Looking beyond the Active Substance: Comprehensive Dissipation Study of Myclobutanil-Based Plant Protection Products in Tomatoes and Grapes Using Chromatographic Techniques Coupled to High-Resolution Mass Spectrometry

A comprehensive
evaluation of the dissipation of a myclobutanil
plant protection product was performed in tomato and grape samples.
Different temperature conditions (3 and 22 °C) were evaluated.
A biphasic kinetic model provided a suitable adjustment (R2 > 0.95), with persistence (residual level, RL50) lower than 24 days in all cases. Solid–liquid extraction
and ultra-high-performance liquid chromatography coupled to high-resolution
mass spectrometry (UHPLC-Q-Orbitrap-HRMS) were used for metabolites’
elucidation, identifying six myclobutanil metabolites, four out of
them described for the first time and one of them confirmed using 1H, 13C, (1H-1H)-COSY, (1H-13C)-HMQC, and (1H-13C)-HMBC
nuclear magnetic resonance (NMR). Their degradation curves were also
evaluated, increasing their concentrations when the myclobutanil concentration
decreases. Additionally, coformulants present in the commercial formulation
were monitored employing headspace solid-phase microextraction method
(HS-SPME)-gas chromatography coupled to HRMS (GC-Q-Orbitrap-HRMS).
Seven coformulants were quantified in tomato samples. Their dissipation
curves were studied, and it was observed that they were almost degraded
12 days after application.