Comparative analysis of smokeless gunpowders by Fourier transform infrared and Raman spectroscopy

Fourier Transform Infrared (FTIR) and Raman spectroscopic techniques were used to perform a comparative study of the spectral profiles of single-base, double-base and triple-base smokeless gunpowders. Preliminary results based on visual comparison of the spectra point out that spectra obtained by both vibrational techniques were useful for a rapid identification of gunpowders containing dinitrotoluene as one of the major components and triple-base gunpowders. Additionally, the Raman spectra of gunpowders with diphenylamine in its primary composition showed a characteristic band, assigned to 2-nitro-diphenylamine, allowing the identification of this type of gunpowders. Further differentiation among the spectra of different types of smokeless gunpowders obtained by both vibrational spectroscopic techniques was investigated by discriminant analysis. Different analyses were applied to spectral data considering the different composition of gunpowders. The presence or absence of different compounds (such as dinitrotoluene, diphenylamine or dibutyl phthalate) or the type of gunpowder according to the number of active components (single-base or double-base gunpowder) has been taken into account. FTIR and Raman spectroscopy in combination with discriminant analyses were successful tools of forensic interest for the classification of gunpowders and the possible identification of unknown samples of gunpowders.