Research previously done at Oak Ridge
National Laboratory focused on the development of
new analytical methods for the analysis of organic explosives. The
extremely low vapor pressures of many organic explosives complicate
the collection and
analysis of these materials from the vapor phase. An analytical method
developed in our laboratory facilitates the analysis of vapor phase
by means of sample introduction through thermal desorption. The method
uses the injection port of a gas chromatograph as a thermal desorption
unit. A vapor sampling tube is inserted directly into the injection
port for desorption and
the explosives are focused on the head of the analytical column at
room temperature. Subsequent analysis by GC-MS with negative ion
ionization results in a well-
resolved chromatograph (shown below right). This method has also been
used in collaboration with scientists at the University
of Montana to assist in the detection of explosives in honeybee hives
as a way of detecting landmines.
In addition to methods development,
we have reported method limits of detection for GC-MS analysis
of organic explosives in electron impact (EI), positive ion
chemical ionization (PICI)and negative ion chemical ionization
(NICI) modes. Although the limits of detection are higher for ionization
this softer mode of ionization
allows the differentiation between nitroesters based on fragmentation
patterns. This differentiation is generally not achieved in EI
or NICI ionization modes.
Our current interests continue to be in the area of new analytical
methods development and the identification of matrix effects on the
of explosives residue from post blast debris. The examination of
impurity components in explosives samples as a method of identifying
possible sources of a sample is also a research focus. In addition
to GC-MS, LC-MS and LC-MS/MS methods are utilized to analyze inorganic
and organic explosives for forensic applications.
For more information
on this research, please consult the following
Sigman, M. E.; Ma, C.-Y. "In-Injection Port Thermal Desorption For the Analysis of Trace Explosives Evidence," Anal.
Chem., 1999, 71, 4119.
Sigman, M. E.; Ma, C.-Y. "Operational Guideline: Teflon Dry Surface Wipe Collection and In-Injection Port Thermal Desorption Analysis of Trace Levels of Organic Explosives," ORNL/TM-1999/315.
Sigman, M. E.; Ma, C.-Y. "Detection limits for GC/MS Analysis of Organic Explosives," J.
Forensic Sci. 2001, 46, 6-11.
Sigman, M. E.; Ma, C. Y.; Ilgner, R. H. "Performance Evaluation of an In-Injection Port Thermal Desorption/Gas Chromatographic/Negative Ion Chemical Ionization Mass Spectrometric Method for Trace Explosive Vapor Analysis," Anal.
Chem. 2001, 73(4), 792.
Gapeev, A., Sigman, M. and Yinon, J. “Liquid Chromatography/Mass
Spectrometric Analysis of Explosives: RDX Adduct Ions,” Rapid
Comm Mass Spectrom., 2003, 17, 943-948.