Gschwend%20thesis.pdf

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gas chromatograph equipped with a flame ionization detector (FID) and
splitless injector. Samples were chromatographed on an SE 54 glass
i.d. x 20 m long) supplied by Dr. K. Grob (EAWAG, Dubendorf, Switzerland).
The columns were held at room temperature for 8 min. and then programmed
from 20 to 2000C at 30C/min. for the SE54 or 20 to l800C at 30C/min. for
the UCON. Helium was the carrier gas (ca. i ml/min.) Compound cone
trations were calculated based on peak height relative to the l-cl-nC8
standard and were not corrected for stripping efficiency and FIU response
(e. g. the Fin is about 4 times more sensitive to l-cl-nC~ than to bromo-
form on a weight basis).
Gas chromatography-mass spectrometry was performed on a Finnigan
3200 GC-MS system using an SE52 glass capillary column (0.3 mm i.d. x 20 m
long). Electron impact spectra were acquired with an electron potential
of 70 eV. Chemical ionization spectra were obtained with methane as the
reagent gas at 950 ~ and with electron energy of l30 eV.
RESULTS
Table 5-2 lists the major components identified, the GC retention times
on the two columns, and whether EI or CI spectra were acquired. Sample
spectra are shown in Appendix V.
relative to the even l-chloro-n-alkanes.
Retention indices were calculated
Algal production and release of individual volatile organic compounds
has been estimated by subtracting the seawater control concentration from
that observed with the algae, and then dividing by the weight
en-
of the sample.
These results are shown in Table 5-3 for the hydrocarbons and Table 5-4 for the
halogenated methanes. Most of the discussion will be restricted to samples
which showed more than 5 times the concentration of a given compound relative
i i
to the control seawater. Increases of only 2 - 5 times over control levels