Texas Tech Traces PFAS. Should Brands be Worried?
Organofluorine compounds—the umbrella term for forever chemicals—are everywhere: not just in clothing or other consumable commodities, but in the ocean, the soil, even the human body.
Recognized as a particularly pesky class of anthropogenic pollutants, PFAs (a subset of organofluorine compounds) take root in both terrestrial and aquatic locales, per the Interstate Technology Regulatory Council (ITRC), once given the opportunity. And the properties that make PFAS so pervasive are the same properties that make them challenging to analyze and remediate, the coalition said.
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However, researchers at the University of Texas at Austin have recently developed a way to “fingerprint” these organofluorine compounds, which could help to trace them to their source.
Broadly speaking, this achievement means brands accused of exacerbating the PFAS problem might want—or, eventually, need—to provide receipts.
“When we first started working on this, we were thinking about astrobiology; how we could identify biotic molecules on Mars, for example,” said Cornelia Rasmussen, a research assistant professor at the University of Texas Institute for Geophysics at the Jackson School of Geosciences. “But then we realized, hey, there’s also other interesting applications by tracing molecules in the environment. Could you fingerprint a dump site, per se, and say this dump is contributing to contamination in this area?”
The answer seems to be yes.
This technique was detailed in a paper recently published in the peer-reviewed journal Environmental Science & Technology, co-authored by Rasmussen and David Hoffman, an associate professor at the Department of Molecular Biosciences in UT’s College of Natural Sciences.
The method involves passing samples through a strong magnetic field before reading the “burst of radio waves” their atoms emit. This reveals the composition of carbon isotopes in the molecule and gives the chemical its unique fingerprint—a feat not previously achieved, likely because of how PFAS are structured.
Forever chemicals have “super strong” molecular bonds, which give them their useful characteristics but also prevent them from breaking down in the environment, the paper said, causing them to accumulate as pollution in soil and organic material “to which they easily stick.”
These super-strong bonds also make tracing forever chemicals difficult.
Conventional chemical fingerprinting attempts to combust the molecules, but, considering the strength of the bond between carbon and fluorine atoms, it was challenging as these bonds—which “almost never happen in nature,” per the research—are “virtually unbreakable.”
The method explored by Rasmussen and Hoffman, however, tapped nuclear magnetic resonance (NMR) spectroscopy. This technology measures the carbon isotope ratios directly within the molecule, specifically where the carbon is bonded to the fluorine, without breaking the molecule apart. The researchers used the NMR instrument alongside their own computational tools to determine the carbon isotopes at each carbon atom position in the molecule.
Quick science break: Isotopes refer to chemical elements with differences in the number of neutrons in its atoms. Forever chemicals are made by bonding carbon isotopes, which have two different stable isotopes, to the element fluorine. Because the mix of carbon isotopes bonding to each fluorine atom is unique to how the chemical was manufactured, this information can be used like a fingerprint to trace a chemical.
Consider it a “built-in barcode for molecules,” Hoffman said. “Each molecule has its own fingerprint or barcode; it provides a way to follow what came from where and what’s going on.”
The duo tested this technique on a few samples, including a common pet flea treatment. The method successfully distinguished molecules that look structurally the same but are, in fact, different in their carbon isotope distribution.
“We found two different brands had different fingerprints,” Hoffman said of the pesticides studied. “If you found those fingerprints in the environment, you could say whether it’s brand name or generic.”
The research, funded by the U.S. Department of Energy’s Basic Energy Sciences program, has a handful of practical applications (outside of government tracking) with potentially extensive impact. Detecting counterfeit drugs, for example, was the “most straightforward” application of the test.
“It’s given us a whole range of possibilities to learn really interesting things about metabolism on early Earth,” Rasmussen said. “It could even tell us whether organics on Mars are the remnants of some ancient Martian life.”
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