Dissipation studies of famoxadone in vegetables under greenhouse conditions using liquid chromatography coupled to high resolution mass spectrometry: putative elucidation of a new metabolite

BACKGROUND: Famoxadone is a pesticide that is used to control fungal diseases and its dissipation in vegetables should be monitored. For that purpose, liquid chromatography coupled to mass spectrometry has been used. RESULTS: The dissipation of famoxadone has been monitored in cucumber, cherry tomato and courgette under greenhouse conditions at different doses (single and double), using ultra high‐performance liquid chromatography coupled to Orbitrap mass spectrometry (Thermo Fisher Scientific, Bremen, Germany). The concentration of famoxadone increased slightly just after the application of the commercial product and then decreased. The half‐lives (DT₅₀) of famoxadone are different for each matrix, ranging from 2 days (courgette single dose) to 10 days (cucumber double dose). The main metabolites, 4‐phenoxybenzoic acid and 1‐acetyl‐2‐phenylhydrazine, were not detected in vegetable samples. Other metabolites described by the European Food and Safety Authority, such as IN‐JS940 [(2RS)‐2‐hydroxy‐2‐(4‐phenoxyphenyl)propanoic acid], IN‐KF015 [(5RS)‐5‐methyl‐5‐(4‐phenoxyphenyl)‐1,3‐oxazolidine‐2,4‐dione] and IN‐MN467 [(5RS)‐5‐methyl‐3‐[(2‐nitrophenyl)amino]‐5‐(4‐phenoxyphenyl)‐1,3‐oxazolidine‐2,4‐dione], were detected in the three matrices. Untargeted analysis allowed for the putative elucidation of a new metabolite of famoxadone in cucumber (up to 290 μg kg⁻¹) and cherry tomato (up to 900 μg kg⁻¹) samples. CONCLUSION: The dissipation of famoxadone has been investigated in three vegetables: tomato, cucumber and courgette. The persistence of famoxadone was low in the three matrices (DT₅₀ less than 10 days). Metabolites of famoxadone were monitored, detecting IN‐JS940, IN‐MN467 and IN‐KF015, and the putative elucidation of a new metabolite of famoxadone was performed by applying software tools. © 2019 Society of Chemical Industry