Magnetic metal–organic frameworks-based chitosan hydrogel as adsorbent for the detection of aflatoxins in grains

A magnetic hydrogel beads were synthesized by incorporating Fe 3 O 4 nanoparticles and NH 2 -UiO-66 into low-cost chitosan via acid-dissolved/alkali-solidified self-shaping method conveniently. The combination of NH 2 -UiO-66 with chitosan may enhance the rigidity and adsorption capacity of the composite. The fabricated magnetic NH 2 -UiO-66-chitosan were characterized using scanning electron microscopy, fourier transform-infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, thermal gravimetric analysis, X-ray photoelectron spectroscopy, and N 2 adsorption–desorption experiments.. Combined with high-performance liquid chromatography-fluorescence detector, these hydrogel beads were applied to magnetic solid-phase extraction of four aflatoxins. The maximum adsorption capacity was 18.3 mg/g, and the adsorption mechanism was discussed. The main extraction parameters were optimized, including adsorbent amount, adsorption time, adsorption temperature, pH value, eluent, and desorption time. Under the optimized conditions, the low limits of detection (S/N = 3) were 0.08 ∼ 0.80 μg/kg. The recoveries of spiked grain samples (rice, glutinous rice, wheat, and soybean) were between 70.8 % and 117.0 % with 1.7 ∼ 15.0 % relative standard deviation (n = 5). Therefore, the magnetic NH 2 -UiO-66-chitosan beads are suitable for the determination of aflatoxins in complicated real grain samples.