Gschwend%20thesis.pdf

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(heated to 60 C to reduce the relative humidity), before reaching a
charcoal trap. The microcharcoal trap consists. of a glass tube in
which about I mg of charcoal has been fixed between two stainless steel
screens glass-blown into the tube. After passing through the trap, the
air returns to the pump for recirculation through the system, The
sample was stripped for 2 hours at a flow rate of about 1.5 liter/min.
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The water sample was heated to 35 C by a water bath. All water samples
were restripped onto a fresh trap for an additional 2 hours immediately
after the first strip (henceforth referred to as a restrip) i
After stripping, the trap was removed from its holder and
with is ~l CS2 (figure 3-3).
extracted
This was done by adding another internal
standard (2 ~l of 20 ng l-chloro-n-octane/~l CS2) onto the trap and then
adding 6 ~l CS2. Cooling the vial of the assembled extraction apparatus
drew the solvent plug down through the charcoal. Warming the vial
pushed
the solvent back up through the charcoaL. After several such passes ,the
solvent was drawn down and away from the charcoal by prolonged cooling,
and with a quick flick was shaken down into the bottom of the vial.
Repeating the extraction with an additional 6 ~l CS2 efficiently completed
the removal of the volatiles from the trap and provided a concentrated
solution for further analysis.
Gas Chromatography and Gas Chromatography ~ Mass Spectrometry
The volatiles were analyzed using gas chromatography (GC) and
combined gas chromatography-mass spectrometry (GCMS). A single SE54
glass capillary column (0.3 mm i.d. x 20 m long; purchased from Jaeggi,
9043 Trogen, Switzerland) was used. A Carlo Erba Model 215l ACgas
chromatograph equipped with a flame ionization detector (FID) and
special Grob inj ec tor was used. Injections were made with the split
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