Study On Electrochemical Sensing System For Detection Of Pesticide Spray Deposition

As a big agricultural country,crop protection plays essential roles to ensure steady yield of agricultural products in agricultural development.Spraying chemicals is the most common precautionary measure,but there are many problems in the process of spraying pesticides.If dosage of pesticides is enough,it cannot kill pests and control diseases.However,excessive use of drugs not only causes a waste of resources and causes environmental pollution,but also threatens human health.At present,most of the methods for spray quality testing are using water-sensitive paper or spectrophotometrys in laboratory,but these methods have some disadvantages.Therefore,the development of a simple,inexpensive portable on-site spray quality detection system is particularly important.Based on electroanalytical chemistry,a direct electrochemical sensor with high sensitivity,good selectivity and stability has been prepared.Then the signal processing circuit hardware processing unit,signal display software processing unit,and the system power circuit design are designed.On the basis of the design of each system unit,the whole system is constructed,and the performance analysis and experiment of the whole system is carried out.The major research works are as follows:(1)The construction of organophosphorus pesticide electrochemical sensor and its performance study.A simple and sensitive enzyme-free electrochemical sensor was prepared by using nitrogen-doped graphene(NG)-modified screen printing electrode for electrochemical detection of methyl parathion(MP).The electrochemical behavior of MP was studied by cyclic voltammetry(CV),differential pulse voltammetry(DPV)and linear sweep voltammetry(LSV).Due to the uniqueness of nitrogen doping structure and properties,NG produces higher electrocatalytic activity for methyl parathion in PBS solution.In the case of a signal-to-noise ratio of 3,the maximum sensitivity of the sensor to MP is 15.32 ?A / ?mol.Under the optimized conditions,the prepared sensor has good stability and selectivity.(2)Analysis and design of key unit for signal detection in the system.The designof hardware unit in system conditioning circuit were carried out,including constant potential circuit design,I / V conversion amplifier circuit,filter circuit and power circuit.With 12 V DC power providing energy,the micro-level current signals were changed into 0-2.5V of the analog voltage signal.In order to get the desired functional results,the signal conversion part of the circuit was tested.And the relationship of the output voltage and the amount of liquid concentration were obtained for software programming.The detection sensitivity of system is 0.6V/?mol.Then the control chip STC89C52,A/D conversion chip PCF8591 and 1602 liquid crystal software were selected for signal display unit.Data show for mass concentration of spraying deposition was achieved through changing the analog voltage signal into a digital signal.(3)Performance tests and the application of the whole system.The overall structure of the detection system was built.Comparing the practical spraying results with obtained spray detecting system and electrochemical workstation,the accuracy and stability of obtained spray detecting system were verified.This system was applied to detect the foliar spray deposition uniformity and the whole spray fraction distribution.The detection system is simple,accuracy,stability,and can be realized miniaturization.The stability detection time of the system is 240 s and the detection error of the application system is less than 5%.The results show that electrochemical sensing system for detection of pesticide spray deposition has the characteristics of stability and portable.This system has a good application prospects in the field of spray quality monitoring.