prior to preparing for analysis. The results of these
Table 4. Comparison of average and standard de-
experiments involving field-contaminated soils
viation of concentrations (mg/kg) for samples re-
were very consistent with the laboratory findings
moved from core barrel liners in the field (D0) vs.
those stored for two and four days at 4 2C in
for this analyte (Table 5), e.g., no statistically sig-
nificant change in concentration over a short two-
core barrel liners covered with a thin metal disk
day holding period, and frequently no significant
lid, then wrapped with a sheet of translucent, non-
change over extended holding periods.
The first laboratory experiment using empty
VOA vials as containers for transporting and stor-
ing soil samples evaluated the effect of storage
temperature. The results in Table 7 show the same
trends in analyte concentration relative to room
temperature and refrigerated storage, as seen in
experiments performed using sealed glass am-
poules as storage chambers (Fig. 2, Hewitt 1995a).
At room temperature there was rapid degradation
of the aromatic compounds. Indeed, after seven
days of storage at 21 2C, Ben, Tol, E-Ben, and p-
Xyl were not detected. When stored at 4 2C for
14 days, these same four aromatic compounds
were reduced in concentration by more than 60%
from the D0 values. With the exception of CDCE,
the chlorinated compounds showed much smaller
losses for these storage periods and conditions.
When these samples were stored at 12 3C, the
concentrations established after 14 days of stor-
age in freezer were within 5% of the values estab-
lished on D0. This table also shows that there was
*n = 4.
good agreement between the spike and D0 analyte
**n = 2.
†ND = Not detected.
In the second experiment, we compared intro-
††Percentage found relative to the D0 analyte concentration.
ducing spiked samples to a VOA vials that already
contained a solution vs. introducing them to empty
VOA vials and then adding solution through the
first two days of storage at 4 2C. Furthermore,
septum after various storage periods and condi-
this slow rate of loss appears to have continued
tions. Direct headspace analysis vs. MeOH extrac-
for Ben and TDCE after the samples in the En Core
tion was also compared. Table 8, which shows the
samplers were moved to the freezer. The remain-
results of these comparisons, indicates (1) there is
ing analytes (TCE, PCE, E-Ben, p-Xyl, and o-Xyl)
no apparent effect caused by introducing the wa-
showed no statistically significant changes in
ter through septa, (2) analyte recoveries relative
analyte concentrations relative to D0, while CDCE,
to the spike concentration were not as accurate for
and Tol showed no statistically significant reduc-
samples dispersed in water and analyzed directly
tion in concentration after being placed in the
as opposed to those extracted with MeOH, and
freezer (e.g., relative to D2).
(3) losses of aromatic compounds decreased when
Each of the 10 field trials (Table 6) involving the
frozen. The first observation suggests that adding
5-g En Core sampler was initially evaluated using
an aqueous solution through septum, as would
the Students' t-test at a 95% confidence interval.
be necessary for either headspace or purge-and-
This statistical analysis showed that in only one
trap analysis, is comparable to having the aque-
case was there a difference between the mean TCE
ous solution present in the VOA vial at the time of
concentrations. The trial (trial 6) that had signifi-
sample collection. The discrepancy in analyte re-
cant difference between the mean values showed
covery relative to these two methods of sample
that a slightly lower (12%) TCE concentration ex-
preparation, i.e., vapor partitioning vs. MeOH
isted for the soil samples obtained and stored in
extraction, is consistent with that of earlier stud-
the En Core sampler for seven days at 4 2C,
ies (Askari et al. 1996, Minnich et al. 1996, Hewitt