杀虫单在小白菜和土壤中的残留及消解动态研究

RESIDUE AND DEGRADATION OF MONOSULTAP IN PAKCHOI AND SOIL

为了解杀虫单在小白菜和土壤中的残留消解动态及最终残留状况,研究了杀虫单在小白菜和土壤中的气相色谱检测方法,并在天津、江苏两地开展了20%阿维菌素.杀虫单可湿性粉剂在小白菜和土壤中的残留消解动态和最终残留田间试验研究.结果表明,在0.02—1 mg.kg-1添加水平范围内,通过外标法定量,获得杀虫单在小白菜和土壤中的平均添加回收率为73.88%—103.65%,其变异系数为6.14%—11.85%;小白菜和土壤中杀虫单的最小检出量均为3.4×10-11 g,最低检出浓度分别为0.002 mg.kg-1和0.001 mg.kg-1,该方法的灵敏度和回收率均可满足杀虫单在小白菜和土壤中的残留分析要求.田间试验结果表明,杀虫单在小白菜和土壤中的残留消解动态规律符合一级动力学反应模型,杀虫单在小白菜和土壤中的残留消解半衰期分别为3.5—4.0 d和3.3 d.按推荐剂量和1.5倍推荐剂量在小白菜上各喷施20%阿维菌素.杀虫单可湿性粉剂2—3次,两次施药间隔为7 d,距最后1次施药5 d时,杀虫单在小白菜中的最高残留量为0.043 mg.kg-1,低于我国农业行业标准中规定的杀虫单在十字花科甘蓝上的最大残留限量标准0.2 mg.kg-1.

In order to find out the degradation dynamics and the residue of monosultap in pakchoi and soil,an gas chromatography（GC） analytical method was developed for determining nereistoxin in pakchoi and soil.Meanwhile,the characteristics of monosultap degradation and residue were investigated through field experiments in Tianjin and Jiangsu Province.The results showed that the average recovery rates of monosultap in pakchoi and soil were in the range of 73.88%—103.65% at spiking levels of 0.02—1 mg · kg-1,with relative standard deviations of 6.14%—11.85%.The limit of detection of monosultap in pakchoi and soil was both 3.4×10-11g.And the limit of quantitation of monosultap in pakchoi and soil were 0.002 mg · kg-1 and 0.001 mg · kg-1,respectively.Field experiments revealed that the residue dissipation dynamics of monosultap in pakchoi and soil conformed to the first order kinetics reaction model,and its residue half-life in pakchoi and soil was 3.5—4.0 d and 3.3 d,respectively.When the recommended dosage and 1.5 times recommended dosages of 20% avermectins monosultap wettability medicinal powder was sprayed for 2—3 times at an interval of 7 d,the maximum residue of monosultap on the fifth day before the last application was 0.043 mg · kg-1,which is lower than the MRL of monosultap for broccoli of cruciferae according to the standards of Ministry of Agriculture of China（0.2 mg · kg-1）.