Aroclor mixtures chromatograms

Figure 2 presents representative glass capillary gas chromatograms for two Industrial Aroclor mixtures used In the area. Aroclor 1242 Is very similar to Aroclor 1016 (not shown) which was the predominant mixture used, but for which we had no standard. Figures 3 and... 

Examination of the gas chromatograms of PCBs In the samples of lobster and crab reveals the marked contrast In composition of PCBs In these types of biota samples and the composition of PCBs In water, sediment, bivalves and Aroclor mixtures. For example, the chlorobiphenyl composition of the lobsters are dominated by lUPAC chlorobiphenyl (CB) numbers 118, 153 and 138 while numbers 118 and 153 dominate the composition In the crab (Figure 2). Several more chlorobiphenyls, e.g. 28, 52, 44, 70, 95, 101, 110, are present In the mussel and sediment samples In addition to 118, 153 and 138 (Figure 2). PCBs In flesh of flounder species (L. maculata and P. amerlcanus) were Intermediate In composition between the lobsters and the mussels based upon examination of the gas chromatograms (not shown), I.e. 118, 153 and 138 predominate but not as much as In the lobsters. The possible reasons for these differences will be discussed below. 

Figure 3 ECD chromatogram of an Aroclor mixture (A1016, A1232, A1248, A1260,1 1 1 1) on a 50m x 0.22 mm x 0. 26 pm CP Sil 19 column. (Reproduced with permission from Larsen B et al. (1992) International Journal of Environment Analytical Chemistry 47 47-68 Taylor Francis Ltd. http //www.tandf.co.uk/journals)...

When large numbers of chromatograms are analyzed visually from chart paper or tabular data, it is difficult to detect minor (or perhaps major) significant differences that may be present in samples from different locations or differences that could be attributed to changing physiochemical processes. A typical gas chromatogram of a PCB mixture (Figure 2) represents a 1 1 1 1 mixture of Aroclors 1242, 1248, 1254, and 1260. It contains more than 100 component peaks, of which 69 were selected for use in these analyses. 

The samples of unknown composition—21-23 and samples 1-20, 24-34 (Appendix I) were those of Aroclors of variable composition. Variables 5-73 are isomer concentrations (Variable 74, the total PCB concentration in ppm was not included in the analysis). Variables 5-73 represent the fractional composition or isomer proportional concentration values. Representative concentration histograms of the data set are presented in Figure 13. Four PLS components were extracted and then used to estimate the Aroclor content of the unknowns and of a standard sample (No. 24). The Aroclor standard is a mixture of three Aroclors in the ratio of 033 0.33 0 0.33. Chromatograms of the samples for which the PLS estimates were made (Table VI) were similar when compared to a chromatogram of a similar mixture of standards. 

Figure 11, Total ion current chromatograms of (A) standard Aroclor 1260 mixture of polychlorinated biphenyls. Programmed temperature analysis two minutes at 206°C, to 230 C/min, isothermal at 230 C. (B) Human adipose tissue extract. Programmed temperature analysis two minutes at 190° C, to 230°C at 5°C/min, isothermal at 230°C.

The composition of the chlorobiphenyl mixtures present In the surface sediment, particulate matter In the water column, filtrate from water column samples, and mussels reflect a combination of Aroclor 1242 and 1254 mixtures of chlorobiphenyls although there are distinct differences In each sample type. The chlorobiphenyl composition of water column samples (gas chromatograms not shown) resembles that of the mussels and surface sediments, although further measurements of a larger set of samples may reveal small but significant differences In composition. 

The visual inspection of gas chromatograms (Figures 2-4) provides only a qualitative impression of the relative differences in composition of PCBs in the biota and their habitat. Therefore, we have calculated a parameter to provide a more quantitative means for evaluating the differences in composition. We have chosen a chlorobiphenyl, lUPAC No. 153, which is present in appreciable quantities in the industrial mixture of Aroclor 1254 and was identified as one of the major components in the samples of biota from the study area, and calculated the following ratio ... 

Figure 9 (A) Overlaid GCxGC- xECD chromatogram on DB-lx007-65HT column set of PCBs (red circle), PBBs (blue circle), PCDEs (orange circle), PBDEs (green circle), PCDTs (grey square), PCNs (white square), PCDD/Fs (black square), OCP (blue cross) individual toxaphene standrads (black cross), and PCAs (PCA-60). (B) PCA (PCA-60), PCTs (Aroclor 5442 + 5460) an toxaphene technical mixture [30].

Figure 9 GCxGC- j,ECD contour plot obtained on ZB-5xHT-8 for a technical mixture of PCTs (Aroclor 5460) showing a structured chromatogram with no wraparound for PCBs (position is indicated with a white circle) but where less volatile PCTs showed a clear wraparound...

Fig.ZZ-3. Chromatogram of Aroclor 1254 recorded by the moni-tor-ECD in the MDGC mode without heart cuts (top), SE-54 capillary column. Chromatogram re-recorded by the monitor-ECD in the MDGC mode, reflecting the cut domains (middle). Chromatogram recorded by the main-ECD reflecting the separation of all possible congeners in the three cuts (lower), with the aid of a synthetic mixture (Schulz, 1990).

Fig. 1. GC-ECD chromatograms (60 m DB-5 column) of the PCB fraction from a Herring Gull (egg), its main prey, the Alewife (a small forage fish) and a mixture of two technical PCBs (Aroclor 1254 and 1260). PCB congeners are identified by lUPAC No. (see Table 1), H is hexachlorobenzene, E is p,p -DDE, N is t-nonachlor, PM is photomirex, and M is mirex.

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