PH adjustment prior to extraction is an important step in water sample pretreatment process for exploration of new/unknown disinfection byproducts (DBPs) in drinking water. To achieve better extraction efficiency, pH of a water sample is usually adjusted to a low level (e.g., &lt; 0.5) to ensure that target DBPs are in their neutral forms. However, such a practice may elude some amphoteric DBPs (especially those nitrogenous DBPs with multiple functional groups) which can accept protons at low pH and lose protons at high pH. In this study, with careful extraction pH selection and optimization, we first report the detection and identification of a new group of heterocyclic nitrogenous DBPs, halogenated pyridinols, in simulated drinking water using ultra-performance liquid chromatography/electrospray ionization-triple quadruple mass spectrometry and time-of-flight mass spectrometry, including 5-chloro-3-pyridinol, 2-bromo-3-pyridinol, 2,6-dichloro-4-pyridinol, 2,6-dibromo-3-pyridinol, 3-bromo-2-chloro-5-pyridinol, 5-bromo-2-chloro-3-pyridinol, 3,5,6-trichloro-2-pyridinol, and 2,4,6-tribromo-3-pyridinol. Based on the Henderson-Hasselbalch equations and recovery tests at different extraction pH values, it was found that only at the pH of 3.0, all the eight new DBPs could achieve recoveries of &gt; 50%. With subsequent instrumental parameter optimization, method detection and quantitation limits of the eight new DBPs were determined to be 0.04−1.58 and 0.15−4.11 ng/L, respectively. The optimized method enabled accurate detection of the eight new DBPs in two real drinking water samples. Further aided with <i>in vivo </i>developmental and acute toxicity assays using zebrafish embryos, the developmental and acute toxicity of the new DBPs were found to be slightly lower than those of halogenated benzoquinones, but dozens of times higher than those of commonly known DBPs such as tribromomethane and iodoacetic acid.

New group of heterocyclic nitrogenous disinfection byproducts (DBPs) in drinking water: Role of extraction pH in unknown DBP exploration

ACS Fall 2021

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