Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Chemistry

Department

Chemistry

First Advisor

James L. Smith

Abstract

In today’s society, it has become necessary to not only identify a terrorist participating in an attack, but determine what explosive was used and what the locations of the terrorist were prior to the attack. Such knowledge helps law officials determine if there are other credible threats, and link terrorists to each other and thereby identify potential terrorist cells.

Much of forensic science depends on Locard’s Exchange Principle, which states that when two objects contact each other there is a transfer of material between them. It is therefore expected that when terrorists handle explosives, explosive materials will be transferred first to their hands, and then to other surfaces their hands touch. If the amount of explosive in these prints can be quantified, it may be possible to determine where a terrorist has been, and the order of events leading up to an attack.

This study therefore aimed to quantify the amount of energetic salt residue found in consecutive prints of ammonium nitrate and potassium chlorate on three different surfaces (filter paper, polypropylene, and polyurethane). By collecting and extracting consecutive prints from surfaces, it was possible to quantify the amount of trace explosive material in each print using ion chromatography (IC). The trends in material deposited in consecutive prints were then compared to each other to determine the reproducibility of prints between people and on different surfaces.

Results indicate both materials typically leave first prints in the amount of several hundred micrograms. Further, while most trials produced decreasing curves, occasional higher amounts were found in later prints. This indicates that occasionally aggregates of particles form and are deposited during printing.

While reproducibility indicates that the roughness of the surface did not significantly affect the rate at which material was deposited, the sorption properties of the energetic salts and the surfaces may play a role in the amount of material deposited. This was determined because the highest amounts of the hygroscopic ammonium nitrate were found on the liquid absorbent filter paper surfaces, while the highest amounts of the ionic powder potassium chlorate were found on the electrostatically chargeable polypropylene surfaces.

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