Studies On Residue Analytical Methods And Dissipation Of Bentazone In Rice And Beans Eco-system

The residual analytical methods for determination of Bentazone in rice soil, rice fieldwater, rice plant, beans soil and beans plant using high performance liquid chromatographywere developed in this paper. And the method for simultaneous determination ofBentazone,6-OH-Bentazone and8-OH-Bentazone in rice and beans was also developed.The dissipation dynamics of Bentazone in rice and beans eco-system after the applicationof80%Bentazone soluble powder were studied. The results will provide a basis to guidethe rational use of80%Bentazone soluble powder, and ensure the quality and safety ofagricultural products. The main findings are as follows:1. Residue analytical methods of Bentazone1.1Residue analytical methods of Bentazone in rice field wate rWater samples were filtered with0.22μm filter membrane, determined by UPLC-MS.By adding the standard solution of0.001mg/L~0.5mg/L to unspiked water, the recoveriesof Bentazone ranged from94.2%~104.0%. The coefficient of variation was between3.5%-7.8%. The minimum detectable concentration was0.001mg/L.1.2Residue analytical methods of Bentazone in soilSoil samples were extracted with solvent (methanol/water/concentrated hydrofluoricacid=90/8/2, V/V/V). The extraction solvent was cleaned up by liquid-liquid partition withdichloromethane, determined by HPLC with UV detector. By adding the standard solutionof0.02mg/L~1.0mg/L to unspiked soil, the recoveries of Bentazone ranged from78.7%~82.5%. The coefficient of variation was between1.4%~2.3%. The minimumdetectable concentration was0.02mg/kg.1.3Residue analytical methods of Bentazone in rice plant and beans plantPlants was extracted with acetonitrile, cleaned up by Florishi SPE column, purified itwith15mL petroleum ether/acetone (V/V=7/3), used15mL acetonitrile as eluent, anddetermined by HPLC with UV detector. By adding the standard solution of0.04mg/L~1.0mg/L to unspiked plant, the recoveries of Bentazone ranged from77.1%~83.8%. Thecoefficient of variation was between3.3%~5.0%. The minimum detectable concentrationwas0.04mg/kg. 1.4Residue analytical methods of Bentazone in rice chaffRice chaff was extracted with methanol, purified with C18SPE column, determined byHPLC with UV detector. By adding the standard solution of0.1mg/L~1.0mg/L tounspiked rice chaff, the recoveries of Bentazone ranged from74.5%~83.2%. Thecoefficient of variation was between3.3%~5.0%. The minimum detectable concentrationwas0.10mg/kg.1.5Residue analytical methods of Bentazone in husked rice and beansHusked rice and beans were extracted with methanol, purified with C18SPE column,determined by HPLC with UV detector. By adding the standard solution of0.05mg/L~1.0mg/L and0.02mg/L~0.2mg/L to unspiked husked rice and beans, the recoveries ofBentazone ranged from99.0%~108.5%and80.7%~92.0%. The coefficient of variationwas between2.0%~4.1%and2.5%~3.0%. The recoveries of6-OH-Bentazone were75.4%~99.0%and74.9%~81.5%, the coefficient of variation was between1.1%~3.3%and4.1%~4.5%. The recoveries of8-OH-Bentazone ranged from74.8%~87.7%and82.4%-89.9%, the coefficient of variation of3.2%-9.2%and1.3%-3.6%.The minimumdetectable concentration was0.05and0.02mg/kg respectively.The results showed that the recoveries of the methods were higher and the coefficientsof variation were less than20%. The minimum detectable concentration of bentazone inrice and beans were lower than maximum residue limits (The MRL of rice and soybeanswere0.1mg/kg and0.05mg/kg, respectively. The residues of bentazone were defined asthe total of bentazone and6-hydroxy-bentazone and8-hydroxy-bentazone.). The accuracy,precision and sensitivity of the methods were meet the requirements of pesticide residueanalysis.2. Residual dynamics of Bentazone in rice and beans field2.1Residual dynamics of Bentazone in rice field waterThe Residual dynamics experiment of Bentazone was conducted in Hefei, Zhengzhouand Zhanjiang during2011~2012. The result showed that half-life of80%Bentazone SPwere0.87~1.82,0.61~0.62and0.50~1.52d in rice field water respectively with2160g.ai/ha doseage in Hefei, Zhengzhou and Zhanjiang.2.2Residual Dynamics of Bentazone in rice soil and beans soilThe Residual dynamics experiment of Bentazone was conducted in Hefei, Zhengzhou and Zhanjiang during2011~2012. The result showed that half-life of80%Bentazone SPwere1.88~3.28,0.98~1.32and1.30~1.95d in rice soil respectively with2160g.ai/hadoseage in Hefei, Zhengzhou and Zhanjiang.The Residual dynamics experiment of Bentazone was conducted in Hefei, Tianjin andJi’nan during2011~2012. The result showed that half-life of80%Bentazone SP were2.79~3.73and4.10~7.62d in beans soil respectively with2250g.ai/ha doseage in Hefeiand Tianjin. In Ji’nan, there had not enough data in two years so that we could not simulatethe residual dynamics.2.3Residual Dynamics of Bentazone in rice plant and beans plantThe Residual dynamics experiment of Bentazone was conducted in Hefei, Zhengzhouand Zhanjiang during2011~2012. The result showed that the half-life of2011in rice plantwas1.31d with2160g.ai/ha doseage in Hefei. But, there had not enough data in2012sothat we could not simulate the residual dynamics. In Zhengzhou, the half-life of2011,2012in rice plant were1.11~1.54d respectively with2160g.ai/ha doseage. In Zhanjiang, thehalf-life of2011,2012in rice plant were0.86~1.39d respectively with2160g.ai/hadoseage.The Residual dynamics experiment of Bentazone was conducted in Hefei, Tianjin andJi’nan during2011~2012. The result showed that half-life of80%Bentazone SP were2.33~3.28d,3.41~4.88d and1.34~1.88d in beans plant respectively with2250g.ai/hadoseage in Hefei and Tianjin and Ji’nan.