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Chemical Hydrocarbon Analyses Performed at ERCO
For hydrocarbon analyses the samples were thawed, dried with
methanol and extracted by high energy shaking with a mixture of
methylene chloride-methanol (9:1). The extract was fractionated into an
aliphatic (f ) fraction and an aromatic (f ) fraction using silica
gel/alumina column chromatography. A 1 cm diameter X 25 cm column (1 cm
alumina on top of 15 cm silica gel) was used. The f. fraction was
eluted with 18 ml hexane; the f fraction subsequently was eluted with
21 ml of a 1:1 mixture of hexane-methylene chloride. After reducing the
volume of solvent by evaporation, the gross amount (weight) of
hydrocarbon in each fraction was determined gravimetrically from an
evaporated and dried aliquot of the extract. The extracts were
subjected to quantitative glass capillary-gas chromatographic (GC)
analysis. Selected aromatic fractions also were analysed by combined
glass capillary gas chromatographic/mass spectrometric (GC/MS) analysis
for qualitative identification of individual compounds and
quantification of minor components. Participation in an
intercalibration exercise under the direction of the National Analytical
Laboratory indicated that these analyses were at the state^ of the art
with repeatable ± 20% detection of hydrocarbons in the ng g dry weight
sediment range. The details of GC and GC/MS analysis employed are as
follows:
CC: Hewlett Packard 5840A reporting GC with glass; splitless
injection inlet system; 30 m glass capillary column coated with SE-30 (s
100,000 theoretical plates); FID detector; temperature programmed at
60-275°C min ; helium carrier gas 1 ml min ; transmission of
integrated peak areas and retention time through HP 18846A digital
communications interface to a PDP-10 computer for storage, retention
index and concentration calculations. Deuterated anthracene (f.) and
androstane (f ) were used as internal standards and response factors
were determined with known concentrations of the reported compounds. GC
analysis was used to quantitate components of the f. fraction.
GC/MS: Hewlett Packard 5985 quadrapole system (GC/MS Computer);
mass spectrometer conditions: ionization voltage=70 eV, electron
multiplier voltage=2200 V, scan conditions 40 amu to 500 amu at 225 amu
s~ . Quantification of components of the f fraction was accomplished
by mass f ragraentography wherein the stored GC/MS data is scanned for
parent ions (m ) . The tabulated total ion currents for each parent ion
is compared with deuterated anthracene (internal standard) and an
instrumental response factor applied. Authentic polynuclear aromatic
hydrocarbon standards were used to determine relative response factors
(when no standard was available a response factor was assigned by
extrapolation) .
In vitro Biodegradation
Sediment was collected at sites 6 and 7 in November, 1979 for in
vitro biodegradation experiments. Replicate one hundred gram portions
of sediment were placed into 250 ml flasks to which 50 ml of a sterile
solution containing 0.5% KNO + 0.5% KH 2 P0 4 and 0.5 ml of light Arabian
crude oil were added. The flasks were agitated on a rotary shaker at