FORENSIC SCIENCES: CRIMINALISTICS - Bio Medical Forensics

A153 The Effects of Carbon Disulfide on the
Elution and Solvation Phases of Light and
Medium Range Ignitable Liquids
Jessica L. Drewicz*, U.S. Air Force Academy, PO Box 1675, USAF
Academy, CO 80841; Candice Bridge, PhD*, U.S. Army Criminal
Investigation Laboratory, 4930 North 31st Street, PO Box 162367, Forest
Park, GA 30297; Carol M. Clemmons, MPA*, U.S. Army Criminal
Investigation Laboratory, 930 North 31st Street, Forest Park, GA 30297;
and Michael J. Salyards, PhD, 45 High Street, Sharpsburg, GA 30277
After attending this presentation, attendees will learn that activated
charcoal strip elution by CS 2 occurs immediately once the CS 2 comes in
contact with the activated charcoal strip. Attendee will also learn that
light and medium range ignitable liquids have a lifespan of one month
when dissolved in the solvent, CS 2 .
This presentation will impact the forensic science community by
demonstrating that elution by CS 2 occurs immediately upon contact with
the charcoal strip. Also, after attending this presentation, attendees will
know that neat ignitable liquids dissolved in CS 2 are stable compounds
for one month. Therefore, fire debris analysts will be able to improve
their practice by keeping their standards for up to one month under proper
conditions instead of remaking a new standard for every case. This will
save supplies, time, and laboraotry finances.
The objective of this research was to understand the effects of CS 2
on the elution and solvation phases of ignitable liquids over time. All data
was collected and analyzed by GC/MS. Statistics were used to determine
differences and/or similarities among the samples over time. An internal
standard, tetrachloroethylene at a concentration of 100 ppm, was used to
compare samples. 1 This particular internal standard was used because:
(1) its retention time falls within the middle of the ranges for all the
ignitable liquid categories tested; and, (2) it allowed for normalization of
the data.
It has been shown that CS 2 is the universal solvent for activated
charcoal strip elution. 2 The elution study conducted explored how well
CS 2 completely extracts ignitable liquid residues (ILRs) from an
activated charcoal strip. This study was comprised of a series of substudies:
a vortex study, an elution period study, and a washing study. The
first sub-study explored whether vortexing for one minute was necessary
for lab procedures by varying the vortex time from no vortex to a one
minute vortex. The second sub-study explored if a 15 minute waiting
period was necessary for complete elution to occur by varying the waiting
period after a one minute vortex from no waiting period to a waiting
period of one hour. The third sub-study determined if CS 2 immediately
extracted any ignitable liquid residue (ILR) from an activated charcoal
strip and whether immediate extraction occurred for all ILRs or only
certain types. This washing study was completed by rinsing three
charcoal strips with varying amounts of CS 2 with neither a vortex period
nor a waiting period.
The second part of the time study, the solvation study, explored the
evaporation pattern of ignitable liquids in CS 2 solution over a one month
period. The ignitable liquids tested included light petroleum distillates
(LPD), gasoline (GAS), medium petroleum distillates (MPD), and
medium range isoparaffins (ISOP). Two milliliters of a 1% ILR solution
v/v in CS 2 were prepared for each sample. The time intervals tested were
immediate sampling of IL/ CS 2 solutions after preparation, and sampling
of each of the solutions after one hour, one day, one week, two weeks,
three weeks, and one month. Samples were stored in a -10°C freezer
between removals for analysis.
Three different statistical tests were used to determine differences or
similarities among the samples in each study over time. These tests
included a Tukey Honestly Significant Difference (HSD) test, Principle
Component Analysis (PCA) with cluster analysis, and Pearson
Correlation with a Student’s t-test and ROC plots. The Tukey test
demonstrated that minimal differences occurred among samples in all
* Presenting Author
studies. Using PCA, it was seen that minimal to no difference existed
among samples in all studies as well. This was followed by cluster
analysis which demonstrated the same results with the observance of
extremely low Euclidean distances in all studies. The Pearson correlation
coefficients for all studies ranged from 0.7000 to 0.9999. These
correlations were followed by the Student’s t-test, where the averages
from two different sample means-those within the same time interval
(STI) and those between different time intervals (DTI)-were compared.
The experimental t-values between the STI and DTI were extremely low
across all studies.
Based on research thus far, a waiting period is not necessary for
complete elution to occur; CS 2 immediately extracts residue from the
activated charcoal strip. From the solvation study, standard light and
medium range ignitable liquids dissolved in CS 2 can be stored under
normal conditions in a freezer for up to one month without evaporating or
chromatographic skewing.
References:
1. Lentini JJ. Scientific Protocols for Fire Investigation. Boca Raton:
CRC Press, 2006. 150.
2. Dolan JA, Newman R, Stauffer E. Fire Debris Analysis.
Burlington: Elsevier, Inc, 2008. 399-439.
Carbon Disulfide, Elution, Solvation
A154 Performance Testing and Comparison of
Different Fire Debris Bags
Jeanet N. Hendrikse, MSc*, Netherlands Forensic Institute of the
Netherlands Ministry of Justice, PO Box 24044, The Hague, 2490 AA,
NETHERLANDS
After attending this presentation, attendees will know that a good
alternative polymer bag has been found for the collection of fire debris
samples for ignitable liquid analysis, as a replacement of the Kapak
FireDebrisPAK bag that was taken of the market several years ago.
This presentation will impact the forensic science community by
teaching more about the performance (advantages/disadvantages) of
different types of commercially available fire debris bags.
World-wide, different containers are used to collect and store fire
debris evidence for ignitable liquid analysis. A questionnaire circulated
among the forensic institutes in Europe revealed the use of metal cans,
glass jars, and a wide variety of polymer bags. Previously published tests
results showed that the polymer bag produced by Kapak was the best
choice of all but because this bag was taken from the market several years
ago, previous Kapak FireDebrisPAK users are searching for an
alternative bag ever since.
A good alternative bag seems to have been found due to the release
of a new fire debris bag in 2010. This bag has a similar polymer
composition as the Kapak FireDebrisPAK bag. The performance of
this new bag material has been studied and compared to the performance
of the most commonly used polymer bags in Europe today. These are
nylon-11 bags and two multilayer bags (four layers or more) with
different layer composition, one of these multilayer bags is aluminium
coated. The bags were tested on the presence or absence of background
interference and on the retention ability of ignitable liquids. The latter
involved a study of potential leak rate, of potential cross-contamination,
of potential adsorption ability, and of the recovery of the ignitable liquids
spiked. For the initial tests, gasoline was used and the performance of the
bags was monitored over a period of seven weeks. The test results were
obtained after dynamic headspace sampling on Tenax, followed by TD-
GCMS analysis. The results demonstrate that the newly released bags
perform best in all tests: they exhibit lowest background, do not leak,
show no cross-contamination, and do almost not adsorb the gasoline
spiked. A full gasoline pattern is recovered from the spiked bag, even
after seven weeks and even when the spiked concentration is high. The
nylon bags also do not release background compounds, but started
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