High‐performance liquid chromatographic/tandem mass spectrometric identification of the phototransformation products of tebuconazole on titanium dioxide

Abstract

Tebuconazole is a widely used fungicide. The formation of by-products on irradiated titanium dioxide as a photocatalyst was evaluated. Several species derived from tebuconazole degradation were identified and characterized by HPLC/MS(n). A pattern of reactions accounting for the observed intermediates is proposed. Different parallel pathways are operating (and through these pathways the transformation of the molecule proceeds), leading to a wide range of intermediate compounds. All these molecules are more hydrophylic than tebuconazole. The main steps involved are (1) the hydroxylation of the molecule with the formation of three species having [M + H](+) 324; the hydroxylation occurs on the C-1 carbon and on the aromatic ring in the two ortho-positions; (2) the cleavage of a C--C bond with the release of the tert-butyl moiety and the formation of a species having m/z 250; analogously to step 1, also on this species a further hydroxylation reaction occurs; (3) through the loss of the triazole moiety with the formation of a structure with m/z 257.

Photocatalytic degradation kinetics and mechanisms of fungicide tebuconazole in aqueous TiO2 suspensions

“…As minor studies [10,11] are available in open literature on TEB photocatalytic degradation using TiO 2 , the present work focuses on the detailed kinetic and mechanistic investigation of TEB in water using suspended TiO 2 under simulated solar light.…”

Degradação fotocatalítica do fungicida tebuconazole em solução aquosa

“…Ao final de 5 h de reação alcançou-se uma conversão maior que 90% do reagente. Apesar de a degradação desta molécula ocorrer através de três rotas paralelas, envolvendo um grande número de intermediários, 3 ao tér-mino do ensaio nenhum deles foi detectado, comprovando a eficácia do processo para a purificação deste tipo de efluente, como pode ser visto na Figura 3.…”

“…1,2 Dentre estes contaminantes encontra-se o tebuconazole, um fungicida amplamente usado na agricultura, principalmente de cereais. 3 Este fungicida pode causar danos à saúde humana, podendo provocar irritação cutânea, ocular e respiratória; além de ser tóxico a micro-organismos aquáticos, algas e peixes. 4 Foram encontrados na literatura alguns trabalhos sobre a degradação fotocatalítica de fungicidas, 5,6 mas, especificamente sobre a degradação fotocatalítica do tebuconazole, as referências são escassas.…”

“…4 Foram encontrados na literatura alguns trabalhos sobre a degradação fotocatalítica de fungicidas, 5,6 mas, especificamente sobre a degradação fotocatalítica do tebuconazole, as referências são escassas. Calza et al 3 realizaram um estudo visando identificar os produtos e os intermediários formados durante a degradação fotocatalítica do tebuconazole em presença de dióxido de titânio. Concluíram que o tebuconazole é degradado por meio de três rotas diferentes, levando à formação de diversos intermediários, todos eles mais hidrofílicos que o composto original.…”

Tubular Titania Nanostructures via Layer‐by‐Layer Self‐Assembly

“…The MO dye, which is very stable and difficult to degrade under normal conditions, can be eventually photodegraded into non-polluting inorganic species such as SO 4 2-, NO 3 -, NH 4 + , CO 2 and water under specific photocatalysts. [38] In this test, 30 mg of as-prepared titania tubes was dispersed in 20 mL 0.012 mM MO solution in a quartz cell. The reaction system was kept saturated with oxygen by a slow stream of oxygen purge and irradiated by a 254 nm UV lamp at room temperature under stirring.…”