Abstract
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.
Highlights
Tea is considered as one of the most popular non-alcoholic beverages throughout the world
Recoveries of dimethoate for fresh tea leaves, made tea, and spent leaves ranged from 80.4% to 85.2% with relative standard deviations (RSDs)
Recoveries of omethoate for fresh tea leaves, made tea, and spent leaves ranged from 55.2% to 59.1%, with an acceptable RSDs
Summary
Tea is considered as one of the most popular non-alcoholic beverages throughout the world. An increasing attention has been paid on tea because of its antioxidant, anticarcinogenic, and antimicrobial properties [1,2,3]. To prevent tea trees from being attacked by a variety of insects and diseases, organophosphorous pesticides were traditional pesticides widely used in the period of cultivation. Due to its high mammalian toxicity, most of the organophosphorous pesticides have been forbidden or replaced by other pesticides. A few organophosphorous pesticides are still used in tea plantation, such as dimethoate [O, O-dimethyl-Smethylcarbamoylmethylphosphorodithioate]. Dimethoate is commonly used for control insects and mites by contact and stomach action [4].
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