1452 Pang et al.: J ournal of AOAC I nternational V ol. 98, N o. 5, 2015 Statistical analysis withAOAC software also proves that method efficiencies for GC/MS, GC/MS/MS, and LC/MS/MS were acceptable ( 1 ) for green tea 20 pesticide fortification samples by the three methods: GC/MS: Avg. C.: 37.5–759.6 μg/kg, Avg. Rec. 87.7–96.0%, RSD r : 2.1–4.9%, RSD R : 6.5–9.9%, HorRat: 0.3–0.5; GC/MS/MS: Avg. C.: 37.5–749.1 μg/kg, Avg. Rec. 87.0–97.1%, RSD r : 3.1–6.0%, RSD R : 6.6–14.8%, HorRat: 0.3–0.7; LC/MS/MS: Avg. C.: 18.2–191.8 μg/kg, Avg. Rec. 91.3–97.7%, RSD r : 4.9–9.4%, RSD R : 8.4–17.1%,

strictly in the first place. Only after they meet the acceptance criteria can they start the official collaborative study. If your practice results have met with the criteria, I believe that you will be able to achieve very good collaborative study results with only one shot.” Now the study has finally achieved the triumphant results of “one sample good only for one shot.” The reason for it is that the pre-study played a vital role in it, which is an important experience for success. Third, there is a lesson that we should learn, which is that several laboratories used a Waters LC/MS/MS instrument in this collaborative study, and the transitions of a target pesticide were recommended by other colleagues because in the Study Director’s laboratory such an instrument is unavailable, and he did not verify the transitions, with the result that mistakes and loss were caused for the collaborators owing to our supplying the incorrect ion information for several laboratories. This reflects the Study Director’s negligence in his work, which is an important lesson to learn, and here the Study Director also extends his deep apology to the collaborators involved. All in all, this is a very complicated and important systematic project, which is unforgettable for all the experts involved with the collaborative study, especially those who directly participated in the study. The Study Director considers AOAC interlaboratory collaborative study is a great undertaking and hopes that more and more analytical chemists will be involved in it, making greater contributions for the development of AOAC Official Methods . Note : Annex 1: Supporting Documents (such as specifications of instruments and SPE cartridges, determination results, statistical results, etc.), Annex 2: The SLV AOAC OMA-2011- Jan-001, and Annex 3: Tea Hydration Method are available on the J. AOAC Int. website. The Study Director thanks the members of the Methods Committee on Pesticides for their advice and guidance in the protocol design and review of the study, as well as the following organizations and individuals who participated in the collaborative study: Renzo Boni, Conserve Italia, Italy Zong-Mao Chen, Feng-Jian Luo, Chinese Academy of Agricultural Sciences (CAAS), P.R. China Asish Chakraborty, SGS India Private Ltd, India Amadeo R. Fernandez, Ana Lozano, EURL-FV, University of Almería, Spain Qi-Lei Guo, National Food Quality & Safety Supervision and Inspection Center, P.R. China Guk-Tak Han, Yu-Ri Lee, Ministry for Food, Agriculture, Forestry and Fisheries, National Agricultural Products Quality Management Service Chungnam Province, Republic of Korea Vincent Hanot, Scientific Institute of Public Health (IPH), Belgium Shan-Mei Huang, Central Chemical Laboratory of SGS- CSTC Standards Technical Services Co., Ltd, Guangzhou Branch, P.R. China Yu-Ju Huang, Tunding Substation, Tea Research and Extension Station, Taiwan, P.R. China Naoki Kanamaru, Japan Grain InspectionAssociation Central Research Laboratory, Japan Acknowledgments

and HorRat: 0.3–0.7; ( 2 ) for oolong tea 20 pesticide fortification samples by the three methods: GC/MS: Avg. C.: 17.3–335.7 μg/kg, Avg. Rec. 81.0–91.1%, RSD r : 2.8–7.8%, RSD R : 12.5–25.0%, HorRat: 0.5–1.3; GC/MS/MS: Avg. C.: 17.5–335.8 μg/kg, Avg. Rec. 77.1–90.8%, RSD r : 1.4–5.4%, RSD R : 7.0–32.7%, HorRat: 0.4–1.3; LC/MS/MS: Avg. C.: 8.5–84.3 μg/kg, Avg. Rec. 82.5–93.7%, RSD r : 3.6–10.2%, RSD R : 13.6–29.7%, and HorRat: 0.4–1.3; ( 3 ) for oolong tea 20 pesticide aged samples by the three methods: GC/MS: Avg. C.: 77.6–1642.6 μg/kg, RSD r : 2.0–5.8%, RSD R : 8.9–16.9%, HorRat: 0.4–0.9; GC/MS/MS: Avg. C.: 72.4–1511.9 μg/kg, RSD r : 4.6–9.6%, RSD R : 21.7–34.7%, HorRat: 1.1–1.8; LC/MS/MS:Avg. C.: 34.2–441.6 μg/kg, RSD r : 5.0–9.1%, RSD R : 16.8–34.6%, and HorRat: 0.7–1.6; ( 4 ) for green tea five pesticide incurred samples by the three methods: GC/MS (pyrimethanil and bifenthrin): Avg. C.: 613.3 and 77.8 μg/kg, RSD r : 3.3 and 4.0%, RSD R : 12.2 and 23.0%, HorRat: 0.7 and 1.0; GC/MS/MS (pyrimethanil and bifenthrin): Avg. C.: 575.4 and 78.6 μg/kg, RSD r : 5.6 and 5.6%, RSD R : 14.1 and 22.2%, HorRat: 0.8 and 0.9; LC/MS/MS (acetochlor, triadimefon, and trifloxystrobin): Avg. C.: 14.1–90.7 μg/kg, RSD r : 8.4–10.6%, RSD R : 21.3–23.6%, HorRat: 0.8–0.9. To sum up the above- mentioned data analysis, Avg. C., Avg. Rec., RSD r , RSD R , and HorRat values all met AOAC technical requirements except for specific data. The Study Director recommends this method as Official First Action. Second, one important experience achieved in this collaborative study is that a pre-study stage must be added in designing the collaborative study protocol for a complex topic. Tea matrixes are relatively complicated, with a certain difficulty for using three techniques for determination of hundreds of pesticide residues. The Study Director very much appreciated Jo Marie Cook (Florida Department of Agriculture and Consumer Services, Bureau of Chemical ResidueLaboratories, Tallahassee, Florida Department of Agriculture and Consumer Services, Bureau of Chemical Residue Laboratories, Tallahassee, FL) for her suggestion of adding a pre-study stage in the collaborative study protocol that was first proposed in 2010. Therefore, the protocol stipulated that the four indexes of recoveries, RSD, R 2 , and ion abundance with target pesticides in the pre-study would have to meet the acceptance criteria, otherwise collaborators would, in principle, forfeit their right to continue analysis of official collaborative study samples. An expert once wrote to the Study Director during the collaborative study period: “If we understood well the final amount is five grams. It means only one testing opportunity, just one shot. We consider important to get some more material (e.g., 10 g) for duplicate analysis. Is it possible?” The Study Director replied: “What you comprehend is absolutely correct. For the official collaborative study, there is only one sample for one preparation, which is what you called “just one shot.” However, we have provided you with sufficient practice samples and request the collaborators to practice

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