A three dimension magnetic bio-char composite-based quick, easy, cheap, effective, rugged and safe method for multi-pesticides analysis of vegetables

Abstract

To improve the efficiency of high-throughput analysis, a three-dimensional (3D) magnetic Fe3O4–biochar composite was synthesized and used as adsorbent of QuEChERS pretreatment method for the analysis of 49 pesticide residues in vegetables containing complex pigments. The structure evolution mechanism of Fe3O4–biochar was discussed and the structural morphology was confirmed by a series of characterization methods. Multivariate approach was employed to optimize the extraction parameters including sample amount, solvent volume, NaCl amount, extraction time, anhydrous MgSO4 amount, adsorbent amount, purification time. The results revealed that extraction time and Fe3O4–biochar amount had significant influences on the recovery yield of pesticides and the 20 min extraction time and 13.9 mg Fe3O4–biochar are optimal conditions. Under these conditions, the Fe3O4–biochar exhibited better cleanup of matrix co-extracts than conventional adsorbents, which reduced matrix effect and simplified extraction process. Moreover, the adsorption mechanism was further probed and turned out that the aromatic sheets on Fe3O4–biochar dominated the π–π EDA (electron donor–acceptor) interaction for interfering substances. The proposed extraction method exhibited good linearity with correlation coefficient greater than 0.9902. The limits of quantitation (LOQs) were in the range of 0.03–0.67 μg kg−1. The average recoveries were between 81.3% and 117.3% with relative standard deviation (intra-day RSD = 0.5–7.5% and inter-day RSD = 0.6–6.9%). All results highlighted the excellent potential of Fe3O4–biochar strategy in analysis of pesticide residues in vegetables containing complex pigments.