Organics
205
8.2.5
Polychlorinated Biphenyls
Markin et al. [591] have also discussed the possible confusion between mirex and
PCBs in the analyses of crabs and shrimps. In their method, the samples were
thoroughly scrubbed to remove mud, algae, and other residues; they were ground
whole and mixed in a Waring blender to make a composite sample. A 20 g subsample
of the composite was removed and analysed as follows. The homogenized sample was
extracted with a mixture of hexane and isopropanol, and the extract subjected to a
concentrated sulphuric acid cleanup. The sulphuric acid destroys dieldrin, endrin,
and organophosphorus insecticides. The final extract was cleaned up on a Florisil
column and concentrated to the desired level for analysis. If PCBs were suspected in
the first analysis, their presence usually being indicated by a series of characteristic
peaks, the sample was reprocessed to separate the PCBs from the insecticides as
described by Armour and Burke [592], Gaul and Cruz-LaGrange [593], and Markin et
al. [594]. After concentrating to the appropriate volume, the extract from both
methods of cleanup were chromatographed on a Hewlett Packard Model 402 dual
column gas chromatograph equipped with dual electron capture detection. Each
sample was analysed on two different columns; the first column was a mixture of
1.5 % OV-17 and 1.95 % QF-l on Gas Chrom Q. The temperatures of the injector,
oven, and detector were 250, 200 and 210 °c respectively. The second column was 2 %
DC-200 on Gas Chrom Q with injector, oven, and detector temperatures of 245, 175
and 205°C respectively. Argon-methane at 80 ml min- 1 was the carrier gas. Level of
detection was 0.001 ppm for DDT and its metabolites, 0.005 ppm for mirex and
0.01 ppm for Aroclor 1260.
Markin et al. [591] comment that they found mirex in only a minority of the
samples they analysed, contrary to results obtained by earlier workers [595-597].
Teichman et al. [598] separated PCBs from chlorinated insecticides in oyster samples using gas chromatography coupled to mass spectrometry. PCBs were separated
from DDT and its analogues and from the other common chlorinated insecticides by
adsorption chromatography on columns of alumina and charcoal. Elution from alumina columns with increasing fractional amounts of hexane first isolated dieldrin and
heptachlor from a mixture of chlorinated insecticides and PCBs. The remaining
fraction, when added to a charcoal column, could be separated into two fractions, one
containing the chlorinated insecticides, the other containing the PCBs, by eluting with
acetone-diethyl ether (25:75) and benzene, respectively. The PCBs and the insecticides
were then determined by gas chromatography on the separate column eluates without
cross-interference.
Teichman et al. [598] used an electron capture gas chromatography (Aerograph
1200) containing a glass column (6 ft x 0.125 in.) packed with 4 % SE-30, 6 % SP-4201
on Chromosorb W (l00 to 120-mesh). Heptachlor epoxide and dieldrin were removed
from the column by extending the elution solvent beyond the 30-ml volume with an
additional, but separate, elution volume of 30 mI. The PCBs remained an integral part
of the mixture containing the insecticides in the first 30 ml of eluate. The elution
pattern of alumina column fraction 1 on the charcoal column shows that the insecticides were separated from the PCBs by means of acetone-diethyl ether eluant. The PCBs
205
8.2.5
Polychlorinated Biphenyls
Markin et al. [591] have also discussed the possible confusion between mirex and
PCBs in the analyses of crabs and shrimps. In their method, the samples were
thoroughly scrubbed to remove mud, algae, and other residues; they were ground
whole and mixed in a Waring blender to make a composite sample. A 20 g subsample
of the composite was removed and analysed as follows. The homogenized sample was
extracted with a mixture of hexane and isopropanol, and the extract subjected to a
concentrated sulphuric acid cleanup. The sulphuric acid destroys dieldrin, endrin,
and organophosphorus insecticides. The final extract was cleaned up on a Florisil
column and concentrated to the desired level for analysis. If PCBs were suspected in
the first analysis, their presence usually being indicated by a series of characteristic
peaks, the sample was reprocessed to separate the PCBs from the insecticides as
described by Armour and Burke [592], Gaul and Cruz-LaGrange [593], and Markin et
al. [594]. After concentrating to the appropriate volume, the extract from both
methods of cleanup were chromatographed on a Hewlett Packard Model 402 dual
column gas chromatograph equipped with dual electron capture detection. Each
sample was analysed on two different columns; the first column was a mixture of
1.5 % OV-17 and 1.95 % QF-l on Gas Chrom Q. The temperatures of the injector,
oven, and detector were 250, 200 and 210 °c respectively. The second column was 2 %
DC-200 on Gas Chrom Q with injector, oven, and detector temperatures of 245, 175
and 205°C respectively. Argon-methane at 80 ml min- 1 was the carrier gas. Level of
detection was 0.001 ppm for DDT and its metabolites, 0.005 ppm for mirex and
0.01 ppm for Aroclor 1260.
Markin et al. [591] comment that they found mirex in only a minority of the
samples they analysed, contrary to results obtained by earlier workers [595-597].
Teichman et al. [598] separated PCBs from chlorinated insecticides in oyster samples using gas chromatography coupled to mass spectrometry. PCBs were separated
from DDT and its analogues and from the other common chlorinated insecticides by
adsorption chromatography on columns of alumina and charcoal. Elution from alumina columns with increasing fractional amounts of hexane first isolated dieldrin and
heptachlor from a mixture of chlorinated insecticides and PCBs. The remaining
fraction, when added to a charcoal column, could be separated into two fractions, one
containing the chlorinated insecticides, the other containing the PCBs, by eluting with
acetone-diethyl ether (25:75) and benzene, respectively. The PCBs and the insecticides
were then determined by gas chromatography on the separate column eluates without
cross-interference.
Teichman et al. [598] used an electron capture gas chromatography (Aerograph
1200) containing a glass column (6 ft x 0.125 in.) packed with 4 % SE-30, 6 % SP-4201
on Chromosorb W (l00 to 120-mesh). Heptachlor epoxide and dieldrin were removed
from the column by extending the elution solvent beyond the 30-ml volume with an
additional, but separate, elution volume of 30 mI. The PCBs remained an integral part
of the mixture containing the insecticides in the first 30 ml of eluate. The elution
pattern of alumina column fraction 1 on the charcoal column shows that the insecticides were separated from the PCBs by means of acetone-diethyl ether eluant. The PCBs