A three dimension magnetic bio-char composite-based quick, easy, cheap, effective, rugged and safe method for...

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.