Preparation Of Graphene Functionalized Modified Electrode And Determination Of Food Additives

A glassy carbon electrode was placed in a mixture of L-glutamic acid and graphene,and a poly-L-glutamic acid/graphene modified electrode（PLG-ERGO/GCE）was prepared by cyclic voltammetry（CV）.The electrochemical behavior of maltol（MA）,ethyl maltol（EMA）and vanillin（VAN）were studied by cyclic voltammetry（CV）,differential pulse voltammetry（DPV）and chronoamperometry（CA）.And established a method for measuring these substances separately.As a new carbon material,graphene has the advantages of high specific surface area and high electrical conductivity.As an inspensable nutrient for living organisms,amino acids contain amino groups and carboxyl groups,which can make certain biomolecules have certain biological activities.In order to increase the sensitivity of the electrode to measure the substance and increase the electron transfer rate,the graphene（GO）and the amino acid are modified on the surface of the electrode by electrochemical methods.Scanning electron microscopy（SEM）and electrochemical impedance spectroscopy methods（EIS）were used to characterize the surface morphology of the modified electrode.The prepared modified electrode was used for the determination of food additives in foods with satisfactory results.In the whole experimental research process,the main problems solved are:（1）Preparation conditions of the poly L-glutamic acid/graphene modified electrode（PLG-ERGO/GCE）by cyclic voltammetry（CV）and to study the characterizations of the modified electrode;（2）to study the electrochemical behavior of maltol（MA）on the ploy L-glutamic acid/graphene modified electrode;（3）to study the electrochemical behavior of ethyl maltol（EMA）on the ploy L-glutamic acid/graphene modified electrode;（4）to study the electrochemical behavior of vanillin（VAN）on the ploy L-glutamic acid/graphene modified electrode.The main works and the detail achievements were exhibited as follows:1.A glassy carbon electrode was placed in a mixture of L-glutamic acid and graphene,and a poly-L-glutamic acid/graphene modified electrode（PLG-ERGO/GCE）was prepared by cyclic voltammetry（CV）.The electrochemical behavior of maltol was studied in pH 6.0 phosphate buffer solution（PBS）by cyclic voltammetry（CV）and differential pulse voltammetry（DPV）.The differential pulse voltammetry was established of determination of maltol.The experimental results show that maltol was mainly controlled by diffusion on this electrode.Under the optimal conditions,the oxidation peak potential of maltol was at 0.711V.Using the differential pulse voltammetry to determine the maltol in the range of 4.00×10^-68.00×10^-4mol/L showed a good linear relationship.The detection limit was 4.0×10^-7mol/L.This method was used to determine maltol in the sample with satisfactory results.2.The electrochemical properties of ethyl maltol（EMA）were investigated by cyclic voltammetry（CV）and differential pulse voltammetry（DPV）on a poly-L-glutamicacid/graphenemodifiedelectrode（PLG-ERGO/GCE）.The experimental results show that the oxidation peak potential of ethyl maltol（EMA）were at 0.951V and 0.852V under the optimal conditions.The concentration shows a good linear relationship in the range of 6.00×10^-61.00×10^-4mol/L and 4.00×10^-64.00×10^-4mol/L.The detection limit was 4.0×10^-7mol/L.Two methods were used to detect ethyl maltol in foods with satisfactory results.3.The electrochemical behavior of vanillin（VAN）was investigated by cyclic voltammetry（CV）and differential pulse voltammetry（DPV）on PLG-ERGO/GCE modified electrode.In the phosphate buffer solution（PBS）with acidity condition of1.0,vanillin showed a sensitive oxidation peak at 0.958V when the sweep rate is100mV/s.It showed a good linear relationship with the oxidation peak when the concentration was in the range of 4.00×10^-62.00×10^-4mol/L by differential pulse voltammetry（DPV）.The detection limit was 6.0×10^-7mol/L.This method is satisfactory for the detection of vanillin in food.