Evidencing generation of persistent ozonation products of antibiotics roxithromycin and trimethoprim.

The mechanism of product formation during ozonation of two widely used antimicrobial agents, macrolide roxithromycin and inhibitor of dihydrofolate reductase (DHFR) trimethoprim was studied in laboratory-scale experiments with two types of matrix: distilled water and secondary wastewater effluent The structures ofthe primary and secondary reaction intermediates were elucidated byquadrupole-time-of-flight (QqToF) instrument, showing that in spite of their high ozone affinity both roxithromycin and trimethoprim oxidation pathway involve to a great degree the *OH radical chain reactions. In total nine ozonation products were detected, whereas two products of roxithromycin exhibited high refractoriness to ozonation, especially in the case of distilled water. Furthermore, the intact tertiary amine moiety of roxithromycin in these products suggests that the antimicrobial activity of the parent compound will be preserved.