title: Identification of ozonation by-products of 4- and 5-methyl-1H-benzotriazole during the treatment of surface water to drinking water.
abstract: During the treatment of surface water to drinking water, ozonation is often used for disinfection and to remove organic trace substances, whereby oxidation by-products can be formed. Here we use the example of tolyltriazole to describe an approach for identifying relevant oxidation by-products in the laboratory and subsequently detecting them in an industrial-scale process. The identification process involves ozonation experiments with pure substances at laboratory level (concentration range mg L(-1)). The reaction solutions from different ozone contact times were analyzed by high performance liquid chromatography - quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) in full scan mode. Various approaches were used to detect the oxidation by-products: (i) target searches of postulated oxidation by-products, (ii) comparisons of chromatograms (e.g., UV/VIS) of the different samples, and (iii) color-coded abundance time courses (kinetic) of all detected compounds were illustrated in a kind of a heat map. MS/MS, H/D exchange, and derivatization experiments were used for structure elucidation for the detected by-product. Due to the low contaminant concentrations (ng L(-1)-range) of contaminants in the untreated water, the conversion of results from laboratory experiments to an industrial-scale required the use of HPLC-MS/MS with sample enrichment (e.g., solid phase extraction.) In cases where reference substances were not available or oxidation by-products without clear structures were detected, reaction solutions from laboratory experiments were used to optimize the analytical method to detect ng L(-1) in the samples of the industrial processes. We exemplarily demonstrated the effectiveness of the methodology with the industrial chemicals 4- and 5-methyl-1H-benzotriazole (4- and 5-MBT) as an example. Moreover, not only did we identify several oxidation by-products in the laboratory experiments tentatively, but also detected three of the eleven reaction products in the outlet of the full-scale ozonation unit.
authors.affiliation: Zweckverband Landeswasserversorgung, Betriebs- und Forschungslaboratorium, Am Spitzigen Berg 1, 89129 Langenau, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Müller
authors.forename: Stefan C
authors.initials: SC
authors.lastname: Weiss
authors.forename: Judith
authors.initials: J
authors.lastname: Beisswenger
authors.forename: H Georg
authors.initials: HG
authors.lastname: Leukhardt
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schulz
authors.forename: Wolfram
authors.initials: W
authors.lastname: Seitz
authors.forename: Wolfgang K L
authors.initials: WK
authors.lastname: Ruck
authors.forename: Walter H
authors.initials: WH
authors.lastname: Weber
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D041961:Deuterium Exchange Measurement; D060766:Drinking Water / Q000737:chemistry*; D005858:Germany; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014230:Triazoles / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D060766:Drinking Water; D014230:Triazoles; D010126:Ozone; C012771:benzotriazole