Study On Electrochemical Methods Of Dichlorvos And Triadimefon And Solid Phase Extraction Techniques For Eleven Pesticides In Water

The use of pesticides provides unquestionable benefits in increasing agricultural production. However, it has the drawback of pestide residues which remain in environment and agricultural products, constituting a potential risk to people because of their toxicity. To protect consumers' health, many countries have restricted the usage of pesticides and have established legal directives to control their levels in food, through the Maximum Residue Levels (MRLs). To monitor enviroment pesticide pollution and provent agricultural production that contain pesticide residue levels higher than the MRLs from entering the marketplace, determination of pesticide residues is indispensable. The method of the Association of Official Analytical Chemists (AOAC), the internationl recognized pesticide residual analysis can detect approximately 325 pesticides and pesticide-related compounds and most of them have undergone rigorous multiaboratory calibration studies, such as those needed to obtain the official acceptance by the AOAC. However, these methods still present disadvanges because their procdures are time consuming, labour intensive and large amount of toxic solvent consuming. So the paper is mainly study the rapid detection of pesticide with electrochemical and solid phase extraction techniques.A Single-sweep polarography was described for the determination of trace dichlorvos (DDVP) with sodium perborate (SPB) and benzidine. The detection limit and the linear range were 1.0ug /mL and 3.0ug/L~7.5mg/mL (R2=0.9992) respectively. The method had been used for determining trace DDVP in plant with satisfactory results. The catalysis of DDVP was indicated by the experimentation, and the mechanism of electrode reduction was also discussed in this paper.The degradation reaction of triadimefon in copper(II) ion solution was examined by electrochemical, HPLC and HPLC-MS method. The results show that triadimefon can be degraded into l-(l,2,4-triazol-l-hydroxyl)-3,3-dimethyl-butan-2-one (THDB) and 4-chlorophenol by copper (II) ion. A electrochemical active complex of copper (II)-THDB formed in the supporting electrolyte of 0.35 mol/L NH3-NH4Cl (pH=8.2), a sensitivereduction peak of the complex was found at -0.566V(vs.SCE) by using single-sweep polarography, which detection sensitivity is nearly 100 times as that of tiradimefon at -1.326V(vs.SCE), the peak current is directly proportional to the concentration of triadimefon over the range of 4.0x10-7 to 1.92x10-5mol/L, the detection limit is 1.0x10-7mol/L. A new sensitive method for indirect determination of triadimefon was established, which has been used for determining triadimefon commodity and its residue in fruit with satisfactory results. Compared with other verify techniques, the method is faster, easier and less reagent consuming. The degradation process of triadimefon and the electrode reaction mechanism of the system were also discussed in this paper.A method was proposed for the simultaneous determination of eleven micro-pesticides (methomyl, imidacloprid, acetamiprid, tricyclazole, carbofuran, metribuzin, pirimicarb, atrazine, diuron, benazolin-ethyl, mefenacet) in tap water and Yangtse river water, using solid-phase extraction (SPE) with Supelclean?LC-18 cartridge and reversed phase high performance liquid chromatography technique. In the concentration range 5mg/L~10ug/L, the correlation coefficients were all up to 0.9997. The fortified recoveries of 11 pesticides were all up to 80% except methomyl, the detection limits of the whole procedure achieved were 0.0118-0.0610 ug/L (S/N=3, enrichment factor: 100), less than 0.1ug/L, which the maximum limit permitted by the European Community standard for drinking water.