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Cyprodinil is a fungicide active on grapes, strawberries, tomatoes, and many other fruits. Under UV-visible irradiation, it undergoes photodegradation through various processes to form transformation products (TPs) whose structures and potential toxicities are unknown. The structures of the TPs were elucidated by comparing the photodegradation of cyprodinil and cyprodinil-D5 . The potential toxicities of these compounds were compared with that of cyprodinil.Aqueous solutions of cyprodinil were irradiated in a reactor equipped with a mercury vapor lamp. Analyses were carried out using high-performance liquid chromatography coupled to a quadrupole time-of-flight (QTOF) mass spectrometer or to a SolarixXR 9.4 Tesla Fourier transform (FT) mass spectrometer. High-resolution mass measurements, MS/MS and isotopic labeling experiments allowed structural elucidation of the cyprodinil TPs. The toxicities were estimated by three tests in silico using the TEST software and in vitro bioassays using Vibrio fischeri bacteria. These bioassays were carried out on irradiated solution for several exposure times and non-irradiated solutions.The structures of 19 photoproducts were characterized by LC/HRMS/MS after 4 h of irradiation of a cyprodinil aqueous solution. The use of cyprodinil-D5 allowed the TPs to be characterized with more confidence. Knowing the structure of the TPs allows the estimation of their potential toxicities by in silico tests. Most of the photoproducts are potentially more toxic than the parent compound, based on the oral rat LD50 values, and most of them might induce more developmental and mutagenic toxicities. In vitro assays on Vibrio fischeri bacteria showed that the global ecotoxicity of the cyprodinil solution significantly increases with irradiation time.Structures of photoproducts were characterized after irradiation of a cyprodinil aqueous solution combining LC/HRMS, LC/HRMS/MS and the use of a labeled compound. Their formations imply several photodegradation reactions, namely direct bond cleavages, cyclization, isomerization and hydroxylation. Most of the TPs exhibit a toxicity significantly higher than that of the parent molecule. Copyright © 2016 John WileySons, Ltd.

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-MS(n) ) coupling. The potential toxicities of these isomers were estimated by in silico tests.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.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 minnow species.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.