Chapter 7.2 - Collaborative Study

Abstract

This AOAC collaborative study was attended by 30 laboratories from 11 countries and regions across America, Europe and Asia, including 8 Brand laboratories, 9 government laboratories, 5 independent laboratories, 3 research institute laboratories, 2 university laboratories, and 3 enterprise laboratories. Comprehensive analytical conditions adopted by 30 laboratories, including 22 different manufactures’ GC–MS, GC–MS/MS and LC–MS/MS instruments, 27 brands’ and 19 technical specifications’ chromatographic columns, 25 different gas chromatographic temperature rising programs, 15 liquid phase gradient elution procedures and 12 SPE cartridges. 30 laboratories, with test result data returned to SD. These data include, ion abundance data, ion abundance ratio data, calibration curves data and 8915 precollaborative study results. Review of test data and related information from 30 laboratories have found that one laboratory has deviated from the collaborative study protocol, which entered directly into official collaborative study with no undertaking the prestudy, with a great deal of outliers from its sample inspection, and this laboratory has been eliminated. A total of target pesticide test data from the remaining 29 laboratories are effective results and inspected with Grubbs and Dixon to eliminate outliers, making up % of the total effective data. In which 1977 effective test data were from GC–MS determination, with outliers detected, making up %; 1704 effective test data were from GC–MS/MS determination, with 65 outliers detected, accounting for 3.8%; effective test data were from LC–MS/MS determination, with outliers detected, making up %. Statistical analysis with AOAC software also proves that method efficiencies for GC–MS, GC–MS/MS and LC–MS/MS were acceptable (1) for Green tea 40 pesticides fortification samples by the three methods: Avg.C.: 18.2–759.6 μg/kg, Avg.Rec 87.0%–97.7%, RSDr: 2.1%–9.4%, RSDR: 6.5%–17.1%, HorRat: 0.3–0.7; (2) for Oolong tea 40 pesticides fortification samples by the three methods: Avg.C.: 8.5–335.8 μg/kg, Avg.Rec 77.1%–93.7%, RSDr: 1.4%–10.2%, RSDR: 7.0%–32.7%, HorRat: 0.4–1.3; (3) for Oolong tea 20 pesticides aged samples by the three methods: Avg.C.: 34.2–1642.6 μg/kg, RSDr: 2.0%–9.6%, RSDR: 8.9%–34.7%, HorRat: 0.4–1.8; (4) for Green tea 5 pesticides incurred samples by the three methods: Avg.C.: 14.1–613.3 μg/kg, RSDr: 3.3%–10.6%, RSDR: 12.2%–23.6%, HorRat: 0.7–1.0. To sum up the above-mentioned analysis, Avg.C., Avg.Rec, RSDR, RSDR, and HorRat values have all met with AOAC technical requirements except for specific data. SD recommends this method as official first action.