A New Group of Heterocyclic Nitrogenous Disinfection Byproducts (DBPs) in Drinking Water: Role of Extraction pH in Unknown DBP Exploration

Abstract

pH adjustment prior to extraction is an important step in water sample pretreatment processes for exploration of new/unknown disinfection byproducts (DBPs) in drinking water. To achieve a better extraction efficiency, the pH of a water sample is usually adjusted to a low level (e.g., < 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 a low pH and lose protons at a 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 quadrupole 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. On the basis of the speciation of dissociated chemical species and recovery tests at different extraction pH values, it was found that, only at a pH of 3.0, all the eight new DBPs could achieve recoveries of >50%. With subsequent instrumental parameter optimization, the 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 an accurate detection of the eight new DBPs in two real drinking water samples. Further aided with in vivo 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.

Halocyclopentadienes: An Emerging Class of Toxic DBPs in Chlor(am)inated Drinking Water

“…55,56 The LC 50 of eight halogenated pyridinols and two halobenzoquinones in zebrafish embryos was 8.1−373 and 4.0−5.5 μM, respectively, which are also much lower than that of THMs and HAAs. 50 However, for marine algae (Isochrysis galbana, Skeletonema costatum, Porphyridium cruentum, and Dunaliela tertiolecta), the EC 50 of 1,2,3,4,5,5-hexachloro-1,3-cyclopentadiene was 0.01−0.37 μM, 40 which is approximately 100,000× lower than that of HAAs and approximately 1800× lower than that of halophenols. In addition, the LC 50 of 1,2,3,4,5,5hexachloro-1,3-cyclopentadiene in freshwater fish and saltwater shrimp was 0.03−0.18 μM, 40 than that of THMs and HAAs and 22−12,433× lower than that of halogenated pyridinols and halobenzoquinones.…”

“…Compared with other emerging aromatic or alicyclic DBPs reported in drinking water, the levels of HCPDs were similar to those of HBQs and chlorophenylacetonitriles 32,48 but were higher than those of halogenated pyridinols and halophenylacetamides. 49,50 Stability of HCPDs. To preliminarily assess the stability of the HCPDs and potential for hydrolysis, the two HCPDs with available standards (HEX and 1,2,3,4-tetrachloro-1,3-cyclopentadiene) were evaluated in nanopure water at pH 7 over 168 h in an incubator in the dark at 25 °C.…”

Formation and Cytotoxicity of Halophenylacetamides: A New Group of Nitrogenous Aromatic Halogenated Disinfection Byproducts in Drinking Water

“…Nontarget analysis with a high-resolution ultra-performance liquid chromatograph/electrospray ionization-hybrid quadrupole time-of-flight mass spectrometer (UPLC/ESI-QTOF-MS) has become a commonly used method for probing unknown DBPs in drinking water. ,, However, it is widely acknowledged that nontarget analysis is considerably labor-intensive and time-consuming due to (but not limited to) the complex water matrix. To simplify the analysis in the initial stage, the replacement of real drinking water samples with chlorinated model precursor samples is regarded as a promising resolution.…”

Research Progress of the Endocrine-Disrupting Effects of Disinfection Byproducts

“…Since the first group of DBPs, i.e., trihalomethanes (THMs), was found in 1974 [ 6 ], more than 800 DBPs belonging to various classes have been gradually determined both in real disinfection plants and in controlled laboratory tests [ 7 , 8 ]. With the development of analytical methods, it is conceivable that more DBPs will be continuously identified [ 9 , 10 , 11 , 12 ]. For example, Zhang, et al [ 13 ] recently analyzed the DBPs in ozonated wastewater, and they identified eight new Br-DBPs, including 2-bromostyrene, 2-bromo-benzaldehyde, and 2-bromophenylacetonitrile.…”