Study Of The High Sensitive Voltammetric Methods For Determination Of Food Ingredient

At present,graphene(GR),as a new type of carbon materials with variety of excellent properties,holds so excellent properties such as excellent mechanical strength,large specific surface area and extremely electric conductivity.However,GR nanosheets are hydrophobic and trend to agglomerate irreversibly by ?-? stacking interaction and Van der waals force,which will breach the excellent of the large specific surface area and destroy the remarkable single-layer electrical properties of GR.This defect seriously limits GR's application in electrochemistry.In order to overcome this problem,the functionalization of GR with manifold polymers has been applied.Functional reagent not only improves GR nanosheets dispersibility,but also allows them to be further decorated with other nanomaterials.Based on this,four kind of voltammetric sensors were fabricated with excellent performance.Then,the electrochemical behaviors of some food additive ingredients were investigated at these modified electrode surface and corresponding electronanlytical methods were established,which provide some reference and basis for the analysis of food.The main researches are expressed as follows:(1)In this part,graphene oxide(GO)was synthesized chemically by modified Hummer's method and reduced by hydrazine hydrate to synthesize graphene functionalized with PSS(PSS-GR).The modified glassy electrode based on PSS-GR composite film was prepared(PSS-GR/GCE),and the electrochemical behaviors of Orange II at this modified electrode were studied by cyclic voltammetry.Under optimum conditions with linear sweep voltammetry(LSV),a good linear relationship was obtained between peak currents and Orange II concentrations in the wider range of 3×10-8-5×10-6 mol L-1,with a detection limit of 1×10-8 mol L-1.The proposed Orange II sensor was successfully applied to real food samples with well recovery.(2)GSH functionalized graphene(GSH-GR)was prepared with green reduction method.The reaction mechanism of GSH-GR composite is a covalent grafting process of GSH to the graphene sheets through the nucleophilic ring-opening reactionof epoxy groups in graphene oxide with the thiol groups in GSH.The modified glassy electrode based on GSH-GR composite film was prepared(GSH-GR/GCE).This voltammetric sensor showed strong accumulation ability and excellent voltammetric response for rutin.Under optimum conditions by square wave voltammetry(SWV),a good linear relationship was obtained between peak currents and rutin concentrations in the wider range of 5×10-9-1× 10-6 mol L-1 with a detection limit of 7× 10-10 mol L-1.In addition,the proposed rutin sensor was successfully applied to test in real samples with good results.(3)In this work,PDDA functionalized grapheme(PDDA-GR)with surface supported Pt nanoparticles(Pt NPs)were prepared with non-covalent bonding method.Characterization was performed by UV-vis,FT-IR,TEM and XRD.Modified GCE with this composite material exhibited a good electrochemical response towards gallic acid.Under optimum conditions by square wave voltammetry(SWV),a good linear relationship was obtained between peak currents and gallic acid concentrations in the wider range of 3×10-8-1×10-6 mol L-1 with lower detection limit of 7×10-9 mol L-1(S/N=3).In addition,the proposed voltammetric method was successfully applied to test gallic acid in real samples with well results.(4)A new and simple strategy for the synthesis of poly(sodium p-styrenesulfonate)(PSS)-functionalized graphene supported palladium nanoparticles nanocomposite(PSS-GR-Pd)was proposed with ultrasonic bath method.Characterization was performed by UV-vis,FTIR,TEM and XRD.Based on the PSS-GR-Pd nanocomposites modified glassy carbon electrode as voltammetric sensor,it exhibited excellent electrochemical response for amaranth and a sensitive determination method was established synchronously.Under optimum conditions by differential pulse voltammetry(DPV),a good linear relationship was obtained between peak currents and amaranth concentrations in the wider range of1×10-7-9×10-6 mol L-1 with detection limit of 7×10-9 mol L-1.The proposed amaranth sensor was successfully applied in soft drink with satisfactory recovery.