| Electrochemical analytical method uses electrochemical features of substances for characterization and measurement. Biosensor is one of the most important field in elec-trochemistry.Tthe biosensor technology which can be applied to the detection of inorganic ions, organism pesticides and biological active ingredient is closely related to physical science, life science and analytical chemistry.The detection sensitivity can reach 10-12 grade. Biosensor research are used more for the determination in water medium at home and abroad than that in the organic phase. Based on the physical and chemical properties of vegetable oil, organic phase enzyme eletrode(OPEE) was prepared while electrochemical characteristics of TBHQ, VE, peroxide and cholesterolin in vegetable oil at the modified electrodes was studied. A novel method and technology for rapid analysis of quality vegetable oil testing was provided. The main research contents are as follows:(1) The antioxidant TBHQ and VE were all electrochemical. So the electrochemical oxidation reaction mechanism of TBHQ and VE in the organic phase using cyclic voltammetry was studied on the bare glassy carbon electrode. The peak position of TBHQ was 800 mV and 640 mV for VE. Electrochemical method was developed for the determination the two kinds of antioxidants and the experimental conditions was optimized, the selected organic solvent was 1,4-dioxane-acetonitrile (3:1, V/V) solution containing 6 mmol/L of sulfuric acid, and the supporting electrolyte was lithium chloride of 0.03 mol/L. Under optimized conditions, the linear range of TBHQ and VE was 4.0×10-5-5.5×10-4 mol/L and 2.0×10-5-7.0×10-4 mol/L respectively determined by differential pulse voltammetry. Detection limit were 1.5 umol/L and 1.6 umol/L respectively. The linear coefficient were 0.998 and 0.997 respectively. Because Voltammetric wave spectrum peak of the two kinds of antioxidants overlaped, conventional methods were difficult to determined respectively, so the partial least squares (PLS) was carried out on the spectrum analysis, and the method was applied for determination the actual oil sample and the recovery was 97.7%-104.2%. Results showed that the method of simultaneous detection of TBHQ and VE in the vegetable oil in organic phase was feasible, without pretreatment, less sample requirements, simple and quick.(2) The glassy carbon electrode was modified with horseradish peroxidase on the "sandwich" structure embedding the chitosan membrane scattering the chitosan membrane of multi-walled carbon nanotubes. A new type MW-CS-FC/HRP/MW-CS biological sen-sor was builded and applied for the detection of peroxide in plant oils. Chitosan that had excellent biological compatibility could keep the bioactivity of the enzyme. The modified electrodes had been characterized by CV and SEM method respectively. The experimental conditions such as HRP enzyme solid loads, buffer pH, concentration of supporting electrolyte, the optimal organic solvent, concentration of electronic media and the electrochemical parameters and so on were optimized. Under the optimal conditions, the detection linear range of lauroyl peroxide was 6×10-6-4×10-4mol/L using differential pulse voltammetry. The detection limit was 2.8μmol/L (S/N=3). The linear coefficient were 0.995. Good repeatability and stablity of the enzyme electrode was found and the content of peroxide value in vegetable oil samples had good current response. The method is rapid, simple and practical.(3) Cholesterol has very important physiological functions, but eating too much cholesterol will be detrimental to health of body. Glassy carbon electrode was modified with carbon nanotubes and chitosan as foundation work electrode. With "sandwich" embedding fixation technology, cholesterol oxidase was embedded in chitosan membrane and adsorpted on the bare glassy carbon electrode surface. A new type of cholesterol biosensor was produced and a kind of simple operation, convenient, sensitive, accurate and effective method for determination of the cholesterol content was established succefully. The experimental conditions such as enzyme solid loads, buffer pH, concentration of supporting electrolyte concentration, sulfuric acid, the most suitable organic solvent, concentration of electronic media and the electrochemical parameters and so on were optimized. Under optimal conditions, the detection linear range of lauroyl peroxide was 8×10-6-6×10-4mol/L using linear sweep voltammetry. The detection limit was 1.2μmol/L (S/N=3). Good repeatability and stability of the enzyme electrode was found and the content of peroxide value in vegetable oil samples had a good current response. The method was rapid, simple and practical. |
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