Can occurrence of pesticide metabolites detected in crops provide the evidence on illegal practices in organic farming?

Modern pesticides rapidly degrade after their application due to both physicochemical factors and through biotransformation. Consequently, pesticide residues in samples might be either undetectable or detected at low concentrations (≤10 μg/kg). Under such conditions, a monitoring of pesticide metabolites in samples might be a conceivable solution enabling the documentation of earlier pesticide use. Analysis of metabolites might pose analytical challenges because pesticide degradation leads to the production of a number of metabolites, differing somewhat in their structure and polarity. This study was focused on the determination of pesticide residues and their metabolites in samples of grapevine and wine using ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry, with the objective of supporting the possibility of the verification of the method of farming. It documents the identification of pesticide metabolites commonly used in conventional farming and provides a characterization of pesticide degradation during grapevine growth, maturation, and during the wine-making process.