Per- and polyfluoroalkyl substances (PFAS) earn their reputation as “forever chemicals” because of the strength of the carbon–fluorine bond. While this stability makes PFAS valuable in industrial and consumer applications, it also complicates efforts to degrade and remove them from the environment. At the PFAS and Emerging Environmental Contaminants Symposium hosted by Separation Science, Angela Radnoff, a graduate researcher at the University of Ottawa, examines how short-chain PFAS undergo distinct degradation pathways—and how analytical techniques can detect their breakdown products.
Radnoff focuses on a critical yet often overlooked question: even when PFAS are degraded, which compounds are formed? “Incomplete degradation can produce smaller, more volatile fluorinated compounds that are still environmentally persistent,” she describes. Understanding these products, she explains, is essential for evaluating the true effectiveness of PFAS treatment technologies.
Why PFAS Degradation Pathways Matter
Short-chain PFAS are increasingly replacing longer-chain compounds in commercial use, yet they are often more difficult to detect and characterize. Radnoff explains that their high bond energies demand extreme conditions for breakdown, such as high-temperature thermal treatment. “The carbon–fluorine bond is exceptionally strong,” she advises. “That strength is what makes PFAS so resistant to conventional degradation methods.”
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Thermal approaches, including incineration and pyrolysis, are frequently proposed for the destruction of PFAS. However, Radnoff emphasizes that these processes do not always lead to complete mineralization. Instead, they can generate a complex mixture of neutral and ionic fragments that require sophisticated analytical tools to identify.
Using Pyrolysis to Probe Neutral Breakdown Products
Radnoff describes pyrolysis as a controlled, oxygen-free thermal degradation process in which volatile PFAS are heated to temperatures approaching 1,000 °C. Under these conditions, parent molecules fragment into neutral products through unimolecular reactions. “Pyrolysis allows us to isolate and study neutral species that form when PFAS break apart,” she notes.
To detect these products, Radnoff combines pyrolysis with imaging photoelectron photoion coincidence (iPEPICO) spectroscopy at a synchrotron facility. This approach ionizes neutral fragments with tunable photon energy, producing highly resolved mass-selected threshold photoelectron spectra. The resulting data provide insight into both molecular identity and vibrational structure.
Confirming Structures with Computation
Analytical measurements alone are not always sufficient to confirm PFAS breakdown products. Radnoff integrates experimental spectra with density functional theory calculations to validate proposed structures. By overlaying simulated Franck–Condon profiles onto experimental spectra, her team confirms product assignments with high confidence. “The computational work lets us connect the experimental signal to a specific molecular structure,” she explains.
This combined approach reveals that thermal degradation frequently leads to the loss of small neutral molecules, such as CO₂ and HF, followed by the formation of shorter fluorinated fragments that may persist in the environment.
Exploring Ion Chemistry with Collision-Induced Dissociation
In addition to neutral products, Radnoff examines how short-chain PFAS behave once ionized in a mass spectrometer. Using collision-induced dissociation (CID) on a triple quadrupole instrument, she tracks how PFAS anions fragment as the collision-induced dissociation (CID) energy increases. “We wanted to compare ion chemistry with the neutral products formed during pyrolysis,” she says.
The CID experiments reveal recurring fragmentation patterns, including loss of CO₂, HF, and formaldehyde. In several cases, multiple competing pathways emerge, with relative abundances governed by energetic and entropic factors. Computational energy profiles help explain why certain fragments dominate, even when they form at higher energies.
What the Results Reveal about PFAS Persistence
Across both thermal and ion-based experiments, Radnoff observes a consistent theme: degradation rarely eliminates fluorinated carbon structures entirely. Instead, PFAS transform into smaller species that retain strong carbon–fluorine bonds. “We see similar products forming across different degradation approaches,” she notes. “That consistency highlights how difficult these compounds are to fully break down.”
These findings have direct implications for PFAS treatment research. Identifying degradation products helps scientists assess whether a process truly destroys PFAS or merely reshapes them into new persistent forms.
Why This Matters for PFAS Research and Analysis
Radnoff’s work provides analytical reference data that can support both environmental studies and laboratory-based PFAS analysis. Understanding how PFAS fragments under thermal stress and within mass spectrometers improves the interpretation of complex spectra and reduces the risk of misidentifying breakdown products.
The on-demand presentation expands on the experimental design, spectral interpretation, and computational modeling behind these results. For researchers investigating PFAS destruction technologies or interpreting PFAS mass spectrometry data, the full session offers a detailed overview of how advanced analytical techniques can elucidate what happens when “forever chemicals” are pushed to their limits.
