Study On The Electrochemical Behavior Of Saccharides On Chemically Modified Electrode

In recent years, chemically modified electrode (CME) has gained a dominant position in the electrochemistry and electroanalytical chemistry. One of the most important chemical applications becomes the study of CME on environment and life science fields. Saccharides are important energy substances, which have been widely applied in medicine, biochemical science, and food industry. Therefore, accurate and fast determination of saccharides has attracted much attention of the researchers. In this work, the main research is the electrochemical behavior of saccharides on the CME.The primary research woek is as follows:1. Electrochemical sensor for heparin based on ploy(thionine) modified glassy carbon electrodePoly(thionine) thin film modified electrode was successfully assembled on the surface of the glassy carbon electrode by means of electrochemical polymerization, which was carried out with cyclic voltammetric sweeping in the potential range from 0 to+1.4 V (vs. Ag/AgCl) in perchloric acid solution containing 0.1 mmol L^-1 thionine. The film modified electrode exhibited a couple of well-defined redox peaks, and the redox peaks decreased correspondingly without the movement of the peak potential after the addition of heparin. The conditions of the binding reaction and the electrochemical detection were optimized. Under the optimum conditions the decrease of the peak current was proportional to the concentration of heparin in the range from 4.0 to 22.0μg mL^-1 and the detection limit of the system was 0.28μg mL^-1. The relative standard deviation (RSD) for five parallel determinations of 10.0μg mL^-1 heparin was 0.93%. The influences of the foreign substances on the determination were investigated and the proposed method was applied to the heparin samples determination with satisfactory results.2. Fabrication of toluidine blue-mercaptoacetic acid self-assembled gold electrode and its application for the determination of heparinPreparation of the mercaptoacetic acid (MA)-toluidine blue (TB) chemically modified electrode by self-assembling MA on the gold electrode surface was reported in this paper. Its electrochemical behavior was evaluated with cyclic voltammetry (CV). The conditions of the binding reaction and the electrochemical detection were optimized. Under the optimum conditions, the decrease of the peak current was proportional to the concentration of heparin in the range from 4.0 to 20.0μg mL^-1 and the detection limit for heparin was 0.48μg mL The proposed method was applied to the determination of heparin in heparin sodium injection samples with satisfactory results.3.4-Formylphenylboronic acid self-assembled layer on the glassy carbon electrode for the determination of sugarsGold nanoparticles (GNPs) were electrostaticly adsorbed on a glassy carbon electrode firstly coated with a carbon nanotubes-chitosan (CNTs-CS) layer. And then L-cysteine was assembled on the surface of gold nanoparticles and connected with 4-formyphenylboronic acid (BA) via schiff's base formation to fabricate the (CNTs-CS)-GNPs-(L-cys)-BA electrode. The properties of the modified electrode were characterized by cyclic voltammetry, electrochemical impedance spectra and difference pulse voltammetry. The biosensor exhibited excellent performances for determining D-glucose, D-fructose, and D-galactose with a wide linear range and good sensitivity.4. Electrochemical recognition for saccharide by CdSe quantum dots modified boronic acid self-assembled monolayerA novel method for immobilization of boronic acid was constructed by modifying glassy carbon electrode with CdSe quantum dots (QDs) and excellent conductive gold nanoparticles (GNPs) though carbon nanotubes-chitosan (CNTs-CS). Transmission electron microscopy (TEM) was employed to characterize QDs. The properties of GC-(CNTs-CS)-QDs-GNPs-BA electrode were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The pK_a values of the BA monolayer before and after combining with sugars were determined. The fabricated electrode exhibited excellent performances for determining D-glucose, D-galactose and D-fructose on the basis of the change in i_p of the Fe(CN)₆^3-/4- ion in the presence of sugars. Based on this, a new biosensor for determining sugars has been developed.