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

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, 2,6-dichlorobenzamide, 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.