Portions of elution solvent (2 ml) were used to transfer the sample 
quantitatively and to rinse down the walls of the column. The solvent 
reservoir of the column was then carefully filled without disturbing the 
chromatographic bed, and the elution continued to completion. Removal 
and replacement of the top 2 cm of column between samples, if insoluble 
or non-elution sample components were observed, could be accomplished 
without affecting the column calibration. 
Normal-phase liquid chromatography . Florisil (magnesium silicate, 60/100 
mesh, pesticide grade. Sigma Chemical) was cleaned, activated at 1250 C 
and stored at 100 C until use. The Florisil column (5 g slurry packed 
in 50/50 methylene chloride/pentane) was direct-coupled to the SEC column 
and switched into the flow after the "F3" elution cut was reached at 
90-95 ml. After elution of the "F3" fraction through the Florisil and 
collection, the Florisil column was decoupled from the SEC column and 
further eluted with 50 ml 10% diethylether in petroleum ether. This 
fraction ("F4") was concentrated and combined with "F3" for GC/ECD. 
Highly polar components were removed from the Florisil column with methanol 
and archived ("F5''). 
Gas chromatography/electron capture detection (GC/ECD) . Extracts were 
solvent exchanged into hexane, spiked with 100 ng/ml decafluorobenzophenone 
(internal standard 1) and 165 ug/ml octachloronaphthalene (internal standard 
2), and subjected to capillary GC/ECD. 
Multi-level internal standard-based response curves for each component 
were established during calibration and verified daily during this analysis. 
Although these curves are substantially linear, a quadratic response 
equation was used to 'fit the calibration data and to quantitate sample 
components. 
Raw chromatographic chart output and integrated response tables were 
manually inspected to verify proper peak integration, to identify merged 
components or other indications of interference, and to identify each 
component of interest, if present. Raw response areas for standard 
components and analytes were entered in an electronic spreadsheet program 
(Microsoft Excel run on a 512K Macintosh personal computer) for quantitation 
and reporting. Hand calculations were used to verify the accuracy of the 
final computations. 
Level 2 organics analysis . After completing the trace organics screen, some 
samples were selected for more detailed analysis ("level 2 analysis"). 
Final extracts (fractions "F3" and "F5" combined) were concentrated to 
100 ul and fractionated by high performance liquid chromatography (HPLC). 
A semi-preparative scale (10 mm i.d. x 250 mm, 5.0 urn amine-bonded 
normal phase, IBM Instruments, Inc.) column was used. Injections were 
made from a 250 ul partially-filled loop. Detection was accomplished 
using tandem UV absorbance (254 nm. Waters Model 480) and fluorescence 
(265 nm excitation and 370 nm emission; Schoeffel Model FS970) spectro¬ 
meters, each reporting to electronic integrators. Instrument response to 
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