Studies On Rapid Detection Of Pesticide Residue Based On Enzyme Biosensor Of Nano-porous Electrode

Organophosphate?OPs?and carbamate?CBs?pesticides,two kinds of effective chemical pesticides,are widely used in crops such as vegetables,melon and fruits diseases and insect pest prevention and governance.However,the abusing of these two pesticides will give rise to excessive pesticide residues in many crops,thus cause serious threat to the safety of human beings.Considering the special inhibitory effect of OPs and CBs to acetychionesterase?AChE?,it is of great significance to study AChE electrochemical biosensor in order to realize efficient,rapid,accurate,convenient detection of pesticide residues.Based on the research of innovative thinking of the preparation of nano-porous pseudo carbon paste electrode,this thesis intend to usenano-porous carbon paste electrode?nano-PPCPE?preparetion of AChE sensor detection of pesticide residues.In the process of preparetion of AChE electrochemical biosensor,the preparation and condition optimization of nano-PPCPE based on nanometer calcium carbonate?CaCO₃?microspheres as templates have been discussed;using nanometer gold as amplified signal yuan;the immobilization of enzyme have been studied and the experimental parameters have been optimized,at the same time,the electrochemical behavior of the prepared enzyme biological electrochemical sensor where nano-porous electrodes are applied to convert acetylthiocholine iodide of acetylcholine to acetylthiocholine has been discussed systematically,finally the prepared AChE biosensor have been applied to detect OPs and CBs pesticide residues,the effect is remarkable.The main content of this paper is as follows:1.The preparation of nano-PPCPE and its electrochemical behavior.An ultrasensitive nano-PPCPE was fabricated based on pyrrole as precursor,CaCO₃ microspheres as a template and graphite powder as padding.The experimental results showed that when the ratio of the applied CaCO₃ microspheres/graphite powder was 1:1.5,and the CaCO₃ microspheres possessed a smaller particle size?60⁸0nm?,the obtained nano-PPCPEs displayed a larger specific surface area which was even up to 923.5 m2/g.The electrochemical behavior of nano-PPCPE wasevaluated by cyclic voltammetry?CV?and electrochemical impedance spectroscopy?EIS?.The results showed that the nano-PPCPE has good electrochemical behavior such as strong current intensity,good stability in comparison with the traditional carbon paste electrode,demonstrating important significance in electrochemical detection and analysis.2.The preparation of AChE modificationtory nano-porous biosensor and its electrochemical behavior.A novel nano-porous AChE electrochemical biosensor was constructed using chitosan?CS?as cross-linking agent,Nafion-methanol solution as the protective agent,gold nanoparticles?Au NPs?for signal amplification,self-made nano-PPCPE as substrate electrode.And the electrochemical behavior of the electrode was studied with acetylcholine iodide as the substrate.Under optimum conditions,there is a good linearity between the response current of the sensor and the concentration of the acetylcholine iodide with the concentration range from 1.0×10^-4 to 1.0×10^-7 M,and the linear equation is y=1.2178x+13.7429,the linear correlation coefficient is R=0.998,the detection limit is 1.0×10^-8 M.The results showed that the sensor takes the advantages of high sensitivity,good stability and repeatability,strong ability of anti-interference and strong current,etc,showing a good practical value.3.The application of AChE modificatory nano-porous electrochemical biosensor to OPs and CBs pesticide residue detection.The sensor is applied to detect to concentration of methyl parathion,marathion and carbaryl detection.The experimental results shows,the biosensor detected methyl parathion in the linear range from 1.0×10^-8 to1.0×10^-?14? g/mL with a detection limit of 5.0×10^-?15? g/mL and detected marathion in the linear range from 1.0×10^-?10? to 1.0×10^-?13? mg/mL with a detection limit of 5.0×10^-?14? g/mL and detected marathion in the linear range from 1.0×10^-7 to 5.0×10^-?10? mg/mL with a detection limit 5.0×10^-?14?mg/mL.The enzyme sensor used for the detection of pesticides has wide linear range,low detection limit,providing a new thought and method for further improving the OPs and CBs pesticide residues detection.