Determination Of The Hydroperoxides In O/wemulsion

The dissertation developed a new electrochemical measurement of hydroperoxides in O/W emulsion based on the reaction of the hydroperoxides and Fe2+.In addition,the EIS method for the evaluation of the oil rancidity was developed depended on the relationship between the impedances decrease and the peroxide values increase during the oil/emulsion rancidity process.The main research contents and results were as follows:1,Extration of hydroperoxides in emulsion Cyclohexane,isopropyl alcohol,petroleum ether and isopropyl alcohol were chosen as the extracants of the hydroperoxides,Experimental results showed that the extratants composition and ratios were greatly influenced the extraction rate of hydroperoxides.It was revealed that the extraction rate of hydroperoxides in O/W emulsion could reach 99.9% when the ratio of petroleum ether and isopropyl alcohol was 3:1.2,Squarewave voltammetry method for the determination of hydroperoxides in O/W emulsion Some important parameters, such as the concentrations and pHs of the supporting electrolyte, the concentrations of ferrocene and the scan rates, etc, were studied, When the concentration of the supporting electrolyte was 0.10mol/L, the pH was 7.0, the concentration of ferrocene was 6×10-4mol/L and the scan rate was 0.64V/s, the linear range of hydroperoxides concentration in O/W emulsion was 6.6×10-6～5.2×10-4mol/L, with a correlation coefficient of 0.998. The detection limit of hydroperoxides was 8.8×10-7mol/L.3,Determination of the hydroperoxides in O/W emulsion with PVA-potassium ferrocyanide modified electrode The electrode modified conditions (the concentrations and dosages of potassium ferrocyanide) and the main parameters for the measurement of hydroperoxides were studied. Experimental results showed that when the concentration of potassium ferrocyanide was 0.08 mol/L, the dosage of potassium ferrocyanide and 0.2 % PVA were 1μL, the maximum respondent current of the modified electrode was observed. The linear range of the hydroperoxides concentration in O/W emulsion was of 1.4×10-6～1.3×10-4mol/L, with a correlation coefficient of 0.998. The detection limit of hydroperoxides was 1.7×10-7mol/L.4,The EIS method for the evaluation of the oil rancidity The new EIS method was based on the polarity materials produced during the oil/emulsion rancidity process which could reduce of the impedances of the system. The effects of the concentration of the supporting electrolyte, the methods to accelerate the oil/emulsion oxidation and some important measuring parameters on the impedance spectra and impedances were thoroughly examined.Experimental results revealed that the concentration of hydroperoxide and some small molecules of acid and aldehydes increased, the impedances significantly decreased during the first few days, The double tangent method was used to obtain the intersection of the time and the impedances or the hydroperoxides values. The intersection corresponding to the stable time of the oil/emulsion oxidation could be used to evaluate the qulity of the oil/emulsion system.The experimental results indicated that the provide electrochemical methods for the determination of hydroperoxides in O/W emulsion have some special characteristics,such as simplicity,rapidity,high precision and sensitivity.The EIS method can directly,rapidly and accurately evaluate the rancidity or qulity of the oil/emulsion system without any preliminary extraction of the hydroperoxides with toxic organic solvents, such as chloroform.