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

Abstract

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.

Screening and identification strategy for 317 pesticides in fruits and vegetables by liquid chromatography-quadrupole time-of-flight high resolution mass spectrometry

“…First, a tool "nd compounds by targeted MS/MS" was applied that extracted the elution prole of each precursor's product ions in the retention time range of the peak. Based on a satisfactory chromatographic performance of separation, 45,46 all of the 317 pesticides in the solvent were eluted from the column during a 23 minute gradient prole. The reverse search, instead of the forward search, was adopted in order to reduce the interference of extraneous peaks from matrices.…”

“…The SDLs (screening detection limits) and LOIs (limits of identication) were established as the lowest spiked concentration level when the target analyte was detected and identied in all test samples (i.e. 45,46 Meanwhile, the LOIs are also listed in Table S1 † in the selected matrices using the targeted MS/MS mode and MS 2 product-ion spectral library. In this paper, the screening method validation has been conducted by a similar strategy to that reported in our previous work, 46 which is in the line of the suggestion of Diaz et al on validation of a multiclass wide-scope qualitative screening method for organic pollutants in waters.…”

“…Q-TOF/MS with a resolving power of 10 000 or more expressed in terms of FWHM (full peak width at one-half maximum) permits MS/MS analysis and provides accurate masses (possibility to yield mass accuracy of 2 ppm with an adequate calibration range) for both the precursor and product ions, which constitutes a higher order mass identication than those afforded by nominal mass measurements obtained by other types of mass analyzers. 45,46 The database and library have been validated in different matrices, e.g. Accurate mass measurement with Q-TOF/MS gives the elemental composition of parent and product ions, avoiding false positive ndings precisely, used to identify unknown substances and a greater differentiation of isobaric species (two different compounds with the same nominal mass but different elemental composition, and thus, different exact masses).…”