High-efficient screening of pesticide residues in vegetables using gas chromatography/quadrupole time-of-flight (GC/Q-TOF)

Abstract

Gas chromatography (GC) and liquid chromatography (LC) coupled with a triple quadrupole mass spectrometer using multiple reaction monitoring (MRM) mode is widely used for pesticide residue analysis. However, MRM mode cannot fulfill the requirements of high-throughput or non-target analysis. High-resolution mass spectrometry such as time-of-flight (TOF) with high mass accuracy enables targeted and non-targeted analysis. This study proposes a qualitative screening method using GC/quadrupole time-of-flight (GC/Q-TOF) to monitor vegetable pesticide residues based on the retention time and accurate mass database of the MassHunter Personal Compound Database and Library (PCDL). GC/Q-TOF screening identified 89 of 92 pesticides in 90 vegetable samples, resulting in a true positive rate of 96.7%. These results were in excellent agreement with those obtained from conventional LC-MS/MS and GC-MS/MS methods (Cohen's Kappa = 0.82). Thiamethoxam exhibited the highest detection frequency at 13.75% (mostly below the MRL), with imported radishes showing the highest occurrence. Moreover, unexpected pesticides and metabolites, including cinmethylin, benzyl benzoate, 2,6dichlorobenzamide, diethyltoluamide, and phthalimide, were detected. This proposed method enables qualitative screening of over 1000 pesticides without using expensive analytical standards. Further manual investigation can be conducted to mitigate false-positive results. Overall, this evaluation demonstrates that the combination of GC/Q-TOF with the commercial PCDL database is robust and suitable for pesticide screening in vegetables.