Carbon-based Fe₃O₄ nanocomposites (C/Fe₃O₄ NCs) were synthesized by a simple one-step hydrothermal method using waste pomelo peels as the carbon precursors. The characterization results showed that they had good structures and physicochemical properties. The prepared C/Fe₃O₄ NCs could be applied as excellent and recyclable adsorbents for magnetic solid phase extraction (MSPE) of 11 triazole fungicides in fruit samples. In the MSPE procedure, several parameters including the amount of adsorbents, extraction time, the type and volume of desorption solvent, and desorption time were optimized in detail. Under the optimized conditions, the good linearity (R² > 0.9916), the limits of detection (LOD), and quantification (LOQ) were obtained in the range of 1–100, 0.12–0.55, and 0.39–1.85 μg/kg for 11 pesticides, respectively. Lastly, the proposed MSPE method was successfully applied to analyze triazole fungicides in real apple, pear, orange, peach, and banana samples with recoveries in the range of 82.1% to 109.9% and relative standard deviations (RSDs) below 8.4%. Therefore, the C/Fe₃O₄ NCs based MSPE method has a great potential for isolating and pre-concentrating trace levels of triazole fungicides in fruits.

We report the synthesis of mesoporous alumina by a template method and its applications as a new solid phase extraction adsorbent with abamectin and ivermectin as the target analytes by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Chromatographic separation was conducted on a C₁₈ column using a gradient mobile phase consisting of methanol (solvent A) and 0.2% formic acid in a 5 mmol L⁻¹ ammonium acetate buffer (solvent B) at a flow rate of 0.3 mL min⁻¹. The linearity of the calibration curves was excellent and yielded correlation coefficients (r² = 0.9990–0.9999) in a range of 0.02–0.50 mg L⁻¹. Samples were spiked with known quantities of the analytes at three different concentration levels (0.05, 0.10 and 0.20 mg L⁻¹), and the recoveries were in the range of 87.3–104.5% with the relative standard deviation (RSD) values ranging between 0.53% and 5.8%. The limits of detections and limits of quantization were 0.16 ng g⁻¹ and 0.53 ng g⁻¹, respectively. These results indicated that mesoporous alumina has enormous potential as a novel solid phase extraction adsorbent material in the food security field.