Chiu, Yin Ting T.Burns, Alyssa M.Rosanka, SimonHu, TiffanyHennigan, ChristopherCarlton, Annmarie G.2025-01-222025-01-222024-12-04Chiu, Yin Ting T., Alyssa M. Burns, Simon Rosanka, Tiffany Hu, Christopher J. Hennigan, and Annmarie G. Carlton. “Chloride Interferences in Wet Chemical Oxidation Measurements: Plausible Mechanisms and Implications.” ACS ES&T Water 4, no. 12 (December 13, 2024): 5399–5407. https://doi.org/10.1021/acsestwater.4c00508.https://doi.org/10.1021/acsestwater.4c00508http://hdl.handle.net/11603/37400Wet chemical oxidation (WCO) methods measure total organic carbon (TOC) in aqueous solutions through the formation and detection of carbon dioxide (CO₂). Prior research documents chloride (Cl⁻) interference during WCO. However, the mechanism that determines WCO interference is not established. We investigate WCO and find that formic acid exhibits TOC recovery (89–108%) within measurement uncertainty in the presence of Cl⁻, while acetic acid recovery is substantially reduced (3–67%). We postulate that chlorine radical (•Cl) formation during WCO alters oxidation pathways for organic compounds with methyl groups to form stable halogenated organic species that are thus not detected as CO₂, reducing observed TOC recovery. We develop a kinetic model of elementary step reactions that reproduces observed TOC recoveries at multiple organic (1 and 5 ppm of C) and Cl⁻ (>0.01 M) concentrations for both acetic and formic acids. Independent experiments with pyruvic acid and different halogen salts are consistent with the proposed mechanism. Our findings provide a plausible mechanistic explanation for Cl⁻ interference in WCO-derived TOC measurements of environmental samples for which halogenated salts are present. A plausible mechanism provides a more complete understanding of how and why the TOC is biased low in environmental aquatic samples from saline environments when WCO is employed.9 pagesen-USAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttps://creativecommons.org/licenses/by-nc-nd/4.0/Text