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

funnel, shaken with 20 ml of 0.9% NaCl, and then stored overnight
stoppered and taped with teflon tape in the refrigerator to
separate. After separation, the lower organic layer was
collected in a 100 mL volumetric, and made to volume with 2:l
chloroform:methanol at room temperature.
Lipid concentration was quantified colorimetrically using
the sulphophosphovanillin method of Barnes and Blackstock (1973).
A 0.5 mL aliquot of lipid extract was evaporated under nitrogen
and 0.5 mL of concentrated sulphuric acid added to the residue.
The tube was stoppered with non-absorbent cotton wool and heated
ten minutes in a boiling water bath. After cooling. 0.1 mL from
each tube was transferred to a clean, dry test tube and 2.5 mL
of the phosphovanillin reagent added. After thirty minutes, the
absorbance was measured at 530 nm against a procedural blank. A
cholesterol standard was used to derive a calibration curve and a
calculation made for total lipid concentration using the
conversion factor given in Barnes and Blackstock which equates 80
mg cholesterol standard to 100 mg total lipid.
The quantity of extract containing less than 200 mg of
lipid was initially determined gravimetrically by the following
procedure. Duplicate 2.5 mL aliquots of the soxhlet extract were
placed on tared (+ 0.02 mg) aluminum weighing boats which were
then dried at 105°C for 10 minutes, cooled in a dessicatsr and
reweighed to + 0.02 mg. The lipid content of the sample was
calculated. The volume containing 200 mg or less lipid was
determined and this volume taken and evaporated down to 1 mL for
gel permeation column clean-up.
Procedural blanks were run with every suite of samples.
True replicates were analyzed by subsampling a homogenized
sample. The precision of the method (relative standard 4%
deviation) was +/- 7% at lipid concentrations of 5.7 and 24.7 %
dry weight. Sp-
b
4k