title: Selective sampling and laser-induced breakdown spectroscopy (LIBS) analysis of organic explosive residues on polymer surfaces.
abstract: A method for selective sampling and analysis of explosive residues on solid surfaces based on laser-induced breakdown spectroscopy (LIBS) is presented. Organic explosives are difficult to analyze when present as residues on organic materials. Under these circumstances LIBS suffers from  the limitations imposed by the limited spectroscopic information available for the analysis. Since ablation and subsequent plasma formation are sensitive to the beam focal conditions and the pulse energy deposited on the surface, the choice of an appropriate set of experimental conditions  increases the surface sensitivity of the analysis and hence a selective inspection of the residue in the absence of spectral contribution from the organic support analyzed. 2-Mononitrotoluene (MNT), 2,6-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT) are used as model residues, whereas  nylon and Teflon are used as illustrative surfaces of daily life objects. The results demonstrate that selective sampling is successfully achieved in all cases when the plasma formation threshold of the residues and the object is substantially different. Plasma imaging demonstrates that the  species distribution along the plume changes with beam focal conditions, which is exploited here to further increase the selectivity of the approach.
authors.affiliation: Department of Analytical Chemistry, University of Málaga, E-29071 Málaga, Spain.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Fernández-Bravo
authors.forename: Patricia
authors.initials: P
authors.lastname: Lucena
authors.forename: José Javier
authors.initials: JJ
authors.lastname: Laserna