Table 6. Comparison of collocated samples collected with a 10-mL syringe vs. 5-g En Core sampler

DISCUSSION - SR99_050019

Table 7. Average and standard deviations (n = 3) of analyte concentrations (mg/kg) for spikes and samples

SR99_05
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14

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)

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-

posed several potential problems with this

method; the most important was that this ap-

proach to bulk sample storage failed to prevent

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

a translucent, nonelastic formulation of Teflon, a

white, elastic formulation of Teflon, and aluminum

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-

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

**Not significantly different at 95% confidence limit

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

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