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

Table 3.13 Replicate analyses of Standard Reference Material CS-7
Compound
-- ----- -- -
Repl icate
1 2 3 4 5 6 Mean S.D.
Aroclor 1254 0.77 0.76 0.76 0.73 0.81 0.65 0.75 jt0.05
HCB 0.059 0.056 0.049 0.063 0.066 0.065 0.063 10.006
p,pl-DDE 0 ,I 3 0.13 0.11 0.11 0.19 0.10 0.13 10.03
alpha-HCH 0.088 0.084 0.062 0.077 0.070 0.070 0.075 t0.01
gamma- HCH 0.054 0.05 0.05 0.076 0.075 0.060 0.061 10.06
heptachlor epoxide 0.050 0.048 0.018 0.031 0.038 0.057 0.040 20.02
When samples were retrieved, silver filters were removed
by forceps, stored in disposable plastic Petri dishes and kept
frozen until analysis (within two months). Filters were fumed
(30 min) over concentrated HC1 prior to drying (80°C overnight)
to remove carbonates. Dry weight of filters was compared with
original filter weight to measure total dry mass of particles
collected. Filters were combusted in a Perkin Elmer Elemental
Analyzer (Model 240) for determination of organic carbon and
nitrogen. Absolute sensitivity (twice blank value) was
approximately 5 pg for carbon and nitrogen.
3.4 Lipids
Lipids were extracted from 100 mg of the pulverized dry
.a,
tissue by homogenisation with 80 ml of 2:l chloroform:methanol in
a Virtis homogenizer for five minutes (Barnes and Blackstock,
1973) . The solution was maintained at 55°C for ten minutes and
then filtered through a No. 1 chloroform:methanol washed Whatman
filter into a 100 ml volumetric flask. The solid residue was
washed with small aliquots of which chloroform/methanol. On the
final washing it was poured into the filter. The solution was
made up to 100 mL and then transferred to a 250 mL separatory