67028-18-6Relevant articles and documents
Isomer distributions of polychlorinated dibenzo-p-dioxins/dibenzofurans formed during de novo synthesis on incinerator fly ash
Addink, Ruud,Govers, Harrie A. J.,Olie, Kees
, p. 1888 - 1893 (1998)
Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) emitted from municipal waste incinerators appear to have a chlorination pattern that is quite constant across various samples and conditions. This suggested that these patterns may be controlled by thermodynamic properties of the individual PCDD/F congeners, such as the free Gibbs energy of formation (Δg°(f,T)). This would make prediction of the isomer composition of a particular sample (and hence its TEQ value) possible, based on values of ΔG°(f,T). A laboratory scale study was carried out with activated carbon on fly ash as the source of PCDD/F formation. Although it was found that the isomer distributions within homologues were independent of the reaction time (proof of thermodynamic control), other observations (lack of equilibrium/isomerization between isomers and lack of similarity between isomer distributions measured and predicted by ΔG°(f,T)) contradicted the possibility of thermodynamic control. Hence, this study could not confirm that de novo formation of PCDD/F could explain thermodynamically controlled isomer distributions in incinerators. Some recommendations for further work- time-based studies with precursors, isomerization studies with single congeners, and more data on ΔG°(f,T) values of PCDD/F-were made. Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) emitted from municipal waste incinerators appear to have a chlorination pattern that is quite constant across various samples and conditions. This suggested that these patterns may be controlled by thermodynamic properties of the individual PCDD/F congeners, such as the free Gibbs energy of formation (ΔG°f,T). This would make prediction of the isomer composition of a particular sample (and hence its TEQ value) possible, based on values of ΔG°f,T. A laboratory scale study was carried out with activated carbon on fly ash as the source of PCDD/F formation. Although it was found that the isomer distributions within homologues were independent of the reaction time (proof of thermodynamic control), other observations (lack of equilibrium/isomerization between isomers and lack of similarity between isomer distributions measured and predicted by ΔG°f,T) contradicted the possibility of thermodynamic control. Hence, this study could not confirm that de novo formation of PCDD/F could explain thermodynamically controlled isomer distributions in incinerators. Some recommendations for further work - time-based studies with precursors, isomerization studies with single congeners, and more data on ΔG°f,T values of PCDD/F - were made.
Isomer-Specific Separation of 2378-Substituted Polychlorinated Dibenzo-p-dioxins by High-Resolution Gas Chromatography/Mass Spectrometry
Buser, Hans Rudolf,Rappe, Christoffer
, p. 442 - 448 (2007/10/02)
All polychlorinated dibenzo-p-dioxin (PCDD) isomers containing four and more chlorine substituents were prepared by micropyrolysis of chlorophenolates.The synthesis included the preparation of all 22 tetra-, 14 penta-, 10 hexa-, 2 hepta-, and octachlorinated species (tetra- to octa-CDD).The gas chromatographic and mass spectrometric properties of these isomers were studied.High resolution gas chromatography (HRGC) on a 55-m Silar 10c glass capillary column allowed the separation of many of these isomers and allowed the unambiguous assignment of the toxic and environmentally hazardous 2378-substituted isomers (2378-tetra-, 12378-penta-, 123478-, 123678-, and 123789-hexa-CDD).Analyses were carried out to determine the occurence of these isomers in environmental samples and in fly ash from municipal incinerators.
