Study On The Electrocatalytic Oxidation Of NADH At The Electrode Modified With Yb-PBAs/Chitosan

In this thesis, a novel modified electrode is prepared by dropping trace amounts of chitosan on GC electrode, which is modified beforehand with Yb-In-Co-MoO42-cyanide-bridged mixed complexes (Yb-PBAs). The electrocatalytic oxidation behavior of NADH on this modified electrode is studied and the inhibitory effect of this modified electrode by adding the glycerol into the coated chitosan solution is explored. The results show that the electrode possesses high catalytic activity and good tolerance to toxic intermediate for the electrochemical oxidation process of NADH, and can be used for the quantitative determination of NADH.There were four chapters in this paper:Chapter one:In this section, we mainly introduce the following three aspects. Firstly, the preparation and application of PBAs modified electrodes is introduced. Secondly, the research current about the electrocatalytic oxidation of NADH is prospected. Finally, the application of some chemically modified electrode, which is employed chitosan as a kind of the modified materials for the electroanalytical chemistry is reviewed in detail.Chapter two:The glassy carbon (GC) electrode modified with Yb-PBAs/chitosan layer-by-layer composite film is successfully prepared for the first time and the electrochemical oxidation of NADH on this modified electrode is studied in detail by using differential pulse voltammetry. Compared with the voltammetric behavior of NADH on a bare GC electrode, the results show that the oxidation peak potential shifts negatively more than20mV and the oxidation peak current increases about ten times on the modified electrode. There exists the wide linear relationship between the oxidation peak current of NADH and its concentration in a range of4to1000μmol·L-1. The heterogeneous rate constant for the oxidation of NADH on the modified electrode surface is also determined and found to be9.94×10-3cm·s-1. Furthermore, the results demonstrate that if the pretreatment process of15cyclic scans are performed on the modified electrode in the solutions containing NADH before each new prepared electrode is used, the measurable value of the peak current for testing NADH samples would tend to stable and the effect of electrode poisoning on the measurement results is eliminated to some extent. The composite film exhibits a good cooperative catalytic action toward the electrooxidation reaction of NADH.Chapter three:In this section, the glycerol is added into the chitosan modified solution, and many factors such as the concentration of every component in chitosan solution, the spreading amount of chitosan on a modified electrode are studied in order to increase oxidation peak currents of NADH and promote the tolerance to toxic intermediate of the composite modified electrode. Based on this condition, the results show that the oxidation peak current of NADH is in proportion to its concentration in a range of4to5000μmol·L-1and the linear range is widened obviously comparing with the electrode which is prepared by dropping trace amounts of only chitosan on Yb-PBAs modified GC electrode. The good linear relationship between the oxidation peak current of NADH and the square root of scan rate in a range of0.1to0.8V·s-1indicates that the electrochemical reaction of NADH is controlled by diffusion process. Meanwhile, when the glycerol is added into the chitosan modified solution, the composite modified GC electrode possesses better stability to the electrocatalytic oxidation of NADH. Therein, the electrochemical signal of NADH still remained commendably after it is stored in the refrigerator for12days.Chapter four:An amperometric electrochemical sensor for NADH is prepared by dropping trace amounts of chitosan solution contained certain concentration of glycerol on Yb-PBAs modified GC electrode and the effect of the working potential on the responses current of NADH is studied. The results show that there exists good linear relationship between the responses current of NADH and its concentration in the range of40～1600μmol·L-1and2000～3400μmol·L-1, respectively. With the modified electrode, the amount of NADH in the tablets sample is measured by using differential pulse voltammetry and the recoveries are between96.3%and109.5%.