Distribution congener

G. M. Frame, A collaborative study of 209 PCB congeners and 6 Aroclor s on 20 different HRGC columns. Part 2. Semi-quantitative Aroclor congener distributions . Anal. Chem. 70 714-722(1997). 

Carrizo D, Grimalt JO (2006) Rapid and simplified method for the analysis of polychlor-onaphthalene congener distributions in environmental and human samples by gas chromatography coupled to negative ion chemical ionization mass spectrometry. J Chromatogr A 1118(2) 271-277... 

Elskus, A.A., J J. Stegeman, J.W. Gooch, D.E. Black, and R.J. Pruell. 1994. Polychlorinated biphenyl congener distributions in winter flounder as related to gender, spawning site, and congener metabolism. Environ. Sci. Technol. 28 401-407. 

Macdonald, C.R. and C.D. Metcalfe. 1989. A comparison of PCB congener distributions in two point-source contaminated lakes and one uncontaminated lake in Ontario. Water Pollut. Res. Jour. Canada 24 23-46. 

Bedard and May [452] used congener-specific GC with electron capture detection and mass spectrometric detection to determine the PCBs in sediments of Woods Pond (Lennox,MA). The congener distributions of all samples showed the hexa-, hepta-, and octachlorobiphenyls characteristic of Aroclor 1260, but key hexa- and hepta-CBs had decreased by as much as 45% relative to Aroclor 1260, and the tri-, tetra-, and penta-CBs had increased. GC-MS analysis revealed unusual tetra-, penta-, and hexa-CBs, many containing 2,4- and 2,4,6-chloro-phenyl rings, which are uncommon in higher Aroclors, and provided strong... 

Overall, the steady-state model for physiochemical weathering provided a good description of observed variations in congener distributions for sur-ficial sediments in the Twelve Mile Creek-Lake Hartwell system. In general,... 

Steady-state model calculations were performed to further examine physiochemical weathering behavior. Results were consistent with congener distributions in surficial sediments. In general, they showed that a preferential depletion of the lower chlorinated congeners occurred in the upper portion of Twelve Mile Creek, where volatilization was the only removal mechanism. In the lower portion of Twelve Mile Creek and the upper portion of Lake Hartwell, burial of PCBs in deeper sediments played a more important role. A preferential depletion of higher chlorinated congeners occurs when burial is the dominant process by physiochemical weathering. 

Fig.5 Mean PCB congener profiles for two technical mixtures (Aroclor 1242 and Aroclor 1254) and at two urban locations (Milwaukee and Chicago). Data from Milwaukee is from [131] and data from Chicago is from the IADN network (Hites RA, 2005, Personal communication). Congener distributions for Aroclor 1242 and 1254 are from [141]...

Focant, J.-F., Eppe, G., Pirard, C., Massart, A.-C., Andre, J.-E., De Pauw, E., 2002. Levels and congener distributions of PCDDs, PCDFs and non-ortho PCBs in Belgium foodstuffs assessment of dietary intake. Chemosphere 48, 167-179. 

Yang, Y.-H., Chang, Y.-S., Kim, B.-H., Shin, D.C., Ikonomou, M.G., 2002. Congener-distribution patterns and risk assessment of polychlorinated biphenyls, dipenzo-p-dioxins and dibenzofurans in Korean human milk. Chemosphere 47, 1087-1095. 

Similar results were observed in analogous rat exposures [278], in which animals exposed to the racemic PCB technical formulation Aroclor 1254 were enriched in El-PCB 95 on Chirasil-Dex and (+)-PCB 149 in adipose, liver, and skin. Enantiomer reversal, such as (—)-PCB 149 enrichment in blood, was also found. However, only E2-PCB 95 on Chirasil-Dex was enriched in rats exposed to extract with racemic PCB 95 from a soil contaminated with Chlorophen, another formulation, suggesting that differences in congener distributions and concentrations affect enantioselective toxicokinetics. 

PCB retention times increase with chlorination level, and within chlorination levels, with less chlorine substitution in the ortho position (i.e., coplanar PCBs are more strongly retained). These relationships are of theoretical interest but are of less use now that accurate retention time assignments are possible with actual standards. The use of commercial mixtures such as Aroclors as quantitative secondary standards for CQCS PCB analysis is now to be discouraged [4], as detailed studies of congener distributions show significantly different proportions among different lots [7]. In the case of Aroclor 1254, there are actually two different mixtures of radically different composition produced by totally different synthetic processes [9]. 

G. M. Frame, J. W. Cochran, and S. S. Bpwadt, Complete PCB congener distributions for 17 Aroclor mixtures determined by 3 HRGC systems optimized for comprehensive, quantitative, congener-spedfic analysis,/. High Resolut. Chromatogr. 19 657 (1996). 

G. M. Frame, Improved procedure for single DB-XLB column GC-MS-SIM quantitation of PCB congener distributions and characterization of two different preparations sold as Aroclor 1254 , J. High Resolut. Chromatogr. 22 533 (1999). 

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