The Japan Society for Analytical Chemistry carried out proficiency testing for a fourth-round determination of dioxins (polychlorodibenzo-p-dioxins, polychloro-dibenzofurans and dioxin-like polychlorobiphenyls) in the combustion dust of a waste incinerator. This proficiency testing of analytical laboratories is based on ISO/IEC Guide 43-1, "Proficiency testing by interlaboratory comparisons". The testing was carried out from June '03 to August '03, with the participation of 117 laboratories. As a result, 107 laboratories (91.5%) were estimated as being "satisfactory", 6 laboratories (5.1%) as "questionable" and 4 laboratories (3.4%) as "unsatisfactory". A tendency was found that the determined values of the toxicity equivalent quantity became large when an SP 2331 liquid phase or the like was applied to the capillary column of the gas chromatograph. This may have come from insufficient separation of some components.
