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.

Gas-liquid chromatographic determination of chlorinated benzenes and phenols in selected biological matrices.

The determination of higher chlorinated benzenes and chlorinated phenols at parts per billion or parts per million levels in biological samples is described. The method includes sulfuric acid digestion, silica gel column chromatography, methylation, alumina column chromatography, and detection by electron capture gas chromatography. Recoveries are reported for fish flesh, rabbit tissues, and duck tissues with detection limits of 10--15 ppb (nb/g tissue).

A search for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in an environment exposed annually to 2,4,5-trichlorophenoxyacetic acid ester (2,4,5-T) herbicides.

As part of a broad study to determine whether 2,3,7,8-tetrachlorodibenzo-P-dioxin (TCDD) is accumulating in the environment due to approved uses of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) based herbicides, samples of fish, water, mud and human milk were collected from areas in Arkansas and Texas where 2,4,5-T herbicides are used and were analyzed for TCDD. No TCDD was detected by a GC-MS procedure with a detection limit which averaged less than 10 ppt.

Combustion of Several 2,4,5-Trichlorophenoxy Compounds: Formation of 2,3,7,8-Tetrachlorodibenzo-p-dioxin.

Grass and paper coated with several compounds containing the 2,4,5-trichlorophenoxy moiety have been subjected to combustion. By using compounds that had been purified to achieve low background amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) together with an efficient cleanup and analysis of the residue, it was possible to detect as little as 0.001 microgram of TCDD in the combustion products of 0.5 gram of the 2,4,5-trichlorophenoxy material. Small self-supported fires converted about 10(-6) of the 2,4,5-trichlorophenoxy material to TCDD.