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Rapid, high-sensitivity analysis of oxyhalides by non-suppressed ion chromatography-electrospray ionization-mass spectrometry: application to ClO4, ClO3, ClO2, and BrO3 quantification during sunlight/chlorine advanced oxidation

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Abstract

A rapid and sensitive method is described for measuring perchlorate (ClO4), chlorate (ClO3), chlorite (ClO2), bromate (BrO3), and iodate (IO3) ions in natural and treated waters using non-suppressed ion chromatography with electrospray ionization and tandem mass spectrometry (NS-IC-MS/MS). Major benefits of the NS-IC-MS/MS method include a short analysis time (12 minutes), low limits of quantification for BrO3 (0.10 μg L−1), ClO4 (0.06 μg L−1), ClO3 (0.80 μg L−1), and ClO2 (0.40 μg L−1), and compatibility with conventional LC-MS/MS instrumentation. Chromatographic separations were generally performed under isocratic conditions with a Thermo Scientific Dionex AS16 column, using a mobile phase of 20% 1 M aqueous methylamine and 80% acetonitrile. The isocratic method can also be optimized for IO3 analysis by including a gradient from the isocratic mobile phase to 100% 1 M aqueous methylamine. Four common anions (Cl, Br, SO42−, and HCO3/CO32−), a natural organic matter isolate (Suwannee River NOM), and several real water samples were tested to examine influences of natural water constituents on oxyhalide detection. Only ClO2 quantification was significantly affected – by elevated chloride concentrations (>2 mM) and NOM. The method was successfully applied to quantify oxyhalides in natural waters, chlorinated tap water, and waters subjected to advanced oxidation by sunlight-driven photolysis of free available chlorine (sunlight/FAC). Sunlight/FAC treatment of NOM-free waters containing 200 μg L−1 Br resulted in formation of up to 263 ± 35 μg L−1 and 764 ± 54 μg L−1 ClO3, and up to 20.1 ± 1.0 μg L−1 and 33.8 ± 1.0 μg L−1 BrO3 (at pH 6 and 8, respectively). NOM strongly inhibited ClO3 and BrO3 formation, likely by scavenging reactive oxygen or halogen species. As prior work shows that the greatest benefits in applying the sunlight/FAC process for purposes of improving disinfection of chlorine-resistant microorganisms are realized in waters with lower DOC levels and higher pH, it may therefore be desirable to limit potential applications to waters containing moderate DOC concentrations (e.g., ∼1–2 mgC L−1), low Br concentrations (e.g., <50 μg L−1), and circumneutral to moderately alkaline pH (e.g., pH 7–8) to strike a balance between maximizing microbial inactivation while minimizing formation of oxyhalides and other disinfection byproducts.

Graphical abstract: Rapid, high-sensitivity analysis of oxyhalides by non-suppressed ion chromatography-electrospray ionization-mass spectrometry: application to ClO4−, ClO3−, ClO2−, and BrO3− quantification during sunlight/chlorine advanced oxidation

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Supplementary files

Article information


Submitted
01 May 2020
Accepted
15 Jun 2020
First published
08 Jul 2020

Environ. Sci.: Water Res. Technol., 2020, Advance Article
Article type
Paper

Rapid, high-sensitivity analysis of oxyhalides by non-suppressed ion chromatography-electrospray ionization-mass spectrometry: application to ClO4, ClO3, ClO2, and BrO3 quantification during sunlight/chlorine advanced oxidation

T. R. Young, S. Cheng, W. Li and M. C. Dodd, Environ. Sci.: Water Res. Technol., 2020, Advance Article , DOI: 10.1039/D0EW00429D

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