ondly, biodegradation caused by a lack of adequate
Table 6. Comparison of collocated samples col-
sample preservation.
lected with a 10-mL syringe vs. 5-g En Core sam-
Another fairly common practice that was
pler. Samples obtained with the syringe were
adopted on a state-by-state basis was the use of
immediately prepared for analysis. Samples ob-
metal core barrel liners covered with sheets of
tained with the En Core sampler were stored
Teflon or aluminum foil as transportation and stor-
under the conditions stated below.
age vessels. Presumably, the same storage condi-
Syringe
En Core
% Recovery
tions, holding period, and sampling practices that
(mg TCE/kg)
(mg TCE/kg)
relative to syringe
existed for samples stored in bottles were used for
core barrel liners. To date only one study has ad-
A. Samples held for two days at 4 2C in En Core
dressed the performance of core barrel liners
samplers (n = 5).
(Hewitt and Lukash 1996). This initial study ex-
89.715.0†
76.319.7**
Trial 1
85%
posed several potential problems with this
26327.8
24337.9**
Trial 2
92%
method; the most important was that this ap-
51336.6
45546.3**
Trial 3
89%
proach to bulk sample storage failed to prevent
50845.1
49240.2**
Trial 4
97%
volatilization losses. However, this earlier study
B. Samples held for seven days at 4 2C in En Core
only considered one of the formulations of Teflon
samplers (n = 5).
sheeting that are commercially available for this
application. Here an evaluation was performed on
23826.1
20462.7**
Trial 5
86%
a translucent, nonelastic formulation of Teflon, a
38036.0
33621.3
Trial 6
88%
55051.3
47170.3**
white, elastic formulation of Teflon, and aluminum
Trial 7
86%
54433.0
51052.3**
foil.
Trial 8
94%
Although the translucent, nonelastic formula-
C. Samples held for two days at 4 2C and additional 12
tion of Teflon was superior to these other cover-
days at 12 3C in En Core samplers (n = 6).
ings, it was also susceptible to volatilization losses
16.111.5
12.74.7**
with both laboratory-treated and field-contami-
Trial 9
79%
19.35.2
17.73.3**
nated soils. The nonelastic version may have per-
Trial 10
92%
formed better than the other type of Teflon, be-
†Average and standard deviation.
cause it is thicker (0.05 mm vs. 0.02 mm) and differs
in physical composition. Independent of formu-
(Student's t-test).
lation, the losses incurred by the Teflon sheeting
were attributed to permeation, while those for the
aluminum foil were initially attributed to a poor
mended in Method 5030. Briefly, bulk samples
seal (folds in the sheeting) around top edge of the
were collected without attention to how much
core barrel liner (Hewitt and Lukash 1996). How-
fragmentation of the substrate occurred while
ever, in addition to the poor sealing quality of alu-
quickly filling a transportation and storage bottle
minum foil, holes can be created in this covering
to capacity. The bulk sample remained in the bottle
with time (six days), presumably caused by gal-
while being transported and stored at 4 2C. Af-
vanic corrosion. This technique for transporting
ter storage, which could last up to 14 days a sample
and storing a bulk sample, nonetheless, is most
of approximately 5 g was removed with a metal
likely superior to using a bottle because the sub-
spatula and weighed in an uncapped vessel prior
strate experiences less exposure and disaggrega-
to either the addition of MeOH or attachment to a
tion before laboratory subsampling. Regardless of
purge-and-trap manifold. This method of collec-
this comparison, storage in covered core barrel lin-
tion, storage, and subsampling causes highly vari-
ers should no longer be recommended when
able losses of VOCs, the extent of which is believed
VOCs are of concern, because these coverings are
to have resulted in the reporting of biased con-
incapable of serving as a hermetic barrier for
centrations that reflected less than 10%, and some-
VOCs, as specified by both Method 5035 and
times less than 1% of the in-situ levels of contami-
D4547-98.
nation (Urban et al. 1989, Siegrist and Jenssen 1990,
The sample collection, handling, and prepara-
Illias and Jaeger 1993, Lewis et al. 1994, Hewitt et
tion methods described here for the VOA vial
al. 1995, Liikala et al. 1996, Smith et al 1996). The
(bottle) and En Core sampler (chamber) limit
loss mechanisms most frequently cited were vola-
sample exposure and substrate disaggregation.
tilization caused by sample exposure, and sec-
Both of these transportation and storage vessels
14
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