Design And Application Of Electrochemical Field Detection System For Foliar Pesticide Concentration

Pesticides play a key role in the control of pests and diseases.The spraying amount of pesticides is insufficient,and it does not play a role in controlling pests and diseases;excessive spraying of pesticides will bring phytotoxicity,pollute the environment,and even endanger human health.Therefore,it is necessary to detect the concentration of pesticides on the foliage.Commonly used pesticide concentration detection methods include chromatography,spectrophotometry,and chemiluminescence.However,the cost of these methods is high,and the professional technical requirements of the instrument operators are relatively high,which cannot meet the real-time detection on site.Aiming at this problem,this paper designed a real-time collection and display system of foliar pesticide concentration based on screen printing electrodes,and analyzed the performance of the detection system.The main work is divided into the following aspects:?1?Construction and performance characterization of foliar spray pesticide concentration detection sensor.The modification of the carbon nanomaterials improves the sensitivity of the screen printing electrode to pesticides,and improves the sensitivity of the detection of the concentration of the pesticide droplets.The electrochemical properties of screen-printed electrodes were characterized by cyclic voltammetry,differential pulse voltammetry and electrochemical impedance.The experimental results show that the average resistance of the same batch of screen-printed electrodes is 1.082K?,the relative standard deviation is 4.51%,the electroactive specific surface area?A?is 0.051cm2,and the electron transfer impedance is 500?.Under the optimal experimental conditions,the prepared screen-printed electrode has better stability and selectivity.This study provides new sensor components for the detection of pesticide concentration in the field.?2?Preparation and characterization of a gel electrolyte for an electrochemical system.In order to realize the real-time detection of real-time foliar droplet pesticides,a gel electrolyte was prepared instead of the liquid electrolyte in the conventional electrochemical system.The microstructure,mechanical properties and electrical properties of the gel electrolyte were characterized.The experimental results show that the gel electrolyte has a viscosity coefficient of6.48 N·s·m^-2,a bulk conductivity of 7.32×10^-4 S·cm^-1,and an ion conductivity of 2.35×10^-5S·cm^-1 at a gel weight percentage of 2.5wt%.Under the optimal experimental conditions,the gel electrolyte exhibits good mechanical properties and electrical conductivity,and can replace the liquid electrolyte in the conventional electrochemical system to realize the detection of the concentration of the droplet pesticide at the screen printing electrode.?3?Design of measurement and control system for foliar droplets pesticide concentration.The leaf surface mist drop pesticide concentration measurement and control system includes two parts:a hardware unit and a software unit.The hardware unit design includes a potentiostatic module,a microprocessor module,and a power supply circuit.In the constant potential mode,the microampere current signal is converted into a detectable analog voltage signal output through the replication and amplification of the current mirror.The software unit includes the lower computer software design,firmware design,and host computer interface design.In the Windows7 system environment,the upper computer interface uses the graphical programming software LabVIEW as the development platform,communicates with the microprocessor through the serial port for data transmission,and monitors the real-time status of the lower computer online,and characterizes the received fog in the form of waveform diagram,Collection information of drop concentration.?4?Performance test and application research of electrochemical on-site detection system for foliar droplet pesticide concentration.The performance test of the system mainly includes two parts:hardware unit performance test and electrochemical test test of the detection device.The high-precision multi-channel PM8500 electrical parameter measuring instrument is used to measure the current control accuracy and current sampling accuracy of the hardware unit of the detecting device.The error between the sampling current value and the measured current value is stable within 0.2?A.Finally,under the optimized conditions,the actual farmland spray pesticides were simulated to verify the reliability of the electrochemical field detection system of the leaf droplets pesticide concentration.The experimental results show that the recovery rate is 97.3%,and the maximum relative error is 14.58%.