title: Analytical approaches to the OH radical induced degradation of sulfonamide antibiotics in dilute aqueous solutions.
abstract: By combining a large variety of analytical techniques this study aimed at elaborating methods to follow up the degradation of sulfonamides in an advanced oxidation process (AOP): irradiation with ionizing radiation in dilute aqueous solution. In this process, besides other radicals, hydroxyl radicals are produced. As pulse radiolysis experiments show the basic initial reaction is hydroxyl radical addition to the benzene ring, forming cyclohexadienyl radical intermediates. In aerated solutions these radicals transform to peroxy radicals. Among the first formed products aromatic molecules hydroxylated in the benzene rings or in some cases in the heterocyclic rings were observed by LC-MS/MS. Chemical oxygen demand (COD) measurements indicate that at the early reaction period of degradation one hydroxyl radical induces incorporation of 1.5 O atoms into the products. Comparison of the COD and TOC (total organic carbon content) results shows gradual oxidation. Simultaneously with hydroxylation ring opening also takes place. The kinetics of inorganic SO4(2-) and NH4(+) formation, analyzed by ion chromatography, is similar to the kinetics of ring degradation (UV spectroscopy), however, there is a delayed formation of NO3(-). The latter ions may be produced in oxidative degradation of smaller N containing fragments. The S atoms of the sulfonamides remain in the solution (ICP-MS measurements) after degradation, whereas some part of the N atoms leaves the solution probably in the form of N2 (total nitrogen content (TN) measurements). Degradation is accompanied by a high pH drop due to formation of SO4(2-), NO3(-) and smaller organic acids. The degradation goes through many simultaneous and consecutive reactions, and with the applied methods the different stages of degradation can be characterized.
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, 1121, Konkoly-Thege Miklós út 29-33, Budapest, Hungary. Electronic address: sagi.gyuri@energia.mta.hu.
authors.forename: Gyuri
authors.initials: G
authors.lastname: Sági
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, 1121, Konkoly-Thege Miklós út 29-33, Budapest, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Csay
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, 1121, Konkoly-Thege Miklós út 29-33, Budapest, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Szabó
authors.affiliation: Department of Chemical and Environmental Process Engineering, Budapest University of Technology and Economics, 1111, Budafoki út 8, Budapest, Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Pátzay
authors.affiliation: Department of Chemical and Environmental Process Engineering, Budapest University of Technology and Economics, 1111, Budafoki út 8, Budapest, Hungary.
authors.forename: Emil
authors.initials: E
authors.lastname: Csonka
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, 1121, Konkoly-Thege Miklós út 29-33, Budapest, Hungary; Óbuda University, Sándor Rejtő Faculty of Light Industry and Environmental Engineering, 1034, Doberdó u. 6, Budapest, Hungary.
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Takács
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, 1121, Konkoly-Thege Miklós út 29-33, Budapest, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Wojnárovits
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002853:Chromatography, Liquid; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D012996:Solutions; D013449:Sulfonamides / Q000737:chemistry*; D053719:Tandem Mass Spectrometry
chemical_list: D000900:Anti-Bacterial Agents; D012996:Solutions; D013449:Sulfonamides; D017665:Hydroxyl Radical
keywords: Advanced oxidation processes; Degradation product; Ion chromatography; LC–MS/MS; Sulfonamide