IDENTIFICATION AND SOURCES OF DIOXIN-LIKE COMPOUNDS .1. POLYCHLORODIBENZOTHIOPHENES AND POLYCHLOROTHIANTHRENES, THE SULFUR-ANALOGS OF THE POLYCHLORODIBENZOFURANS AND POLYCHLORODIBENZODIOXINS

Polychlorodibenzothiophenes (PCDTs) and polychlorothianthrenes (PCTAs) were analyzed by gas chromatography/mass spectrometry (GC/MS) and MS/MS. PCDTs and polychlorodibenzodioxins (PCDDs) have the same nominal molecular masses and high-resolution MS at resolutions of 18000 or more would be required to distinguish these compounds. EI fragmention, however, is different and MS/MS techniques can be used to distinguish these compounds. QUAD MS/MS was highly selective for detecting PCDDs and polychlorodibenzofurans (PCDFs) via reaction M+ --> (M-COCl)+ and MIKE MS/MS was valuable for detecting PCDTs via reaction M+ --> (M-2Cl)+. PCDTs were identified in fly ash from 2 municipal solid waste incinerators (MSWIs) and from an electric-arc furnace of a car shredding facility. The congeners detected were tetra- and pentachlorinated with rather complex isomer profiles; among the isomers was 2,3,7,8-tetra-CDT. The sources and routes of formation of the new compounds are still unknown. Various pathways seem plausible, and as an example we report on the formation of PCDTs and PCTAs from the thermal reaction of chloro aromatic compounds (polychlorobiphenyls, PCBs, chlorobenzenes) with elemental sulfur. PCDTs (not the 2,3,7,8-substituted) were also detected in aquatic organisms from the Newark Bay/New York Bight area.