The degradation and metabolism of chlorfluazuron and flonicamid in tea: A risk assessment from tea garden to cup

摘要

Degradation and metabolism of chlorfluazuron and flonicamid from tea garden to cup were simultaneously investigated by a modified QuEChERS method coupled with UPLC-MS/MS quantification. The dissipation half-lives of chlorfluazuron, flonicamid, and total flonicamid (the sum of flonicamid and its metabolites TFNG, TFNA, and TFNA-AM) in fresh tea leaves during tea growth were 6.0 d, 4.8 d, and 8.1 d, respectively. TFNG and TFNA were generated during tea growth. After tea processing, the residues of chlorfluazuron, flonicamid, and its metabolites in black tea were higher than those in green tea. The average processing factors of chlorfluazuron, flonicamid, and total flonicamid in black tea were 2.54,3.02, and 2.87, respectively, while in green tea they were 2.40,2.93, and 2.79, respectively. TFNG, TFNA, and TFNA-AM were formed rapidly during the drying step. Considering the influence of water content at various processing steps, the average loss rates of chlorfluazuron, flonicamid, and total flonicamid residue from fresh tea leaves to black tea were 16.7%, 33.8%, and 20.7%, respectively, and 29.6%, 14.0% and 18.2%, respectively, in the case of green tea. The highest leaching rates of chlorfluazuron, flonicamid, and total flonicamid during tea brewing were 6.8%, 97.0%, and 97.4%, respectively, in black tea infusion, and 6.0%, 98.9%, and 98.6%, respectively, in green tea infusion. The metabolites, especially TFNG, had a higher leaching rate during tea brewing. The migration of chlorfluazuron from fresh leaves to tea infusion was low, and the migration of flonicamid was high. The RQc and RQa of chlorfluazuron and total flonicamid were less than 1. This result indicates that the potential dietary intake risk of chlorfluazuron from tea is negligible. However, the risk of total flonicamid intake is three times higher than that of chlorfluazuron. There is a potential risk of intake of flonicamid and its metabolites in tea for human consumption.