Performance and matrix effect observed in QuEChERS extraction and tandem mass spectrometry analyses of pesticide residues in different target crops

The method performance and matrix effect related to quantitative determination of pesticide residues was assessed after QuEChERS extraction and LC-MS-MS analysis. Dicloran, phosmet and phosmet-oxon, pirimiphos-methyl, and BNOA were analyzed in peach, apple, melon, cereals, tomato, and strawberry. The matrix effects, as well as recovery and process efficiencies, were determined for a fungicide, two insecticides, and a plant growth regulator. Crop samples were spiked either pre- or post-extraction, then the peak area was compared with the peak area in neat solvent. The mean recovery ranged from 73% to 98%, and repeatability (as RSD) was between 3% and 16%, depending on the compound and spiking level. The matrix effect occurred as ionic suppression and was found in the range of 5% to 22% depending on the compound. Recovery efficiencies were good and substantially comparable, being in the range of 93-96%. Although the suppression observed still appears to be acceptable considering the overall process efficiency, it seems evident that the matrix effect is important when a reliable quantitative method must be applied.