CBP's Powerpoint template for scientific posters

1
Elemental Analysis of Unburned Matches by SEM/EDS
for Forensic Comparison Lance Allen1, David
Neff2, Catherine G. Rushton1 1Forensic Science
Program and 2Chemistry Department, Marshall
University, Huntington, West Virginia
Introduction Matches can be found at a variety
of crime scenes arsons, bombings, clandestine
labs, and so forth. A technique capable of
comparing a match found at a crime scene to a
book of matches found in a suspects possession
would be valuable in associating the suspect to
the crime scene. Andrasko1 used SEM/EDS to
identify burned matches, and Dixon2 used the
fibers in book matches to identify a match
originating from a specific book. SEM/EDS
analysis has also been used to analyze unburned
matches, but not to distinguish one producer from
another.
Preparation Method 2 A razor blade was used to
remove the entire match head from a match. The
match head was ground with a mortar and pestle to
homogenize the sample. This sample was placed
between two glass microtome blades and pressed
flat with a minimum pressure of 50 psi. Samples
from five different matches of the same book were
prepared for two of the match producers.
Results A spectrum was collected from five
matches from each book for all seven match
producer (ex. A1a - Ale). The major elements in
all the matches were the same (silicon, sulfur,
chlorine, and potassium), But spectra were
visibly different based on relative amounts of
major and trace elements.
Figure 5. Dendrogram of the PCA analysis of
samples prepared by method 2.
Figure 2. Dendrogram of the PCA analysis. Shows
the amount of dissimilarity between the samples.
Materials and methods SEM/EDS Parameters A JEOL
5310 LV scanning electron microscope with an
Oxford Pentafet electron dispersive spectrometer
detector with thin beryllium window and ISIS
analysis package was used. The settings used
were 300 mtorr low vacuum, 25 keV acceleration
voltage, 24 mm working distance, and 109 mAmps
condenser lens current (spot size). To ensure the
spectra reflected the real composition of the
matches and not just a few particles in the
match, a magnification of 350x was used. A live
time of 300 seconds was used as the collection
time of each sample. Sample Preparation Matche
s produced by seven different match companies
were analyzed. A list of the companies along
with the samples corresponding to those match
producers can be seen in Table 1. The samples
were prepared by two methods. The second method
produced a more homogenous sample. Preparation
Method 1 A razor blade was used to cut a flake
of the match head from the match. This flake was
then placed between two microtome blades and
pressed flat with a minimum pressure of 50 psi.
Samples from five different matches of the same
book were prepared for all seven match producers.
Although the variation in each of the two sets
(U1 and L1) decreased, the U1 samples still were
not distinct from the L1 samples. This suggests
reanalysis of all samples after being prepared by
method 2 would reduce the variability in each
set.
A large amount of variation can be seen in each
set of match samples, thus not allowing for
differentiation between one producer and another.
Sample preparation method 2 was devised to
improve uniformity of the sample, and reduce
variation. Sample preparation method 2 was used
to prepare more samples for U1 and L1. U1 was
chosen because there was a large variability in
the samples. L1 was chosen because the sample
were similar to U1. It was hoped using
preparation method 2 the U1 samples would have
less variation and be distinct from the L1
samples.
Conclusions The spectra of some matches showed
a visible difference in the amount and types of
elements. These differences ranged from large
variability in the amount of major elements to
the presence or absence of trace elements. Even
with the visible differences in many spectra, the
variation in each match producer set made
comparisons impossible. With the second method
of sample preparation the particle size was
significantly smaller. Thus, the homogeneity was
improved and variations within a set reduced.
While it has been shown that even with the second
preparation method some matches are not distinct
from others, groups of certain match producers
may be distinct from other groups of match
producers. Future work would include
preparation of sample for the other five match
producers using the second preparation method.
These could then be analyzed by the SEM/EDS. The
PCA analysis would then show if groups of match
producers differ from other groups.
Figure 3. Lion Match Company sample (L1b)
prepared by a flake of the match head cut off and
pressed flat.
Literature cited Andrasko, J. Identification of
Burnt Matches by Scanning Electron Microscopy.
J. Forensic Sci. 1978, 23, 637-642.
Dixon, K.C. Positive Identification of Torn
Burned Matches with Emphasis on Crosscut and Torn
Fiber Comparisons. J. Forensic Sci. 1983, 28,
351-359.
Table 1.
Match Producers Samples
Atlas Match A1a - A1e
Atlantis Match AT1a - AT1e
DDBean Sons DDB1a - DDB1e
Diamond Match Company D1a - D1e
Lion Match Corporation L1a - L1j
Ohio Match Company O1a - O1e
Universal Match Corporation U1a - U1j
Figure 4. Lion Match Company sample (Lig)
prepared by entire match head being ground and
pressed flat.
Acknowledgments The authors would like to thank
Dr Michael Norton for providing accessible and
well equipped microscopy facilities, supported in
part by NFS COBRE grant (period 2004-2009). We
also appreciate the help of Dr. Graham Rankin
with the PCA analysis and Dennis Ward with
guidance on sample preparation.
Figure 1. Spectra of A1b, D1d, and L1e. Elements
present are similar, but relative abundance
differs.
The particle size is much smaller in the sample
ground with mortar and pestle (method 2), figure
4, than in the sample prepared by method 1,
figure3. The ratios for the samples prepare by
method 2 were used for more PCA analysis.

• Energy windows were used to calculate the
  integral values of eleven different elements.
  Relative abundance ratios were calculated from
  the integrals of each element in relation to
  potassium. These ratios were compared by
  Principle Component Analysis (PCA).