| Patr1. Analysis of the spillage of manganese ion during the using of pressure cookerIn this work, the spillage of manganese ion during the using of pressure cooker cooking food was studied. The research covers the most critical influence on the spillage of manganese ion, including the contents of manganese in the material of pressure cooker inner tank and all kinds of factors affects in the process of cooking. Firstly, the XRF-1800X-ray fluorescence spectrometer was used for the detection of the content of manganese in the pressure cooker inner tank. The Results showed that the middle of the tank is made up of Fe and Al, the inner surface coating is mainly composed of Fe, Si, Al, Ni, Mn and Cu. Then, the manganese content in coating materials at the bottom of the tank is higher than wall; Secondly, the samples were prepared and tested by the graphite furnace-atomic absorption spectrophotometry (GF-AAS), to analyze the various effect factors during cooking.(1) The manganese content in the tank material has a certain impact on manganese overflow, and the impact is different of the difference of manufacturing process;(2) In the process of cooking, the added content of salt and vinegar affects the quantity of manganese overflow; After Using frequency reaches a certain value, manganese overflow volume tends to be stable. And the longer the holding time and place time, the more manganese spillage.Patr2. The voltammetry determination of spillage of manganese using carbon fiber micro-electrodesOn the basis of the first part, an new electrochemical method was developed for the determination of Mn2+by differential pulse voltammetry method, based on self-manufacturing carbon fiber micro-electrode (CFME). In the pH=9.5NH3-NH4C1buffer solution, the first step is to scan the oxidation process from0.6to-0.4V, when Mn2+changed to Mn4+; then, the peak current of Mn4+is recorded. In the range of1.5×10mol·L-1～6.0×10mol·L-1and6.0×10-9mol·L-1～8.0×10-7mol·L-1, it has a good linear relationship with c1/2Mn2+with a detection limit of1.00×10-10mol·L-1. In addition, the proposed method was successfully applied to the determination of manganese ion spillage while rice cooker was cooking food, with satisfactory results. The result shows this method has a high sensitivity, low detective limit, simple operation and rapid process.Patr3. Photooxidation assisted sensitive detection of trace Mn2+in tea by NH2-MIL-125modified carbon paste electrodeThe NH2-MIL-125(Ti), as a highly porous titanium-based MOF, modified carbon paste electrode (NH2-MIL-125(Ti)/CPE) was firstly established for convenient and sensitive detection of Mn2+. The NH2-MIL-125(Ti)/CPE was prepared by doping NH2-MIL-125(Ti) yellow powder which was synthesised in the graphite powder. Fourier transform infrared spectrometer, the Bruker D8advance diffractometer, Perkin-Elmer Lambda900spectrophotometer and S-4800scanning electron microscopy (SEM) were used to affirm the characterization of NH2-MIL-125(Ti). More significantly, powder of NH2-MIL-125(Ti) has the photocatalytic properties. Compared with the bare carbon paste electrode (CPE), the NH2-MIL-125(Ti)/CPE exhibited an efficient photooxidation activity towards to the oxidation of Mn+Under the optimum conditions, linear calibration curves was obtained from2.0×10-8～1.0×10-5mol·L-1for Mn2+. The designed electrode also exhibits high sensitivity, low detection limit and widee linear range for detection of Mn2+. This method has been successfully applied for the detection of Mn2+in tea samples, and the results were in close agreements with those obtained by atomic absorption spectroscopic method. |
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