The Residual Dynamics In Soil And Plant Of Soybeans And Adsorption Study Of Imazethapyr

Imazethapyr is a selective imidazolinone herbicide used to control a wide spectrum of broad-leaved weeds and grasses in soybean and several other leguminous crops. Imazethapyr is a uniquely flexible herbicide which can be applied pro-emergence or post-emergence.The determination and degradation of Imazethapyr in soil,plant and seeds of soybeans were studied with HPLC. The adsorption of Imazethapyr by soil was also studied.The study provides theoretical reference for making the rules of MRL and using the pesticide properly.HPLC-VWD was selected as the analysis method to determine the residue of Imazethapy. The soil samples were extracted with methanol-sodium Carbonate solution. After the solution collected was adjusted pH to 2.0±0.1 with a pH meter and 1M HC1. The pH 2.0 solution was transfered to a 500ml round bottom flask and evaporated it to no water on a rotary evaporator at 36℃,Then the methanol phase was secondly adjusted pH to 2.0±0.1 with a pH meter and1M NaOH. The methanol phase tranfered was cleaned up with dichloromethane.The dichloromethane collected was evaporated just to dryness at 35℃ .HPLC analysis was performed with Zorbax C₁₈ column.The compound extracted was eluted with methanol.In order to attain Imazethapyr,the plant samples and seeds of soybeans were extracted with hydrochloric acid-methanol mixtures.The method was simple.On the level of 0.02-1.00mg/kg,the average recovery of imazethapyr in soil,plant and seeds were 83.83% -88.03%,86.38%-92.08%,87.48%-90.50%, respectively.The recovery of the method was simple. The minimum detectable concentration of imazethapyr in soil,plant and seeds of soybean were 0.02mg/kg, and 0.01mg/kg, 0.01mg/kg, respectively.The degradation of Imazethapyr in soil,plant and seeds of soybeans were studied by HPLC method in Jilin province. The soil and plant of soybeans were treated with Imazethapyr at 202.5g(ai)/hm². Sample the soil and plant of soybeans at different time to do degradation dynamics analysis. The degradation procedure of Imazethapyr was correspond to the mathematic pattern, C=C₀e^-kt. In soil, the dynamic equation in 2003 was c=0.3087e^-0.0266t and the half-life was 26.06d, and the dynamic equation in 2004 was c=0.6562e^0.0227t and half-life was30.54d. In the plant of soybeans, the dynamic equation in 2003 was c=7.1995e^0.1802 and the half-life was 3.84d, and the dynamic equation in 2004 was c=7.3495e^0.1195t and half-life was 5.80d. Imazethapyr was not detected in the plant and seeds of soybeans at harvest. The result showed that Imazethapyr was dissipated in the plant of soybeans rapidly, but thedegradation of Imazethapyr in soil was more slowly than in the plant of soybeans.The adsorption of Imazethapyr by soil was studied by the equilibrium method. Three different soil types were used in the study. Imazethapyr solutions (25mL) of different density were added to soil (5g) and were shaken on a shaker at 25 ±2°C, A HPLC method was carried out to detect the Imazethapyr amount in water after 24 hours. The result showed that the adsorption of Imazethapyr was mainly influenced by organic carbon content and pH of soil.As pH increased,imazethapyr was less absorbed.added mobility and plant availability.