苯醚甲环唑和嘧菌酯在水稻中的残留消解动态及残留分析

本文建立了气质联用仪测定稻田环境中苯醚甲环唑和嘧菌酯的残留分析方法,对苯醚甲环唑和嘧菌酯在水稻、土壤和田水中的消解动态和残留规律进行了研究。苯醚甲环唑和嘧菌酯在糙米、稻壳、植株、土壤和田水中的最低检测浓度均为0.20 mg/kg,最小检出量为0.2 ng,在不同样品中的平均加标回收率为80.8%~109.5%,相对标准偏差在1.7%~19.7%之间。田间试验结果表明,苯醚甲环唑和嘧菌酯在水稻植株和田水中的残留消解动态规律均符合一级动力学反应模型,苯醚甲环唑在水稻植株和田水中的残留消解半衰期分别为6.3~11.6 d和1.4~11.6 d;嘧菌酯在水稻植株和田水中的残留消解半衰期分别为3.6~8.7 d和2.9~23.1 d。以推荐剂量600 g/hm2和1.5倍推荐剂量900 g/hm2,最多施药3次,距最后一次施药15 d时,苯醚甲环唑和嘧菌酯在糙米中的最高残留量分别为0.461 mg/kg和0.634 mg/kg,低于我国国家标准《食品中农药最大残留限量》(GB2763-2014)中规定的糙米中苯醚甲环唑最大残留限量0.5 mg/kg和欧盟、美国规定的糙米中嘧菌酯最大残留限量5.0 mg/kg。

Residues and Analysis of Degradation of Difenoconazole and Azoxystrobin in Rice

A method for the simultaneous determination of difenoconazole and azoxystrobin in rice filed environment has been eatab-lished. Meanwhile, the characteristics of difenoconazole and azoxystrobin degradation and residue were investigated by field experi-ments in Harbin, Zhengzhou and Nanjing. The minimum detectable concentrations of difenoconazole and azoxystrobin in unpolished rice, rice shell, plant, soil and field water were 0.01 mg/kg, and the minimum detectable limit of difenoconazole and azoxystrobin was 0.2 ng. The results showed that the average recovery rates of difenoconazole and azoxystrobin in rice field water, soil, plant, rice shell and unpolished rice were in the range of 80.8%~109.5%, with their relative standard deviations of 1.7%~19.7%. The field experiments revealed that the residual dissipation dynamics of difenoconazole and azoxystrobin in plant, soil and water conformed to the first order kinetics reaction model, and they belong to easily degradable pesticide(t1/2<30 d). When the recommended dosage and 1.5 times rec-ommended dosages of 32.5% difenoconazole and azoxystrobin SC was sprayed for 2~3 times at an interval of 15 day, the maximum residual concentration of difenoconazole and azoxystrobin on the 15th day after the last application were 0.461 mg/kg and 0.634 mg/kg respectively. These values are below the Maximum Residue Limits(MRL) for difenoconazole in rice(0.5 mg/kg) by the standards of China, and the MRL for azoxystrobin in unpolished rice(5.0 mg/kg) by the EU.