Study And Application Of Three-Dimensional Draphene Composite Material In Rapid Determination Of Trace Cadmium In Food

Compared with the traditional heavy metal detection methods,the electrochemical method has the advantages of simple operation,relatively low equipment price,fast detection speed,and simple sample preparation.However,compared with the AAS(Atomic Absorption Spectroscopy)method,the electrochemical method also has certain limitations,mainly in the minimum detection limit and the weak stability.As a new developing material,graphene has been widely used in chemically modified electrodes due to its excellent surface area,good mechanical properties and electrochemical properties.The research status of graphene composite modified electrode in electrochemical detection of heavy metals was summarized in the first chapter of this paper,in which the possible shortcomings in the research was pointed out,which provides reference and guidance for the future research of electrode modification materials.In the second chapter of this study,the three-dimensional structure graphene was prepared by hydrothermal reduction using sheet graphene,which overcomes the defect that the graphene sheet layer is easy to produce p-? stack after the solvent is removed from the solvent,resulting in a decrease in specific surface area.Simultaneously,the hydrothermal reduction method has the advantages of simple operation,no waste acid,waste alkali and toxic and harmful substances,and is a green environmental protection and energy saving method.Nevertheless,in order to facilitate the separation of three-dimensional graphene from the solvent,a hydrothermal reduction method is also used to prepare a magnetic three-dimensional graphene composite material by reacting with a ferric chloride solution under the action of dimethyl hydrazine,which can be easily Separation under an external magnetic field eliminates the cumbersome process of traditional centrifugation methods,making separation faster and easier.The morphology and elements of the prepared materials were characterized by Fourier transform infrared spectroscopy(FT-IR).The electrochemical properties of the modified materials were tested by EIS,CV and polarization curves.In the third chapter of the research,the conditions for the detection of heavy metals by magnetic three-dimensional graphene modified electrode were optimized,including the concentration of modification solution,Nafion solution concentration,buffer system,pH,stirring speed and enrichment time.The study found that when the concentration of the magnetic three-dimensional graphene modification liquid is 7 mg/mL,the volume of the modification liquid is 30 ?L,the concentration of the polymer Nafion is 0.1%,and the concentration of the polymer Nafion is 0.1%,and the concentration is 1200 rpm in the phosphate buffer of pH=5.When the method has good detection results.The experimental results show that under the optimized conditions,the detection limit of cadmium ion on magnetic three-dimensional graphene modified electrode(S/N>3)is 0.1?g/L;The RSD=0.95%in the eight repeated test results of the same modified electrode,which proves that the modified electrode has good stability;Reproducibility RSD = 2.56%in three different electrodes.Linear fit showed that the fitting equation of the modified electrode was y=22.173x-3.8426,where R2=0.998,in the concentration range of 0.2-1000 ?g/L,R2=0.99;The relative standard deviation of the recovery experiment is 2.6%-6.7%;The anti-interference experiment results show that the magnetic three-dimensional graphene modified electrode has good anti-interference ability to Pb2+,Zn2+,Hg2+,but is greatly affected by high concentration of Cu2+.In general,interference can be eliminated by complexation reactions.In addition,in the actual sample test application in Chapter four,18 samples of Lentinula edodes fruit bodies in Hunan Province was collected for testing,and verified the detection results of the electrochemical detection methods in this experiment by atomic absorption spectrometry.The experiment results show that the detection results of 18 mushroom samples measured by modified electrode are compared with those measured by atomic absorption spectrometry,which has a standard deviation is between one hundredth and one ten thousandth,and the test error is extremely small.It can be concluded that the detection of heavy metal cadmium in food by magnetic three-dimensional graphene modified electrode has good accuracy and has broad application prospects.