Perparation Of Chemical Modified Elecrfode And Its Application To The Determination Of Biomolecules

Chemical modified electrode is widely used in environment, food, pharmaceutical andbiology. There are several advantages on chemical modified electrode which include highersensitivity, selectivity, less time consumption, low cost, instrument simple and easy inminiaturization. On the analysis of testing aspect, the electrocatalytic ability towards targetmolecules will significantly improve when carbon nanomaterials and polymer materialsdevelop for the fabrication of chemical modified electrode. In this thesis, materials such ascholine, acid yellow9, graphene and double-walled nanotubes were applied for the designand fabrication of modified electrode. The details are described as follows:1A novel protocol for simultaneous determination of ascorbic acid (AA), dopamine(DA) and uric acid (UA) based on double-walled carbon nanotubes (DWNTs)/choline (Ch)modified glassy carbon electrode (GCE) was presented. Ch was covalently immobilized onthe GCE through oxygen atom. The Ch monolayer provides a positively charged monolayer,which could attract negatively charged DWNTs through electrostatic interaction. In thesimultaneous determination of AA, DA and UA using cyclic voltammetry, the electrochemicalsignals were well separated into three peaks with peak potential differences of182mV(AA-DA),146mV (DA-UA),328mV (AA-UA), respectively. In amperometric studies of AA,DA and UA, the modified electrode exhibited wide linear ranges of1.0×10-7~7.8×10-4mol·L-1,6.0×10-8~3.1×10-4mol·L-1and2.5×10-7~3.4×10-4mol·L-1and low detection limitsof3.0×10-8,3.0×10-8, and5.0×10-8mol·L-1, respectively. Amperometric responses of AA, DAand UA were within1s. Moreover, this modified electrode was further applied to determineAA, DA and UA in real samples with satisfactory results.2A new method for electroanalytical determination of guanine (GA) and uric acid(UA) based on double-walled carbon nanotube-graphene nanosheet hybrid film/acid yellow9modified glass carbon electrode (DG/AY/GCE) is reported. It is found that the DG/AY/GCEexhibited excellent analytical performance for determination GA and UA in0.1mol L-1phosphate buffer solution (pH4.0) since it not only increases the oxidation peak current butalso lowers the oxidation overpotential. The oxidation currents of GA and UA were foundlinearly related to concentration over the range from2.0×10-9to6.8×10-5mol·L-1for GA and5.0×10-9to9.5×10-5mol·L-1for UA using amperometric method. The detection limits werefound to be6.7×10-10mol·L-1for GA and1.7×10-9mol·L-1for UA. The proposed method wasused to detect GA and UA in human urine samples with satisfactory results.