Rapid screening and confirmation of 281 pesticide residues in apples,tomatos and cabbages by liquid chromatography/quadrupole time-of-flight mass spectrometry

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.