Development of a Suspect Screening Strategy for Pesticide Metabolites in Fruit and Vegetables by UPLC-Q-Tof-MS

A multi-pesticide metabolite screening method using liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-Tof-MS) was developed for the detection of pesticide metabolites in fruit and vegetable samples. Based on a retrospectively created accurate mass compound database, a suspect screening approach was established for pesticides of high concern applied to a wide scope of plant-derived commodities. For each matrix, an individual scope of characteristic pesticides was selected and a scientific library of corresponding metabolites generated. The metabolite database contained a total of 648 pesticide metabolites originating from 58 active compounds. In 500 samples from daily routine analysis, 96 samples with positive detects for a total of 26 pesticides were re-analyzed for the occurrence of corresponding metabolites. Forty-seven different phase-I and phase-II metabolites were identified, respectively. The developed metabolite database can be applied for a suspect screening approach for pesticide metabolites identification in all kinds of fruits and vegetables. By the means of the results of the suspect screening workflow, a targeted screening method by UHPLC-MS/MS was established for individual pesticide metabolites. Positive detects for metabolites may give an unequivocal evidence for an illegal application of plant protection products, even if the active compound is not detectable anymore.