| Sample pretreatment plays a significant role in the determination of tetracycline residues in food by chromatography.It is important to study new adsorption materials with low cost,environmental friendliness,high adsorption efficiency and easy separation for simplifying the pretreatment procedure,improving the efficiency of pretreatment and the sensitivity of detection.In this study,two types of tetracycline-imprinted biochar composites microspheres with high adsorption efficiency and selective adsorption capacity were synthesized by Pickering emulsion polymerization combined with molecular imprinting technology.The solid phase extraction?SPE?-high performance liquid chromatography?HPLC?and magnetic solid phase extraction?MSPE?-HPLC pre-treatment were established using the two synthetic materials as adsorbent for the detection of tetracyclines residues in tap water,chicken and fish samples.The main results are as follows:?1?A stable water-in-oil Pickering emulsion was prepared by using biochar as stabilizer,and then tetracycline?TC?as template molecule,methacrylic acid as functional monomer,divinylbenzene as crosslinker,azodiisobutyronitrile as initiator and toluene as poregen for the preparation of TC-imprinted biochar microspheres in the biochar-based emulsion.The particle size of biochar composites microspheres could be adjusted by regulating water-oil ratio and biochar addition amounts.The morphology,structure and stability of the materials were characterized by scanning electron microscopy,Fourier transform infrared spectroscopy and thermogravimetric analysis.The adsorption properties of the synthetic materials were studied and analyzed by adsorption kinetic test,isothermal adsorption test,selective test and competitive test.As a result,the synthesized material was a well-structured spherical structure with good thermal stability and selective adsorption ability to tetracycline.The imprinting factor is 1.46 and the selectivity coefficient to other compounds is 1.82?82.00.Further,a method for detecting trace residues of two kinds of tetracyclines veterinary drugs in tap water,fish and chicken samples was established by using the synthesized imprinted biochar microspheres as the filler of solid phase extraction column combined with high performance liquid chromatography analysis.The established method has good linear relationship in the range of 0.1?1.0 mg/L,and the detection limit is 3.51?g/L.The spiked recovery of two tetracyclines in water,chicken and fish samples was 73.35%?94.84%,and the RSD was0.28?8.36%.A novel and efficient biochar adsorption material was introduced for trace pollutant residue detection in food.?2?Magnetic response imprinted biochar microspheres were prepared by using biochar and Fe3O4 nanoparticles as co-stabilizer for Pickering emulsion,TC as template molecule,methacrylic acid as functional monomer,and divinylbenzene as crosslinker and azodiisobutyronitrile as initiator.The morphology,structure,magnetic properties and stability of the synthesized materials were characterized by scanning electron microscopy,nitrogen adsorption desorption,fourier transform infrared spectroscopy,X ray diffraction and thermogravimetric analysis.The adsorption properties of the materials were studied and analyzed by adsorption kinetic test,isothermal adsorption test,selective test and competitive test.The as-prepared materials have good adsorption properties?maximum adsorption of tetracycline is 11.68 mg/g?,specific adsorption ability to target molecules?imprinting factor is 3.66?and good magnetic separation properties.Futher,the magnetic the TC-imprinted biochar composites mircrospheres were applied for MSPE,and a method for the detection of two tetracycline residues in tap water,chicken and fish samples was established by MSPE coupled to HPLC.Under the optimal conditions,the three samples spiked with two tetracyclines at three leves,the results showed that recovery range from 90.57%to 103.39%and the RSD range from 1.23%to 9.99%. |
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