INVESTIGATION OF VARIOUS DOPANT MATERIALS FOR INCREASED SPECIFICITY OF EXPLSOIVE IN ION MOBILITY SPECTROMETRY (IMS)

Tim M. Brewer, Mike Verkouteren and Greg Gillen

Surface and Microanalysis Science Division,

National Institute of Standards and Technology

Gaithersburg, MD 20899-8371, USA

Ion Mobility Spectrometry (IMS) is an extensively employed analytical technique capable of detecting and identifying trace amounts of explosives. For this purpose, the specificity of IMS can be enhanced with the addition of “dopant” compounds to the carrier gas, usually materials with some substance with high electron affinities (e.g. halogens). The dopant preferentially ionizes the desired explosive, while blocking potential interferences. The IMS spectrum of these materials is characterized through the formation of abundant cluster ions (M + Halogen)^-. In the current work, various species with high electron affinities (e.g. Cl) are added to the explosive compounds in solution and deposited onto various sample swipes prior to desorption to promote the formation of cluster ions in the ionization source volume. A series of halogens as well as nitrate- and nitrite-containing compounds have been identified and are being used to explore possible routes and mechanisms for ion yield enhancements of explosives. Limits of detection are presented from selectively doping swipes with high electron affinity dopants and compared to those from commercially available dopants. It is envisioned that compounds with high electron affinities can be added to swipes following sample collection of explosives in order to increase ion yields and therefore sensitivity and specificity.

Your name: Tim M. Brewer

Mentor’s name: Dr. Greg Gillen

Division: Surface and Microanalysis (837)

Room and Building address: B203 Bldg. 217

Mail Stop: 8371

Telephone #: (301) 975-3926

FAX #: (301) 216-1134

Email: timothy.brewer@nist.gov

Sigma Xi member: No

Category: Chemsitry