One-step fabrication of alkali–acid modified three-dimensional magnetic biochar for the determination of pesticides in pigment-rich vegetables

Abstract

Magnetic biochar was successfully synthesized via a one-step method through simultaneous activation and magnetization with alkali–acid modified citrus peel as the raw material, which could effectively penetrate interfering substances. The characterization analysis showed that the magnetic biochar exhibited high graphitic degree, higher specific surface area and smaller pore diameter, which resulted in superior adsorption performance. The magnetic biochar was used as an adsorbent for the cleanup and extraction of 22 pesticides (consisting of insecticides, fungicides and herbicides) from vegetables and the quantitative detection was completed by gas chromatography-mass spectrometry (GC-MS). The Plackett–Burman experimental design (PBD), central composite design (CCD) and response surface methodology (RSM) were employed to identify significant factors and optimal experimental conditions. Under optimal conditions, the methodological linearity was in the range of 1–100 μg kg⁻¹ with the coefficients of determination ranging from 0.9969–0.9999, while the limits of detection (LODs) and limits of quantification (LOQs) were 0.31–0.91 μg kg⁻¹ and 1.03–3.05 μg kg⁻¹, respectively. The recoveries of the analytes from spiked samples were in the range of 78.1–112.5%. It was confirmed that the method established by using magnetic graphitic biochar as the adsorbent is an efficient pretreatment procedure and could be successfully applied for analysis of food safety.