PCBs AND ASSOCIATED AROMATICS 921
THE ANALYSIS OF PCBSThe widespread applicability of PCBs since their introduc-
tion in 1930 up to 1976 resulted in worldwide environmental
contamination. By 1968, PCBs had become the most abun-
dant of the chlorinated aromatic pollutants, rivaling DDE
(Risebrough et al., 1968).
Jensen’s paper in 1966 confirmed the presence of PCBs
in fish after repeated encounters of gas chromatographic elu-
tion patterns while analyzing for DDT and other chlorinated
pesticides. The earlier failures by researchers in this field to
recognize the presence of PCBs must certainly have contrib-
uted to the overestimation of DDT in the environment. The
shift in emphasis to the analysis of PCBs in environmental
matrices after 1966 reversed the roles almost overnight and
PCB residues were then described to have interferences from
a wide variety of organochlorine pesticides.
Use of a halogen-sensitive detector such as an electron
capture detector in conjunction with a nonpolar stationary
phase such as OV-101 or SE-30 in a gas chromatographic
system had resulted in interferences with DDT, DDD
and DDE as well as early eluting pesticides such as BHC
isomers, aldrin, and heptachlor epoxide because of similar
retention times.
Dependent upon the matrix selected for analysis, three
distinct analytical protocols emerged involving either no
prior separation, separation via column chromatography
or separation with destruction or conversion of interfering
compounds.
Cleanup methods have been devised to separate DDT
and its analogues from some of the PCBs (Amour and Burke,
1970).
The figure below shows the structural similarity between
DDT and PCB structures. PCBs extracted from air have beenTABLE 44
Thermal decomposition products from RTEmp
% YieldDecomposition product 700°C/N^2
Cyclopentadiene 0.11
Cyclohexadiene/methylcyclopentadiene 0.055
Benzene 0.28
Toluene 0.13
Ethylbenzene 0.05
Xylene 0.022
Styrene 0.061
C^3 -alkylbenzene 0.028
Indene 0.042
Methylbenzofuran 0.012
Methylindene 0.013
Naphthalene 0.038
Methylnaphthalene 0.012
Acenaphthalene 0.0099TABLE 45
Thermal decomposition products of RTEmp at 600°C in air% YieldDecomposition product 700°C/N^2
Benzene 0.14
Acetic acid 0.060
Toluene 0.020
Styrene 0.0074
Quinone 0.0058
Benzaldehyde 0.016
Phenol 0.089
Benzofuran 0.0036
Naphthalene 0.0058
Phthalic anhydride 0.0063analyzed by Jacobs (1949) before the advent of gas chroma-
tography. The PCBs were quantitated by determining chlo-
rine after combustion over heated platinum.
Several papers in the late 1960’s and early 1970’s discuss
problems associated with the sampling of environmental
matrices for PCB analysis. Harvey and Teal (1973) showed
that nylon netting adsorbs PCBs and hydrocarbons and that
they are desorbed if exposed to water containing PCBs and
hydrocarbons in lower than equilibrium concentration.
The boat used to take water samples can be an impor-
tant source of analytical contamination (Grice et al., 1972).
Polystyrene particles recovered from the ocean were found
(Carpenter et al., 1972) to contain 5 ppm Aroclor 1254.
Jensen et al. (1972) found that plankton samples collected
from the wake of the boat were contaminated by PCBs from
the ship’s paint and contained 4 to 14 times more PCBs than
samples collected 7 ft. abeam of the boat.
Laboratory contamination is always of concern in trace
analysis and several workers have found that significant
interferences can be retained by reagent water unless pre-
cautions are taken (Bevenue et al., 1971). Several workers
(Giam and Wong, 1972; Bevenue et al., 1971; Levi and
Nowicki, 1972) have discussed cleanup treatments for solid
materials used in PCB analyses such as silica gel, florisil,
sodium sulfate, glass wool and aluminum foil. Lamont
and Cromartie (1969) recommended a cleanup method for
extraction thimbles used to hold solid samples during sol-
vent extraction of PCBs.
Ahling and Jensen (1970) extracted PCBs from water by
passing the water sample over a coated solid material. From
10 to 176 L of water were treated in this way and then the
solid material was extracted with petroleum ether to recover
the PCBs. Gesser et al. (1971) described the use of polyure-
thane foam to quantitatively extract PCBs from water.C016_003_r03.indd 921C016_003_r03.indd 921 11/18/2005 1:12:41 PM11/18/2005 1:12:41 PM