Detection Of Nitrite And Hydrogen Peroxide In Micro Polluted Water With Chemically Modified Electrode

With the rapid development of industry and the fast advancement of urbanization, the problem of environmental pollution has become one of objects that people pay increasing attention to and which should be addressed urgently. Water environment is closely linked with human life, whose pollution is receiving more and more attention from people. As relatively common substances in micro-polluted water, nitrite ion and hydrogen peroxide are easily soluble in water. However, large doses of intake will be extremely toxic to human bodies and even pose a threat to human life. With regard to this issue, an increasing number of researchers are focusing on studying new materials to detect water quality.Common detection methods mainly include spectroscopy, chromatography, chemiluminescence method, and electrochemical methods and so on, among which electrochemical method takes advantage of chemically modified electrodes to detect water samples and is widely used because of its advantages such as simple operation, low cost and sensitive response. However, the poor stability of chemically modified electrodes has been its disadvantage. Therefore, it is necessary to prepare electrochemical detection electrodes with low limit of detection and high stability so as to detect micro-polluted water.In this paper, FTO was taken as the base and two-step electrodeposition method was applied to successfully prepare Ni/Ag/MWNTs/FTO modified electrode with simple operation and stable performance based on Ni, Ag and MWNTs. According to the research, the electrode possessed good ability in catalyzing and oxidizing NO2-. From the ampere response of the modified electrode to nitrite ion, it could be seen that a good linear relationship existed between ampere response and the concentration of nitrite ion in the concentration range of 1 μmol·L-1 to 0.5 mmol·L-1. The correlation coefficient was r2=0.9932. Through conducting several experiments, the lowest limit of detection was obtained, namely 4.6×10-7 mol·L-1.With high sensitivity and reproducibility and good capacity of resisting disturbance of a variety of cations and anions, the electrode could be applied to detect practical samples.Based on Ni/Ag/MWNTs/FTO modified electrode, the performance was improved and glassy carbon electrode (GCE) was taken as the base electrode to successfully prepare Cu/Ag/MWTNs/GCE electrode with stable performance and simple operation modified by Cu, Ag and MWNTs. The electrode possessed good ability in catalyzing and oxidizing NO2-, whose limit of detection reached 2×10-7 mol·L-1 which was more than half lower than the limit of detection of Ni/Ag/MWNTs/FTO (4.6×10-7 mol·L-1). From the amperometric detection of Cu/Ag/MWNTs/GCE modified electrode for nitrite ion, it could be noticed that electric current showed a good linear relationship with the concentration of nitrite ion in the range of 1 μmol·L-1 to 0.05mmol·L-1. The electrode had high sensitivity and capacity of resisting disturbance of various cations and anions.In the process of studying the detection of electrode for hydrogen peroxide, substep electrodeposition method was used to successfully prepare Sn/AgNWs/MWNTs modified electrode. In the concentration range of 0.001 mmol·L-1 to 0.1 mol·L-1, the current response of the electrode presented a good linear relationship with the concentration of hydrogen peroxide and r2=0.9960. The electrode had obvious ampere response to hydrogen peroxide and relatively sensitive current response value to low-concentration H2O2. The limit of detection reached 1.05×10-6 mol·L-1. Through inspecting the relationship between peak current and sweep speed, the reaction process of the electrode involved adsorption control.In this research, MWNTs was also modified. N-doped MWNTs was successfully prepared by means of hydrothermal method and N-MWNTs/AgNWs/GCE electrode was prepared with the method of electrodeposition method. With good electrochemical response to hydrogen peroxide, the electrode could detect H2O2 under the condition of low concentration. When the concentration range of H2O2 varied from 1 μmol·L-1 to 0.08 mol·L-1, the electrochemical response value of the electrode showed a good linear relationship with the concentration of H2O2. The lowest limit of detection reached 2.74×10-7 mol·L-1. The electrode possessed good ability in resisting interfering substances including citric acid (CA), glucose, ascorbic acid and so on. The corresponding current curve of hydrogen peroxide could quickly restore stability and maintain good stability and reproducibility after adding interfering substances.Researches showed that, the several kinds of electrodes prepared in this paper, all had relatively low detection limit and strong stability.These electrodes had anti-interference ability for a variety of ions or matter, could be applied in slightly polluted water.