Publications by authors named "Aijuan Bai"

6 Publications

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Residue changes and processing factors of eighteen field-applied pesticides during the production of Chinese Baijiu from rice.

Food Chem 2021 Oct 29;359:129983. Epub 2021 Apr 29.

Longping Branch, Graduate School of Hunan University, Changsha 410125, China; Hunan Plant Protection Institute, Hunan Academy of Agricultural Science, Changsha 410125, China. Electronic address:

The fate of eighteen pesticides in field-collected rice samples during Chinese Baijiu production was systematically studied. The results indicated that steeping decreased flonicamid residue by 73.2% due to its high water-solubility and low octanol/water partition coefficient. The steaming step reduced pesticide residues by 32.0%-75.3% through evaporation or thermal degradation. After steaming, the pesticide residues were further reduced by 39.8-74.2% in fermentation which might be caused by biological degradation. In addition, distillation was shown to be most effective, responsible for greater than 90% losses of the remaining pesticide residues. The processing factors (PFs) were generally lower than 1 for different processes and the whole procedure. These results revealed that the procedure of Chinese Baijiu production could dramatically decrease residues of all the eighteen pesticides. Overall, this study provide important references for monitoring pesticide residue levels during the production of Chinese Baijiu from rice, and ensuring proper risk assessment from pesticide contamination.
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http://dx.doi.org/10.1016/j.foodchem.2021.129983DOI Listing
October 2021

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

J Sci Food Agric 2021 Apr 13. Epub 2021 Apr 13.

Longping Branch, Graduate School of Hunan University, Changsha, China.

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 once or twice, the terminal residues of tolfenpyrad and total dinotefuran in green tea were lower than 19.6 and 7.13 mg kg , 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 RQ and RQ 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.
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http://dx.doi.org/10.1002/jsfa.11253DOI Listing
April 2021

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

J Sci Food Agric 2021 Mar 5;101(5):1998-2005. Epub 2020 Oct 5.

Longping Branch, Graduate School of Hunan University, Changsha, 410125, China.

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 in celery after application two or three times and were below 0.029 mg kg 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.
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http://dx.doi.org/10.1002/jsfa.10817DOI Listing
March 2021

Influence of different planting seasons of six leaf vegetables on residues of five pesticides.

J Agric Food Chem 2013 Sep 10;61(38):9036-44. Epub 2013 Sep 10.

Department of Applied Chemistry, College of Science, China Agricultural University , Beijing 100193, People's Republic of China.

To investigate the influence of different planting seasons on the dissipation of pesticides, field experiments of thiophanate-methyl, metalaxyl, fluazifop-P-butyl, chlorpyrifos, and λ-cyhalothrin on six crops including pakchoi, rape, crown daisy, amaranth, spinach, and lettuce were designed and conducted. In this study, a high-performance liquid chromatography and electrospray ionization-tandem mass spectrometer with multiple reaction monitoring was used to simultaneously determine thiophanate-methyl and its metabolite carbendazim, metalaxyl, and fluazifop-P-butyl in various samples; gas chromatography with an electron capture detector was used to detect chlorpyrifos and λ-cyhalothrin. The limits of quantitation (LOQs) of these six pesticides were in the range of 0.001-0.01 mg kg(-1) for all samples, and the average recoveries of all pesticides ranged from 60.1 to 119.1% at 0.01 and 0.1 mg kg(-1) spiked levels. The relative standard deviation (RSD) ranged from 1.1 to 13.9%. All maximal concentrations of the six pesticides in six leaf vegetables in autumn were higher than in summer in Beijing. For most pesticides half-lives in autumn were longer than in summer. The results showed that the initial concentration, maximal concentration, and half-lives of pesticides were influenced not only by environmental factors such as light, heat, moisture, and rainy climate but also by plant matrices.
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http://dx.doi.org/10.1021/jf4029078DOI Listing
September 2013

Dissipation and residues of bispyribac-sodium in rice and environment.

Environ Monit Assess 2013 Dec 21;185(12):9743-9. Epub 2013 Jun 21.

Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China.

The dissipation and residues of bispyribac-sodium in rice cropping system were studied. Bispyribac-sodium residues were extracted by a simple analytical method based on QuEChERs and detected by LC-MS/MS. The limit of detection for bispyribac-sodium of this method was 0.375 × 10(-3) ng. The limit of quantification (LOQ) was 5.0 μg/kg for rice plant samples, 2.0 μg/kg for rice hull, 0.2 μg/kg for water, and 0.1 μg/kg for soil and husked rice samples. The average recoveries of bispyribac-sodium ranged from 74.7 to 108%, with relative standard deviations less than 13%. The half-lives of bispyribac-sodium in rice plant, water, and soil were in the range of 1.4-5.6 days. More than 90% of bispyribac-sodium residue dissipated within 5 days. The final residues of bispyribac-sodium in rice were all below LOQ at harvest time.
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http://dx.doi.org/10.1007/s10661-013-3287-zDOI Listing
December 2013

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.

J AOAC Int 2013 Mar-Apr;96(2):353-6

China Agricultural University, College of Science, Department of Applied Chemistry, Beijing, People's Republic of China.

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.
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http://dx.doi.org/10.5740/jaoacint.12-160DOI Listing
July 2013