Residue behavior, transfer and risk assessment of tolfenpyrad, dinotefuran and its metabolites during tea growing and tea brewing.

BACKGROUND: Tolfenpyrad and dinotefuran are two representative pesticides used for pest control in tea gardens. Their application may bring about a potential risk to the health of consumers. Therefore, it is essential to investigate the residue behavior, transfer and risk assessment of tolfenpyrad, dinotefuran and metabolites from tea garden to teacup. RESULTS: An effective analytical method was established and validated to simultaneously determine tolfenpyrad, dinotefuran and its metabolites (DN and UF) in tea. The average recoveries of tolfenpyrad, dinotefuran, DN and UF were in the range 72.1-106.3%, with relative standard deviations lower than 11.8%. On the basis of the proposed method, the dissipation of tolfenpyrad and dinotefuran in fresh tea leaves followed first-order kinetics models with half-lives of 4.30-7.33 days and 4.65-5.50 days, respectively. With application amounts of 112.5-168.75 g a.i. ha-1 once or twice, the terminal residues of tolfenpyrad and total dinotefuran in green tea were lower than 19.6 and 7.13 mg kg-1 , respectively, and below their corresponding maximum residue limits . The leaching rates of tolfenpyrad and total dinotefuran during the tea brewing were in the ranges 1.4-2.3% and 93.7-98.1%, respectively. CONCLUSION: Tolfenpyrad and dinotefuran in tea were easily degraded. The RQc and RQa values for tolfenpyrad were 37.6% and 5.4%, which were much higher than for dinotefuran at 24.7% and 0.84%, respectively. The data indicated that there was no significant health risk in tea for consumers at the recommended dosages. The results provide scientific data regarding the reasonable use of tolfenpyrad and dinotefuran aiming to ensure safe tea consuption. © 2021 Society of Chemical Industry.

Study on degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion under field application.

BACKGROUND: Propiconazole is widely used to control fungal diseases in field crops, including celery and onion. The potential risk to the environment and human health has aroused much public concern. Therefore, it is significant to investigate the degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion. RESULTS: A sensitive analytical method for determination of propiconazole residue in celery and onion was established and validated through high-performance liquid chromatography tandem mass spectrometry. The average recovery rate of propiconazole ranged from 85.7% to 101.8%, with a relative standard deviation of 2.1-6.3%. For the dissipation kinetics, the data showed that propiconazole in celery and onion was degraded, with half-lives of 6.1-6.2 days and 8.7-8.8 days respectively. In the terminal residue experiments, the residues of propiconazole were below 4.66 mg kg-1 in celery after application two or three times and were below 0.029 mg kg-1 in onion after application of three or four times with an interval of 14 days under the designed dosages. The chronic and acute dietary exposure assessments for propiconazole were valued by risk quotient, with all values being lower than 100%. CONCLUSION: Propiconazole in celery and onion was rapidly degraded following first-order kinetics models. The dietary risk of propiconazole through celery or onion was negligible to consumers. The study not only offers a valuable reference for reasonable usage of propiconazole on celery and onion, but also facilitates the establishment of maximum residue limits in China. © 2020 Society of Chemical Industry.

Detection of caffeine in tea, instant coffee, green tea beverage, and soft drink by direct analysis in real time (DART) source coupled to single-quadrupole mass spectrometry.

Ambient ionization direct analysis in real time (DART) coupled to single-quadrupole MS (DART-MS) was evaluated for rapid detection of caffeine in commercial samples without chromatographic separation or sample preparation. Four commercial samples were examined: tea, instant coffee, green tea beverage, and soft drink. The response-related parameters were optimized for the DART temperature and MS fragmentor. Under optimal conditions, the molecular ion (M+H)+ was the major ion for identification of caffeine. The results showed that DART-MS is a promising tool for the quick analysis of important marker molecules in commercial samples. Furthermore, this system has demonstrated significant potential for high sample throughput and real-time analysis.