title: Photodegradation of azithromycin in various aqueous systems under simulated and natural solar radiation: kinetics and identification of photoproducts.
abstract: This article describes the photolysis of azithromycin, a macrolide antibiotic with reported occurrence in environmental waters, under simulated solar radiation. The photodegradation followed first-order reaction kinetics in five matrices examined. In HPLC water, the degradation rate was the slowest (half-life: 20h), whereas in artificial freshwater supplemented with nitrate (5mgL(-1)) or humic acids (0.5mgL(-1)) the degradation of azithromycin was enhanced by factors of 5 and 16, respectively, which indicated the role of indirect photolysis involving the formation of highly reactive species. Following chromatographic separation on a UPLC system, the characterization of the transformation products was accomplished using high-resolution QqToF-MS analysis. The presence of seven photoproducts was observed and their formation was postulated to originate from (bis)-N-demethylation in the desosamine sugar, O-demethylation in the cladinose sugar, combinations thereof, as well as from hydrolytic cleavages of the desosamine and/or cladinose residue. Two of these photoproducts could also be detected in natural photodegradation process in river water which was spiked with azithromycin.
authors.affiliation: MOE Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Tong
authors.forename: Peter
authors.initials: P
authors.lastname: Eichhorn
authors.forename: Sandra
authors.initials: S
authors.lastname: Pérez
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Wang
authors.forename: Damià
authors.initials: D
authors.lastname: Barceló
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000737:chemistry*; D017963:Azithromycin / Q000032:analysis / Q000737:chemistry*; D005618:Fresh Water / Q000737:chemistry; D006207:Half-Life; D007700:Kinetics; D010782:Photolysis; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D017963:Azithromycin