联苯菊酯在茶叶中的消解动态及最终残留

Degradation Dynamics and Final Residue of Bifenthrin in Tea

[目的]了解联苯菊酯在茶叶中的消解动态及最终残留情况,确定其施用的安全间隔期和次数。[方法]在田间试验中,以安徽省舒城县916茶场采集的茶叶为试材,用2.5%联苯菊酯乳油推荐量的2倍对其进行施药,药后1h以及1、2、3、5、7、14、21、30、45d分别取样,采用丙酮和石油醚提取,气相色谱检测,样品添加回收率为77.0%。[结果]联苯菊酯在茶叶中降解速率很快,施药量是推荐浓度的2倍时,1d后取样检测消解率为44.7%,半衰期为T1/2=3.83d。在推荐剂量为90ga.i/hm2和施药4次的条件下,在最后1次施药3、7、14d后取样联苯菊酯残留量均小于5mg/kg,尤其14d后取样联苯菊酯残留量为0.08mg/kg。[结论]若以5mg/kg作为残留量参考指标,建议施用联苯菊酯的安全间隔期可定为3d,施药次数不超过4次。

[ Objective ] The study aimed to understand the degradation dynamics and final residue of bifenthrin in tea and confirm its safe application plastochron and times. [ Method] In the field test, with tea selected from 916 tea farm in Shueheng County of Anhui Province as the tested material, it was applied by 2.5% bifenthrin EC at 2 times of its recommended rate. The applied tea were sampled after application for 1 h and 1, 2, 3, 5, 7, 14, 21, 30 and 45 d resp. and the samples were extracted by acetone and petroleum ether and then measured by gas chromatogram （GC）, with the adding recovery of test being 77.0%. [ Result] The bifenthrin was dissipated rapidly in tea. When bifenthrin was applied to the tea according to twice of recommended rate, the degradation ratio of bifenthrin from the samples after application for 1 d was 44.7% , and the half-life was 3.83 d. When the recommended dosage of bifenthrin was 90 g a. i/hm^2 for applying 4 times, the residue of bifenthrin in tea was less then 5 mg/kg after final application for 3, 7, 14 d, specially, that in tea was 0.08mg/kg after final application for 14 d. [ Conclusion] If taking the bifenthrin residue in tea of 5 mg/kg as the reference index, it was suggested that the safe application plastoehron of bife.nthrin was confirmed as 3 d and the application times didn＇ t exceed 4 times.