Aqueous photodegradation of sethoxydim herbicide: Qtof elucidation of its by-products, mechanism and degradation pathway

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• 作者：Beatriz Sevilla-Mor谩n ; Carmen L贸pez-Goti ; Jos茅 Luis Alonso-Prados ; Pilar S ; 铆n-Espa帽a
• 关键词：Sethoxydim ; Photolysis ; By-products ; Qtof ; Degradation pathway
• 刊名：Science of the Total Environment
• 出版年：15 February, 2014
• 年：2014
• 卷：472
• 期：Complete
• 页码：842-850
• 全文大小：397 K

文摘

The photochemical fate of sethoxydim herbicide in water was studied under simulated sunlight radiation (Suntest apparatus). This compound exhibited a rapid degradation rate in water with a half-life of approximately 1 h, which is in accordance with the high calculated value of the quantum yield (桅 = 0.26). Consequently, the photolysis of sethoxydim should be considered as an efficient route of sethoxydim removal in aqueous media.

During the photodegradation studies, ten by-products were detected, and their identification was accomplished using high-performance liquid chromatography (HPLC) coupled with quadrupole time-of-flight mass spectrometry (Qtof) and electrospray ionization in positive mode (ESI +). A detailed and exhaustive study of the mass spectra of the precursor ions and their MS/MS fragmentation patterns allowed for their identification. The photodegradation products resulted from the cleavage and isomerization of the N<noscript>noscript>O bond of the oxime, oxidation of the sulfur atom, oxidative C<noscript>noscript>S bond cleavage and Beckmann rearrangement followed by intramolecular cyclization.

Additionally, the reactive species involved and a plausible mechanism for the photodegradation of sethoxydim in water are discussed. Finally, based on the identified products, a rational pathway for the photodegradation of sethoxydim in water is proposed.