for recovering explosives from metal surfaces. Similar
Once retrieved, the coupons and pieces of range scrap
observations were made by Thompson et al. (1999)
should be submersed in acetone for extraction in prepa-
when they sampled for residues of explosives from a
ration for analysis. The solvent extracts could be ana-
variety of surfaces. The better performance of cotton is
lyzed on-site using GC/TID when same-day results were
most likely attributable to the amount of solvent it de-
needed. Rapid-turn-a-round results are likely to be
livers to the surface during wiping, and perhaps to the
needed during preliminary trials designed to establish
greater surface area it provides as compared to a filter
the optimal heat soak parameters and pile configura-
paper, as mentioned earlier. Independent of wiping ma-
tion. Confirmation analysis by either Method 8330 or
terial, there is a general trend showing that it is easier
8095 will also be done at a later date.
to recover residues of explosives from a smooth sur-
A two-tiered analytical process is recommended for
face as compared to one that is rusted (pitted). Owing
characterizing range scrap, as the distribution and con-
to the uncertainty of recovery of analytes from rough
centration of explosive residues is thought to be very
surfaces, wiping methods in general should not be con-
heterogeneous. The first step in this process is to use
sidered to be quantitative. However, there were features
on-site rapid colorimetic tests to identify the presence
that make this process easy to do and eliminate unnec-
of explosives, so authoritative samples can be collected
essary variables. On the basis of the above findings,
for subsequent analyte-specific methods of analysis. The
the following procedure is currently recommended for
commercially available Expray kit appears to be par-
obtaining residues of explosives from the surface of
ticularly well suited for this purpose because it is eas-
range scrap:
ily transported, simple to apply, and detects a wide range
of explosives compounds. Once the presence of explo-
Repeatedly wipe the surface with an acetone-moist-
sives has been indicated, obtaining a wipe sample or
ened cotton ball held with metal tweezers (the cot-
collecting a small quantity of material would follow.
ton balls used in this study weighed 0.2 0.04 g
Although not used during the initial characterization
and were moistened with 1 mL of acetone; heavier
exercise conducted for this study (laboratory trials were
cotton balls could be moistened with greater
performed after the site visit), the wipe sample should
amounts of acetone).
be collected with a cotton ball moistened with acetone.
Allow the cotton ball to air dry.
This technique is easy to use and gives greater recover-
Extract the cotton ball with acetone.
ies than filter paper wipes. The experimental results
show that this technique is qualitative; however, it can
An additional step, filtering the extract, is necessary
provide a conservative estimate of the surface concen-
for analysis by Method 8330 or Method 8095. This can
tration. Solvent immersion procedures are recom-
be done by passing a portion of the solvent extract
mended when more quantitative estimates of the con-
through a 0.45-m Millex SR filter. For convenience,
centration of explosives on range scrap are necessary.
the cotton balls used for sample collection can be moist-
ened before the field exercise, and stored in 20-mL VOA
LITERATURE CITED
vials before and after a surface is wiped. The cotton
balls should be air dried and extracted in a laboratory
setting in preparation for analysis.
ASTM (1999) Standard practice for field collection of
settled dust samples using wipe sampling methods for
lead determination by atomic spectrometry techniques.
SUMMARY
ASTM E 1728. American Society for Testing and Ma-
terials, West Conshohocken, Pennsylvania.
This study has shown that QA coupons could be used
Crockett A.B., H.D. Craig, T.F. Jenkins, and W.E.
to monitor how completely explosives decompose on
Sisk (1997) Field sampling and selecting on-site ana-
range scrap treated by HGD. Coupons with spiked con-
lytical methods for explosives in soil. Federal Facili-
centrations near 1 mg for TNT, RDX, and HMX can be
ties Forum Issue. EPA/540/R-97/501.
precisely prepared and were found to retain the spiked
Hewitt, A.D., and T.F. Jenkins (1999) On-site method
concentration when stored in a freezer for extended
for measuring nitroaromatic and nitramine explosives
periods (2 weeks and perhaps longer). Range scrap that
in soil and groundwater using GC-NPD: Feasibility
is known to be contaminated by residues of explosives
study. U.S. Army Cold Regions Research and Engineer-
should also be used to monitor the effectiveness of
ing Laboratory, Special Report 99-9
HGD. During an HGD trial, both the QA coupons and
Hewitt A.D., T.F. Jenkins, and T. Ranney (2000) On-
selected pieces of range scrap could be housed in a
site method for nitroaromatic and nitramine explosives
chamber that can easily be retrieved from the scrap pile.
in soil and groundwater using a GC-thermionic ioniza-
9
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