Orbitrap Mass Spectrometry Could Improve Tracking of PFAS Contamination

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a class of synthetic chemicals widely used in industrial processes and consumer products because of their resistance to heat, water, and oil. However, these same properties also make them highly resistant to environmental degradation. As a result, PFAS, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been detected in various environmental matrices, including soil, drinking water, and the atmosphere. Identifying the sources of these contaminants is an important step toward understanding and managing PFAS pollution. One such approach for identifying pollution sources is stable isotope analysis, a technique that measures small variations in the ratios of naturally occurring isotopes within chemical compounds. However, applying this technique to non-volatile PFAS compounds, such as PFOS and PFOA, has remained a challenge.

In a recent study led by Professor Hiroto Kawashima from the Department of Bioscience and Engineering at Shibaura Institute of Technology (SIT), Japan, researchers investigated whether Orbitrap high-resolution mass spectrometry could be used to measure the stable carbon isotope ratios (δ¹³C) of PFAS compounds. Joining him in this collaboration were Tomoha Iezumi, a student from the Department of Bioscience and Engineering at SIT, and Momoka Suto and Dr. Sachi Taniyasu from the National Institute of Advanced Industrial Science and Technology, Japan. Their findings were published in Environmental Science & Technology Letters on March 03, 2026.

Explaining the motivation behind the work, Prof. Kawashima says, “PFAS contamination has become a serious environmental issue worldwide, but identifying their sources remains challenging. We were interested in whether high-resolution mass spectrometry, such as Orbitrap, could be used for stable isotope analysis to address this challenge.”

Traditionally, compound-specific isotope analysis relies on isotope ratio mass spectrometry (IRMS), which often requires chemical conversion steps such as combustion before isotope ratios can be measured. These additional procedures can complicate analysis, particularly for chemically stable compounds such as PFAS. To address this limitation, the researchers explored whether Orbitrap mass spectrometry, known for its extremely high mass resolution and accuracy, could directly measure isotopic variations in PFAS molecules. Describing the key advance of the study, Prof. Kawashima explains, “This study demonstrates a new analytical approach to measure the stable carbon isotope ratios of PFAS compounds such as PFOA and PFOS using Orbitrap mass spectrometry. The method enables high-precision isotope analysis without the need for conventional isotope ratio mass spectrometry. This opens a new pathway for identifying the sources and environmental behavior of PFAS contamination.”

To test the method, the researchers analyzed standard samples of PFOS and PFOA using Orbitrap mass spectrometry and compared the results with measurements obtained using elemental analysis–IRMS (EA-IRMS), a widely used reference method. The Orbitrap instrument detects molecular variants known as isotopologues, which differ slightly in mass depending on their isotopic composition. The results showed that the isotope ratios obtained using Orbitrap measurements closely matched those measured by EA-IRMS. The differences between the two methods were no more than ±2.0‰ (per mile), indicating that the Orbitrap-based approach can provide reliable compound-specific isotope data. Importantly, the method allows isotope measurements without the combustion steps typically required in conventional isotope ratio analysis.

The researchers also evaluated whether the technique could work in real water samples. For this purpose, they analyzed three river water samples spiked with PFAS compounds at nanomolar concentrations. The Orbitrap system successfully measured the isotopic signatures of the compounds in these samples, suggesting that the approach could potentially be used in environmental monitoring studies.

“One important application is identifying the sources of PFAS contamination in rivers, groundwater, and drinking water. By analyzing isotope signatures, it could help distinguish between different industrial sources of PFAS pollution,” says Prof. Kawashima, highlighting the practical implications of their work. 

Overall, this study represents a step toward developing new analytical tools for tracing PFAS pollution in the environment. By demonstrating that Orbitrap mass spectrometry can measure the stable carbon isotope ratios of PFAS compounds, such as PFOS and PFOA, the findings open new possibilities for investigating the sources and environmental behavior of these persistent contaminants.