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

To improve the efficiency of high-throughput analysis, a three-dimensional (3D) magnetic FeO-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 FeO-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 MgSO amount, adsorbent amount, purification time. The results revealed that extraction time and FeO-biochar amount had significant influences on the recovery yield of pesticides and the 20 min extraction time and 13.9 mg FeO-biochar are optimal conditions. Under these conditions, the FeO-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 FeO-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. 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 FeO-biochar strategy in analysis of pesticide residues in vegetables containing complex pigments.