Study Of The High Sensitive Voltammetric Determination Methods For Pesticide Residues

Pesticides are chemicals of using to prevent, eliminate or control the harm of agriculture, forestry disease, insect, grass, other harmful organisms and purposefully regulating growth of plants, insects or are a substance deriving from biological, other natural substances or mixture of several substances and their preparations. In the current agricultural production, pesticide is indispensable substance which is used for the prevention and treatment of disease, insect or weeds damaging to the crops. And pesticide has an extremely important role promoting agricultural production.Pesticide residue refers to after the use of pesticides in agriculture, part of pesticides directly or indirectly remaining in grains, vegetables, fruit, livestock,aquatic products and the phenomenon of soil and water. Currently in use of pesticides,some in a relatively short period of time can become harmless by biodegradable material, it will be difficult to degradation for organochlorine pesticides which are persistent pesticides. Residue exceeding of vegetable pesticides will directly endanger the human body’s nervous system and important organs such as liver and kidney.Pesticide pollutions in addition to have an impact on human health, also have great influence on the environment and national strategic security. Because our country farming system is spread, safety consciousness is weak for farmers to use pesticides,the necessary checks and admittance system are lack for crops and food circulation management, pesticide pollution is basically in a state which is out of control in China.Therefore, it is very urgent to determinate accurately pesticide residues for agricultural products such as fruits and vegetables in the social life.This paper aims to establish a simple, rapid and sensitive voltammetric determination method used in the determination of pesticide residues, and satisfactory results are also obtained. The main research contents and results are as follows:(1) Using the electrochemical method to carry on the simple processing for bare glassy carbon electrode, electrochemically pretreated glassy carbon electrode was fabricated to use for the determination of pesticide pymetrozine. Using the sensor, we systematically investigated electrochemical behavior of pymetrozine and some kinetic parameters were researched. Under optimized conditions, a good relationship was obtained between peak current and pymetrozine concentration from 1.0 × 10-7 ~ 5.0 ×10-6 mol L-1, the detection limit was 8.0 × 10-8 mol L-1. Finally, we also studied thedegradation experiments of pymetrozine in natural soil and acquired satisfactory results.(2) In this experiment system, L-Norvaline was first used as modified material in the preparation of electrochemical sensor. In this paper, we systematically studied the influence on polymerization film forming conditions of L-Norvaline and optimized conditions were used for the determination of herbicide metribuzin. Using the modified electrodes, sensitive electrochemical response of metribuzin was observed.Based on the research of metribuzin properties, we also derived the electrochemical reaction mechanism of metribuzin. Under established analytical method, a good relationship was obtained between peak current and metribuzin concentration from3.0 × 10-8~ 5.0 × 10-6mol L-1, the detection limit was 1.0 × 10-8mol L-1. In the analysis of the real sample, a satisfactory recovery was also obtained.(3) Firstly, multiwalled carbon nanotube fabricated was coated on the bare glassy carbon electrode. Then, the electrode was put into the solution consisting L-histidine carrying on electrochemical polymerization. Thereby a simple and stable L-histidine/multi-walled carbon nanotubes modified glassy carbon electrode was fabricated. Based on the modified electrodes to research electrochemical behavior of thiamethoxam and establish analytical methods, we deduced the electrochemical reaction mechanism of thiamethoxam. A calibration plot of peak current versus thiamethoxam concentration was linear in the range of 5.0 × 10-7~ 3.0 × 10-5mol L-1.The detection limit of thiamethoxam was found to be 3.0 × 10-7 mol L-1. Using this method, we successfully got satisfactory results of thiamethoxam in real sample analysis.