| Summary: | A method for the simultaneous screening of 258 pesticide residues in silage using modified QuEChERS combined with liquid chromatography (LC)- and gas chromatography (GC)- quadrupole-Orbitrap mass spectrometry (Q-Orbitrap/MS) has been developed. After hydration, the silage was homogenized with a 1% acetic acid–acetonitrile solution, and the extract was purified using C<sub>18</sub>, PSA, and anhydrous magnesium sulfate. Finally, the sample was detected using LC/GC-Q-Orbitrap/MS, and quantified using an external standard method. The results showed that 258 pesticides had an excellent linear relationship in the range of 0.1–50 μg L<sup>−1</sup>, and that the coefficients of determination (R<sup>2</sup>) were more than 0.99. The screening detection limit (SDL) of silage was in the range of 0.5–50 μg kg<sup>−1</sup>, and the limit of quantitation (LOQ) was in the range of 1–50 μg kg<sup>−1</sup>. The accuracy and precision of the method were verified at the spiked levels of 1-, 2- and 10-times LOQ, and the recovery of 258 pesticides was in the range of 66.5–119.8%, with relative standard deviations (RSDs) of less than 20% (<i>n</i> = 6). This method was simple, rapid, and reliable, and could be applied to screen and quantify multi-pesticide residues in silage.
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