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  2. IodoFinder: Machine Learning-Guided Recognition of Iodinated Chemicals in Nontargeted LC-MS/MS Analysis

IodoFinder: Machine Learning-Guided Recognition of Iodinated Chemicals in Nontargeted LC-MS/MS Analysis

  • Environ Sci Technol. 2025 Mar 11;59(9):4530-4539. doi: 10.1021/acs.est.4c12698.
Tingting Zhao 1 Qiming Shen 2 Xing-Fang Li 2 Tao Huan 1
Affiliations

Affiliations

  • 1 Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver Campus, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
  • 2 Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada.
Abstract

Iodinated disinfection byproducts (I-DBPs) pose significant health concerns due to their high toxicity. Current approaches to recognize unknown I-DBPs in mass spectrometry (MS) analysis rely on negative ionization mode, in which the characteristic I- fragment can be observed in tandem mass spectra (MS/MS). Still, many I-DBPs ionize exclusively in positive ionization mode, where the I- fragment is absent. To address this gap, this work developed a machine learning-based strategy to recognize iodinated compounds (I-compounds) from their MS/MS in both electrospray positive (ESI+) and negative ionization (ESI-) modes. Investigating over 6000 MS/MS spectra of 381 I-compounds, we first identified five characteristic I-containing neutral losses and one diagnostic I- fragment in ESI+ and ESI- modes, respectively. We then trained Random Forest models and integrated them into IodoFinder, a Python program, to streamline the recognition of I-compounds from raw LC-MS data. IodoFinder accurately recognized over 96% of the 161 I-compound standards in both ionization modes. In its application to DBP mixtures, IodoFinder discovered 19 I-DBPs with annotated structures and an additional 17 with assigned formulas, including 12 novel and 3 confirmed I-DBPs. We envision that IodoFinder will advance the identification of both known and unknown I-compounds in exposome studies.

Keywords

exposome; fragmentation pattern; high-resolution mass spectrometry; iodinated compound; iodinated disinfection byproducts; machine learning; nontargeted analysis.

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