Stable Isotopic Labeling and Automated Reactivity-Directed Approach Accelerating Discovery of Toxic Disinfection Byproducts in Chlorinated and Chloraminated Waters

Reactivity-directed analysis facilitates
prioritization
of toxic
disinfection byproducts (DBPs), yet its data processing remains laborious
and inefficient. Herein, we developed an automated approach integrating
stable isotopic labeling with reactivity-directed principles. Normal
and deuterated glutathione (GSH) probes were used to generate paired
isotopic signatures enabling precise localization of reactive DBPs.
Customized bioinformatics tools were employed to efficiently extract
paired GSH–DBP adducts. The workflow allowed rapid automated
processing of large data sets within minutes while maintaining high
coverage and accuracy. When applied to chlorinated and chloraminated
water samples, 255 adducts were screened from >50 000 raw
features,
leading to annotation of 202 DBPs, including 193 newly reported. GSH
reaction mechanism analysis attributed 65 chlorinated and 132 unsaturated
DBPs to nucleophilic substitution and addition, respectively. Notably,
5 sulfur-containing DBPs enabled thiol oxidation, indicating a new
GSH reaction pathway. Among annotated DBPs, chlorination favored unsaturated
carbonyls, while chloramination generated more nitrile/nitro group
DBPs. Toxicity predictions verified that annotated DBPs exhibited
toxicities comparable to or greater than those of regulated DBPs.
Prevalent toxic DBPs exhibited a high molecular weight or structural
characters, such as benzene rings, carbonyls, and Cl/N functionalization.
This approach significantly accelerated toxic DBP discovery, and the
findings provided new insights into toxicity drivers in disinfected
waters.