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Pan R.,Chinese Academy of Agricultural Sciences | Pan R.,University of Chinese Academy of Sciences | Chen H.,Chinese Academy of Agricultural Sciences | Chen H.,Key Laboratory of Tea Quality and Safety and Risk Assessment | And 8 more authors.
Journal of Agricultural and Food Chemistry | Year: 2015

The enantioselective dissipation of acephate and its metabolite, methamidophos, was investigated during tea cultivation, manufacturing, and infusion, using QuEChERS sample preparation technique and gas chromatography coupled with a BGB-176 chiral column. Results showed that (+)-acephate and (-)-acephate dissipated following first-order kinetics in fresh tea leaves with half-lives of 1.8 and 1.9 days, respectively. Acephate was degraded into a more toxic metabolite, methamidophos. Preferential dissipation and translocation of (+)-acephate may exist in tea shoots, and (-)-methamidophos was degraded more rapidly than (+)-methamidophos. During tea manufacturing, drying and spreading (or withering) played important roles in the dissipation of acephate enantiomers. The enantiometic fractions of acephate changed from 0.495-0.496 to 0.479-0.486 (P ≥ 0.0081), whereas those of methamidophos changed from 0.576-0.630 to 0.568-0.645 (P ≥ 0.0366 except for green tea manufacturing on day 1), from fresh tea leaves to made tea. In addition, high transfer rates (>80%) and significant enantioselectivity (P ≥ 0.0042) of both acephate and its metabolite occurred during tea brewing. © 2015 American Chemical Society.

Pan R.,Chinese Academy of Agricultural Sciences | Chen H.-P.,Chinese Academy of Agricultural Sciences | Chen H.-P.,Key Laboratory of Tea Quality and Safety and Risk Assessment | Zhang M.-L.,Chinese Academy of Agricultural Sciences | And 6 more authors.
PLoS ONE | Year: 2015

Residue levels of dimethoate and its oxon metabolite (omethoate) during tea planting, manufacturing, and brewing were investigated using a modified QuEChERS sample preparation and gas chromatography. Dissipation of dimethoate and its metabolite in tea plantation followed the first-order kinetic with a half-life of 1.08-1.27 d. Tea manufacturing has positive effects on dimethoate dissipation. Processing factors of dimethoate are in the range of 2.11-2.41 and 1.41-1.70 during green tea and black tea manufacturing, respectively. Omethoate underwent generation as well as dissipation during tea manufacturing. Sum of dimethoate and omethoate led to a large portion of 80.5-84.9%transferring into tea infusion. Results of safety evaluation indicated that omethoate could bring higher human health risk than dimethoate due to its higher hazard quotient by drinking tea. These results would provide information for the establishment of maximum residue limit and instruction for the application of dimethoate formulation on tea crop. © 2015 Pan et al.

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