Characterization of intermediate compounds formed upon photoinduced degradation of quinolones by high-performance liquid chromatography/high-resolution multiple-stage mass spectrometry

The paper deals with the photocatalytic transformation of atenolol, 4-[2-hydroxy-3-[(1-methyl)amino]propoxyl]-benzeneacetamide, a cardioselective β-blocking agent used to treat cardiac arrhythmias and hypertension, under simulated solar irradiation using titanium dioxide as photocatalyst. The investigation involved monitoring drug decomposition, identifying intermediate compounds, assessing mineralization, and evaluating toxicity. HPLC coupled to HRMS via ESI interface was found to be a powerful tool to identify and measure the degradation products; 23 main species were identified. Intermediates were characterized through their chromatographic behavior and evolution kinetics, coupled with accurate mass information. Through the full analysis of MS and MSn spectra and a comparison with parent drug fragmentation pathways, the diverse isomers were characterized. Neither atenolol nor the intermediates formed exhibit acute toxicity. All intermediates are easily degraded themselves and no compound recognized can withstand 2h irradiation. Photomineralization of the substrate in terms of carbon mineralization and nitrogen release was rather quick and within 4 h of irradiation, organic nitrogen and carbon were completely mineralized.