Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor's Name

Bruce McCord

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Yong Cai

Second Advisor's Committee Title

committee member

Third Advisor's Name

Stewart D'Alessio

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Piero Gardinali

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Joong-Ho Moon

Fifth Advisor's Committee Title

committee member

Keywords

Mass spectrometry, electrospray, improvised explosives, urea nitrate, ammonium nitrate, electrochromatography, smokeless powder, organic gunshot residue, paper microfluidics

Date of Defense

7-1-2016

Abstract

Improvised explosives may be based on smokeless gunpowder, fertilizers, or inorganic oxidizers such as nitrate (NO3-), chlorate (ClO3-), and perchlorate (ClO4-) salts.

Identification is a priority for the military and law enforcement but due to their varying physical properties and complexity, identification can be challenging. Consequently, three methods have been developed to aid in presumptive and confirmatory detection.

Smokeless powder contains plasticizers, stabilizers, dyes, opacifiers, flash suppressants, and other compounds. Identification of these additives can narrow down or identify the brands of smokeless powder used in a device. Fourteen organic smokeless powder components were identified by capillary electrochromatography (CEC) using a hexyl acrylate monolithic stationary phase coupled to UV detection and time-of-flight mass spectrometry (TOF-MS). The CEC-UV method efficiently detects all 14 organic components, while TOF-MS provides sensitivity and selectivity. A mixed smokeless powder component standard was analyzed and the composition of the additive package in commercial smokeless powders determined. Detection limits ranged from 1.0 – 3.2 μg/ml and analysis time was 18 minutes.

Second, a procedure for the detection of urea nitrate (UN) and ammonium nitrate (AN) by infusion electrospray ionization - mass spectrometry (ESI-MS/MS) was developed. Solubility tests were performed to find a solvent for both UN and AN that did not cause UN to dissociate. Two adduct ions were detected for each explosive: for AN, m/z 178 [2AN+NH4]+ and m/z 258 [3AN+NH4]+ ions, and for UN m/z 185 [UN+NO3]− and m/z 248 [UN+HNO3+NO3]−. Specificity of the analysis was examined by mixing the explosives with various salts and interferents. Gas-phase adduct ions were useful in distinguishing between ion pairs and mixed salts.

Finally, a paper microfluidic device (PMD) was developed as a presumptive test using colorimetric reagents for the detection of ions associated with improvised explosives. The device was configured to test for nitrate (NO3-), nitrite (NO2-), chlorate (ClO3-), perchlorate (ClO4-), and urea nitrate (UN). Proof of concept was performed using extracts of soil containing inorganic oxidizers.

The development of these analytical methods allows the detection of smokeless powder components, fertilizers, and oxidizers and expands the suite of analytical methods available for the analysis of improvised explosives.

Identifier

FIDC000771

Available for download on Saturday, July 29, 2017

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