Degradation of flumequine by the Fenton and photo-Fenton processes: evaluation of residual antimicrobial activity.

Flumequine is a broad-spectrum antimicrobial agent of the quinolone class, and it is widely used as a veterinary drug in food-producing animals. The presence of flumequine in the environment may contribute to the development of drug resistant bacterial strains. In this study, water samples fortified with flumequine (500 μg L(-1)) were degraded using the Fenton and photo-Fenton processes. The maximum degradation efficiency for flumequine by the Fenton process was approximately 40% (0.5 mmol L(-1) Fe(II), 2.0 mmol L(-1) H(2)O(2) and 15 min). By applying UV radiation (photo-Fenton process), the efficiency reached more than 94% in 60 min when 0.25 mmol L(-1) Fe(II) and 10.0 mmol L(-1) H(2)O(2) were used. Under these conditions, the Fenton process was able to reduce the biological activity, whereas the photo-Fenton process eliminated almost all of the antimicrobial activity because it was not detected. Four byproducts with an m/z of 244, 238, 220 and 202 were identified by mass spectrometry, and a degradation pathway for flumequine was proposed. The byproducts were derived from decarboxylation and defluorination reactions and from modifications in the alkylamino chain of the fluoroquinolone.