Capillary gas chromatography/atmospheric pressure negative chemical ionization mass spectrometry of the 22 isomeric tetrachlorodibenzo-p-dioxins

A study of he 22 tetrachlorodibenzo-p-dioxin (TCDD) isomers has been carried out by using combined capillary gas chromatography/atmospheric pressure ionization mass spectrometry. The isomer-specific determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) by this technique was demonstrated. The branching ratios for the four major ionization pathways were determined and compared with previous findings. The ionization mechanism was shown to be highly specific for the 2:2 chloro-substituted dibenzo-p-dixoin isomers. Polychlorinated biphenyls, chlorinated methoxybiphenyls, and several chlorinated pesticides (including toxaphene and p, p'-DDE) were shown not to interfere when this method was used.