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THE CREATION OF EXPLOSIVE CONTAMINATION STANDARDS:
deposition mechanisms and surface interactions studies
Michael Ramírez, Leonardo Pacheco-Londoño, Oliva Primera-Pedrozo, William
Ortiz, Marcos Barreto-Cabán, Pedro Fierro and Samuel P. Hernández-Rivera
Chemical Imaging Center / Center for Sensors
Development
Department of Chemistry
University of Puerto Rico-Mayagüez
This research focuses in studies of surface contamination
properties, trace sample preparation methodologies,
detection systems response and generation of explosive
contamination standards for trace detection systems.
Homogeneous and reproducible sample preparation is
relevant for trace detection of chemical agents: warfare
agents, explosives and toxic industrial chemicals. The
objective is to develop technologies capable of producing
explosives nanoparticles with controlled size and
distribution over a surface to generate specimens that
reproduce real contamination conditions.
Parameters
600 dpi
3
2.5
2
1.5
1
0.5
0.5
Coupons were rinsed with
25-100 mL of acetonitrile
a.
TNT
RDX
1.5
IR spectra of RDX on surface of SS to 107, 86.9, 7.2
and 3.6 ng/cm2 and assignment of band
3.5
4.5
5.5
GC-MS determination of TNT deposited on SS by
Inkjet
Isopropanol
Ethanol
Acetonitrile
Acetone
Methanol
Standard desviation
Chromatogram of TNT from coupon
0.3
0.25
0.2
0.15
0.1
0.05
0
Solvent
Zero dead volume union
2.5
Number of passes
d.
c.
Syringe pump
y = 0.765x - 0.281
R2 = 0.9893
4
3.5
Dissolved in Acetonitrile, Methanol and 2-propanol mixture
Explosives residues deposited on stainless steel
by a smearing method.TATP 80 ug/cm2,
TNT and DNT 11 ug/cm2,and RDX 1.6 ug/cm2.
Needle
holder
5
4.5
0
0 dot spacing
Pneumatically
Assisted Nebulization
Needle
nebulizer
5.5
2
Thermal Inkjet (TIJ)
2,4 DNT
TATP
Experimental
Smearing
Results
Smearing
Loading concentration (ug/cm )
Introduction
GC- μECD
Graph of loading concentration vs
number of passes
IR image and spectra of ∼ 10 μg/ cm2 of TNT
deposited with different solvents. a ,methanol.
b. acetone; c. acetonitrile; d. ethanol.
e. isopropanol. f. Plot of the standard deviation for
peak areas in the images for each solvent
Lab jack
ƒ
ƒ
ƒ
ƒ
ƒ
Pneumatically
Assisted Nebulization
100 μg/mL RDX solution in methanol
Rate of 10 μL/min
Nebulizer pressure set at 16 psi.
Room temperature.
Distance of the nozzle to the substrate = 0.9 in
Thermal Inkjet (TIJ)
Exposure
Time (s)
Amount of
RDX
deposited
(ng)*
Amount per
Area
ng/mm2
10
82
11
32
30
246
60
480
alpha
beta
2700
2800
2900
3000
3100
3200
-1
Raman Shift (cm )
Raman detection
limit = 10 ng/cm2
In thermal ink jet technology a thin film resistor superheats less that
0.5% of the fluid in the chamber to form a gas bubble. This bubble
rapidly expands in less than ten microseconds and forces a drop to be
ejected through an orifice
Path forward
SEM images of RDX deposited with PAN
at 11 ng/cm2 and 60 ng/cm2
Intensity (arb. units
Standards were prepared using a ‘’smearing
method’’. Stainless Steel (SS) metal sheets
(non-magnetic, type 316) with an effective area
of 46.3 cm2 (3.0 cm x 15.4 cm) were used.. Four
explosive were deposited: RDX, DNT, TNT and
TATP.
Amount of RDX
deposited was estimated
from calibration curve
obtained for Eosin Y
63
The viscosity and surface tension of the medium
used for RDX solutions is similar to the medium
used for the deposition of the fluorescent
colorant
Control on the crystalline form being deposited of this material
• Trace samples with different properties can be generated with a
variety of deposition mechanisms.
• Surface interaction and vehicle properties are critical for particle
size, adhesion, distribution, deposition homogeneity and
reproducibility.
• Surface concentration, vapor pressure have an impact on particle
morphology and sample stability.
Path forward
o Deposition reproducibility and efficiency studies.
o Detection reproducibility and precision will be studied for
detection over different surfaces.
o Samples stability and storage will be characterize.
o A final publication is expected for 2009.
Contact info
[email protected]
[email protected]