The Japan Society for Analytical Chemistry carried out a second proficiency testing on the determination of dioxins (polychlorodibenzo-p-dioxins, polychlorodibenzofurans and coplanar polychlorobiphenyls) in fly-ash of a waste incinerator, the same as the 1st one. The proficiency testing of analytical laboratories is based on ISO/IEC Guide 43-1, “Proficiency testing by interlaboratory comparisons”. This testing was carried out in the term from June ’01 to August ’01 with the participation of 71 laboratories. The test results were; 1.747 ng-TEQ/g of total Dioxin concentration on average, 11% in robust coefficient of variation. There have only been 3 labs estimated to be unsatisfactory because of their large z score in the robust method, over 3 in absolute value.
