Synthesis of polychlorinated terphenyl mixtures and gas chromatography with mass spectrometry data of tetra- to octachlorinated ortho-, meta-, and para-terphenyls

Abstract

Polychlorinated terphenyls (PCTs) are a class of polyhalogenated compounds previously used in similar applications as polychlorinated biphenyls (PCBs). According to present knowledge all industrial production was closed in the 1970s. The total PCT manufacture reached about 5% of the production of PCBs. Unlike the PCBs, PCTs have been scarcely analyzed in environmental samples mostly due to analytical difficulties. PCTs were synthesized by the chlorination of technical terphenyl which consists of ortho-, meta- and para-terphenyls. This procedure led to very complex mixtures of polychlorinated compounds whose composition, especially with regard to the terphenyl backbones, remained unknown. Here we report the individual chlorination of the three terphenyl backbones to mixtures of Tetra- to OctaCTs, respectively. The average degree of chlorination of the ortho-, meta- and para-PCTs ranged from 6.8 to 7.4. These products were analyzed by gas chromatography with mass spectrometry in electron ionization (GC/EI-MS) and electron capture negative ion (GC/ECNI-MS) modes. The elution order of isomers was ortho-PCTs≪meta-PCTs<para-PCTs. In both GC/MS modes, the mass spectra of ortho-PCTs differed from those of the meta- and para-homologues in that the molecular ion was less prominent (GC/EI-MS) or very frequently absent (GC/ECNI-MS). In addition, the relative GC/ECNI-MS responses of para-PCTs were on average higher compared with meta- and ortho-PCTs.