Y. Lassalle, E. Nicol, C. Genty, S. Bourcier, S. Bouchonnet
Rapid Commun. Mass Spectrom. 29 (14) 1335 (2015). DOI

Travail réalisé sur le site de l’Ecole Polytechnique.

Abstract

"RATIONALE : Fenbuconazole is a fungicide commonly used for the protection of vineyards, vegetables and grain crops. Under UV-visible irradiation, it undergoes isomerization through various cyclization processes. Isomeric structures were elucidated by liquid chromatography/high-resolution multiple-stage mass spectrometry (LC/HR-MSn) coupling. The potential toxicities of these isomers were estimated by in silico tests.

METHODS : Aqueous solutions of fenbuconazole and grapes treated with this fungicide were irradiated in a self-made reactor equipped with a mercury vapor lamp. Analyses were carried out using high-performance liquid chromatography (HPLC) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS). High-resolution m/z measurements, multiple-stage mass spectrometry and isotopic labeling experiments allowed structural elucidation of the isomers of fenbuconazole. In silico toxicity estimations were carried out using the T.E.S.T. program.

RESULTS : Seven isomers of fenbuconazole were detected after irradiation of the fungicide in aqueous solution ; the major ones were also detected in the flesh of treated grapes irradiated under laboratory conditions. Elucidation of their chemical structures owing to high resolution measurements and multi-stage collision induced dissociation experiments allowed confirmation of photo-transformation pathways mainly dominated by cyclization processes. Photo-induced isomers exhibited higher potential toxicities than fenbuconazole for Daphnia magna and fathead min now species.

CONCLUSIONS : UV-visible irradiation of fenbuconazole in aqueous solution and on grapes leads to the formation of isomers, all of which being potentially much more toxic than the parent fungicide. "