| Chemically modified electrodes?CMEs?/biosensor have become an ideal system integrated separation,enrichment and selectivity,which is the most active field in electrochemistry and electroanalytical chemistry.Chemically modified electrodes are popularly used in the determination of inorganic matter,organic substance,biological constituents and poisonous and harmful substances in food,the detection limit can reach sub micromolar level.Nanomaterials can enhance electron transfer,biological compatibility and catalytic activity with large specific surface,which improve the detectionsensitivityofbiosensororchemicallymodifiedelectrodes.The poly?L-cysteine/multi-walled carbon nanotubes?modified glassy carbon electrodes,Chitosan/GNPs AFB1 immunosensor and The poly-L-Asp/MWNTs modified electrodes were prepared and used in determination of nitrite,aflatoxin B1 and phenolic acid in foods,the results are agreed with those of standard methods.The poly?L-cysteine/multi-walled carbon nanotubes?modified glassy carbon electrode was prepared by electrical aggregation method.The Voltammetric behavior of nitrites on the poly?L-Cys/MWNTs?modified electrode was studied.A novel method for the determination of nitrite in foods by differential pulse voltammetry was established.At pH 4.5 phosphate buffer solution,the modified electrode exhibited good electrocatalytic activity on the oxidation of NO2-,and the electrode reaction of NO2-was a diffusion control process.In the optimized conditions,the calibration curves for the determination of nitrite in foods demonstrated an excellent linear response in the range from5×10-72.7×10-55 mol/L with the detection limit of 7×10-33 mg/kg?S/N=3?.The proposed method was successfully applied in the simultaneous determination of nitrites in vegetables,these results of agreed with the national standard method of spectrophotometric method and with rapid,convenient advantages and less requirement of chemical reagent.A nano immunosensor for highly sensitive determination of aflatoxin B1 in food has been constructed by the modified chitosan immobilization of aflatoxin B1 antibody and gold nano particles?GNPs?on glass carbon electrode,the preparation conditions and detection parameters were optimized in this article.Based on the Specific immune reaction between antibody and antigen of AFB1,the effects of immune response on the immunosensor response current were invetigated by cyclic voltammetry and differential pulse voltammetry using K3[Fe?CN?6]as the probe.The results showed that the immune response currents increased linearly with the concentration of aflatoxin B1 in the range of0.11.1 ng·mL-1;Excellent stability and reproducibility of the prepared CS-GNPs/AFB1-Ab immunosensor was observed in the selected condition.The developed method was applied to the determination of aflatoxin B1 in peanut and peanut oil,maize and maize oil samples,and the results well agreed with those obtained by enzyme-linked immunosorbent assays method.Being more precise and accurate than ELISA method,it is practicable for rapid determination of aflatoxin B1 in vegetable oils with simple pretreatment.The poly-L-Asp/MWNTs modified electrodes were prepared combining electro-polymerization and absorption method.Voltammetric behavior of gallic acid on the poly-L-Asp/MWNTs modified electrode was studied in this article.A novel method for the determination of phenolic acid in wheat bran by differential pulse voltammetry was established.In disodium hydrogen phosphate and citric acid buffer solution?pH 3.0?,the modified electrode exhibited strong electrocatalytic activity on the oxidation of gallic acid,and the electrode reaction of gallic acid was an adsorption control process.In the optimized conditions,the calibration curves for the determination of gallic acid in foods demonstrated an excellent linear response in the range from 2×10-65.6×10-55 mol/L.The developed method was successfully applied in the determination of total phenolic acid in wheat bran,these results well agreed with the national standard method of Folin-Ciocalteu colorimetric method.It is feasible using poly-L-Asp/MWNTs modified electrodes for fast determination of phenolic acid in food with less requirement of chemical reagent.This paper studies the fat-soluble antioxidants TBHQ,VE,PG and water-soluble antioxidants GA,VC,TP the six kinds of commonly used food antioxidants on the glassy carbon electrode electrochemical behavior,and,respectively,with using the method of removal ability of DPPH free radicals and hydroxyl radical scavenging ability for the determination of single antioxidant antioxidant capacity.The test result has carried on the preliminary study.The results showed that In terms of single antioxidant capacity,the method of electrochemical analysis results for VE>TBHQ>PG and VC>TP?GA.The effect of scavenging free radicals is PG>TBHQ>VE and TP?GA>VC.In the analysis of electrochemical oxidation potential of the lower VE and VC has the high oxidation activity,but the minimum clearance of free radicals.The distribution between the antioxidants,electrochemical analysis to the result of TBHQ and PG,VC and GA performance the positive synergy after synergies;the method of DPPH free radicals spectrophotometry to the result of TBHQ and PG,VE and PG,VCand TP,VC and GA show the positive synergy after synergies. |
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