Results of 8th and 9th Proficiency Testing on Determination of Dioxins Based on ISO/IEC Guide 43-1

The Japan Society for Analytical Chemistry carried out its eighth and ninth series of proficiency testing on the determination of dioxins (polychlorodibenzo-p-dioxins, polychlorodibenzofurans and dioxin-like polychlorobiphenyls). The samples were a mixture of two kinds of incinerator dust for the eighth testing and synthetic wastewater for the ninth. These proficiency testing concerning the ability of analytical laboratories were based on ISO/IEC Guide 43-1, "Proficiency testing by interlaboratory comparisons". The eighth testing were carried out from August to November '06 with the participation of 101 laboratories, and the ninth from August to November '07 with the participation of 91 laboratories. Laboratories were evaluated using z scores based on a robust method. As a result, 87 laboratories (86%) were estimated to be "satisfactory (| z |≤2)", 9 laboratories (9%) as "questionable (2<| z |<3)" and 5 laboratories (5%) as "unsatisfactory (| z |≥3)" in the eighth testing using incinerator dust. In the ninth testing using wastewater, 76 laboratories (84%) were estimated to be "satisfactory", 5 laboratories (5%) to be "questionable" and 10 laboratories (11%) to be "unsatisfactory".