Degradation characters and influence 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 25oC 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