924 PCBs AND ASSOCIATED AROMATICS
TABLE 47
PCB composition of Aroclors 1242 and 1016Mol. % Mol. % Mol. %PCB 1242 1016 PCB 1242 1016 PCB 1242 1016BP 0.01 0.50 2,2,6,6 0.17 0.19 2,3,3,4,5 0.46 0.16
2 0.68 0.80 2,2,3,6 0.90 1.00 2,2,3,4,4 0.40 —
3 0.04 0.10 2,2,5,6 0.97 1.07 2,2,3,4,5 0.09 —
4 0.22 1.00 2,2,5,5 4.08 4.35 2,3,3,4,4 0.25 —
2,6 0.13 0.20 2,4,4,6 2.18 2.40 2,2,3,5,5 0.12 —
2,2 3.99 4.36 2,2,3,5 0.44 0.47 2,2,4,4,5 0.55 —
2,5 0.31 0.34 2,2,3,6 0.31 0.33 2,2,4,5,5 0.27 —
2,4 1.04 1.16 2,2,4,5 1.33 1.41 2,3,4,5,5 0.31 —
2,3 1.24 1.37 2,2,4,5 3.28 3.48 2,3,4,4,5 0.36 —
2,4 8.97 10.30 2,2,3,5 1.06 1.14 3,3,4,5,5 0.05 —
3,5 0.35 0.37 2,2,3,4 1.67 2.00 3,3,4,4,5 0.03 —
3,4 0.09 0.11 2,2,3,3 0.15 0.18 2,2,3,4,5,6 0.07 —
3,4 0.12 0.12 2,3,3,4 0.60 — 2,2,3,4,4,5 0.08 —
4,4 0.99 1.07 2,2,4,4 1.65 1.81 2,2,4,4,5,5 0.02 —
2,2,6 0.97 1.08 2,4,4,5 2.02 1.35
2,2,5 9.36 10.87 2,3,4,5 1.11 — Monochloro (%) 0.94 2.40
2,2,4 2.92 3.14 2 ,3,4,5 trace — Dichloro (%) 17.23 19.40
2,2,3 3.25 3.50 3,3,4,5 0.52 — Trichloro (%) 51.67 56.31
2,3,6 0.54 0.58 3,4,4,5 0.28 — Tetrachloro (%) 24.65 21.32
2,4,6 2.15 2.31 3,3,4,4 0.34 — Pentachloro (%) 5.24 0.40
2,3,5 0.55 0.62 2,3,5,5 0.33 — Hexachloro (%) 0.17 —
2,4,5 4.53 4.72 2,3,4,4 0.81 0.14
2,3,4 1.68 1.79 3,3,4,5 0.24 —
2,4,4 13.30 14.48 2,3,4,4 0.21 —
2,3,3 3.64 3.99 2,3,4,5,6 0.92 —
2,3,4 2.64 2.80 2,2,3,4,6 0.13 0.04
2 ,3,4 2.83 3.08 2,2,3,5,6 0.53 0.18
3,3,4 0.66 0.38 2,3,3,5,6 0.39 0.01
3,4,4 1.62 1.89 2,2,3,4,6 trace —
3,4,5 1.03 1.08 2,2,3,3,6 0.38 0.01compounds in the oil matrix. The signal then combines to
give a resultant which is unintelligible to the mass spectrom-
eter’s computer.
If, at first, a standard method of quantitation does not
provide an unequivocal identification of PCBs, an uncon-
ventional method might be adopted. For example, extensive
cleanup of the sample, starting with solvent extraction to
concentrate the PCBs, if present, and followed by the recom-
mended cleanup protocols would yield a sample which could
be usefully analysed by a combination of coupled instru-
ments known as gas chromatography/mass spectrometry/
mass spectrometry (GC/MS/MS).
The coupled technique is typically used for ultra-trace
analysis of dioxins and was designed to provide unequivocal
identification of trace amounts of PCB-like compounds.Quantitation of the gas chromatographic results obtained
from the use of packed columns and an electron capture
detector, i.e., GC/ECD, are calculated on the assumption that
peak area is directly proportional to the amount of PCB pres-
ent. The relationship between peak area and component con-
centration is usually linear and a sample peak which is half
the size of a standard peak will result from a sample which
contains half as much as the standard. If, however, some of
the peak area is the result of a co-eluting material which is
not the analyte of interest then it will appear that there is
more present than is actually the case and the quantitative
result will be biased on the high side.
PCBs are not highly volatile compounds and conse-
quently the GC conditions have to be such that the column
used for separation must be heated to about 200°C. TheC016_003_r03.indd 924C016_003_r03.indd 924 11/18/2005 1:12:42 PM11/18/2005 1:12:42 PM