Electrochemical Behaviors And Determination Of Food Additives

The poly L-lysine modified glassy carbon electrode(PLL/GCE),poly L-methionine modified glassy carbon electrode(PLM/GCE),poly L-methionine/graphene modified glassy carbon electrode(PLM/GO/GCE),and poly(L-arginine/ electrochemically reduced graphene)modified glassy carbon electrode(PLA/ERGO/GCE)were prepared in this paper.Electrochemical impedance spectroscopy(EIS)was used to characterize the electrodes.The electrochemical behavior of some food additives,such as iodine and lemon yellow,was studied on the surface of the naked electrode and the self-made modified electrode using cyclic voltammetry(CV),linear sweep voltammetry(LSV)and differential pulse voltammetry(DPV).A new chemically modified electrode was established with functional design of the surface of the glassy carbon electrode,which was suitable for the determination of iodine and lemon yellow in the sample.Throughout the research process,the main problems to be solved are: 1)The optimal condition and characterization of PLL/GCE,PLM/GCE,PLM/GO/GCE and PLA-ERGO/GCE modified electrodes;2)The electrochemical behavior of iodide ion at bare electrodes and modified electrodes such as PLL/GCE,PLM/GCE,PLM/GO/GCE,etc;3)Electrochemical behavior of lemon yellow at PLA-ERGO/GCE modified electrode;4)The optimal conditions for the determination of iodide ions at bare electrodes and modified electrodes such as PLL/GCE,PLM/GCE,and PLM/GO/GCE;5)Determination of lemon yellow at the PLA-ERGO/GCE modified electrode.The main research content is as follows:1.The electrochemical properties of iodine at glassy carbon electrode werestudied by cyclic voltammetry.In this experiment,electrochemical methods were usedto optimize the experimental conditions.Under the optimal conditions,the electrochemical behavior of iodide ions on the glassy carbon electrode was studied.A linear range of 5.00×10-6 to 1.00×10-3 mol/L and a detection limit of 1.0×10-6 mol/L for iodine were obtained in phosphate buffer solution(PBS)with pH 5.0.2.A PLL/GCE was prepared by cyclic voltammetry in a polymer solution of L-lysine in phosphate buffer solution(PBS).The modified electrode exhibits better catalytic ability and faster electron transfer rate for iodide ion(I-).In order to investigate the reaction mechanism in the electrocatalytic oxidation of iodide ion,CV and LSV methods were used.Results indicated that the oxidation of iodide ion on thesurface of the modified electrode was diffusion-controlled.Iodide ion was determinedby LSV under optimal experimental conditions in the concentration range of 2.5×10-6to1.0×10-3mol/L.The detection limit(signal to noise is 3)was 8.0×10-7mol/L.Theabove results are satisfactory.3.A PLM/GCE was prepared by cyclic voltammetry,and the electrochemical properties of iodide ion at this modified electrode were investigated.A variety of electrochemical methods were applied to optimize the experimental conditions.Under the optimal conditions,the electrode exhibited good catalytic performance for iodide ion.The voltammetric determination for iodine has a linear range of 2.50×10-6 to1.00×10-3 mol/L with a detection limit of 8.0×10-7 mol/L.High selectivity and stability make it very suitable for the determination of trace amounts of iodine in actual samples.4.A PLM/GO/GCE was prepared by cyclic voltammetry,and the electrochemical properties of iodine at the modified electrode were investigated.The electrode showed good catalytic performance for iodide ion.In the phosphate buffer solution(PBS)of pH 4.0,the linear range of iodide ion is 2.50×10-6 ~1.00×10-3mol/L,and the detection limit is 6.0×10-7mol/L.High selectivity and stability make it very suitable for the determination of trace amounts of iodide ion in actual samples.5.A PLA-ERGO/GC was prepared by incorporating L-arginine andelectrochemically reduced graphene.The GCE and PLA-ERGO/GCE modifiedelectrodes were characterized by electrochemical impedance spectroscopy(EIS).The electrochemical behavior of lemon yellow at this modified electrode was explored using CV and DPV techniques.A well-defined oxidation wave with a peak potential of 1.012 V was obtained in phosphate buffer of pH 2.0.The determination conditions of DPV were optimized.The linear range of lemon yellow is 1.00×10-6 ~2.50×10-4 mol/L,and the detection limit is 2.5×10-7 mol/L.Results of this work showed that this modified electrode exhibited an effective catalytic activity in the electrochemical oxidation of lemon yellow in actual samples.