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Residue dissipation, transfer and safety evaluation of picoxystrobin during tea growing and brewing.

BACKGROUND
Picoxystrobin is a new osmotic and systemic broad-spectrum methoxyacrylate fungicide with a good control effect on tea anthracnose, so it was proposed to spray picoxystrobin before the occurrence and onset of tea anthracnose during the tea bud growth in order to protect them. However, there was few report about the residue analysis method, field dissipation, terminal residue and risk assessment of picoxystrobin in tea. And there was not a scientific and reasonable MRL of picoxystrobin in green tea.


RESULTS
A rapid and sensitive analysis method of picoxystrobin residue in fresh tea leaf, green tea, tea infusion and soil was established by UPLC-MS/MS. The spiked recoveries of picoxystrobin ranged from 73.1% to 111.0%, with RSDs from 1.8% to 9.2%. The LOQs were 20 μg kg-1 in green tea, 8 μg kg-1 in fresh tea leaves and soil, and 0.16 μg kg-1 in tea infusion, respectively. The dissipation half-lives of picoxystrobin in fresh tea leaf and soil were 2.7-6.8 days and 2.5-14.4 days, respectively. And the maximum residue of picoxystrobin in green tea was 15.28 mg kg-1 with PHI at 10 days for terminal test. The total leaching rate of picoxystrobin during green tea brewing was lower than 35.8%.


CONCLUSION
According to safety evaluation, the RQc and RQa values of picoxystrobin in tea after 5 to 14 days for the last application were significantly lower than 1, therefore, the MRL value of picoxystrobin in tea that we suggested to set at 20 mg kg-1 can ensure the human drinking safety of tea. This article is protected by copyright. All rights reserved.