Interlaboratory comparison of the determination of chlorinated dibenzo-p-dioxins and dibenzofurans according to regulatory methods EN 1948 and EPA 1613b

Four laboratories participated in a collaborative study to determine differences in analytical results generated according to two different compliance methods, US EPA Method 1613b and European Union Method EN 1948 for the determination of chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/CDFs). Various sample matrices containing the analytes at levels ranging from parts-per-quadrillion (ppq) to parts-per-billion (ppb) were used to illustrate differences and similarities between the two analytical methods. The choice of the sample matrices analyzed in this study was made to mirror many of the real-world samples that are of interest to Dow and also to test the laboratories on many different, complex matrices. For this reason, commercially available performance evaluation samples were not used. The study results indicate that the 1613b requirement for confirmation of analyte identity and concentration on a second, polar gas chromatographic column for 2378-tetrachlorodibenzofuran (TCDF) only may lead to quantitative results which are biased high compared to EN 1948 which additionally requires confirmation for all 2378-substituted tetra – through hexachlorodibenzo-p-dioxins and dibenzofurans.