OMB First to Final Action Recommendation Checklist 11-12-18

C HANG ET AL .: J OURNAL OF AOAC I NTERNATIONAL V OL . 99, N O . 4, 2016 1049

RESIDUES AND TRACE ELEMENTS High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VI: Study of the Degradation of 271 Pesticide Residues in Aged Oolong Tea by Gas Chromatography- Tandem Mass Spectrometry and Its Application in Predicting the Residue Concentrations of Target Pesticides Q IAO -Y ING C HANG Yanshan University, College of Environmental and Chemical Engineering, Qinhuangdao, Hebei 066004, People’s Republic of China G UO -F ANG P ANG 1 Yanshan University, College of Environmental and Chemical Engineering, Qinhuangdao, Hebei 066004, People’s Republic of China; Chinese Academy of Inspection and Quarantine, Beijing 100176, People’s Republic of China C HUN -L IN F AN and H UI C HEN Chinese Academy of Inspection and Quarantine, Beijing 100176, People’s Republic of China Z HI -B IN W ANG Yanshan University, College of Environmental and Chemical Engineering, Qinhuangdao, Hebei 066004, People’s Republic of China

The degradation rate of 271 pesticide residues in aged Oolong tea at two spray concentrations, named a and b ( a < b ), were monitored for 120 days using GC–tandem MS (GC-MS/MS). To research the degradation trends and establish regression equations, determination days were plotted as horizontal ordinates and the residue concentrations of pesticide were plotted as vertical ordinates. Here, we consider the degradation equations of 271 pesticides over 40 and 120 days, summarize the degradation rates in six aspects (A–F), and discuss the degradation trends of the 271 pesticides in aged Oolong tea in detail. The results indicate that >70% of the determined pesticides coincide with the degradation regularity of trends A, B, and E, i.e., the concentration of pesticide will decrease within 4 months. Next, 20 representative pesticides were selected for further study at higher spray concentrations, named c and d ( d > c > b > a ), in aged Oolong tea over another 90 days. The determination days were plotted on the x -axis, and the differences between each determined result and ¿UVW WLPH GHWHUPLQHG YDOXH RI WDUJHW SHVWLFLGHV ZHUH plotted on the y -axis. The logarithmic function was REWDLQHG E\ ¿WWLQJ WKH GD\ GHWHUPLQDWLRQ UHVXOWV allowing the degradation value of a target pesticide RQ D VSHFL¿F GD\ WR EH FDOFXODWHG 7KHVH ORJDULWKPLF functions at d concentration were applied to predict the residue concentrations of pesticides at Received March 03, 2016. Accepted by AK March 24, 2016. 1 Corresponding author’s e-mail: ciqpang@163.com Supplemental information is available on the J. AOAC Int . website, http://aoac.publisher.ingentaconnect.com/content/aoac/jaoac DOI: 10-5740/jaoacint.16-0063

c concentration. Results revealed that 70% of the 20 pesticides had the lower deviation ratios of predicted and measured results. A s one of the world’s three major health drinks, tea makes up the majority of exported traditional commodities of China. The tea plant is prone to be attacked by various pests and diseases during its growth because it is mostly planted in warm temperate zones and subtropical areas. Different kinds of pesticides have been widely used to control pests and plant diseases of tea in an effort to increase harvest productivity. However, pesticide residues in tea may cause damage to human health (1–4). With the strengthening of food safety policies in different countries and regions of the world, the awareness of pesticide residues in tea has generated great public concern (5–8). The study of degradation regularity of pesticides, together with a model to simulate the dynamics in a tea sample, can be applied to analyze and predict pesticide residues in tea. This research is signi¿cant for guiding farmers to spray pesticides on tea plants in a reasonable way and is helpful for predicting the risk of pesticide residues in the tea trade. The degradation of pesticides is a complex process affected by many factors, including temperature, humidity, sunshine, metals, etc. (9, 10). Many studies have been carried out on the degradation of pesticides in agricultural products using different kinetic models (11–13). Ozbey and Uygun (14) investigated the behavior of some organophosphorus pesticide residues in peppermint tea during the infusion process. Manikandan et al. (15) studied the leaching of certain pesticides, such as ethion, endosulfan, dicofol, chlorpyrifos, deltamethrin, hexaconazole, fenpropathrin, propargite, quinalphos, and Ȝ -cyhalothrin, from powdered black tea into the brew. Lin et al. (16) studied the