Study On The Residues In Rice Field And The Photodegradation Of Indoxacarb

Indoxacarb is a kind of carbamate pesticides that was developed by dupont in the United States.It belongs to sodium channel inhibitor.Indoxacarb is a kind of low residual,broad-spectrum and efficient pesticide,it is no teratogenic,no carcinogenic and no mutagenic effects,and there is no interaction resistance with other pesticides.In order to evaluate the residues in environmental media and the stability in storage system of indoxacarb,degradation dynamics and final residues of indoxacarb 3%LDL in rice field and photolysis in different solvents have been studied.The main results were as follows:1.A new method was developed with HPLC to determine indoxacarb residue in rice field.Water was extracted with dichloromethane.Soil,plants,rice and rice hull were extracted with the mixture of acetone and dichloromethane(2:1,v/v).Then,the extracts were purified with Florisil.The reconstituted sample solution was analyzed by HPLC-PDA.C18 was taken as the analytical column,and acetonitrile-water(60:40,v/v)was taken as the mobile phase.The results showed that the linear relationship of indoxacarb was found better in the concentration range from 0.05 to 10.00 mg/L with the linear correlation of 0.9999.At three spiked concentration levels,the average recoveries of indoxacarb were from 81.9%to 101.2%with the relative standard deviations(RSDs,n=5)of 0.2%?5.8%in different matrix(water,soil,plants,rice and rice hull).The limit of quantitation of indoxacarb was 0.01 mg/kg in water,soil and rice,0.02 mg/kg in plants,and 0.04 mg/kg in rice hull,respectively.The method is simple,fast,sensitive,reproducible and practical for the determination of indoxacarb residue in environmental systems.2.An experiment was conducted to reveal the dissipation rate and residue analysis of indoxacarb in rice field.Indoxacarb was determined by HPLC-PDA.The studies on the dynamic degration of indoxacarb 3%LDL in rice field were carried out in Hunan,Henan,Jiangsu in 2012 and 2013.The degradation curve was conformed to the first-order dynamic equation.The half-lives in plants,soil and water were 2.40?11.34 d,?0.95 d and 0.27?2.40 d in three provinces,respectively.These results suggested that indoxacarb was a kind of easily dissipated fungicide.When the rice field was treated by indoxacarb 3%LDL,in high dose and low dose twice and thrice used,respectively,on day 21 after the last application,the terminal residues of indoxacarb in rice were lower than 0.1 mg/kg,which was lower than the maximum residue limit of Korea.3.Under controlled conditions,the photodegradation dynamics of indoxacarb in different medium was explored with UV lamp and xenon lamp as the light source,respectively.HPLC-PDA was used for qualitative and quantitative analysis.The order of photodegradation rate in cdifferent solvents is Hexane>methanol>acetonitrile>acetone.