DEVELOPMENT OF CHROMATOGRAPHY AND MASS SPECTROMETRY METHODS FOR EXPLOSIVES ANALYSIS A dissertation presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy John A. Mathis March 2004 This dissertation entitled DEVELOPMENT OF CHROMATOGRAPHY AND MASS SPECTROMETRY METHODS FOR EXPLOSIVES ANALYSIS BY JOHN A. MATHIS has been approved for the Department of Chemistry and Biochemistry and the College of Arts and Sciences by Bruce R. McCord Associate Professor of Chemistry Leslie A. Flemming Dean, College of Arts and Sciences MATHIS, JOHN A. Ph.D. March 2004. Analytical Chemistry. Development of Chromatography and Mass Spectrometry Methods for Explosives Analysis. (199 pp.) Director of Dissertation: Bruce R. McCord Novel methods for the analysis of explosives and related compounds were developed in this research. A gradient reversed-phase high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESIMS) method was used in the positive ion mode for the analysis of the organic additives in smokeless powders. Gas chromatography (GC) methods with electron capture detection (ECD) and negative chemical ionization mass spectrometry (MS) were developed for the separation and detection of common high explosives. Negative ion ESIMS was used for the detection of high explosive adducts. An isocratic HPLC-ESIMS method was evaluated for the simultaneous analysis of high explosives using the negative ion mode. Smokeless powders are used as propellants for small arms ammunition but have also been used as the energetic material in improvised explosive devices such as pipe bombs. Smokeless powders contain organic additives that facilitate production procedures, prevent degradation, and enhance energetic efficiency. The gradient HPLC- ESIMS method was used to determine compositional differences among smokeless powders by simultaneously quantifying the organic additives. The relative ESIMS intensities of the powder constituents were also evaluated as a function of the solution parameters associated with the gradient elution method. The newly developed HPLC- ESIMS method was used for the analysis of different unburned smokeless powders and pipe bomb samples containing these powders. Two GC methods were developed for the separation and detection of high explosives using selective detectors. The application of GC/ECD and GC with negative chemical ionization mass spectrometry allowed for the quantitation of nitrated explosives. Detection limits in the ng/mL range were determined using the GC/ECD method. The GC-MS instrument was equipped with a large bore capillary column that was split to a fused silica transfer line to minimize the thermal degradation of the energetic compounds. The negative ion ESIMS detection of adducts of high explosives with chloride, formate, acetate, and nitrate was accomplished. The relative stability of the adduct species was determined to illustrate the gas-phase interaction of neutral explosives with the anions. An isocratic HPLC-ESIMS method was developed for the separation and detection of selected high explosives as anionic adducts to provide structural information that can be used for compound identity. Approved Bruce R. McCord Associate Professor of Chemistry Acknowledgments I would like to express my appreciation to my parents, family, and friends. Without their moral support and encouragement, this achievement would not have been possible. My gratitude is extended to my research advisor, Bruce McCord for support, guidance, and above all his patience. All my group members deserve sincere thanks for their cooperation and friendliness. I wish to acknowledge Mark Miller of the FBI Forensic Science and Counterterrorism Research Unit for his assistance and giving me the opportunity to participate in the Visiting Scientist Program during the summer of 2001. I also extend my admiration to the staff and faculty in the Department of Chemistry and Biochemistry. The members of the department staff deserve special recognition for their continued support. I thank the members of my committee Drs. Howard Dewald, Peter Harrington, Gary Pfeiffer, and Guy Riefler. Their assistance and encouragement were greatly appreciated. 6 Table of Contents Abstract ................................................................................................................................3 Acknowledgments................................................................................................................5 Table of Contents.................................................................................................................6 List of Figures ....................................................................................................................11 List of Tables .....................................................................................................................15 List of Abbreviations .........................................................................................................17 I. Chapter 1. Introduction...................................................................................................21 A. Overview of Explosives ...........................................................................................21 1. Smokeless Powders..............................................................................................23 2. High Explosives....................................................................................................27 B. Forensic Application of Explosives Analysis...........................................................28 C. Aims of This Research.............................................................................................31 II. Chapter 2. Instrumental Analysis of Explosives: Theory and Applications ................33 A. Introduction..............................................................................................................33 B. Sample preparation...................................................................................................34 C. Gas Chromatography................................................................................................35 1. Electron Capture Detection..................................................................................37 2. Mass Spectrometry...............................................................................................39 a. Negative Chemical Ionization Mass Spectrometry..........................................42 i. Resonance Electron Capture.........................................................................43 D. High-Performance Liquid Chromatography ............................................................43 7 1. HPLC-MS.............................................................................................................44 2. Electrospray Ionization Mass Spectrometry.........................................................46 a. Positive Ion ESIMS..........................................................................................50 b. Negative Ion ESIMS........................................................................................53 III. Chapter 3. Experimental Procedures............................................................................57 A. Introduction............................................................................................................57 B. Smokeless Powder Analysis...................................................................................57 1. Chemicals ...........................................................................................................58 2. Instrumentation...................................................................................................58 a. Positive Ion Electrospray Ionization Mass Spectrometry...............................58 b. Gradient Reversed-Phase HPLC-ESIMS .......................................................59 3. Sample Preparation.............................................................................................60 a. Unburned Powders..........................................................................................60 b. Pipe Bomb Samples........................................................................................61 C. Survey of Environmental Background Interferences Affecting Explosive Residue Analysis ................................................................................................................62 1. Chemicals ...........................................................................................................62 2. Instrumentation...................................................................................................63 a. Gas Chromatography/Electron Capture Detection.........................................63 b. Gas Chromatography-Mass Spectrometry......................................................63 3. Sample Preparation.............................................................................................65 a. Cotton Swab Samples.....................................................................................65 8 D. Detection of Explosives and Related Compounds Using ESIMS in the Negative Ion Mode...............................................................................................................66 1. Chemicals .........................................................................................................66