Tracking photodegradation products and bond-cleavage reaction pathways of triclosan using ultra-high resolution mass spectrometry and stable carbon isotope analysis

• Published in: Environmental pollution (1987) Vol. 264; p. 114673
• Main Authors: Liu, Yi, Mekic, Majda, Carena, Luca, Vione, Davide, Gligorovski, Sasho, Zhang, Gan, Jin, Biao
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2020
• Subjects: Photodegradation; Stable carbon isotope; Toxic products; Triclosan; Ultra-high resolution mass spectrometry; Photodegradation; Stable carbon isotope; Ultra-high resolution mass spectrometry; Triclosan; Toxic products
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.114673

Triclosan (TCS) is an antimicrobial compound ubiquitously found in surface waters throughout the world. Although several studies have focused on the photochemical degradation of TCS, there is still limited knowledge about its environmental fate. In this study, we got molecular-level insights into the photochemical degradation of TCS. Significant stable carbon isotope fractionation was observed during photodegradation; different bond-cleavage reaction pathways under different photolytic conditions were characterized, using compound specific isotope analysis (CSIA). Photochemical modeling of TCS photodegradation showed that direct photolysis would be the main transformation pathway if pH > 7, even in presence of dissolved organic matter. Moreover, by use of ultrahigh resolution mass spectrometry, FT-ICR-MS, a broad and complex spectrum of organic by-products (some of which potentially toxic, as assessed by a quantitative structure-activity relationship approach) were identified. A detailed reaction mechanism was developed on the basis of the detected compounds. A possible sequence of steps leading to some of the detected product compounds in aqueous solution is suggested. [Display omitted] •Significant carbon isotope fractionation occurs during TCS photodegradation.•Several toxic products were unambiguously identified by FT-ICR-MS.•Direct photolysis accounts for most photodegradation of the TCS anionic form.•TCS direct photolysis undergoes inhibition by humic acids. TCS photo-transformation products were identified, and the concurrent bond-cleavage reaction pathways under different photolytic conditions were characterized.