Application Of Adsorption/Extraction Technologe Based On Functional Graphene In The Analysis Of Antibiotic Residues

Antibiotics are a kind of drugs which are used in the treatment of bacterial infection diseases and promoting animals' growth.They have been widely applied in the producing and living since discovered for the first time.However,antibiotics have been persistently remained in environmental and food due to their long-term irrational use,which as "emerging contaminant" poses a serious threat to the ecological environment and human health.Solid phase extraction(SPE)is one of the most widely used technologies for complex matrix pretreatment due to its advantages of high efficiency,simplicity,time-saving,low organic solvent consumption and easy to automation.Adsorption has been one of the most effective methods for the removal of organic pollutants in water environment owing to its high efficiency,facile operations and low energy consumption.Among them,the adsorbent material is the key to determine the efficiency of solid phase extraction and adsorption.In recent years,graphene and its functional materials have attracted much attention as a promising adsorbent for detecting and removing of antibiotics in environment and food because of its large specific surface area and rich electronic two-dimensional aromatic structure.Based on the above points and the review of previous studies,this thesis designed and synthesized three functional graphene materials which possess high adsorption performance.Two of them were used as the adsorbents of magnetic solid phase extraction and self-assembly pipette-tip solid phase extraction for determination of antibiotic residues in the products of animal origins,and other one as the adsorbent material was applied for the efficient removal of chlortetracycline from aqueous solution.The main contents are as follows:(1)A novel magnetic metal-organic framework/graphene oxide(Fe3O4/MIL-100(Fe)/GO)material was synthesized and employed as magnetic solid phase extraction(MSPE)adsorbent for the extraction of enrofloxacin from milk sample.The Fe3O4/MIL-100(Fe)/GO nanocomposite was fabricated by simple and facile one-step HF-free hydrothermal method and characterized by scanning electron microscopy(SEM),FT-IR,X-ray diffraction(XRD)and vibration sample magnetometer(VSM).The parameters affecting extraction efficiency including sample pH,amount of sorbent,adsorption time and acidity of elution solvents were optimized in detail.The optimal extraction conditions were as follows:100.0 mL sample at pH of 8.0,20.0 mg of Fe3O4/MIL-100(Fe)/GO as sorbent,extraction time 30 min and 4.00 mL of 15%(v/v)formic acid in methanol as eluent.Good linear relationship(10.00-350.00 ?g L-1)between the fluorescence intensity and the concentrations of enrofloxacin was obtained with correlation coefficient(r)= 0.9979.The limit of detection was 0.65 ?g L-1(S/N=3)and the relative standard deviations of intraday and interday analysis were 1.6 and 2.8%,respectively.The proposed method was applied for the determination of enrofloxacin in milk sample with recoveries ranged from 85.7 to 106.3%.(2)The miniaturization of pipette-tip solid phase extraction(PT-SPE)based on graphene oxide/polypyrrole(GO/PPy)foam material coupled with high performance liquid chromatography was developed for the determination of seven SAs in honey and milk.Parameters that affected extraction efficiency including amount of the GO/PPy,sample pH,rotation speed and elution solvent and volume were optimized in detail.Under the optimal conditions,good linearity(0.01-10.00 mg L-1)between the peak areas and the concentrations of the analytes was obtained with correlation coefficients(r)? 0.9996.The limits of detections(LODs,S/N=3)and limits of quantification(LOQs,S/N=10)were less than 1.50 ?g L-1 and 5.05 ?g L-1,respectively.The relative standard deviations(RSDs)of intra-and inter-day analysis were less than 1.1 and 2.6%,respectively.The proposed method was applied for the analysis of SAs in honey and milk with acceptable recoveries 62.3-109.0%and 66.6-106.9%.The RSDs were less than 10.7%and 10.8%,respectively.The results indicate that GO/PPy is an efficient and promising adsorbent for SAs.The developed PT-SPE-HPLC method is convenient,time-saving,low cost and reduced consumption of adsorbent and reagent,which could be applied to detect SAs in complex matrix.(3)Graphene oxide/titanium dioxide(GO/TiO2)nanocomposite was synthesized via in situ hydrolysis of tetra-n-butyl titanate(Ti(BuO)4)to TiO2 particles on GO sheets and used as adsorbent for efficient adsorptive removal of chlorotetracycline(CTC)from aqueous solution.The obtained GO/TiO2 was systematically characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),Fourier transformed infrared(FT-IR),Raman spectroscopy and X-ray photoelectron(XPS).Adsorption kinetics,isotherms and thermodynamics were systematically investigated to evaluate the adsorption properties of GO/TiO2 and adsorption mechanism was further analyzed by FT-IR,UV-Vis and XPS.The results indicated that adsorption kinetics closely followed the pseudo-second order model.The maximum adsorption capacity determined by Langmuir model was 261.10 mg/g at 298K.The thermodynamic studies revealed that the adsorption of CTC onto the GO/TiO2 was an spontaneous and endothermic process.Moreover,the interactions between CTC and GO/TiO2 were presumed to be ligand exchange,?-? electron donor-acceptor interaction,hydrogen bond and cation-? bonding between CTC and GO.Finally,the GO/TiO2 was applied for the efficient removal CTC from Wu River water.