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Novel Chlorination Byproducts of Tryptophan: Initial High-Yield Transformation Products versus Small Molecule Disinfection Byproducts
journal contribution
posted on 2020-02-07, 19:08 authored by Lap-Cuong Hua, Euna Kim, Daniel L. McCurry, Chihpin Huang, William A. MitchBecause of the difficulty of carbon–carbon
bond cleavage
needed to liberate the small molecule chlorine disinfection byproducts
(DBPs; e.g., trihalomethanes), they typically form at <1% yields.
By using N-acetyl-tryptophan (NacTrp) as a model
reactive peptide-bound monomer within natural organic matter (NOM),
this study illustrates the characterization of its initial chlorine
transformation products as an alternative approach to identify high-yield
DBPs. When NacTrp was treated at 1–10 chlorine/NacTrp molar
ratios, seven novel initial transformation products were purified
and characterized by high-resolution mass spectrometry, including
two chlorine-containing DBPs. The total concentrations of these novel
DBPs accounted for 55–100% conversion of the parent NacTrp
at 1–5 chlorine/NacTrp molar ratios over 24 h, compared to
≤5% for the total concentrations of small molecule DBPs. At
a 10:1 molar ratio, the novel DBP concentrations declined over 24
h to account for 25% molar conversion, while small molecule DBP concentrations
increased, yet still accounted for only 20% molar conversion. A reaction
pathway consistent with these initial transformation products was
proposed. The high yields of these novel DBPs are attributable to
the lack of carbon–carbon bond cleavage. This study illustrates
the identification of initial transformation products of important
monomers as an efficient option to characterize the unknown DBPs.
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model reactive peptide-bound monomermolarSmall Molecule Disinfection ByproductsNovel Chlorination Byproductsmolecule chlorine disinfection byproductschlorine transformation productsNOMtransformation productsnovel DBP concentrationsmolecule DBP concentrationsInitial High-Yield Transformation Productsnovel DBPs24 h
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