| Pesticides are chemicals used to control and/or eliminate plant or animal pests and diseases?pests,nematodes,pathogens,weeds and rodents?.Therefore,they are widely used in agriculture to ensure the normal growth of crops and human food supply.However,their excessive use brings about severe contaminations of food and environmental,causing various diseases,threats to human health.In recent years,with the continuous improvement of people's consumption level,food safety has become a public concern.Detection of pesticide residues in the food has become even important.Therefore,the development of repaid detection methods is great importance.At present,several detection methods have been employed to the detection of pesticide residues,include the chromatography,enzyme-linked immunoassay?ELISA?,enzyme biosensor,ultraviolet spectrophotometry,molecularly imprinted sensor,etc.These methods can be used for accurate and sensitive detection of pesticides residues.However,these methods require tedious sample preparation process,and expensive equipment and they are difficult to meet the requirements of on-site rapid detection.Therefore,it is necessary to develop some fast,simple and sensitive detection methods.Compared with the traditional detection methods,electrochemical sensors have advantages of high selectivity,high sensitivity,fast analysis speed,low composition and in-situ detection.However,the traditional electrochemical sensor does not satisfy the request of the high sensitivity for the detection of pesticide residues.In order to improve the sensitivity,the sensor?electrode?needs to be specifically modified.But with such modification,the electrode preparation and post-use regeneration operation are complicated,meanwhile sample pre-processing takes a lot of time and time in the whole detection and analysis,Which is disadvantageous for rapid analysis.To Solve these problems.In this paper,prepared a series of conductive materials has the function of pesticide enrichment ability and modified the working electrode,thus the improved the sensitivity of pesticide detection.In addition,based on the electrochemical analysis method,the electrode ink which can be used for in-situ detection is prepared and directly used on the surface of the vegetable sample to realize the actual sample detection without sample pretreatment,and provides a new technology for rapid detection of residual pesticide;At the same time,this method can also be used for the detection of a variety of electroactive substances,providing a new idea for the development of in-situ rapid detection technology,which is of great significance.In addition,by using copper or copper compounds high affinity to sulfur-containing compounds,using copper oxide as a electrode material,and modifying the working electrode,fabricated a non-enzymatic sensor with non-toxicity,high electrocatalytic activity,and good chemical stability,and instead of high sensitivity and high selectivity enzyme sensor.The main research contents,results and conclusions of this paper are as follows:?1?Prepared a silicon carbide nanomaterial having an enhanced effect on the electrochemical performance of the pesticide parathion,and using facile drop coasting method constructed the electrochemical sensor,the prepared electrode exhibited the dual function of enrichment and detection for parathion pesticide,and successfully used direct detection of parathion pesticide residues in actual samples.The sensor preparation process were characterized by scanning electron microscopy?SEM?,Cyclic voltammetry?CV?,and Electrochemical Impedance Spectroscopy?EIS?.Utilize the electrochemical method,the silicon carbide nanoparticles modified electrode has the function of pesticide enrich by solid-phase extraction,thus improving the detection sensitivity and simplifying the process of operations.Compared with bare glassy carbon,the modified eletrode can significantly increase the detection sensitivity of a parathion in the sample.And the proposed sensor appears wide linear detection orange is 1 x 10-9 to 1 x 10-5g/m L with the accumulation time of6 min in p H 6.0 PBS buffer solution.the detection limit of parathion estimated to be 5×10-10g/m L?S/N=3,n=3?.Furthermore,The sensor also exhibits good reproducibility and stability,and has been successfully used for the determination of parathion in real water samples with the recoveries between 99.8%and 101.2%.?2?Prepared a paintable electrode ink,and used the on-site direct detection of parathion residuals from vegetable products.The electrode is simple to prepare,fast detection response,and without sample pretreatment is required.The electrode ink was mainly fabricated by silicon carbide and multi-walled carbon nanotubes and the resulted painted electrode was further stabilized by a layer of chitosan acting as a fixing glue.The painted electrode shows significant sensitivity for parathion with a detection limit of 2×10-8 g/ml.In on-site practice of real samples of some common local supermarket vegetables such as Chinese cabbage,Sweet potato leaf and cucumber,the painted electrode successfully used to monitor the evaporation of parathion with satisfied results of recoveries between 76%and 96.2%.?3?We prepared a highly sensitive electrochemical sensor for the free-enzymatic indirect detection of malathion.The electrochemical sensor was based silicon carbide and copper oxide nanocomposite material.The structural and morphological properties of the Si C@Cu O-NPs/GCE nanocomposite were characterized by scanning electron microscopy?SEM?and X-ray diffraction?XRD?.Si C-NPs has the function of malathion pre-concentration and Si C@Cu O-NPs nanocomposite was noted to possess high affinity towards malathion.thus the redox reaction of Cu O could be hindered.This feature was utilized to design as a simple strategy for electrochemical detection of malathion.Electrochemical detection of malathion was investigated via cyclic voltammetry?CV?,differential pulse voltammetry?DPV?,respectively.Under the optimized experimental conditions,the inhibition rate displays a good linear relationship with the concentration of malathion,the linear range is 0.03 n M?3.0n M,and the detection limit is 0.01n M?S/N=3?.In addition,the sensor exhibits good selectivity,stability and reproducibility,and has been successfully used in the detection of malathion in actual water samples with recoveries between 99.33%and 106.6%,which is satisfactory experimental results. |
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