FORENSIC SCIENCES: CRIMINALISTICS - Bio Medical Forensics

syntheses (2g-88g) of TATP were also performed. Detonation of these
large scale synthesis samples were conducted in the field at a test range,
and post-blast samples were collected and analyzed both in the field and
later in the laboratory.
Views presented do not reflect the position of the government or infer
endorsement.
Triacetone Triperoxide, Analytical Chemistry, Trace Evidence
A95 Analysis and Potential Differentiation of
Soot From Different Fuels Using Laser-
Induced Thermal Desorption Fourier
Transform Mass Spectrometry
(LITD-FTMS)
Katherine Hutches, MSFS*, Donald P. Land, PhD, and Diana Wang,
University of California at Davis, One Shields Avenue, Davis, CA 95616
After attending this presentation, attendees will have been
familiarized with laser-induced thermal desorption (LITD) coupled with
FT-MS, pyrolysis products of common fuels, soot formation mechanisms,
and the application of LITD-FTMS for the analysis of soot deposited onto
glass surfaces.
This presentation will impact the forensic science community by
introducing its members to a new analytical technique and the potential
applications of this technique to surface and soot analysis.
This study seeks to determine whether LITD-FTMS can be used as
a tool for the analysis of soot deposited onto glass surfaces during
compartment fires. Fire debris chemists have long recognized the
presence of varying pyrolysis products from different fuels, such as
styrene from polystyrene and nitrogen-containing compounds from
polyurethane. If the soot and soot-adsorbed species that deposited onto
glass surfaces were likewise different from one fuel to another, then it
might be possible to differentiate between fuel sources, and possibly
determine the order of deposition (and first fuel), using this surfaceanalyzing
technique.
The deposits from polystyrene, flexible polyurethane foam, and
gasoline have been analyzed and compared for visible “marker” peaks.
Polyurethane is easily distinguished by peaks at m/z 122 and 148, which
correspond to toluene diamine (TDA) and toluene aminoisocyanate (TAI)
respectively. These are known pyrolysis products of flexible
polyurethane foam, which is typically based on toluene diisocyanate
(TDI). The polystyrene and gasoline deposits share many peaks in their
mass spectra, which vary greatly with incident laser power density. High
power densities yield mainly low-m/z peaks that may be attributed to the
C 2n H 2m?? + ions predicted by the hydrogen-abstraction C2 H 2 -addition
(HACA) theory of soot formation. At low incident laser power densities,
both fuels yield spectra dominated by aromatic compounds such as
benzene, naphthalene, and other conjugated ring systems. At these low
incident power densities, the spectra for gasoline deposits are dominated
by a large peak at m/z 202, which may be attributed to several isomers of
C 16 H 10 . This peak is typically significantly smaller for the polystyrene
deposits. The relative abundance of other peaks, such as m/z 91 and 128,
is also a potential indicator of the identity of the initial fuel. The first laser
shot in a given location typically yields the greatest relative abundance of
high-m/z peaks, with later laser shots yielding a range of compounds.
Simple two-layer samples are also prepared and likewise analyzed.
Where one layer contains polyurethane deposits, this layer is
easily distinguishable by the TAI and TDA peaks. The gasoline and
polystyrene layers are more difficult to distinguish, in some cases being
* Presenting Author
inseparable using only the markers noted in earlier portions of the study.
It is noted that as successive laser shots are fired in the same location, the
peaks from the topmost layer are often visible in spectra from later laser
shots.
While the single-component samples are separable using this
method, further method development will be required before this method
can become a viable tool for the analysis of more complicated layered
samples, which would be necessary for fire investigation. Towards this
end, some initial analyses of single-component samples using principle
component analysis will be presented.
Soot, Fourier Transform Mass Spectrometry, Laser
A96 Analysis and Detection Limits of Smokeless
Powder Components by Capillary
Electrochromatography – Time-of-Flight
Mass Spectrometry
Inge Corbin, BS*, Miami-Dade Police Department, 9105 Northwest 25th
Street, Room 2149, Doral, FL 33172; Maximilien Blas, PhD, Apartment
211, 10491 Southwest 15 Lane, Miami, FL 33174; and Bruce R. McCord,
PhD, Department of Chemistry, Florida International University,
University Park, Miami, FL 33199
After attending this presentation, attendees will have learned how
the components of commercial smokeless gunpowder can be detected and
identified using capillary electrochromatography – mass spectrometry
(CEC-TOF-MS).
This presentation will impact the forensic science community by
providing the details of a fast and robust analytical method requiring
minimal sample preparation that avoids the sample instability and
degradation that can occur with methods such as gas chromatography. In
this process, unburned particles of smokeless powder such as those that
might be found at a bombing scene are analyzed in an attempt to associate
evidence found at the crime scene to a particular brand or lot of powder.
Using the data obtained from this analysis, investigators may be able to
generate leads or narrow the number of potential sources of the smokeless
powder used in the bombing.
A mixed standard of commonly found smokeless powder additives
was prepared by dissolving 1.0 mg of each standard in 1.0 ml of
methylene chloride. A standard calibration curve was prepared by
measuring an aliquot of each standard, evaporating the methylene
chloride, and reconstituting the sample in a run buffer. Samples were run
by capillary electrochromatography on a hexyl acrylate-based monolith.
All standards were analyzed with an Agilent capillary electrophoresis unit
run in CEC mode, connected to an Agilent time-of-flight mass
spectrometer (TOF-MS). Detection limits were determined for eleven
compounds found in smokeless powders: nitroglycerin, diphenylamine,
dimethylphthalate, diethylphthalate, dibutylphthalate, methyl centralite,
ethyl centralite, 2-nitro- and 4-nitrodiphenylamine, and 2-nitroso- and 4nitrosodiphenylamine.
The use of CEC-TOF-MS represents a promising analytical scheme
for the detection, identification, and quantitation of smokeless powder
components. It is a fast, reproducible technique for the discrimination of
smokeless gunpowder that avoids the problems presented by the
breakdown of thermally labile components of smokeless powder during
GC-MS analysis. Resolution in the CEC mode is high and sample
preparation requirements are minimal.
Smokeless Powder, CEC-TOF, Improvised Explosive Device
168