Study On Electrochemical Analysis Method About Common Organophosphorus Pesticide

Organophosphorus pesticide is used for preventing and controlling plant disease、insect and harm of organic compounds, which can improve the agricultural productionin agriculture, however, it also has vary degrees of damage to plants、animals and theenvironment. In recent years, with peoples’ living standard rising, the problem of"food safety" has aroused people’s great concern, especially; pesticide residue mustnot be overlooked in the "food security" problem. With development and applicationof hyper-efficiency pesticides, and the increase of the inspected samples, so there aremore stringent requirements for the sensitivity, specificity and rapidity of pesticideresidue analysis techniques, and research rapid、simple and high sensitivity ofpesticide detection technology has great significance.Electrochemical detection method is a rapid, sensitive and accurate methods fortrace components, In recent years, the sensitive electrochemical method has takenmore and more great potential and advantages in the field of organic analysis,moreover, that in the application of pesticides analysis is also growing. In this paper,taking chlorpyrifos, phoxim, dimethoate and triazophos and isocarbophos five kindsof common organophosphorus pesticides as the research objects, and establishing twomethods of electrochemical detection for a common organophosphorus pesticideresidues by single sweep polarography and molecularly imprinted polymer modifiedelectrodes voltammetry.1.Taking organophosphorus pesticide chlorpyrifos as representative, utilize itsassociation complx which formed by combing with cetyltrimethyl ammoniumbromide (CTMAB) in the neutral medium to reduce inhibitory effect of CTMAB onpeak current of Salicylfluorone (SAF), and establishing a new polarographic analysismethods of determination for chlorpyrifos, phoxim, dimethoate, isocarbophos andtriazophos. The peak current is linearly proportional to the concentration ofchlopyrifos in the range of0.0192~24.0μg/mL, and the detection limit is0.012μg/mL. The recoveries of samples is in the range of90.36%~103.3%.Thedynamic ranges for other organophosphorus pesticide which including phoxim, dimethoate, isocarbophos and triazophos are0.016~25.2μg/mL,13.41~33.52μg/mL,17.42~34.84μg/mLand0.0110~21.2μg/mL, respectively.2. The method for the determination of organophosphorus pesticides phoximresidues indirectly by single sweep polargraphy has been established. It’s based on theinhibitory effect of phoxim on the formation of complex among Tween-80and TitanYellow (NY) in acidic medium. The optimal determination condition is4.0×10-4mol/L Titan Yellow-8.8×10-4mol/LTween-80-Na2HPO4-KH2PO4(pH=6.7)-5.0mg/LPolyethylene Glycol (20000). The starting potential is-0.15V (vs, SCE) and the peakpotential is-0.38V (vs, SCE) by JP-303polarography. The peak current is linearlyproportional to the concentration of phoxim over the range of0.0094~28.22mg/L.The detection limit is0.0086mg/L. The recoveries of samples are from93.62%to105%.3. This study with phoxim as template, α-methacrylic acid (MAA) as monomer,ethylene glycol dimethylate (EDMA) as cross-linker and2,2-azobisisobutyronitrile(AIBN) as initiator, the phoxim molecular imprinted polymers (MIPs) wassynthesized by polymerization in acetonitrile. MIPs were modified with glasscarbon electrode by voltammetry determination of phoxim residue. MIPs werecharacterized by scanning electron microscope (SEM) and infrared spectroscopy(FTIR). Scatchard analysis method combines with equilibrium experiment. Scattermolecularly imprinted polymers in medium solution and spin coating adhesion onglassy carbon electrode electrode surface is sensitive to phoxim molecularly imprintedmembrane electrode. The tests use three electrode system (namely film glassy carbonelectrode as working electrode, calomel electrode as the reference electrode, platinumelectrode as auxiliary electrode), and the optimum incubation time is5minutes.Linear sweep voltammetry (LSV) is used in the process of electrochemicalmeasurement, which lets observe that the linear will be response if with detectionlimit is6.0×10-8mol/L and phoxim in the concentration of1.2×10-7-6.0×10-3mol/L.The sensor is applied in the analysis of phoxim in real sample with recoveries of93.8%~96.2%. The electrode modified with phoxim molecular imprinted polymer exhibiteda good selectivity and sensitivity to phoxim when it is exposed to a series of closelyrelated compounds that are similar with elertochemical characteristics. Suchas,triazophos, chlorpyrifos and dimethoate.