Pang et al.: J ournal of AOAC I nternational V ol. 98, N o. 5, 2015  1429

( 3 ) a 3-month detection study on deviation ratios of 275 pesticides in Youden paired tea samples ( 4 ) a 3-month study of the ruggedness of the method ( 5 ) a 3-month study on the degradation kinetics for 227 pesticides in aged tea samples ( 6 ) a 3-month verification study of the applicability of EU performance criteria standard (EU Document No. SANCO/10684/2009) (30) in an AOAC collaborative study ( 7 ) a 3-month experimental field study on the degradation patterns and stability of pesticides in incurred tea samples Most recently (2011–2012), the method was used in a comparative study to evaluate the influence of tea hydration on the extraction efficiency of the pesticide multiresidue method to extract pesticide residues from tea (31). The extensive research conducted over almost 4 years has generated over 500 000 test results. The research results, at different stages, were presented and discussed at four AOAC Annual Meetings from 2009 to 2012, and a series of related papers were published subsequently (32–35). This AOAC collaborative study was conducted to complete the requirements for final consideration under the AOAC Official Methods SM process. Thirty laboratories from 11 countries and regions participated in the collaborative study. A total of 560 samples were analyzed using GC/MS, GC/MS/MS, and/or LC/MS/MS. Three categories of samples were included: fortified green tea, fortified oolong tea, aged samples from oolong tea, and incurred samples from green tea. This paper describes the results of the collaborative study. Need/Purpose The purpose of this collaborative study was to evaluate the reproducibility of the single-laboratory validated analytical method for the determination and confirmation of 653 multiclass pesticide residues in tea and determine whether it meets the criteria for consideration as an AOAC First Action Official Method . This method is applicable for the qualitative, quantitative, and confirmatory analysis of 653 pesticides and chemical pollutant residues in tea (green tea, black tea, oolong tea, and puer tea). The LOQs for 490 pesticides determined by GC/MS ranged between 1.0 and 500 μg/kg and between 0.03 and 4820 μg/kg for 448 pesticides determined by LC/MS/MS. This method was also demonstrated to be suitable for the regulatory monitoring of pesticide residues in tea in some countries where there are applicable MRLs. Collaborative Study Protocol Scope/Applicability Design of the validation plan for the multilaboratory collaborative study: (a)  Scope of analytes to include in the collaborative study. —It would be unimaginably difficult in terms of resources, time, and personnel for each collaborator to participate in a collaborative study on a method such as this one that covers residues of 653 pesticides and chemical Materials and Matrixes

1704 GC/MS/MS results (3.8%), and 57 outlier results out of 2957 LC/MS/MS results (1.9%), representing 0.98, 0.98, and 0.86%, respectively, of the 6638 results generated in the study. Analysis with the AOAC statistical software package also confirmed that the method is rugged, and average recovery, average concentration, RSD r , RSD R , and HorRat values all meet recovery and reproducibility criteria for use in multiple laboratories. The Study Director is recommending this method for adoption as an AOAC First Action Official Method SM . T ea is considered to be one of the three most consumed beverages in the world and is enjoyed by over 2.0 billion people from more than 160 countries and regions in the world (1). It is reported that in 2011 alone, more than 50 countries around the globe grew tea, with tea plantation areas covering about 3.2 million hectares with an annual output of 4.7 million tons. China, India, Kenya, Sri-Lanka, and Turkey are the world’s five largest tea producers, and their tea output makes up about 76% of the total world production (2). Tea grows mostly in warm temperate zones and subtropical regions and is subject to threats from diseases and pest infestations, so pesticides are widely used and hence the potential threat from pesticide residue contamination. At present, 17 countries and international organizations, including the Codex Alimentarius Commission, the European Union (EU), Germany, Holland, Switzerland, Hungary, Israel, Italy, China, Japan, Korea, United States, Australia, India, Kenya, and South Africa (until 2006), have established maximum residue limits (MRLs) for over 800 pesticide residues (3). With growing awareness of the effect of food contamination on consumer health, an increasing demand to move to organic farming practices, and the capability of today’s analytical laboratories to detect lower and lower levels of contamination in foods, it is imperative that high throughput multiclass, multianalyte methods be available to monitor residues of pesticides and other contaminants in a high-production food like tea. It is for this reason that this method was developed. There are over 1000 listed pesticides and chemical contaminants used around the world for agricultural purposes. In the early 2000s, the author’s team focused on the development of sensitive analytical methods and have published a series of papers (4–9) covering the study of the persistence of between 400 and 500 pesticide residues in 20 agricultural and fishery products including fruits and vegetables (10, 11), grains (12, 13), teas (14, 15), Chinese medicinal herbs (16, 17), edible fungi (mushrooms; 18, 19), animal tissues (20, 21), aquatic products (22, 23), raw milk and milk powders (24, 25), honey, fruit juices and fruit wines (26–28), and potable water (29). Since 2009, the authors have developed analytical methods for the determination and confirmation of 653 pesticide residues in tea and used the method to conduct some pivotal studies in an attempt to obtain a better understanding of the fate, distribution, and persistence of pesticide residues in tea. The method was used to conduct: ( 1 ) a 3-month stability study for 460 pesticides in six different types of solutions ( 2 ) a 3-month stability study for 345 pesticides in tea

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