title: Photolysis of difloxacin and sarafloxacin in aqueous systems.
abstract: The photodegradation of two fluoroquinolone veterinary antibiotics, difloxacin (DIF) and sarafloxacin (SARA) has been explored for the first time in aqueous systems. The study was performed to evaluate the influence of pH, inorganics, humic substances, and other additives. The drugs followed first-order degradation kinetics in matrix free aqueous medium with a rate constant 'k' value of 0.82 and 0.26 h(-1) for DIF and SARA, respectively. Studies performed at various pH revealed that the photolysis rates dropped sharply at pH >7 for DIF, while SARA dissipated faster with increasing pH. Humic substances acted as light barriers by attenuating the light intensity, to retard the drug degradation process. However, rapid drug dissipation was observed in the presence of additives like acetone, hydrogen peroxide, and phosphates, while inorganics such as fluoride, nitrate, and sulfate did not influence the drug photodegradation. Studies on the photolysis of DIF and SARA in river water revealed that both the drugs degraded rapidly under conditions that were relevant to natural systems, following direct photolysis mechanism. It was observed that SARA was the primary photoproduct of DIF and showed relatively a higher persistence than DIF. The findings were also substantiated by the quantum yield (Phi(c)) calculations. The analytical measurements were carried out with LC-MS/MS.
authors.affiliation: Institute of Environmental Research (INFU), Dortmund University of Technology, Otto-Hahn-Strasse 6, D44221 Dortmund, Germany.
authors.forename: Deivasigamani
authors.initials: D
authors.lastname: Prabhakaran
authors.forename: Premasis
authors.initials: P
authors.lastname: Sukul
authors.forename: Marc
authors.initials: M
authors.lastname: Lamshöft
authors.forename: Mohan Akhila
authors.initials: MA
authors.lastname: Maheswari
authors.forename: Sebastian
authors.initials: S
authors.lastname: Zühlke
authors.forename: Michael
authors.initials: M
authors.lastname: Spiteller
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002939:Ciprofloxacin / Q000031:analogs & derivatives* / Q000737:chemistry; D052918:Environmental Restoration and Remediation; D006207:Half-Life; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D010782:Photolysis; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D006812:Humic Substances; D014874:Water Pollutants, Chemical; D014867:Water; D002939:Ciprofloxacin; C047225:difloxacin; C047224:sarafloxacin