The application of QuEChERS coupled to liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) for screening 281 pesticide residues in apples, tomatos, and cabbages has been investigated. The established method includes the extraction by acetonitrile/acetic acid (99:1, v/v), and clean-up by primary secondary amine (PSA) sorbent. The resultant residues were further analyzed by LC-Q-TOF/MS. For apples, tomatos, and cabbages, the percentages of pesticides with the average recoveries (n = 5) in the range of 70%-120% were 98.6%, 99.3%, and 98.2%, respectively; and the relative standard deviations (RSDs) for the recoveries were not more than 20%; in the concentration range of 0.25-10 MRL, the percentages of the pesticides with the correlation coefficients (r2) greater than 0.99 were 95.7%, 96.1%, and 98.2%, respectively; the LODs were 0.03-4.47 microg/kg, 0.01-4.49 microg/kg and 0.02-3.61 microg/kg, respectively. Rapid screening and confirmation can be achieved with accurate mass database and library search without the standard compounds. The method has been applied to 30 fruit and vegetable samples randomly purchased from the local markets, and the 13 pesticides were detected. It was found that the level of methamidophos in one cabbage sample exceeded the MRL regulated by China of GB 2763-2012 and the MRL regulated by European Union (EU), and the level of rotenone in one tomato sample exceeded the MRL regulated by EU.

The performances of gas chromatography-tandem mass spectrometry (GC-MS/MS) and gas chromatography quadrupole time of flight mass spectrometry (GC-QTOF/MS) for the determination of 208 pesticide residues in fruit and vegetable samples, including apple, orange, tomato and cucumber, were compared comprehensively. Based on the differences of the two instruments, their respective characteristics and scopes of application in the detection of the pesticide residues were presented, which provided the reference for the analysis of pesticide residues. The performance parameters of the two instruments, such as overall recoveries, precisions, limits of detection, linear ranges, identification points and matrix effects, were evaluated according to a designed experiment. At three spiked levels (5.0, 10.0 and 20.0 µg/kg), the average recoveries for the majority of pesticides (93.0%) ranged from 70% to 120% in the four matrices with relative standard deviations below 20%. The limits of detection for most of the pesticides by GC-MS/MS and GC-Q-TOF/MS were less than 5.0 µg/kg. Compared with GC-QTOF/MS, GC-MS/MS showed relatively lower limits of detection and wider linear ranges, and its performance was more satisfactory in accurate quantitative analysis due to its superior sensitivity. On the other hand, GC-QTOF/MS provided accurate mass measurement, which was proved to be an efficient analytical tool on the rapid screening and confirmation of a large number of pesticides and non-target compounds.