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Biotransformation of the UV-Filter Sulisobenzone: Challenges for the Identification of Transformation Products

Beel, Rita, Lütke Eversloh, Christian, Ternes, Thomas A.
Environmental Science & Technology 2013 v.47 no.13 pp. 6819-6828
UV filters, Vibrio fischeri, activated sludge, biodegradation, biotransformation, chemical structure, decarboxylation, liquid chromatography, mass spectrometry, nuclear magnetic resonance spectroscopy, oxidation, prediction, sulfonic acid, sunscreens, toxicity, wastewater treatment
The UV-filter substance Sulisobenzone (BP-4) is widely employed in sunscreens and other personal care products. In the current study, its behavior during biological wastewater treatment was investigated. In contact with activated sludge BP-4 was degraded in aerobic batch experiments forming at least nine transformation products (TPs). The mass balance in the batch experiments was closed, as measurements with LC-UV underlined that the quantity of the TPs was comparable to the BP-4 quantity transformed. The chemical structures of the nine TPs could be proposed based on accurate mass measurements by high resolution mass spectrometry (LTQ-Orbitrap-MS), several fragmentation experiments up to MS⁶ and synthesis of one TP. NMR analyses of the main TP confirmed its proposed chemical structure. At the beginning of the biotransformation of BP-4, a benzhydrol analogue was formed due to the reduction of the keto moiety. Further reactions (e.g., oxidation, demethylation, decarboxylation) led to the formation of extremely polar TPs. A biodegradation pathway was proposed based on the TP structures identified and the sequence of the TP formation. The isolated TPs exhibited higher toxic effects on Vibrio fischeri than BP-4. The results contribute to a better general understanding and prediction of the biotransformation of aromatic sulfonic acids in WWTPs.