Pre-Screening for Explosives Residues
5
Expray claims this product can detect a minimum of 20 nanograms of RDX
and 5 nanograms of TNT. In our tests, application of 1 L of 20 ppm RDX (20
ng) and 1 L of 5 ppm TNT (5 ng) onto the test paper failed to yield a visually
detectable color change. A granular sample tested at these masses may very well
produce a color change; however, we did not perform those tests.
Method
TNT, RDX, HMX, and NG are the analytes most commonly found in soils
at DoD training ranges and therefore these four were selected for this study. The
TNT, RDX, and HMX standards were made from Standard Analytical Reference
Material (SARM) obtained from the U.S. Army Environmental Center and were
prepared in acetonitrile (ACN) at 1 g/L, and NG is obtained in solution form.
Dilutions were prepared from these standards with ACN and concentrations were
confirmed by HPLC analysis using a system consisting of a Spectra System
P1000 pump, AS3000 autosampler, and UV 2000 dual wavelength detector.
Eluent consisted of 85:15 MilliQ filtered water:2-propanol. The column was a
Waters NovaPak C8, 150 mm 3.9 mm at 28C.
Eight types of paper were chosen for this study to determine whether
screening results were dependent on the type of paper used. The eight are
1. Expray sample paper. Unknown composition, appears to be a more robust
form of glass fiber with an impervious backing and raised fluffed areas.
2. Boise Aspen. White/20 lb/10.0 M copy paper, 30% post-consumer fiber.
3. Whatman's Filter Paper #1. Qualitative cellulose filters.
4. Whatman's Filter Paper #2. Qualitative cellulose filters.
5. Fisher Filter Paper #09-803-5, P2. Unknown composition, most likely
cellulose.
6. Baroid Filter Paper #988. Unknown composition, most likely cellulose.
7. Reeve Angel Filter Paper #934 AH. 100% borosilicate glass fiber,
chemically inert.
8. VWR Scientific Filter Paper Grade 417. Qualitative cellulose filter.
The test paper was prepared by placing a Pasteur pipette into the standard,
drawing approximately 810 L of liquid into it, and then touching the tip briefly
to the test paper, which drew the liquid out. Because it was found that some of
the paper drew differing amounts of solution, all tests were performed by placing
the total volume (810 L) drawn into the pipette onto each type of paper and
therefore holding the testing volume constant (see Fig. 2).
Previous Page
