Detection of microscopic traces of explosive residues on textile fabrics by Raman spectroscopy

Direct or cross-contamination of explosive residues on clothing is of high occurrence when handling explosive materials, leading to physically trapped particles between the fibres. In this work, the detection and identification of trace amounts of organic explosives, inorganic explosives, and oxidizing salts trapped between the fibres of dyed and undyed synthetic and natural textile clothing fabrics were studied using two (desktop and portable) confocal Raman microscopes. The results show that, despite the contribution of the textile fabric in terms of fluorescence and vibrational bands coming from the fibres and dyes, detection and identification of the explosive/oxidizing salt particles trapped on highly interfering surfaces was possible. Limits of detection were estimated in the nanogram/picogram range depending on the explosive and fabric. However, problems involving the burning of either some explosive particles or dark cloth textiles were verified, which can cause a destruction of the sample. Also, the analysis of improvised homemade explosives (potassium nitrate mixed with 10 different fuel substances) was studied to evaluate possible interferences.