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Xiang, Y.* ; Gonsior, M.* ; Schmitt-Kopplin, P. ; Shang, C.*

Are we characterizing the true peaks of disinfection byproducts? Establishment of a rapid and accurate 14/15N-haloFormula methodology for FT-ICR-MS.

Environ. Sci. Technol. 60, 5724–5734 (2026)
DOI PMC
Open Access Green as soon as Postprint is submitted to ZB.
Ultrahigh-resolution mass spectrometry offers exceptional resolving power, yet formula assignment, particularly for nitrogenous disinfection byproducts (N-DBPs), remains challenged by the limited isotopic signature of 15N and elemental ambiguities. We developed HaloFormula, a software for high-confidence formula assignment of dissolved organic matter (DOM) and DBPs. The workflow integrates candidate selection from a newly constructed formula database, dynamic in situ generation of an isotope matrix database, and formula assignment based on spectral similarity indices, achieving high computational efficiency and assignment accuracy. By incorporating a dual-isotope labeling strategy using equimolar 14N/15N-labeled monochloramine, HaloFormula enhances assignment accuracy and enables differentiation of nitrogen origins. The method was validated across diverse FT-ICR-MS data sets, including DOM and model compounds treated by chlor(am)ination and UV-based processes. HaloFormula assigned 1,875 formulas for a Suwannee River Fulvic Acid data set, of which 937 exhibited 13C isotopes. For halogenated compounds, over 900 Cl-containing formulas were assigned, with more than 1,400 isotopic peaks exhibiting accurate isotopic distributions. Up to 17 isotopologues were detected for individual N-DBPs due to enhanced 15N detection from the dual-isotope labeling strategy, enabling unambiguous formula assignment and nitrogen origin tracking. This novel methodology is readily adaptable for elucidating nitrogen sources in other systems and extendable to broader elemental analyses.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Ft-icr-ms ; Disinfection Byproducts ; Formula Assignment ; Nitrogenous Dbps ; Software Development; Natural Organic-matter; Drinking-water; N-nitrosodimethylamine; Formula Assignment; Nitrogen; Chloramination; Chlorine; Dbps; Uv/monochloramine; Genotoxicity
ISSN (print) / ISBN 0013-936X
e-ISSN 1520-5851
Journal Environmental Science & Technology
Quellenangaben Volume: 60, Issue: 7, Pages: 5724–5734 Article Number: , Supplement: ,
Publisher American Chemical Society (ACS)
Publishing Place Washington, DC
Reviewing status Peer reviewed
Institute(s) Research Unit BioGeoChemistry and Analytics (BGC)
Grants Research Grants Council, University Grants Committee