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Oxidative processes - insights in reaction mechanisms gained by high resolution and isotope ratio mass spectrometry
Oxidative and phototransformation processes frequently contribute to micropollutant degradation in natural or engineered systems. For the remediation of contaminated sites or water treatment processes these may be, e.g., ozone (O3), hydroxyl radicals (•OH), chlorine dioxide (ClO2) or UV/vis light if the micropollutants contain one or more chromophores. However, the corresponding reaction mechanisms which are important to assess the formation of undesired transformation products (TPs) are mostly unknown. Currently, TP studies are regularly performed with the analysis by high-resolution mass spectrometry (HRMS) which enables the derivation of the TP sum formulas based on the exact masses. However, the reactive site and point of attack, respectively, remain mostly unknown. Here, compound-specific stable isotope analysis (CSIA) may be a useful tool to enlighten and further investigate reactions of micropollutants since degradation processes may reveal specific isotopic fractionation, which are related to the site of primary attack. Therefore, this study investigates the use of CSIA and HRMS as complementary tools to characterize various oxidative and phototransformation processes in order to elucidate the underlying reaction mechanisms. The sulfonamide antibiotic sulfamethoxazole (SMX) is chosen as a model compound in order to systematically investigate the pH dependent transformation caused by the oxidative and phototransformation processes listed above. SMX is a widely detected micropollutant in surface, ground- and wastewaters which may occur as neutral or anionic specie at typical pH values of water treatment or in natural waters. In case of the oxidative processes, O3 in presence and absence of •OH and ClO2, the reaction stoichiometry, product formation and reaction mechanisms were systematically investigated for reactions with SMX. Two moles of ClO2 and approximately three moles of O3 were consumed per mole SMX degraded. As revealed by HRMS, the oxidation of SMX with O3 and ClO2 leads to six major TPs in both ...
Oxidative processes - insights in reaction mechanisms gained by high resolution and isotope ratio mass spectrometry
Oxidative and phototransformation processes frequently contribute to micropollutant degradation in natural or engineered systems. For the remediation of contaminated sites or water treatment processes these may be, e.g., ozone (O3), hydroxyl radicals (•OH), chlorine dioxide (ClO2) or UV/vis light if the micropollutants contain one or more chromophores. However, the corresponding reaction mechanisms which are important to assess the formation of undesired transformation products (TPs) are mostly unknown. Currently, TP studies are regularly performed with the analysis by high-resolution mass spectrometry (HRMS) which enables the derivation of the TP sum formulas based on the exact masses. However, the reactive site and point of attack, respectively, remain mostly unknown. Here, compound-specific stable isotope analysis (CSIA) may be a useful tool to enlighten and further investigate reactions of micropollutants since degradation processes may reveal specific isotopic fractionation, which are related to the site of primary attack. Therefore, this study investigates the use of CSIA and HRMS as complementary tools to characterize various oxidative and phototransformation processes in order to elucidate the underlying reaction mechanisms. The sulfonamide antibiotic sulfamethoxazole (SMX) is chosen as a model compound in order to systematically investigate the pH dependent transformation caused by the oxidative and phototransformation processes listed above. SMX is a widely detected micropollutant in surface, ground- and wastewaters which may occur as neutral or anionic specie at typical pH values of water treatment or in natural waters. In case of the oxidative processes, O3 in presence and absence of •OH and ClO2, the reaction stoichiometry, product formation and reaction mechanisms were systematically investigated for reactions with SMX. Two moles of ClO2 and approximately three moles of O3 were consumed per mole SMX degraded. As revealed by HRMS, the oxidation of SMX with O3 and ClO2 leads to six major TPs in both ...
Oxidative processes - insights in reaction mechanisms gained by high resolution and isotope ratio mass spectrometry
Willach, Sarah (author) / Schmidt, Torsten Claus
2020-07-08
Theses
Electronic Resource
English
| American Chemical Society | 2024