Magnetic dispersive solid-phase extraction of triazole and triazine pesticides from vegetable samples using a...

Maltodextrin- and β-cyclodextrin-functionalized magnetic graphene oxide (mGO/β-CD/MD), a novel hydrophilic-lipophilic composite, was successfully fabricated and used for the co-extraction of triazines and triazoles from vegetable samples before HPLC-UV analysis. mGO/β-CD/MD was synthesized by chemical bonding of β-CD and MD to the surface of mGO, using epichlorohydrin (ECH) as a linker. The successful synthesis of mGO/β-CD/MD was confirmed by characterization tests, including attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Barrett-Joyner-Halenda (BJH) analyses. The hydrophobic cavity of β-CD and a large number of hydroxyl groups on the MD structure contributed to the co-extraction of mentioned pesticides with a wide range of polarity. Under the optimized condition (sorbent amount, 30 mg; desorption time, 10 min; desorption solvent volume, 300 μL; desorption solvent, methanol/acetonitrile (1:1) containing 5% (v/v) acetic acid; extraction time, 20 min; and pH of sample solution, 7.0), good linearity within the range 1.0-1000 μg L^-1 (r² ≥ 0.992) was achieved. Extraction efficiencies were in the range 66.4-95.3%, and the limits of detection were 0.01-0.08 μg L^-1. Relative recoveries for spiked samples were obtained in the range 88.4-112.0%, indicating that the matrix effect was insignificant, and good precisions (intra- and inter-day) were also achieved (RSDs < 9.0%, n = 3). The results confirmed that the developed method was efficient for the determination  of trace amounts of pesticides in potato, tomato, and corn samples.