The Research Of Enzyme Sensor For Organophosphorus Pesticides Rapid Detection In Vegetables And Water

Organophosphorus pesticides are commonly applied in agriculture field because of their high insecticidal activity,which play an important role in controlling diseases and insects effectively and increasing crop yield.However,these pesticides belong to one kind of neurotoxins,which can irreversibly inhibit the acetylcholinesterase(AChE)activity of human central nerve system,and thus block the reaction that AChE catalyze the hydrolysis of acetylthiocholine chloride,resulting in central nervous system symptoms and nicotinic signs and symptoms or even death due to respiratory paralysis.As one of the most widely used insecticides in China,organophosphorus pesticides has poses a serious threat to food safety and human health because of its residue and accumulation in agricultural products.Therefore,it is of great significance develop a rapid,sensitive and accurate method to detect pesticide residues in environment.Recently,the electrochemical biosensor method have received high attention because of various advantages,such as easy-to-operate,rapid response,high sensitivity,low cost and suitability for the on-site analysis of pesticide residues.With the development of nanomaterials and new electrochemical analysis methods,new electrochemical sensors will play an important role in the trace analysis of po llutants.This study provides a new electrochemical sensor for organophosphorus pesticides detection and studies their application in practical application.In this study,a sensitive and stable electrochemical AChE sensor has been developed for the quantitative detection of organophosphorus pesticides,and N-doped ordered mesoporous carbon(N-OMC)was synthesized and employed to modify the electrode surface to provid a stable platform for AChE immobilization combined with AuNPs and L-cysteine self assembled monolayer,which is favorable to maintaining and restoring the enzyme activity as well as improving the stability and repeatability of the biosensor.Scanning electron microscope(SEM)and transmission electron microscopy(TEM)were used to investigate the structure and morphology.Fourier transform infrared spectroscopy(FTIR)was applied to analyze the likely existence of functional groups.Nitrogen adsorption measurements were performed to determine the pore size distribution,the surface area and the total pore volume.The characterization of the materials showed that the preparation of N-OMC was successful and N-OMC had highly ordered mesoporous structure,large surface areas and plentiful amino group,which was appropriate as the modification material for enzyme sensor.Differential pulse voltammetry(DPV)was applied to detect organophosphorus pesticides.Electrochemical impedance spectroscopy(EIS)and cyclic voltammetry(CV)were used to study the electrochemical properties of the modified electrode.The electrochemical characterization of the modified electrodes showed that each step of self-assembled process of the working electrode is successful,besides,compared with bare electrodes,the conductivity of the modified electrode is obviously enhanced.Some experimental parameters were optimized,including the pH of PBS,the amount of immobilized AChE and the inhibition time of inhibitor on the biosensor.Under the optimized conditions of pH 7.38,5?L AchE and 10 min for inhibition time,the prepared biosensor displayed satisfactory reproducibility,excellent repeatability and good stability,and the fabricated electrode exhibited linear calibration curves ranged from 3 nM to 24 nM for paraoxon,with the correlation coefficients of 0.99501,and the limits of detection were 0.02 nM(S/N=3).Compared with other reported AChE biosensors,the construction of this prepared biosensor was more stable and the analytical performances of this biosensor were excellent.This resulting biosensor was applied to analyze pesticide residues in vegetable samples and tap water,which demonstrated that the biosensor has high accuracy and excellent reliability for organophosphorus pesticides detection.Consequently,this study not only expands the application of nanomaterials in developing biosensors and extends for the development of other new sensors for organics determination,but also provides a promising way to detect pesticide residue in real agricultural samples.