Advanced oxidation of the antibiotic sulfapyridine by UV/H2O2: Characterization of its transformation products and ecotoxicological implications

• Removal of sulfapyridine was studied upon UV/H2O2 treatment.
• Ten major and minor transformation products were elucidated.
• HRMS was successfully applied, using a LTQ-Orbitrap-MS analyzer.
• Exact mass measurements of new by-products were made by means of MS2 and MS3 scans.
• Combined ecotoxicity of parent drugs and TPs was evaluated during the experiment.

The aim of the present work is to investigate, under lab-scale conditions, the removal and transformation of the antibiotic sulfapyridine (SPY) upon advanced oxidation with UV/H2O2. High resolution mass spectrometry (HRMS) analyses by means of an ultra-high pressure liquid chromatography (UHPLC)-linear ion trap high resolution Orbitrap instrument (LTQ-Orbitrap-MS) were carried out in order to elucidate the different transformation products (TPs) generated. The abatement (>99%) of the antibiotic was only achieved after 180 min, highlighting its resilience to elimination and its potential persistence in the environment A total of 10 TPs for SPY were detected and their molecular structures elucidated by means of MS2 and MS3 scans. Finally, the combined ecotoxicity at different treatment times was evaluated by means of bioluminescence inhibition assays with the marine bacteria Vibrio fischeri.