Gas chromatographic characteristics of authentic chlorinated dibenzofurans. Identification of two isomers in American and Japanese polychlorinated biphenyls

Abstract

Retention times of 15 authentic standards of chlorinated dibenzofurans containing from three to six chlorine atoms were determined relative to dieldrin on gas chromatograph columns of four different polarities (3% OV-1; 5% SP-2401; 1.5% OV-17/1.95% QF-1; and 3% OV-1/5% OV-210/6% OV-225). On the basis of coinjections of the standards with extracts from American (Aroclor) and Japanese (Kanechlor) polychlorinated biphenyls (PCB), two of the compounds in those extracts have been identified as 2,3,7,8-tetra-and 2,3,4,7,8-pentachlorodibenzofuran. The concentrations of the compounds were estimated to range from 0.08 to 0.83 *ig/g of PCB.Vos et al. (1970) have identified toxic components of European polychlorinated biphenyls (PCB) as two chlorinated dibenzofurans. Subsequently, several additional chlorinated dibenzofurans were found in the German preparation examined by Vos et al. (Bowes et al., 1973). Further investigations have led to the detection by high-resolution mass spectrometry of those contaminants in American (Aroclor) PCB (Bowes et al., 1975). A recent study reports unidentified tri-, tetra-, and possibly pentachlorodibenzo-

Chemistry of PCBs and PBBs

“…An additional claim that a Cl-DBF contaminated an Aroclor was not sufficiently supported by the evidence presented (93). In the PCBs of U. S. manufacture, the range of Cl-DBFs found was from dichloro through hexachloro, and sufficient evidence was obtained to show that 2,3,7,8-tetrachloro-and 2,3,4,7,8-pentachlorodibenzofuran are present in Aroclors (94). That the Cl-DBFs reported were actual contaminants and not artifacts resulting from the experimental procedures used, was considered in two instances (6,92).…”

Synthesis of specific polychlorinated dibenzofurans

“…Removal of solvent under reduced pressure from the first reaction solution left a dark orange oil which was chromatographed on alumina. Elution with hexane yielded a white solid which was chromatographed on silica gel and eluted with hexane to give 1.9 g (7%) of lb: 98.5% pure (GLC); mp 116-117 °C; NMR (CDC13) 7.78 (d, 1, J = 2 Hz, Hi), 7.50 (d, 1, J = 2 Hz, H3), 7.79 (m, 1, Hg), 7.36 (m, 2, H7 + H8); mass spectrum m/e 274 (36), 272 (96), 270 (100), 209 (15), 207 (23), 137 (14), 136 (10), 135 (11). 1.3.4.7.8-Pentachlorodibenzofuran (le).…”

General Summary and Conclusions

“…A range of Cl-DBFs (from dichloro through hexachloro) have been reported in various Aroclors (15,16) and two specific compounds, the 2,3,7,8tetrachloro-and 2,3,4,7,8-pentachlorodibenzofurans, have been identified (17). Quantitation of Cl-DBF contaminants in PCB mixtures, a difficult procedure, suggests total Cl-DBF levels in the low parts per million range (16,18).…”