screening method can easily show the presence of 0.5
Coupons of both types of metal, from three differ-
g of an explosive analyte when concentrated in a dis-
ent preparation batches, were each placed in a 20-mL
crete location on a white surface (filter paper). For soil,
VOA vial and extracted with 1 mL of acetone. Analy-
a sample containing 4 1 mg TNT/kg was found to
ses of these extracts were used to assess the precision
give a visible response using the above procedure.
of the spiking procedure. Triplicate coupons of both
types of metal were heated for 1 hour at 500 20F
All of the samples listed in Appendix A were re-
(260 6.6C) in a muffle furnace. Following this ther-
turned to the Cold Regions Research and Engineering
Laboratory (CRREL) for extraction and analysis. The
mal treatment, each type of metal coupon was com-
samples were extracted with acetone by adding 1 mL
bined into a single 20-mL VOA vial (composited) and
to the auto sampler vials (2 mL) that contained the fil-
extracted with 3 mL of acetone. This experiment as-
ter paper, soil, or small pieces of rubber/plastic gasket
sessed the efficiency of thermal decomposition under
materials, while up to 10 mL was added to larger VOA
this condition.
vials (20 mL) that contained waxy substances. After
Two further experiments assessed the concentration
initially analyzing all of the samples by GC/TID, sev-
stability of TNT, RDX, and HMX on the coupons dur-
eral were reanalyzed by Method 8095 (U.S. EPA 1999)
ing storage. In one experiment, triplicate QA coupons
after they were appropriately diluted.
of both metals were stored in a plastic dish that was
held at room temperature (21 2C) for 7 days. In the
Coupon performance
other, one of each type of metal coupon was placed in
Experiments assessed the QA coupons, their han-
three separate chambers (electrical boxes), then each
dling, and the efficiency of different methods of wip-
chamber was wrapped with aluminum foil and placed
in a freezer (12 3C) for 14 days. After these storage
ing their surface to quantitatively recover the residues
of explosives. Many of these experiments used steel
periods were over, individual coupons were placed into
and aluminum coupons spiked with approximately 1
a VOA vial and extracted with 1 mL of acetone.
mg of TNT, RDX, and HMX. The coupons were spiked
by sequentially adding 5-L aliquots of the stock solu-
Wiping and sample preparation experiments
tions prepared in-house (mentioned previously) and al-
Several experiments assessed different techniques
lowing the solvent to evaporate. The aliquots were
of wiping the coupon surface to recover the explosive
placed directly onto the surface of the coupon with a
residues. In addition, a couple of different sample prepa-
10-L glass syringe (Hamilton); the solvent evaporated
ration procedures were evaluated. For assessing wip-
in less than 0.5 minutes. The spike aliquot appeared to
ing techniques, triplicate QA coupons of both types of
remain in the dimple on the aluminum coupons, while
metals were used.
often the entire top surface of the rusted steel coupons
For the first technique, a 1.5-cm-diameter filter pa-
became visibly wetted. Coupons were spiked in batches,
per (Whatman, type 1), soaked in methanol, was pressed
so that each one in the batch was treated with a single
onto the coupons (approximately 80% coverage) with
aliquot prior to the start of the next treatment round.
the aid of clean stainless steel tweezers. Once each fil-
The coupons were spiked with the HMX solution first,
ter paper had dried, it was folded (using the tweezers)
followed by RDX, then TNT. To achieve concentra-
and placed into a separate 2-mL amber glass vial and
tions close to the target level of 1 mg for each explo-
extracted with 1.0 mL of acetone.
sive, ten, five, and one 5-L aliquots of the HMX, RDX,
For the second technique, the entire spiked surface
and TNT stock solutions, respectively, were placed on
of the coupon was wiped several times with a 1.5-cm-
each coupon. For a batch of 12 coupons, this spiking
diameter filter that had been soaked in acetone. As
process took approximately 20 minutes to complete. In
before, the filter paper was allowed to dry, then folded
addition to the experiments that involved wiping the
and placed in a 2-mL amber glass vial for extraction.
surface of a QA coupon, one experiment was performed
For the third technique, a Q-tip (paper post with a
using range scrap.
cotton swab on each end) that had one end soaked in
acetone was first pressed against the wall of the vessel
Coupon preparation, thermal treatment, and
to removed excess solvent. Then, the entire top surface
storage experiments
of the coupon was rubbed at least twice while it was
The initial experiments assessed the following:
held on the table surface with clean metal tweezers.
The wetted end of the Q-tip was then inserted into the
The reproducibility of the QA coupons.
mouth of a 2-mL amber vial, the tip was cut off with
The effect of thermal treatment on the QA coupons.
scissors, and it was allowed to air dry. Then it was ex-
The stability of the explosives on the coupons un-
tracted with 1.0 mL of acetone.
der two storage conditions.
Cotton balls were used for the fourth test. Before a
5
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