Metronidazole photodegradation in aqueous solution by using photosensitizers and hydrogen peroxide

BACKGROUND: The effectiveness of UV radiation on the indirect photodegradation of metronidazole (MNZ) conducting a kinetic study of the process in the presence of radical promoter (H 2 O 2 ) and photosensitizer (Sens) promoters (duroquinone, tetrahydroxyquinone, tetrachloro‐1,4‐benzoquinone, 4‐carboxy‐benzophenone, 2,4‐dihydroxybenzophenone, 4‐hydroxybenzophenone, and 4,4′‐dihydroxybenzophenone) was investigated. RESULTS: The electron‐donating groups of photosensitizers may favor MNZ photodegradation through electron transfer. However, the photosensitizers studied showed low effectiveness of MNZ photodegradation in aqueous phase. The presence of H 2 O 2 substantially increased MNZ photodegradation rate, which was enhanced by increasing the concentration of hydrogen peroxide in the system. The contribution of direct photolysis of MNZ in the UV/H 2 O 2 system was drastically decreased with increasing H 2 O 2 concentrations. CONCLUSIONS: The low effectiveness obtained with most of the Sens used demonstrates that metronidazole cannot be photoxidized by indirect photooxidation in aqueous solution. Copyright © 2012 Society of Chemical Industry