Electrochemical Detection Of Bioactive Small Molecules

Chemically modified electrodes (CME) originated in 1975 is one of the foremost fields of electrochemistry and electroanalytical chemistry at present. Nowadays, CME has been widely used in electrochemical analysis because of its fast analysis speed, simple and easy operation, low cost, low reagent consumption, high sensitivity, good selectivity, and other advantages. An important application of CME is applying the electrocatalytic activity of the modifer into the increase in sensitivity and selectivity of analysis. Detection of bioactive small molecules such as dopamine (DA), uric acid (UA), and ascorbic acid (AA) has attracted a wide interest.The main research works of this thesis are the following aspects: Part 1 Electrochemical behavior and determination of dopamine at L-cysteine modified glassy carbon electrodeThe L-cysteine modified electrode was prepared with L-cysteine as the electrode surface modifier and the influence of experimental conditions containing the concentration of modifier, pH value and number of scan round on the performance of the modified electrode was discussed detailedly. Furthermore, electrochemical behavior of dopamine at the modified electrode was studied. The results showed that the modified electrode prepared under the optimum experimental conditions had large electrochemical response. The oxidation peak current presented a good linear relationship in the concentration range of 1.0×10-6～1.0×10-3mol/L with the linear regression equation of Ipa (μA)=-9.8038 logC(DA)+59.4098 (R2=0.9923) and the detection limit of 1.0×10-7 mol/L at signal to noise ratio of 3.Part 2 Voltrammetric detection of uric acid at the poly (L-glutamic acid) modified glassy carbon electrode The glassy carbon electrode was modified with L-glutamic acid modifier and electrochemical behavior of uric acid (UA) at the bare electrode and modified electrode were investigated by cyclic voltammetry. The experimental results showed that the poly (L-glutamic acid) modified glassy carbon electrode has been demonstrated to have obvious electrocatalytical function to electrochemical oxidation reaction of UA. Based on the optimization of UA test conditions, it is concluded that the oxidation peak current has a good linear relationship in the UA concentration range of 2.5 x 10-6～1.0 x 10-3 mol/L with the linear regression equation for Ipa(μA)=-149.9583+25.5 log C(UA) and correlation coefficient of R2=0.9948. The detection limit for UA is 1.0 x 10-6 mol/L at signal to noise ratio of 3. The experimental results, compared with similar modified electrodes, demonstrated the characteristics of simple preparation, wide linear range and low detection limit. It is expected that the modified electrode will be applied to detect UA in urine and related research.Part 3 Electrocatalytic behavior and selective detection of uric acid in the presence of ascorbic acid at the cinnamic acid modified glass carbon electrodeUnder the optimized conditions of electrode preparation, the glassy carbon electrode was modified by constant potential deposition with cinnamic acid modifier. The electrochemical behavior of UA at the bare electrode and cinnamic acid modified electrode was investigated by cyclic voltammetry and the detection of UA was accomplished in the case of high concentration (1.0 x 1O-3 mol/L) of A A coexistence and the stability and reproducibility of the electrode were studied. The experimental results showed that cinnamic acid modified electrode has obvious electrochemical activity to oxidation of UA and the detection limit of 1.0 x 10-6 mol/L at signal to noise ratio of 3. Under the optimum conditions, the oxidation peak current had a good linear relationship in the UA concentration range of 2.0 x 10-6～2.0 x 10-4 mol/L with the linear regression equation of Ipa(μA)=22.4948+0.2195 logC(UA) and correlation coefficient of R2=0.9902. A new electrochemical method for the determination of UA was developed.