Insight from Carbon and Nitrogen Isotope Fractionation of Sulfamethoxazole during Oxidative vs Reductive Transformation.
- 1Chair of Analytical Chemistry and Water Chemistry, Department of Chemistry, TUM School of Natural Sciences, Technical University of Munich, Lichtenbergstraße 4, 85748Garching, Germany.
Abstract
The antibiotic sulfamethoxazole (SMX) is frequently detected in aquatic systems, raising environmental concerns. Therefore, it is necessary to investigate its transformation pathways under diverse environmental conditions. Here, we explored information from stable isotope fractionation during reductive transformation of SMX with Fe(II)-amended goethite suspensions vs oxidative transformation with MnO2. Transformation of SMX by surface-bound Fe(II) showed significant carbon isotope fractionation (εC = -3.6‰ ± 0.1‰ and εC = -2.9‰ ± 0.2‰, with and without buffer, respectively), pronounced nitrogen isotope fractionation (εN = -12.8‰ ± 0.6‰ and εN = -13.0‰ ± 0.2‰, with and without buffer, respectively), and evidence of transformation products that are consistent with initial reductive N-O bond cleavage. In contrast, reaction with MnO2 caused normal carbon but inverse nitrogen isotope fractionation (εC = -1.7‰ ± 0.1‰ and εC = -2.7‰ ± 0.2‰, with and without buffer, respectively, εN = +1.9‰ ± 0.2‰ without buffer) indicative of an initial oxidative electron transfer. Oxidation products were not easily identified by high-resolution mass spectrometry, emphasizing the importance of compound-specific isotope analysis (CSIA) as an alternative for detecting ongoing transformation. Our study thus highlights the potential of CSIA to detect transformation in settings where concentration and product analysis would be inconclusive and to distinguish between reductive and oxidative transformation pathways of SMX in the environment.
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BibTeX
@article{canavan2026insight,
title = {{Insight from Carbon and Nitrogen Isotope Fractionation of Sulfamethoxazole during Oxidative vs Reductive Transformation.}},
author = {Aoife Canavan and Christopher Dirr and Martin Elsner},
journal = {Environmental science \& technology},
year = {2026},
month = oct,
doi = {10.1021/acs.est.6c07718},
url = {https://europepmc.org/article/MED/42916011},
note = {CC BY},
}
RIS
TY - JOUR
TI - Insight from Carbon and Nitrogen Isotope Fractionation of Sulfamethoxazole during Oxidative vs Reductive Transformation.
AU - Aoife Canavan
AU - Christopher Dirr
AU - Martin Elsner
PY - 2026
DA - 2026/10/01
JO - Environmental science & technology
DO - 10.1021/acs.est.6c07718
UR - https://europepmc.org/article/MED/42916011
AB - The antibiotic sulfamethoxazole (SMX) is frequently detected in aquatic systems, raising environmental concerns. Therefore, it is necessary to investigate its transformation pathways under diverse environmental conditions. Here, we explored information from stable isotope fractionation during reductive transformation of SMX with Fe(II)-amended goethite suspensions vs oxidative transformation with MnO2. Transformation of SMX by surface-bound Fe(II) showed significant carbon isotope fractionation (εC = -3.6‰ ± 0.1‰ and εC = -2.9‰ ± 0.2‰, with and without buffer, respectively), pronounced nitrogen isotope fractionation (εN = -12.8‰ ± 0.6‰ and εN = -13.0‰ ± 0.2‰, with and without buffer, respectively), and evidence of transformation products that are consistent with initial reductive N-O bond cleavage. In contrast, reaction with MnO2 caused normal carbon but inverse nitrogen isotope fractionation (εC = -1.7‰ ± 0.1‰ and εC = -2.7‰ ± 0.2‰, with and without buffer, respectively, εN = +1.9‰ ± 0.2‰ without buffer) indicative of an initial oxidative electron transfer. Oxidation products were not easily identified by high-resolution mass spectrometry, emphasizing the importance of compound-specific isotope analysis (CSIA) as an alternative for detecting ongoing transformation. Our study thus highlights the potential of CSIA to detect transformation in settings where concentration and product analysis would be inconclusive and to distinguish between reductive and oxidative transformation pathways of SMX in the environment.
SN - 0013-936X
SN - 1520-5851
ER -