Non-Targeted Screening and Quantitative Analysis of Pesticides and Veterinary Drug Residues in Brassica rapa chinensis Using an Improved Quechers Method Based on Magnetic Materials

An improved QuEChERS method based on magnetic nanomaterials was established, and coupled with ultra-high-performance liquid chromatography and a quadrupole electrostatic field orbitrap mass spectrometer, enabling non-targeted screening and quantitative analysis of commonly used pesticide and veterinary drug residues in <i>Brassica rapa chinensis</i>. The combination of magnetic PSA and magnetic multi-walled carbon nanotubes (MWCNTs) was utilized for purification of 121 organic compounds spanning a wide range of polarities. Spiking experiments showed that the developed non-target screening workflow exhibited convincing identification results, with over 89.3% of chemical substances being screened out even at spiking levels as low as 2 μg/kg. The linear ranges of these target substances were between 1 and 200 μg/kg, with determination coefficients all exceeding 0.99. The limits of quantification were between 2 μg/kg and 10 μg/kg. The average recovery rates were in the range of 61.7% to 121.6%. Nineteen compounds were confirmed (meeting all the restriction conditions) and quantified from <i>Brassica rapa chinensis</i> collected from vegetable-planting bases in Jiangsu Province. The results indicated that the magnetic bead-based pretreatment strategy can be utilized for the simultaneous screening and quantitative analysis of pesticide and veterinary drug residues in <i>Brassica rapa chinensis</i>.