The realm of chemical substances that we encounter in our day-to-day lives is vast and complex. Among this wide array of substances, a family known as Polyfluoroalkyl substances (PFAS), stands as a veritable Pandora’s box of potential dangers for both humans and the environment.
PFAS are a group of organic compounds, characterized by the replacement of most, or all, hydrogen atoms bound to carbon atoms with fluorine atoms. Their unique chemical structure equips them with distinctive waterproof, oil-resistant, and dirt-resistant properties. This makes them highly sought after in manufacturing products ranging from nonstick pans and outdoor clothing, to packaging materials.
PFAS also find their use in other items such as fire-suppressing foam, paint, and car polish. As useful as these compounds may be, the adverse effects they wield when released into the environment are of significant concern. Resilient to breakdown, these compounds tend to concentrate and bio-accumulate in plants, animals, and human beings.
The Extent of the Peril
Among the multitude of PFAS, two members are particularly notorious – perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). These chemicals have been linked to organ damage, cancer, and disruption of the endocrine system, flagging them as significant health hazards.
To regulate the PFAS levels in drinking water, the EU has set limits of 100 ng/l for individual specific PFAS substances and 500 ng/l for the sum of all PFAS. Additionally, in Germany, regulation mandates that water providers must commence testing drinking water for PFAS by 2026. Stricter standards are implemented by the US Environmental Protection Agency, setting the upper limit for PFOS and PFOA at 4 nm/l for each substance.
Current Methods of Detection
The standard procedure to detect PFAS involves chromatography and mass spectrometry. While effective, these methods come with their own set of drawbacks. They are time-consuming, expensive, and necessitate the use of complex equipment and skilled personnel.
The Dawn of a New Technique
Recognizing the need for a more efficient, cost-effective, and user-friendly method, researchers Timothy M. Swager and Alberto Concellón at the Massachusetts Institute of Technology (MIT) have introduced a novel technique. This method employs a portable, inexpensive test that uses fluorescence measurements to detect PFAS in water samples selectively and easily.
The test centers around a polymer – either in the form of a thin film or nanoparticles – with fluorinated sidechains. These sidechains contain fluorinated dye molecules (squaraine derivatives) embedded within them. This specially designed polymer backbone (poly-phenylene ethynylene) absorbs violet light and transfers this light energy to the dye via an electron exchange (Dexter mechanism), causing the dye to fluoresce red.
When PFAS are present in the sample, they infiltrate the polymer and displace the dye molecules by a fraction of a nanometer. This minuscule displacement is enough to halt the electron exchange and consequently, the energy transfer. As a result, the dye’s red fluorescence is “switched off,” and the blue fluorescence of the polymer is “switched on.” The degree of fluorescence change can be directly linked to the concentration of PFAS in the sample.
The Impact and Potential of the New Technique
This innovative technique demonstrates a detection limit in the µg/l range for PFOA and PFOS, making it suitable for on-site detection in highly contaminated regions. Even trace amounts of these contaminants in drinking water can be accurately detected after pre-concentration of the samples by solid-phase extraction.
Such advancements represent a significant step forward in managing the risks associated with PFAS. By enabling more straightforward and cheaper detection of these harmful substances, we can better control and limit their impact on the environment and human health.
Although the complexities of PFAS and their effects are still being unravelled, the contribution of researchers like Swager and Concellón bring us one step closer to understanding and managing these substances more effectively.
Note: Alberto Concellón is presently a Ramón y Cajal Researcher at the University of Zaragoza, Spain
Reference: Concellón, A., Swager, T. M. (2023) Detection of Per- and Polyfluoroalkyl Substances (PFAS) by Interrupted Energy Transfer Angew. Chem. Int. Ed. e202309928. Doi: 10.1002/anie.202309928
The original research can be found in the post “Sensitive on-site testing for PFAS in water samples” on Mapping Ignorance.