Electrochemical Analysis Of DNA Related Substances On Ionic Liquid Modified Electrode

Deoxyribonucleic acid (DNA) is the carrier of genetic information and the material basis of gene expression. It has very important functions in life processes, such as growth, development, breeding, heredity, aberrance and conversion. The study on the electrochemical behavior of DNA is of important theoretical and practical significance in life science. Room temperature ionic liquids (RTILs), which are consisted of a large organic cation with a weak coordination anion, have attracted the interests of electrochemist for their specific properties. As a green solvent, RTILs can be used as the supporting electrolyte or the modified materials for electrode. In this thesis the electrochemical investigation on DNA and its related substances were carried out by electroanalytical method. The paper can be summarized as follows:1. Two room temperature ionic liquids (RTILs) modified carbon paste electrodes (CPE) were constructed based on the substitute of paraffin with N-butylpyridinium hexafluorophosphate (BPPF6) or 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) to mix with graphite power. The optimal conditions for preparation were selected and the surface morphologies of the carbon ionic liquid electrode (CILE) were scanned by a scanning electron microscopy. The electrochemical behaviors of the CILE were investigated by using K3[Fe(CN)6] as probe and compared with that of traditional CPE. It was found that the CILE showed good electrocatalytic activity to electrochemical response, which was attributed to the presence of ILs on the electrode surface and the CILE showed good mechanic property and stability.2. The electrochemical behaviors of ssDNA, dsDNA, adenine and guanine on the CILE were investigated by the cyclic voltammetry, and the results were compared with that of the CPE. The MWCNTs/CILE was fabricated by applying multi-walled carbon nanotubes (MWCNTs) on the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified carbon ionic liquid electrode (CILE) and used for the investigation of guanosine. The results indicated that the CILE exhibited a great response of electrocatalytic activity with the increase of the peak currents and the negative shift of the peak potentials in contrast to that on the traditional CPE. The electrochemical parameters such as the charge transfer coefficient (α), the electron transfer number (n), the electrode reaction standard rate constant (ks) and the surface concentration of the electroactive substance (Г) were further calculated. Under the selected conditions, the peak currents increased linearly with the concentration in a certain range. The modified electrode showed good stability and reproducibility without the influence of the coexisting substances.3. The direct oxidation of catechol was studied by CILE. In pH 3.0 phosphate buffer solution (PBS) a pair of redox peaks appeared on the CILE with the anodic and the cathodic peak potential located at 387 mV and 330 mV (vs.SCE), respectively. The electrochemical behaviors of catechol on the CILE were carefully investigated and the electrochemical parameters were calculated with the results of the electrode reaction standard rate constant ks as 1.27 s-1, the charge transfer coefficientαas 0.58 and the electron transfer number n as 2. Under the selected conditions, the anodic peak current increased linearly with the catechol concentration over the range of 1.0×10-6 to 8.0×10-4 mol/L by cyclic voltammetry at the scan rate of 100 mV/s. The detection limit was calculated as 6.0×10-7 mol/L (3σ). The CILE showed good ability to separate the electrochemical responses of catechol and ascorbic acid (AA) with the anodic peak potential separation as 252 mV (vs.SCE). The proposed method was further applied to the synthetic samples determination with satisfactory results.