Comparison of Swipe Materials for Chemical, Biological, and Explosive Residue Discrimination with Laser-Induced Breakdown Spectroscopy

Report No. ARL-TR-5231
Authors: Jennifer L. Gottfried
Date/Pages: June 2010; 30 pages
Abstract: The performance of two swipe materials (a cotton twill wipe and a sterile non-adherent rayon and polyester pad) for the discrimination of the nerve agent simulant diethyl ethyl phosphonate (DEEP), the anthrax surrogate Bacillus globigii (BG), the military explosive cyclotrimethylenetrinitramine (RDX), and six possible confusants (granulated sugar, diesel particulate [soot], Alternaria alternata [mold], Arizona road dust, plant food fertilizer, and liquid detergent) was evaluated using laser-induced breakdown spectroscopy (LIBS). The LIBS spectra were recorded using a benchtop commercial LIBS system using single laser pulses (200 mJ, 1064 nm) in air. Although the LIBS spectra of both swipe materials contained numerous emission lines also found in the residue samples, as well as contributions from atmospheric oxygen and nitrogen, the residues were easily discriminated on both materials using a chemometric analysis technique called partial least squares discriminant analysis (PLS-DA). The true positive rate for the detection of the DEEP, BG, and RDX residues was >98% for both swipe materials, and the false positive rate was <3%. Our results suggest that the ability of LIBS to discriminate residues using PLS-DA is not strongly dependent on the choice of swipe material
Distribution: Approved for public release
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Last Update / Reviewed: June 1, 2010