Preparation Of Magnetic Graphene Oxide Nanocomposites And Its Application In Food Safety Detection

Food safety is related to the national economy and people's livelihood.In recent years,due to the frequent occurrence of food safety accidents,people pay particular attention to food safety.Therefore,it is very necessary to carry out food safety detection.The focus of food safety detection is to determine the toxic and harmful substances contained in food,so it is of great significance to develop a simple,rapid and accurate method for food safety detection.Due to the complexity of food components and the low concentration of toxic and harmful substances,the process of separation and enrichment is necessary before the determination.Magnetic solid phase extraction(MSPE)has attracted wide attention of researchers because of its simple operation,short separation time and high extraction efficiency.Among the many factors affecting magnetic solid phase extraction,the type of magnetic solid phase extractant is one of the key factors.Magnetic graphene oxide nanocomposites have the advantages of both graphene oxide and magnetic materials,that is,good dispersibility in aqueous solution,large specific surface area and good magnetic separation performance.In this paper,a series of magnetic graphene oxide nanocomposites were prepared and applied to food safety detection.The contents of the study are as follows:1.A method for magnetic solid phase extraction of pesticide linuron with magnetic graphene oxide nanocomposites(Fe3O4@SiO2-GO)coupled with high performance liquid chromatography(HPLC)was established.Fe3O4@SiO2-GO was characterized by SEM,TEM,FTIR and so on.The factors affecting the extraction efficiency and elution efficiency were studied(the dosage of extractant,pH,extraction time,type of eluent and elution volume,etc).Under the optimum conditions,the linear range was 0.008-0.120 ?g mL-1,the detection limit(LOD)was 0.001g mL-1 the correlation coefficient(R2)was 0.9993,the relative standard deviation(RSD)was 1.9%(c=0.020 ?g mL-1,n=3)and the enrichment factor was 14.The method has been applied to the llysis of linuron in fruits,vegetables and water samples with recoveries of between 90.5%and 105.0%,and the results were satisfactory.Moreover,the adsorption isotherm model was studied,and the Langmuir model was more suitable to describe the adsorption process.2.A method for the separation and analysis of dye sunset yellow using ?-cyclodextrin modified magnetic graphene oxide nanocomposites(?-CD-Fe3O4@SiO2-GO)as extractant combined with UV-vis spectrophotometry was established.The ?-CD-Fe3O4@SiO2-GO was characterized by SEM,TEM and VSM.The factors affecting the extraction and elution were optimized,such as the dosage of extractant,pH,the type of eluent and elution time.Under the best experimental conditions,the linear range of the method was 0.2-10.0 ?g mL-1,the detection limit was 0.04 ?g mL-1,the correlation coefficient(R2)was 0.9969,the relative standard deviation was 0.79%(c=1.0 ?g mL-1,n=3),and the enrichment factor was 10.The sunset yellow in the beverage was analyzed by this method,and the recoveries were between 94.8%and 101.0%,indicating that the method can be used for the determination of sunset yellow in the real sample.Meanwhile,the adsorption isotherm model was studied,and the Freundlich model was more suitable to describe the adsorption process.3.A novel ionic liquid supported magnetic graphene oxide nanocomposite(TEDAIL-Fe3O4@SiO2-GO)was prepared,and a new method for separation and analysis of dye brilliant green was established by using the nanocomposite as magnetic solid phase extractant combined with UV-vis spectrophotometry.The material was characterized by SEM,TEM,FTIR and VSM.The various factors(the dosage of extractant,pH,extraction temperature,type of eluent and elution volume,etc)affecting extraction efficiency and elution efficiency were investigated.Under the optimum conditions,the linear range of the method was 0.05-1.0?g mL-1,the detection limit was 0.01 ?g mL-1,the correlation coefficient(R2)was 0.9960,the relative standard deviation was 1.3%(c=0.40 ?g mL-1,n=3),and the enrichment factor was 5.The brilliant green in the water sample was analyzed by this method,and the recoveries were between 96.7%and 102.5%.4.A tryptophan ionic liquid modified magnetic graphene oxide nanocomposite(TrpIL-Fe3O4@SiO2-GO)was prepared.A new method for simultaneous determination of Sudan ?-? by high performance liquid chromatography(HPLC)using this material as magnetic solid phase extractant was established.The namocomposite was characterized by SEM,TEM,FTIR and VSM.The factors affecting the extraction efficiency and elution efficiency of Sudan ?-?were studied,such as the dosage of extractant,pH,extraction time,temperature,sample volume,type of eluant,elution time and elution temperature.Under the optimum conditions,the linear ranges of the method for the determination of Sudan ?-? were 0.01-0.5 ?g mL-1,the detection limit were 0.001 ?g mL-1,the correlation coefficients(R2)were 0.9932-0.9985,the relative standard deviations were 1.3%-4.3%(c=0.20 ?g mL-1,n=3),and the enrichment factor were 10.The method was applied to the determination of Sudan ?-? in chill and water samples with the recoveries of 87.7%-110.6%and the results were satisfactory.Furthermore,the adsorption mechanism was studied,including adsorption kinetics and thermodynamic parameters.The results of adsorption kinetics and thermodynamic parameters were consistent,indicating that the process was chemical adsorption.5.A metal-organic framework functionalized magnetic graphene oxide nanocomposite(Ni-MOF-Fe3O4@SiO2-GO)was prepared.A new method for the separation and analysis of pesticide epoxiconazole using the nanocomposite as magnetic solid phase extractant prior to high performance liquid chromatography(HPLC)was established.The nanocomposites were characterized by SEM,TEM and X-ray diffraction.The experimental conditions affecting the extraction process and elution process were optimized,such as the dosage of extractant,pH,extraction temperature,sample volume,type of eluant,elution volume and elution temperature.Under the optimum conditions,the linear range of the method was 0.01-2.00 ?g mL-1,the detection limit was 0.001 ?g mL-1,the correlation coefficient was 0.9989,the relative standard deviation was 3.6%(c=0.2 ?g g-1,n=3),and enrichment factor was 15.The method has been successfully applied to the determination of epoxiconazole in fruits and vegetables,and the recoveries are in the range of 90.4%-112.2%.In addition,the adsorption mechanism was studied,including adsorption kinetics,thermodynamic parameters and adsorption isotherm model.The results of adsorption kinetics and thermodynamic parameters were consistent,indicating that the process was chemical adsorption.