Polychlorinated dibenzo-p-dioxins. Separation and identification of isomers by gas chromatography-mas spectrometry.

Attempts were made to synthesize all polychlorinated dibenzo-p-dioxin isomers containing six to eight chlorine atoms by micro-scale pyrolysis of different polychlorophenates. Eight of the ten possible hexachlorodibenzo-p-dioxins, the two hepta- and the octachlorodibenzo-p-dioxin were observed and separated by gas chromatography using glass capillary columns. Without actual isolation of these toxic materials, isomers were characterized by gas chromatography and mass spectrometry. Commercial chlorinate phenols were analyzed for the presence of these isomers. The major hexachlorodibenzo-p-dioxin observed in two commerical products was the unexpected 1,2,3,7,8,9-substituted isomer, which was not formed as the main dioxin component in any of the pyrolysis experiments. The same isomer was reported to be isolated from toxic fat and identified by X-ray crystallography.