烟叶中多菌灵农药残留的降解规律和影响因素

为探索有效控制烟叶中多菌灵农药残留的措施，采用液相色谱-串联质谱检测技术，研究了多菌灵及其他常见苯并咪唑类杀菌剂在烟草上的农药残留特征及环境因子、采收后处理方式和储存条件对其降解的影响，明确了合理使用条件下多菌灵农药残留水平与形成机制。结果表明:基于QuEchERS前处理与液相色谱-串联质谱检测技术可以快速、准确检测3种常用苯并咪唑类杀菌剂，标准曲线、定量限、添加回收率符合农药残留检测方法要求；多菌灵、苯菌灵、甲基硫菌灵在鲜烟叶中的理论半衰期为6.8、6.3、6.6 d；25℃、湿度60%的环境最利于多菌灵降解；3种农药残留在冻干、杀青、烘烤过程的加工因子分别为5.11~5.66、3.95~4.55、2.96~3.39；多菌灵在常温和恒温条件下储存烟叶中的半衰期为224~365 d。在植物体内活性酶的作用下，田间降解是农药残留降解的主要方式，施药时药液浓度、末次施药到采收的间隔时间对多菌灵残留量有显著影响，加工方式、储存环境及储存时间也与其有一定关系。 

Degradation characters and influencing factors of carbendazim residues in tobacco leaf

In order to effectively control carbendazim pesticide residues in tobacco leaves, a modified QuEChERS combined with LC-MS/MS method to detect and characterize pesticide residue of carbendazim and other three benzimidazole fungicides in tobacco leaf was developed. The method successfully indicated influence of environmental factors, processing methods and storage conditions on degradation, and clearly demonstrated the level and formation mechanism of carbendazim residue under reasonable utilization. Results showed that the standard curve, the quantitative limit and the recoveries conformed to the requirements of pesticide residue detection method. The theoretical degrading half-life of carbendazim, benomyl and thiophanate-methyl in fresh tobacco leaf was 6.8, 6.3 and 6.6 days, respectively. The best condition for degradation of carbendazim was 25℃ and 60% humidity. The processing factors of freeze-drying, editing and curing for the three pesticide residues were 5.11-5.66, 3.95-4.55 and 2.96-3.39, respectively. The half-life of carbendazim in cured tobacco leaf was 224-365 days in normal and constant temperature. Findings of this study also suggested that the degradation rate of carbendazim were obviously different with a rapid and crucial dissipation in growing period under active enzyme, and the carbendazim residue level was significantly influenced by the original pesticide concentration and intervals between last pesticide application and harvest. Moreover, the processing method, storage conditions and duration also had some impact on the residue level.