Distribution of Chlorinated Hydrocarbon Pesticides and PCBs in the ...

to 1 mL in an N2 stream. 1 mL dichloromethane was added to
prepare the extract for gel permeation column clean-up.
The extract was placed on a calibrated Biobeads SX-3 gel
permeation column (60 g 3.0 cm x 50 cm) and eluted with 1:l
dichloromethane/hexane at 5 mL/min. The 150 - 300 mL fraction
was collected and evaporated down for florisil column separation.
3.1.7 Sample Clean-Up and Se~aration
Extracts from the first and second sampling trips (86
samples) were cleaned up and separated by the following
procedure.
Florisil (8 g deactivated with 3% w/w water) was slurried
in hexane, packed with tapping into a hexane filled 10 mm x 200
mm column, and capped with a 10 mm layer of sodium sulphate. The
column was flushed with 50 mL hexane and the solvent level run
down to the top of sodium sulphate layer.
Sample extracts were blown down to 1 mL with nitrogen and
quantitatively transferred to the florisil column and eluted with
hexane (37 mL) , 6% diethyl ether in hexane (37 mL) and 15%
diethyl ether in hexane (37 mL). The first 27 mL was collected
as fraction 1, the next 47 mL as fraction 2 and the last 37 mL as
fraction 3. Aliquots of internal standard (1.0 mL 22.96 ng
decachlorobiphenyl) was added to fractions 2 and 3 and all were
taken down by vacuum rotary evaporation to 2 mL for GC/EC
analysis. (Additional activated copper treatment of sediment
contract fraction 1 was necessary to remove residual sulphur.)
The column cut points, determined for each prepared batch
of florisil was typically as below:
Fraction 1: polychlorinated biphenyls, hexachlorobenzene,
o,pr-DDE, ppr-DDE, alpha-HCH (40%), heptachlor,
aldrin, ppr-DDT (70%), Mirex.