Studies On Residual Degradation Of Metamifop In Rice And Environment And The Adsorption And Mobility Of Profenofos In Soils

In this paper, it was studied that the residue analysis of Metamifop and its three major metabolites and the residue dynamics and final residues in rice plant, paddy water, and soil. Under laboratory conditions, the adsorption and mobility of profenofos in three kinds of soils were also studied using batch equilibrium technique and soil thin layer chromatography. The results could be summarized as followings:1. The high performance liquid chromatographic method was developed for the simultaneous determination of Metamifop and its three major metabolites in rice and environment. Residues were extracted with a mixture of acetonitrile and water, followed by cleanup with a silica gel column, and determinationed by HPLC with a linear gradient elution program of acetonitrile and water as the mobile phase and ultraviolet detection at 224 nm.The results showed that the linear range of Metamifop and its metabolites were from 0.5 to 20mg/L, the correlation coefficients were 0.9993 to 0.9999, the limit of detection were 0.432ng,0.502ng,0.268ng,0.317ng, respectively. The minimum detectable concentration of the 4 analytes in soil, rice straw,rice hulls and unpolished grain samples were all O.lmg/kg, and 0.02mg/kg in paddy water samples.Average recoveries were 78.2 to 106.9%,and the coefficient of variation ranged from 2.0 to 11.7%. Under the same operation condition, good chromatographic separation of the 4 analytes was achieved. The Sensitivity, accuracy and repeatability of the method were fitted for the requirement of pesticide residue analysis and detection, and it was easy to perform in practice.2. Degradation dynamic of 10% Metamifop EC and its metabolites in rice and environment was studied by a two-year field experiment. The results showed that the degradation procedure of Metamifop in paddy water, soil and rice straw all accorded with the one-level dynamic equation Ct=Coe-kt; the half-life of Metamifop in paddy water, soil and rice straw were 3.3-7.4d,9.1-14.3d and 1.5-2.2d, respectively. The degradation of its three major metabolites (HFMPA, HPFMPA and 6-CBO) was irregular.3. Terminal residue of Metamifop and its metabolites in rice plant and soil was studied by a two-year field experiment. The results showed that when 10% Metamifop EC was applied at 120-240g.ai/ha one time, and the interval between harvest and the last pesticide application was 83-90 days, the final residual quantities of Metamifop and its three major metabolites in soil, rice straw,rice hulls and unpolished grain samples were both lower than the minimum detectable concentration. And 10% Metamifop EC was safe at this recommended dosage in the early growth of rice.4. An analytical method for determining Profenofos residues in water and soil by GC was described.The samples were extracted with acetonitrile, detected by GC with FPD detector. The results showed that the linear range of Profenofos was from 0.2 to 20mg/L, the correlation coefficient was 0.9999; the minimum detectable concentration in soil and water samples were 0.05mg/kg,0.005mg/kg, respectively; average recoveries were 87.2 to 103.6%, and the coefficient of variation ranged from 4.8 to 9.9%. The results of test have met the requirement of pesticide residue analysis.5. The adsorption and mobility of Profenofos in three kinds of soils were studied using batch equilibrium technique and soil thin layer chromatography. The results showed that absorption constant (Kd) of Profenofos in sand,1oam and clay is 12.70, 33.65 and 74.92, respectively. The soil adsorption capacity of Profenofos is positively related with the contents of soil organic matter. The mobility of Profenofos in three soils was shown that Profenofos don't easily move in 1oam and sand, don't move in clay.