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

Abstract

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.