Detection and identification of degradation products of sulfamethoxazole by means of LC/MS and -MSn after ozone treatment.

The ozonation of the antibiotic sulfamethoxazole has been studied, in order to elucidate the structures of some of the degradation products generated throughout the process. Under the conditions applied, a complete destruction of sulfamethoxazole was achieved after 10 minutes of reaction. The biodegradability of the resulting solution has been also determined, and this parameter undergoes a gradual increase along during the reaction time. The acute toxicity of the reaction mixture, on the contrary, is only decreased during the first 5 minutes of reaction while it increases subsequently. Some of the intermediates resulting during ozonation seem to be more toxic to Daphnia magna than the untreated sulfamethoxazole. The structures of selected degradation products found in the solution are determined and identified. Ozone predominantly attacks sulfamethoxazole via the amine group of the aniline ring in some cases giving rise to nitro-aromatic compounds. IWA Publishing 2008.