毒死蜱在茶叶上的残留消解动态与使用安全性

目的探讨毒死蜱在茶园的使用安全性。方法采用室内检测和田间试验方法,对45%毒死蜱乳油在茶叶上的残留消解动态进行研究。样品采用含体积分数1%乙酸的乙腈溶液超声提取,分散固相萃取净化,气相色谱电子捕获法测定。结果在0.005~2.0 mg/L范围内,毒死蜱的质量浓度与其峰面积呈良好的线性关系,相关系数大于0.9990;添加浓度为0.01、0.2和1 mg/kg时,毒死蜱在茶叶中的平均回收率为81.7%~110.7%,RSD小于10%,检出限、定量限分别为0.003 mg/kg、0.01 mg/kg。施药剂量为有效成分540~1080 g/hm2时,毒死蜱在茶叶上的残留量与施药剂量密切相关,施药后初期残留量迅速降低,而后平缓下降,消解动态符合一级动力学反应模型,半衰期为3.78 d~4.16 d,施药后21 d,残留量小于0.1 mg/kg。结论毒死蜱为适于在茶园使用的农药品种,参照欧盟茶叶上毒死蜱的最大残留限量标准(MRL),45%毒死蜱乳油按常规方法喷雾,制剂有效成分用量不超过1080 g/hm2,施药1次,安全间隔期大于21 d,在茶叶上的残留是安全的。但由于毒死蜱在茶树上尚未登记,因此不建议在茶园中使用。

Residual degradation dynamics and safety of chlorpyrifos used in tea

Objective To evaluate the safety of chlorpyrifos sprayed on tea plantation. Methods Residual dynamics of 45% chlorpyrifos EC in tea was studied by using the methods of laboratory test and field trial. Samples were extracted ultrasonically with 1% acetic acid-acetonitrile solution, purified by dispersive solid phase extraction and determined by gas chromatograph with electronic capture detector. Results A good linearity between concentrations and peak areas was achieved in the concentration range of 0.005~2.0 mg/L for chlorpyrifos, with the correlation coefficient higher than 0.9990. The average recoveries of chlorpyrifos in tea were 81.7%~110.7% with relative standard deviations less than 10% at the spiked levels of 0.01, 0.2 and 1 mg/kg. The limits of detection and quantification were 0.003 mg/kg and 0.01 mg/kg, respectively. When 45% chlorpyrifos EC was sprayed once at effective concentration of 540~1080 g/hm2 in tea, its residual amount was closely related to application rate and decreased rapidly at early stage and then tended to slow down. Dissipation of chlorpyrifos in tea conformed to the first order kinetic equation model with the half life of 3.78~4.16 d and residue dissipated dropped to 0.1 mg/kg in 21 d after last application. Conclusion Chlorpyrifos is proved to be a suitable insecticide used in tea plantation. When employed to kill insects and mite pests in tea production, the pre-harvest interval of 45% chlorpyrifos EC should be set as 21 d and sprayed one time at the dosage no more than 1080 g/hm2, with reference to maximum residue limit (MRL) of tea of European Union. The tea harvested at this time is safe to drink. However, chlorpyrifos has not been registered for using in tea plants in China, so it is not recommendable to apply the insecticide in tea plantation.