Preparation of double-network hydrogel consisting of chitosan, cellulose and polyacrylamide for enrichment of tetracyclines

A double-network hydrogel was prepared with the chitosan-cellulose composite as the rigid network and polyacrylamide as the flexible network (abbreviated as CCP hydrogel). A deep eutectic solvent synthesized by choline chloride and malic acid was used as the assistant solvent to dissolve cellulose for preparation of the CCP hydrogel. The obtained CCP hydrogel was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and stress-strain test. The properties of the CCP hydrogel are obviously better than those of the single network hydrogel. The compressive strength of CCP hydrogel is 2.8 times that of the chitosan-cellulose single network hydrogel. The CCP hydrogel exhibits the favorable swelling performance (swelling ratio of 955 %-1377 %), water-locking ability (water retention value of 40 %), and stability in aqueous system. Moreover, the CCP hydrogel performs the excellent adsorption capacity, fast adsorption efficiency, and good selective towards tetracyclines. The effects of temperature and solution pH on the adsorption properties of CCP hydrogel were assessed. The Langmuir, Freundlich, pseudo-first-order, pseudo-second-order, and thermodynamic models were applied to explore the adsorption characteristics of CCP hydrogel. After multiple adsorption/desorption cycles, the CCP hydrogel still maintains 84.3 %-93.4 % of adsorption capacity. Finally, the CCP hydrogel combined with ultra-performance liquid chromatography-mass spectrometry were used to analyze tetracyclines in food samples. The tetracycline (0.14 mu g/mL) and minocycline (0.080 mu g/mL) in milk, tetracycline (0.082 mu g/mL) and minocycline (0.089 mu g/mL) in fish, and tetracycline (0.078 mu g/mL) and demeclocycline (0.10 mu g/mL) in chicken were detected by CCP-hydrogel method with a high accuracy (recoveries of 75.82 %-108.8 %). Furthermore, for comparison with the CCP-hydrogel method, the traditional precipitation method was also applied to detect the tetracyclines in foods. The CCP-hydrogel method possesses a higher accuracy than traditional method, and can more accurately and satisfactorily detect tetracyclines in foods.