Study On The Detection Of Pesticides In Vegetables By Electrochemical Sensor Based On Nanocomposites

In view of the technical requirement of rapid detection of pesticide residues in food safety field,the new methods for rapid detection of pesticide residues in food had been explored in this paper by combining nanotechnology,biochemistry and electrochemical sensing technology.The main contents,results,and conclusions were as follows:1.Electrochemical rapid detection of fenitrothion pesticide residues based on gold nanorods/chitosan nanocompositesBased on the electrochemical activity of some pesticides and the adsorption of gold nanorods to pesticides,Au NRs/CS nonenzymatic electrochemical sensor was prepared and some parameters that affect the performance of the sensor analysis were optimized.The results showed that under the conditions of Au NRs with CS solution volume ratio of 5:1,the nanocomposites volume of 7 mL,electrolyte solution p H value of 6.5 and adsorption time in pesticide of 5 min,the electrochemical sensor had the best detection performance.The concentration of fenitrothion detected by this electrochemical sensor was linear in the range from 5-300 mg/L with a correlation coefficient of 0.999(R).The detection limit of the developed electrochemical sensor was estimated to be 1.8 mg/L.In addition,the electrochemical sensor showed strong anti-interference ability to organics with similar molecular structure,indicating good specificity.In real samples detection,the electrochemical sensor showed good detection characteristics,and the detection results by the sensor were similar to that of the GC-MS,indicating that the electrochemical sensor had a good application prospect.2.Construction of CNTs/PSA/Ach E biosensors and detection of organophosphates pesticide residues in vegetablesBased on the inhibition effect of pesticide on acetylcholinesterase(Ach E),enzyme biosensor was constructed by using carbon nanotubes(CNTs)/polystyrene-acrylic nanospheres(PSA)nanocomposites to embed enzymes to realize highly sensitive detection of organophosphates pesticides in vegetables.In the experiment,some parameters affecting the performance of the biosensor analysis were optimized.The results showed that under the conditions of the detection potential of 0.3 V,the Ach E amount of 10.8 mg,electrolyte solution p H value of 7.5,the substrate thioacetylcholine(ATCh Cl)concentration of 2.4 m M and the inhibition time of 20 min,the biosensor had the best detection performance on pesticide.The concentration of chlorpyrifos detected by this biosensor was linear in the range from 10-350 ?g/L with a correlation coefficient of 0.998(R).The detection limit of the biosensor was estimated to be 2.2 ?g/L.And the linear range for malathion was 10-1.4×103 mg/L,the correlation coefficient R was 0.999 and the detection limit was 0.9 mg/L.In the real sample detection,the recovery rate of chlorpyrifos was 83.7-105.3%,the recovery rate of malathion was 91.5-109.2%,and the detection results were similar to that of GC-MS,indicating that the biosensor had good accuracy.3.Preparation of biosensor based on platinum functionalized carbon nanotubes and detection of pesticide residues in vegetablesBased on the inhibition effect of pesticides on Ach E,biosensor was constructed via layer-by-layer self-assembly method and further used for the rapid detection of pesticides in vegetables.Some factors that affect the performance of the biosensor analysis were investigated.The results showed that under the conditions of the detection potential of 0.6 V,the Ach E amount of 15.4 mg,the Pt NPs/PDDA-CNTs composites volume of 10 ?L,electrolyte solution p H value of 7.5,the substrate ATCh Cl concentration of 1.9 m M and the inhibition time of 10 min,the biosensor displayed the best detection performance on pesticides.The concentration of phoxim detected by the biosensor was linear in the range from 5-400 ?g/L with a correlation coefficient of 0.994(R).The detection limit of the biosensor was estimated to be 1.2 ?g/L.And the linear range for isoprocarb was 4-550 mg/L,the correlation coefficient R was 0.998 and the detection limit was 0.6 mg/L.In the real sample detection,the recovery rate of phoxim was 89.9-104.7%,the recovery rate of isoprocarb was 89.5-105.6%,and the detection results were similar to that of GC-MS,indicating that the biosensor had good accuracy.