workflow closer to targeted PFAS methods. That creates an opportunity for laboratories to perform a single extraction, then split the final concentrated aliquot between targeted PFAS analysis and combustion ion chromatography for organic fluorine measurement.
That offers one of the most cost-effective ways to add broader fluorine screening without sacrificing throughput. The main limitation is that extractable organic fluorine does not yet have a standardized method. Even so, laboratories do not have to choose between targeted and broader fluorine analysis. With the right workflow design, the two can complement each other.
Sarah Ortbal's work recently earned her the 2026 Metrohm Young Chemist Award.
