Dissipation kinetics and safety evaluation of tebuconazole and trifloxystrobin in tea under tropical field conditions

Dissipation kinetics of tebuconazole, trifloxystrobin and its acid metabolite residues were studied in tea under tropical field conditions using GC-MS (SIM). The average recoveries ranged from 80.7% to 105.8%, with a RSD of <9.3%. Dissipation rate for both doses applied followed first-order kinetics, with half-lives in green leaves in the range of 2.8–3.3 and 2.9–3.3 days; ranges in processed tea were 2.7–3.6 days for trifloxystrobin and 3.0–3.1 days for tebuconazole. The trifloxystrobin residues were not transferred into the tea infusion during the infusion process; tebuconazole did transfer, in the range of 14.3–18.9%. As the theoretical maximum residue contributions on tea from initial deposits were found to be less than the maximum permissible intake values, at the recommended application dose a withdrawal period of 23 days before consumption should be applied to reduce risk.

本研究于热带田间条件下，采用气相色谱-质谱联用（GC-MS，选择离子监测模式SIM），对茶叶中戊唑醇（tebuconazole）、醚菌酯（trifloxystrobin）及其酸性代谢物的残留消解动力学展开了探究。实验测得平均回收率介于80.7%至105.8%之间，相对标准偏差（RSD）小于9.3%。两种施药剂量下的消解速率均符合一级动力学模型：鲜叶中的半衰期范围分别为2.8~3.3天与2.9~3.3天；加工成品茶中的半衰期范围则为：醚菌酯（trifloxystrobin）2.7~3.6天，戊唑醇（tebuconazole）3.0~3.1天。冲泡过程中，醚菌酯残留未向茶汤发生迁移，而戊唑醇的迁移率处于14.3%~18.9%的区间内。鉴于初始沉积量对应的茶叶理论最大残留贡献量低于最大允许摄入量，故在推荐施药剂量下，应设置23天的安全间隔期后方可采摘饮用，以降低健康风险。