Research on Stable Isotope Analysis of Halogenated Organic Compounds Published in Analytica Chimica Acta

Research by Sota Maehara (a second-year master's student in our graduate school), was published online in the international academic journal Analytica Chimica Acta on August 2, 2026 (Reiwa 8).

Journal: Analytica Chimica Acta

Title: Measurement of stable isotope ratios of halogenated organic compounds by liquid chromatographic, high-temperature combustion isotope ratio mass spectrometry

Authors: Sota Maehara, Hiroto Kawashima, Sachi Taniyasu

Website: https://doi.org/10.1016/j.aca.2026.346061

Halogenated organic compounds, represented by trichloroacetic acid (TCA) and trifluoroacetic acid (TFA), are of international concern as disinfection by-products and persistent environmental pollutants (including PFAS). Because these compounds have extremely strong carbon–chlorine and carbon–fluorine bonds, analysis of their stable isotope ratios has been difficult.

In this study, the researchers newly developed a combustion interface that operates at a higher temperature and pressure than conventional systems—200 to 600°C and 5.2 MPa—and connected it to a liquid chromatograph–isotope ratio mass spectrometer (LC-IRMS). With this method, chlorinated and brominated acetic acids (such as TCA and TBA) were measured with high precision and accuracy that had previously been difficult to achieve: a carbon recovery rate of 94–108% and an isotope ratio error within ±1‰. TCA in particular has long been considered a compound that is difficult to measure reliably by LC-IRMS, so we believe that achieving stable measurements across reagents from multiple manufacturers represents a significant advance. On the other hand, fluorinated compounds (TFA, PFPrA, PFBA, etc.) still showed substantial isotope fractionation due to incomplete oxidation stemming from the strength of the C–F bond, indicating that further optimization of oxidation conditions is needed going forward. The method was also confirmed to be applicable to aromatic chlorinated compounds and phenols, suggesting potential future applications in elucidating the environmental fate of water-soluble aromatic pollutants.

This research was supported by a Grant-in-Aid for Scientific Research (A) (Grant Number 21H04929), "Elucidation of the Environmental Behavior of Water-Soluble Hazardous Chemical Substances Using Stable Isotope Ratios," with Hiroto Kawashima serving as principal investigator.