Test of a stand-off laser-induced breakdown spectroscopy sensor for the detection of explosive residues on solid surfaces

The detection and characterization of energetic materials at distances up to 45 m using stand-off laser induced breakdown spectroscopy (LIBS) has been demonstrated. A field-portable open-path LIB spectrometer working under a coaxial configuration was used. A preliminary Study allowed choosing a single-pulse laser source over a double-pulse system as the most Suitable source for the stand-off analysis of organic samples. The C-2 Swan system, as well as the hydrogen, oxygen and nitrogen emission intensity ratios were the necessary parameters to identify the analyte as all organic explosive, organic non-explosive and non-organic samples. O/N intensity ratios of 2.9 and 2.16 with relative standard deviations of 4.03% and 8.36% were obtained for 2,4-dinitrotoluene and aluminium samples, respectively. A field test with known samples and a blind test were carried out at a distance of 30 in from the sample. Identification of energetic compounds in such conditions resulted in 19 correct results out of 21 samples.