Photochemical Degradation of Marbofloxacin and Enrofloxacin in Natural Waters

• Published in: Environmental science & technology Vol. 44; no. 12; pp. 4564 - 4569
• Main Authors: Sturini, Michela, Speltini, Andrea, Maraschi, Federica, Profumo, Antonella, Pretali, Luca, Fasani, Elisa, Albini, Angelo
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.06.2010
• Subjects: Antimicrobial agents; Applied sciences; Chemicals; Environmental Processes; Environmental science; Exact sciences and technology; Fluoroquinolones - chemistry; Fluoroquinolones - radiation effects; Hydrogen-Ion Concentration - radiation effects; Kinetics; Organic Chemicals - chemistry; Oxidation; Photochemistry - methods; Photolysis - radiation effects; Pollutants; Pollution; Rivers - chemistry; Salts - chemistry; Sunlight; Surface water; Water - chemistry; Drug; Marbofloxacin; Pollutant behavior; Solvolysis; Chemical degradation; Veterinary medicine; Antimicrobial agent; Defluorination; Enrofloxacin; Antibiotic; Fluoroquinolone derivatives; Surface water; Reaction mechanism; Oxidation; Kinetics; Solar radiation; Degradation product; Organic compounds; Photochemical degradation
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es100278n

The photochemical fate of Marbofloxacin (MAR) and Enrofloxacin (ENR), two Fluoroquinolones (FQs) largely used as veterinary bactericides known to be present in surface waters, was investigated in aqueous solution. The degradation of these pollutants (5−50 μg L−1 starting concentration) was complete in about 1 h by exposure to solar light (summer) and obeyed a first-order kinetics. The structure of the primary photoproducts was determined. Those from ENR arose through three paths, namely, oxidative degradation of the piperazine side-chain, reductive defluorination, and fluorine solvolysis. More heavily degraded products that had been previously reported were rationalized as secondary photoproducts from the present ones. As for MAR, this underwent homolytic cleavage of the tetrahydrooxadiazine moiety to give two quinolinols. All of the primary products were themselves degraded in about 1 h. The photoreactions rates were scarcely affected by Ca2+ (200 mg L−1), Mg2+ (30 mg L−1), Cl− (30 mg L−1), and humic acid (1 mg L−1), but increased in the presence of phosphate (20 mg L−1). The fastest degradation of ENR occurred at pH about 8 where the zwitterionic form was present, while in the case of MAR the cationic form was the most reactive.