Study On Residue Analytical Method And The Degradation Of Emamectin Benzoate In Cabbage And Soil

First a simple and efficient residue analytical method was developed for the analysis of emamectin benzoate,then the residue trends of emamectin benzoate in cabbage and soil was studied by field experiment.At the same time, the degradation of emamectin benzoate in sterilized and non-sterilized soil were studied in laboratory .The results could be summarized as followings:1.The emamectin benzoate in the water was extracted by ethyl acetate, and the extract was derived by NMIM and TFAA under the dark condition. The derivative was detected by HPLC. The results showed that, the recoveries of emamectin benzoate were 78.4~115.2% and the method coefficient of variation were 3.0~11.3%, for spiked water samples at the concentration of 0.0001~0.01mg·L-1. The limit of detection (LOD) was 0.064 ng and the limit of quantification (LOQ) was 0.0036mg·L-1.2. The emamectin benzoate was extracted by ethyl acetate-water in the cabbage sample, the extract was directly derivatised by NMIM and TFAA then detected by HPLC-FLD. The recovery and C.V. of the method ranged from 78.5 to 96.3% and 2.6 to 11.3% respectively at added level of 0.001-0.05 mg/kg. The limit of detection (LOD) was 0.17 ng and the limit of quantification (LOQ) was 0.001mg/kg.3.The soil sample was extracted by acetone-water. The extract was derivatised by NMIM and TFAA then detected by HPLC-FLD. The recovery and C.V. of the method ranged from 75.9 to 108.5% and 0.66 to 6.56% respectively at added level of 0.001-0.1 mg/kg. The limit of detection (LOD) was 0.15 ng and the limit of quantification (LOQ) was 0.0004mg·L-1.4.The degradation of emamectin benzoate in cabbage field was studied during 2007and2008 in Hefei and Beijing city , the results showed that the degradation procedure was correspond to the mathematic pattern, C=C0e kt. In 2007 and 2008 the half life of emamectin benzoate in soil of Hefei were 4.83 and 4.10 day and the dynamic equations were C = 6.7883e-0.1436t and C = 6.9778e-0.1691t respectively.In 2007 and 2008 the half life of the pesticide in the cabbage were 2.28 and 2.67 day and C=17.578e-0.3042t. C=20.331e-0.2598t were the dynamic equations. In 2008 the half life of the pesticide in soil and cabbage of Beijing were 7.95 and 4.12 day and the dynamic equations were C = 3.7932e-0.0872t and C=6.4047e-0.1682t respectively. So the pesticide emamectin benzoate was easy to degrade in the cabbage field.5. The degradation of emamectin benzoate in different types of sterilized and non-sterilized soil was studied under laboratory condition ,the results showed that:(1) The degradation rate of emamectin benzoate was significant difference between sterilized and non-sterilized soil in Hefei and Beijing.The degradation half-life was 38.5 d and 28.52 d in the sterilized and non-sterilized soil of hefei respectively,and it was 30.00 d and 16.86 d in the sterilized and non-sterilized soil of Beijing respectively.It indicated that micro-organisms have a certain effect on the degradation of emamectin benzoate in the soil.(2). The degradation rate of emamectin benzoate was different in three types of soil , the order was as follows: brown soil of Beijing > red soil of Xuancheng > yellow-brown soil of Hefei. Its half-life of degradation is 16.86 d, 19.47 d and 28.52 d respectively, It suggesting that emamectin benzoate should be very degradable pesticide.