Polychlorinated dibenzofurans PCDFs

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

Long, G., J. McKinney, and L. Pedersen. 1987. Polychlorinated Dibenzofuran (PCDF) Binding to the Ah Receptor(s) and Associated Enzyme Induction. Theoretical Model based on Molecular Parameters. Quant. Struct.-Act. Relat. 6, 1. 

Mader, B.T., Pankow, J.F. (2003) Vapor pressures of the polychlorinated dibenzodioxins (PCDDs) and the polychlorinated dibenzofurans (PCDFs). Atmos. Environ. 37, 3103-3114. 

C. Rappe and R. Lindahl, "Formation of Polychlorinated Dibenzofurans (PCDFs) and Polychlorinated Dibenzo-p-Dioxins (PCDDs) from the Pyrolysis of Polychlorinated Diphenyl Ethers,"Chemosphere, 2, 351 (1980). 

Loonen, H., J.R. Parsons, and H.A.J. Govers. 1994a. Effect of sediment on the bioaccumulation of a complex mixture of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) by fish. Chemosphere 28 1433-1446. 

Dioxins is a generalized name of the large group of polychlorinated dibenzoparadioxins (PCDD) and polychlorinated dibenzofurans (PCDF). 

Figure 19. General formulas of polychlorinated dibenzo-pdioxins, PCDDs (left) and polychlorinated dibenzofurans, PCDFs (right).

Fig. 7 Generic chemical structures of polyhalogenated compounds. X=C1, Br. (I) Polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs) (II) chlorophenols (CPs), bromophenols (BPs) (III) polychlorinated diphenyl ethers (PCDE), polybrominated diphenyl ethers (PBDE) (IV) polychlorinated dibenzo-p-dioxin (PCDD), polybrominated dibenzo-p-dioxin (PBDD) (V) polychlorinated dibenzofuran (PCDF), polybrominated dibenzofuran (PBDF) (VI) tetrabromobisphenol A (TBBPA)...

Two-dimensional GC can be used to separate complex mixtures of polyaromatic compounds, and MS used to subsequently identify the compounds. In this method, the original sample is injected into a gas chromatograph with one type of column. As the components exit the first GC, they are fed into a second GC, with a different column, for further separation and finally into a mass spectrometer. In this way, compounds that coeluted from the first column are separated on the second. Focant et al. [19] were able to separate polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar polychlorinated biphenyl (cPCB) using this type of analytical procedure, including isotope dilution TOF-MS. These compounds are frequently found as contaminants in soils surrounding industrial settings thus, the ability to separate and identify them is extremely important [6,12,19],... 

When PCBs burn, polychlorinated dibenzofurans (PCDFs) are among the products that may form. Examine the structure shown below, and circle and name the functional groups. 

GC-EI-MS permits the direct analysis of mixtures, e.g., to analyze synthetic byproducts an advantage that made GC-EI-MS benchtop instruments become widespread in modem synthetic laboratories. The GC-EI-MS combination is especially successful in monitoring environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-dioxins (PCDDs), polychlorinated dibenzofuranes (PCDFs), or other volatile organic compounds (VOCs). 

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), Pentachlorophenol m(PCP, mercury and organic mercury compounds, cadmium, lead and organic lead compounds, brominated flame retardants), nonylphenol/ethoxylates (NP, NPEs) amongst others in the OSPAR Strategy with regard to Hazardous Substances... 

Polychlorinated dibenzodioxins (PCDDs) Polychlorinated dibenzofurans (PCDFs) Polychlorinated biphenyls (PCBs) Polyaromatic hydrocarbons (PAHs) Pentachlorophenol Short chain chlorinated paraffins Hexachlorocyclohexane isomers Mercury and organic mercury compounds Cadmium... 

Polychlorinated Dibenzodioxins (PCDDs) and Polychlorinated Dibenzofurans (PCDFs) by High-Resolution GC/High-Resolution MS 8310 Polynuclear Aromatic Hydrocarbons... 

Morita, M., Nakagawa, J., and Rappe, C. Polychlorinated dibenzofuran (PCDF) formation from PCB mixture by heat and oxygen. Bull. Environ. Contam. Toxicol, 19(6) 665-670, 1978. 

It should be realized that with the exception of a few groups of chemicals (such as some organophosphorous and carbamate pesticides as well as some polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs), precise mechanistic information on their toxic effects are scarce. In realizing that the exact molecular mechanism is not known for most chemicals the term mode of action is used to describe toxicides that appear to be similar albeit the mechanism is not known in detail, see also Section 4.2.6. For several groups of endocrine disrupters this terminology seems appropriate. 

This approach was initially developed to estimate the potential toxicity of mixtures of polychlorinated dibenzo- -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dioxin-like biphenyls (PCBs). Over the years, a number of different TEF systems for PCDDs, PCDFs and PCBs have been used. A system was internationally agreed upon at a WHO Consultation in 1997 (WHO-TEF) as published by Van den Berg et al. (1998). A WHO update has been published recently (Van den Berg et al. 2006) (Table 10.3). 

For halogenated aromatic hydrocarbons like polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dibenzo-p-dioxins (PCDDs) the binding to the aryl hydrocarbon (Ah) receptor regulates their toxicity [89]. The Ah receptor controls the induction of one of the cytochrome P450 enzymes in the liver. Toxic responses such as thymic atrophy, iveight loss, immu-notoxicity and acute lethality are associated ivith the relative affinity of PCBs, PCDFs and PCDDs for the Ah receptor [89]. The quantitative structure-activity relationship (QSAR) models predicting the affinity of the halogenated aromatic hydrocarbons ivith the Ah receptor describe the electron acceptor capability as well as the hydrophobicity and polarizability of the chemicals [89[. 

For the quantitative determination of polychlorinated diben-zodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), sample treatment and conservation play crucial roles, too. Only some of the 75 PCDD isomers and 135 PCDF isomers are highly toxic. The collection and analysis of the hazardous compounds present at ultratrace levels in environmental samples must preferably be isomer-specific. The exposure routes for these compounds originate from combustion processes (18-19). 

Technical CP formulations contain impurities such as polychlorinated phenoxyphenols (PCPPs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) (Humppi et al., 1984 Kitunen et al., 1985 Jackson Bisson, 1990). Therefore, PCPPs, PCDFs, and PCDDs are often found in CP-contaminated wood treatment sites (Kitunen et al., 1985, 1987 Jackson Bisson, 1990 Kitunen Salkinoja-Salonen, 1990 Trudell et al., 1994). PCPP concentrations up to 78 mg/kg, PCDF up to 3-8 mg/kg, and PCDDs at 13 mg/kg have been detected in CP-contaminated sites (Kitunen et al., 1987 Jackson Bisson, 1990). 

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