| Based on the transition metal properties of cobalt and nickel,hydroxides were in-situ modified on the surface of carbon paste electrodes.The complex of transition metals with nitrogen and sulfur atoms in pesticides,solid phase microextraction of and electrocatalytic properties modified electrodes were used to detect pesticide residues.Nickel hydroxide and cobalt hydroxide were in-situ modified on the surface of the electrode.The electrocata lytic and electrochemical detection methods of Diuron,a semicarbazide pesticides,Phoxim,an organophosphorus pesticide and Chlorothalonil,an organochlorine pesticide are explored and innovated.Cyclic voltammetry method?CV?,Electrochemical Impedance Spectroscopy method?EIS?and the PM7 semi-empirical molecular orbital calculation in MOPAC 2016 software were used to characterize and discuss the electrons transfer process and the reaction of the complexes.The calculation results are consistent with the experimental ones and corroborate each other.The main results are as follows:1.Diuron,a semicarbazide herbicide,was extracted onto the surface of the electrode by electromembrane theory under the electrode voltage.Nickel hydroxide was in-situ modified on the surface of carbon paste electrode by CV method,and the modified electrodes were characterized by XRD.Diuron interacts with nickel hydroxide and forms a complex.Cyclic voltammetry results show that the reduction process is controlled by adsorption.The logarithm of reduction peak current changed linearly with diuron concentration in the range of 0.775×1030.775×10-3?g/mL.The detection limit is 0.775×10-3?g/mL.It has been used for the detection of diuron residual in paddy wastewater in the Pu River.Calculation results indicate that the coordination of nickel hydroxide with diuron is stable.?Gr<0 shows the reactions are thermodynamically spontaneous.The molecular parameters of the coordination compounds are discussed by the theory of frontier molecular orbits.The calculation results provide theoretical basis for the experiment results.2.Cobalt hydroxide was in-situ deposited on the surface of carbon paste electrode by electrochemical method.Phoxim,an organophosphorus pesticide,was solid phase micro-extracted onto the electrode surface.The adsorption process follows the isothermal adsorption model.Working curve is a linear function in the range of0.9929.92×10-3?g/mL and 9.92×10-39.92×10-8?g/mL respectively.The detection limit is 9.92×10-8?g/mL.It has been used for the detection of phoxim pesticides in spinach.Calculation results show:the complex of cobalt hydroxide with phoxim is stable.The reaction can go spontaneously in two concentration ranges.CV,EIS and PM7 methods were used to characterize the process of the reaction.3.Cobalt hydroxide modified electrode was further used to detect chlorothalonil,an organochlorine pesticide.Metal ions react with the drugs and form a complex which is adsorbed on the surface of the electrode.The experimental conditions such as quite time,adsorption time and initial potential were optimized.The reduction peak current and chlorothalonil concentration shows linear relationship in the range of8.858.85×10-7?g/mL.The detection limit is 8.85×10-7?g/mL.Theoretical calculation results show:the complex of cobalt hydroxide with chlorothalonil is stable.Calculation results combined with EIS method were used to explore the reaction process. |
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