CHARACTERIZATION OF PHENAZONE TRANSFORMATION PRODUCTS ON LIGHT-ACTIVATED TiO2 SURFACE BY HIGH RESOLUTION MASS SPECTROMETRY

The paper examines the transformation of phenazone (2,3-dimethyl-1-phenyl-3-pyrazolin-5-one), a widely-used analgesic and antipyretic drug, under simulated solar irradiation in pure water, using titanium dioxide, and in river water. High resolution mass spectrometry was employed to monitor the evolution of photoinduced processes. Initially, laboratory experiments were performed to simulate drug-transformation pathways in aqueous solution, using TiO2 as photocatalyst. 13 main phenazone transformation products were detected, and full analysis of their MS and MSn spectra identified the diverse isobaric species. All these transformation products were themselves easily degraded, and no compounds were recognized to remain until 1h of irradiation. Photo-mineralization of the substrate, in terms of carbon mineralization and nitrogen release, occurred within 96 h of irradiation, when the nitrogen had been stoichiometrically transformed into NH4+ and NO3- ions. From these findings, a tentative degradation pathway is proposed to account for the photoinduced transformation of phenazone in natural waters. These simulation experiments were verified in the field, seeking phenazone in River Po water samples.