152
Fish
In light of these findings, and because of the dearth of data pertaining to the
occurrence of these compounds in the environment, they included polychlorinateddibenzo-p-dioxins and polychlorinated biphenyls as target compounds in their survey
of fish and sediments in US rivers and lakes.
The analytical method developed for this investigation was required to meet six criteria:
(1) permit determinations of the majority of these compounds, especially those
possessing more than three chlorine substituents;
(2) permit isomer-specific determinations of the most toxic or otherwise important
components;
(3) provide a lower limit of detection for individual components of between 1 and 5
parts per trillion (pptr) in a variety of environmental samples;
(4) generate data with an acceptable and adequately defined level of accuracy and
precision;
(5) exhibit a very low and well-defmed susceptibility to interference and falsepositive determinations;
Fig. 7.4
Flow chart of total
procedure (from [463)).
Preparation of
homogeneous sample
Column extraction
------~-------Potassium silicate
---------------Silica gel
1 - - - - - - - - - - - - - - - - -
Part I
Potassium silicate
f - - - - - - - - - - - - - - - -
Silica gel
" - - - - - - - - - - - - - - - -
Carbon/glass fibers
Cesium silicate
f - - - - - - - - - - - - - - - - - -
Sulfuric acid· Silica gel
~---------------Alumina
GC/MS/DS AnalysiS