Enmanuel Cruz Muñoza, Giorgio Tseberlidisb, Amin Hasan Huseinb, Simona Binettib,   Fabio Gosettia,c 

aDepartment of Earth and Environmental Sciences, University of Milano-Bicocca, 20126 Milano, Italy
bDepartment of Materials Science and Solar Energy Research Center, University of Milano-Bicocca, 20125 Milano, Italy
cPOLARIS Research Center, University of Milano-Bicocca, 20126 Milano, Italy

This study evaluates the influence of UV-Vis radiation alone and the use of quaternary chalcogenide nanoparticles, kesterite, (Cu2 ZnSnS4) as the catalyst in the degradation of diclofenac in aqueous media to assess its partial or total elimination, and the formation of transformation products.  A ultra-high-performance liquid chromatography coupled with a high-resolution quadrupole time-of-flight-mass spectrometry method was developed for the elucidation of the transformation products following a non-targeted approach based on mass data-independent acquisition (MSE). 

The identification of twelve transformation products, two of which for the first time with respect to the other diclofenac degradation studies present in the literature, led to the elucidation of a photodegradation mechanism, which was based on the accurate tandem mass spectrometry information obtained. Moreover, a toxicity assessment of the photoproducts was performed in silico using quantitative structure-activity relationships (QSARs). On the one hand, UV-vis photolysis completely degrades diclofenac after 120 min of irradiation, but the formed transformation products persist at the end of the degradation. These are mainly carbazole derivatives with comparable toxicity and similar persistence in the environment to that of diclofenac. On the other hand, the use of the kesterite catalyst is a successfully promising process for diclofenac photodegradation, resulting in its elimination and the formation of less toxic products at the end of degradation process.

Keywords: diclofenac, transformation products, non-target analysis, mass spectrometry