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Chen H.,Chinese Academy of Agricultural Sciences | Chen H.,Tea Quality and Supervision Testing Center | Liu X.,Chinese Academy of Agricultural Sciences | Liu X.,Tea Quality and Supervision Testing Center | And 2 more authors.
Food Chemistry | Year: 2013

The residues of gibberellic acid (GA3) in tea shoots, made tea, and tea infusion were determined by ultra-performance liquid chromatography tandem mass (UPLC-MS/MS) to study its degradation pattern during tea planting, processing, and brewing. The dissipation rate of GA3 was described using first-order kinetics. Its half-life ranged from 1.67 to 2.01 days in tea shoots. Degradation and concentration during green tea processing had equally important functions on GA3 residues in product intermediates and made tea. Except for water content, little GA3 residue difference was found in tea shoots and made tea. GA3 dissipated rapidly in the baking stage during processing. The transfer coefficient of GA3 residues from made tea to infusion was from 26.23% to 54.55%. GA3 extraction efficiency varied with different infusion times and concentrations of GA3 in made tea. This research revealed that GA3 may be safe when applied in tea gardens at suitable doses and picking intervals. © 2012 Elsevier Ltd. All rights reserved.

Chen H.,Chinese Academy of Agricultural Sciences | Chen H.,Key Laboratory of Tea Quality and Safety & Risk Assessment | Chen H.,Tea Quality and Supervision Testing Center | Hao Z.,Chinese Academy of Agricultural Sciences | And 19 more authors.
Human and Ecological Risk Assessment | Year: 2015

Tea is the second widely consumed beverage next to water. Tea drinking is one of the important pathways for human exposure of organonphosphorus pesticide. Consequently, incidence of organonphosphorus pesticide residues and risk assessment should be clear. In this study, the level of organonphosphorus pesticide residues in 810 Chinese teas manufactured between 2010–2013 was investigated using gas chromatography coupled with tandem mass spectrometry and a flame photometric detector. Incidence of organonphosphorus pesticide residues occurred with a frequency of 29% and the average concentration of 93 μg kg−1. The residue levels varied from tea types, sale spots, and production area. Chlorpyrifos, isocarbophos, and triazophos were the only three organonphosphorus pesticides with detectable residues, and the detectable rates were 13.0%, 13.6%, and 17.4%, respectively. The corresponding average daily intake of chlorpyrifos, isocarbophos, and triazophos by tea drinking was 0.000083 μg kg−1 bw day−1, 0.0036 μg kg−1 bw day−1, and 0.0022 μg kg−1 bw day−1. These results showed that the total hazard quotient of organonphosphorus pesticide pesticides from tea drinking was less than 0.02 and that the tea-drinking originated organonphosphorus pesticide exposure had a little adverse health effect for human being. 2015 Copyright © Taylor & Francis Group, LLC

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

Determining the transfer rate of pesticides during tea brewing is important to identify the potential exposure risks from pesticide residues in tea. In this study, the transfer rates of 19 typical pesticides from tea to brewing were investigated using gas chromatography tandem mass and ultraperformance liquid chromatography tandem mass. The leaching rates of five pesticides (isocarbophos, triazophos, fenvalerate, buprofezin, and pyridaben) during tea brewing were first reported. The pesticides exhibited different transfer rates; however, this result was not related to residual concentrations and tea types. Pesticides with low octanol-water partition coefficients (Logkow) and high water solubility demonstrated high transfer rates. The transfer rates of pesticides with water solubility > 29 mg L-1 (or <15 mg L-1) were >25% (or <10%), and those of pesticides with LogKow < 1.52 (or >2.48) were >65% (or <35%). This result indicates that water solubility at approximately 20 mg L-1 and LogKow at approximately 2.0 could be the demarcation lines of transfer rate. The results of this study can be used as a guide in the application of pesticides to tea trees and establishment of maximum residue limits of pesticides in tea to reduce pesticide exposure in humans. © 2014 American Chemical Society.

Chen H.,Chinese Academy of Agricultural Sciences | Chen H.,Tea Quality and Supervision Testing Center | Yin P.,Chinese Academy of Agricultural Sciences | Wang Q.,Chinese Academy of Agricultural Sciences | And 5 more authors.
Food Analytical Methods | Year: 2014

A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for the simultaneous determination of 70 pesticides in tea was developed using gas chromatography-tandem mass spectrometry. Prior to acetonitrile extraction of the target compounds from tea matrix, samples were soaked in distilled water to improve the extraction efficiency. A mixture of adsorbents containing primary-secondary amine, octadecylsilane, graphite carbon black, and multiwalled carbon nanotubes was applied for the cleanup. Additional steps of concentration and solvent exchange were performed to reduce the amount of co-extracts and to decrease the limit of detection of the method. For all pesticides, good linear calibrations with coefficients (R 2) ≥0.99 were obtained at the concentration levels of 10, or 50 to 1,000 μg ml-1. The limits of quantifications (LOQs) were 5-25 μg ml-1, respectively. The recovery rates of samples spiked with 20, 100, and 200 μg kg-1 of analytes ranged from 71 % to 105 %. In addition, the relative standard deviations were lower than 20 %. A total of 331 tea samples were analyzed using this method, and the levels of five pesticide residues in nine tea samples exceeded the strictest maximum residual limits (MRLs). © 2014 Springer Science+Business Media New York.

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