Preparation And Monitoring Application Of Tetracyclines Multi-template Molecularly Imprinted Magnetic Composite

The abuse of tetracyclines has resulted in the presence of tetracycline antibiotic in environmental waters,which poses a certain threat to ecological environment safety and human health.Because the content of tetracyclines in environmental water is extremely low with complex matrices,sample separation and enrichment is required before instrumental analysis.In this work,tetracyclines multi-template molecularly imprinted magnetic composite with good adsorption performance and adsorption selectivity,was synthesized by sol-gel method and surface molecular imprinting technology,using tetracycline,oxytetracycline,chlortetracycline and doxycycline as template molecules,N-[3-?trimethoxysilyl?propyl]ethylenediamine?KH-792?and anilinomethyltriethoxysilane?KH-42?as dual-functional monomers,and mesoporous silicon coated magnetic graphene as carrier.The composite was then used as the adsorbent for magnetic solid phase extraction of tetracyclines,and combined with high performance liquid chromatography,for trace detection of tetracycline,oxytetracycline,chlortetracycline and doxycycline in environmental water samples.The main research contents are as follows:1.A novel tetracyclines multi-template molecularly imprinted magnetic composite was prepared by using mesoporous silicon coated magnetic graphene oxide as the carrier,tetracycline,oxytetracycline,chlortetracycline,and doxycycline as the template molecules and KH-792 and KH-42 as the functional monomers.Fourier transform infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,fully automatic specific surface area analyzer,vibration magnetometer,X-ray diffraction,and thermogravimetric analyzer were used to characterize the materials synthesized at each stage.2.The adsorption properties of tetracyclines multi-template molecularly imprinted magnetic composite were evaluated.The results of adsorption kinetics showed that the adsorption equilibrium time was 60 min,and the kinetics followed a quasi-second-order kinetic model.The adsorption capacity for tetracycline,oxytetracycline,chlortetracycline,and doxycycline after reaching adsorption equilibrium were 5.89?5.66?19.54 and 11.89 mg g^-1,respectively.The results of the adsorption isotherm investigation showed that the adsorption capacity increased with the increase of temperature and initial concentration,and the fitting data followed the Fueundlich model,which indicated that the adsorption sites were heterogeneous and multi-layered.The adsorption thermodynamics results indicated that adsorption was a spontaneous endothermic process.Results also showed that the imprinted material has good selective adsorption performance,the relative selectivity coefficients of tetracycline,oxytetracycline,chlortetracycline and doxycycline to metoxytetracycline were:5.54,7.88,13.32,4.81,and the relative selectivity coefficients to ciprofloxacin were:9.36,13.32,16.92,8.14,respectively.After five adsorption-elution cycles,the adsorption capacity of MIP for OTC,TC,CTC and DC decreased by 4.5%,5.2%,10%and 6.5%,respectively,the imprinted material had good recycling performance.3.Using the synthesized tetracyclines multi-template molecularly imprinted magnetic composite as solid phase extraction?SPE?sorbent,and combining high performance liquid chromatography?HPLC?,a new method for the determination of trace tetracycline,oxytetracycline,chlortetracycline and doxycycline in environmental water samples was established.The effects of p H,water volume,extraction time,eluent volume,and elution time on the recovery of solid phase extraction were investigated.The optimal extraction conditions were obtained.The analytical performance of the SPE-HPLC method was evaluated.The results show that the linear range of this method for tetracycline,oxytetracycline,chlortetracycline and doxycycline was 5-50?g L^-1,the detection limit of tetracycline,oxytetracycline,chlortetracycline and doxycycline by this method was 0.74,0.67,0.92,0.95?g L^-1,and the limit of quantification was 2.37,2.13,3.31,3.50?g L^-1,respectively.The proposed method was applied to the analysis of river water,lake water,and pond water samples.The spiked recoveries were between 82.7-103.3%and the relative standard deviation?RSD?was between 1.0-8.8%.In conclusion,the synthesized molecularly imprinted magnetic composite has good adsorption performance and adsorption selectivity towards tetracycline antibiotic.The developed analytical method for detection of tetracycline antibiotics in environmental water samples has the advantages such as low detection limit,high accuracy,good reproducibility and simple operation,which is suitable for the separation,enrichment and detection of tetracyclines in actual water samples.