Aqueous chlorination of levofloxacin: kinetic and mechanistic study, transformation product identification and toxicity.
The aim of this study was to gain further insight into the fate of levofloxacin during the chlorination process. First, a kinetic study was thus performed at pH 7.2, 20 °C and in the presence of an excess of total chlorine. A slower apparent removal of levofloxacin (k ~ 26 M(-1) s(-1)) was noted when sodium thiosulfate was used to stop the chlorination reaction compared to the degradation observed without using a reducing agent (k ~ 4400 M(-1) s(-1)). The formation of a chlorammonium intermediate which could be converted back into the parent compound through a reaction with thiosulfate was thus expected. This intermediate would result from an initial chlorine attack on the tertiary amine function of levofloxacin. Secondly, four chlorination transformation products were detected by LC/UV/MS analysis. The chemical structures of two of them are proposed. It was suggested that these compounds could come from a secondary reaction of the chlorammonium intermediate on levofloxacin. A reactional pathway is then proposed. Finally, a bioassay using Vibrio fisheri was carried out to study the toxicity pattern during levofloxacin chlorination. An increase in toxicity was observed during chlorination suggesting that the first transformations products formed were more toxic than the parent compound.
University of Poitiers, Institute of Chemistry of Materials and Natural Resources, UMR CNRS 7285, Department of Water Chemistry and Water Treatment, ENSIP, Poitiers, France.
Nasma Hamdi
NH
El Najjar
Marie
M
Deborde
Romain
R
Journel
Nathalie Karpel
NK
Vel Leitner
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D024841:Fluoroquinolones / Q000737:chemistry; D054879:Halogenation; D007700:Kinetics; D064704:Levofloxacin; D015394:Molecular Structure; D015242:Ofloxacin / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D014874:Water Pollutants, Chemical; D014867:Water; D064704:Levofloxacin; D015242:Ofloxacin; C012976:flumequine