| Among the constituents of nucleic acid, only bases can undergo reduction and/or oxidation at the electrodes. Electrooxidation of nucleic acid bases often takes place at highly positive potentials on the solid electrodes. In recent years ionic liquids (ILs) have received great attention due to their specific characteristics such as good chemical and thermal stability, high ionic conductivity, negligible vapor pressure and wide electrochemical windows. ILs modified electrodes have been exhibited the advangtages including the increase the electron transfer rate of electroactive compounds, the decrease the overpotential for biomolecules and the enhancement of the electrochemical signals. In this thesis the electrochemical investigation on nucleic acid bases and its related derivatives were carried out with the results summarized as follows:1. Two kinds of carbon ionic liquid electrodes (CILE) were constructed by mixing graphite powder with hydrophobic ionic liquids N-butylpyridinium hexafluoro- phosphate (BPPF6) or N-hexylpyridinium hexafluorophosphate (HPPF6). The electrochemical behaviors of guanosine and adenosine were studied on the CILE, respectively. Compared with that of CPE, both the oxidation peaks potentials were shift to the negative direction and two oxidation peaks current increased on the CILE, which indicated the presence of ionic liquid in the carbon paste not only as the binder but also as the modifier and the promoter. The electrochemical parameters of guanosine and adenosine were calculated respectively. Under the optimal conditions, a good linear relationship was established between the cyclic voltammetric current and guanosine concentration in the range from 1.0×10-6 mol/L to 1.0×10-4 mol/L with the detection limit of 2.61×10-7 mol/L (3σ); the differential pulse voltammetric current showed a good linear relationship with the adenosine concentration in the range from 1.0×10-6 mol/L to 1.4×10-4 mol/L with the detection limit of 9.1×10-7 mol/L (3σ). Both the proposed method was applied to the human urine samples detection with satisfactory results.2. An hydrophile ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) modified carbon paste electrode was prepared by mixing graphite powder, liquid paraffin and IL together. The fabricated ionic liquid carbon paste electrode (IL-CPE) was used for the simultaneous determination of guanosine and adenosine by differential pulse voltammetry. Under the optimal conditions the linear calibration curves were obtained over the concentration range from 1.0×10-6 mol/L to 1.6×10-4 mol/L for guanosine and from 1.0×10-6 mol/L to 2.7×10-4 mol/L for adenosine in pH 3.5 B-R buffer solution. Coexisting substances in the biological samples showed no interference for guanosine and adenosine determination and the proposed method was successfully applied to the human urine sample detection without preliminary pre-treatments. The ionic liquid modified carbon paste microelectrode (m-IL-CPE) was prepared by packing ionic liquid modified carbon paste at the end of a pipette tip and contacting with a copper wire. The electrochemical oxidation of 2'-deoxyguanosine-5'-triphosphate (dGTP) was investigated on the m-IL-CPE by cyclic voltammetry. Then the electrochemical processes of dGTP on the m-IL-CPE were recorded with the oxidation mechanism discussed. Under the optimal conditions the differential pulse voltammetric response was proportional to the dGTP concentration in the range of 1.0×10-6 mol/L to 7.0×10-4 mol/L with the linear regression equation as logIpa(A) =0.771logC(mol/L) - 4.082 (n=9,γ=0.999) and the detection limit as 1.0×10-6 mol/L (3σ). The proposed method showed good selectivity and stability without the interferences of coexisting substances.3. Electrochemical oxidation of cytosine was investigated on a carbon paste electrode. In pH 5.0 Britton-Robinson (B-R) buffer solution a well-define irreversible oxidation peak appeared at the potential of 1.412 V, which indicated the oxidation of cytosine on the electrode. The electrochemical parameters such as the electron transfer number (n), the electron transfer coefficient (α), and the electrode reaction standard rate constant (ks) was calculated with the results as 2.14, 0.15 and 1.049×10?3 s-1 respectively. Under the selected condition the cytosine concentration showed a good linear relationship with the differential pulse voltammetric current in the range from 1.0×10-5 mol/L to 1.0×10-3 mol/L with the linear regression equation as Ip(μA) = 0.0519C(μmol/L) +0.419 (n=9 ,γ=0.999) and the detection limit as 1.9×10-6 mol/L (3σ). Coexisting substances showed no inferences on the cytosine detection.
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