Residue pattern of chlorpyrifos and its metabolite in tea from cultivation to consumption

Chlorpyrifos (CPF) is a broad-spectrum organophosphorus pesticide widely used to control tea geometrid (Ectropis oblique) and tea green leafhoppers (Empoasca pirisuga Matsumura) in tea trees. The major metabolite of CPF in water, plants, and animals is 3,5,6-trichloro-2-pyridinol, which is more toxic than CPF. However, the dissipation pattern of CPF in tea is unknown.

An optimized QuEChERS sample preparation method combined with ultra-performance liquid chromatography-tandem mass spectrometry was applied to determine the residues of chlorpyrifos and its metabolite in tea during tea planting and green tea processing. During tea planting, the sum of chlorpyrifos and its metabolite dissipated rapidly with a half-life of 1.93 days for tea shoots. The residues of chlorpyrifos and its metabolite in made green tea were 96.89 and 35.88 μg kg^-1 on the seventh day. The values for processing factors of chlorpyrifos and its metabolite were all less than 1, showing that each green tea manufacturing step was responsible for the reduction. The transfer rates of chlorpyrifos and its metabolite from made green tea to its infusion were 0.68-4.62% and 62.93-71.79%, respectively.

The risk of chlorpyrifos was negligible to human health based on the hazard quotient, which was 7.4%. This study provides information relevant to the reasonable application of chlorpyrifos in tea planting and is potentially helpful for tea exporting and importing countries to establish harmonized maximum residue limits. © 2020 Society of Chemical Industry.