Development and validation of a modified QuEChERS method based on magnetic zirconium dioxide microspheres for the determination of 52 pesticides in oil crops by gas chromatography tandem mass spectrometry

Abstract

The residue analysis of pesticides in high-fat oil crops is a challenging task because of the high amount of lipid co-extracts, which could seriously affect the extraction efficiency and the performance of instruments. In this study, a modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method based on magnetic mesoporous ZrO₂ microspheres (m-ZrO₂@Fe₃O₄) and n-octadecylphosphonic acid modified magnetic microspheres (Fe₃O₄-OPA) was established for the determination of 52 pesticides in oil crops by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). The ability of m-ZrO₂@Fe₃O₄ to remove fatty acids from acetonitrile extracts of oil crops has been evaluated. The results indicated that m-ZrO₂@Fe₃O₄ showed better performance in the removal of fatty acids than that of PSA, a commonly used sorbent to remove acidic co-extracts in the QuEChERS method. The parameters affecting the cleanup performance including the amounts of m-ZrO₂@Fe₃O₄ and Fe₃O₄-OPA were also investigated. Under optimal conditions, the method was validated in four kinds of oil crops (peanuts, rapeseed, soybean and sesame) by GC-MS/MS. The linear correlation coefficients (R²) of all four oil crops were higher than 0.9904. The limits of detection (LODs) were found to be in the range of 0.1–4.1 μg kg⁻¹. The average recoveries of all analytes ranged from 69.1% to 120.0% (except p,p′-DDE, p,p′-DDD, o,p′-DDT and p,p′-DDT) with the intra-day and inter-day relative standard deviations (RSDs) less than 14.7% and 14.9%, respectively.