Fast Identification of Components Commonly Used in Homemade Explosives by Spectroscopic and Chemometric Methods

Homemade explosives (HMEs) have become a global pandemic. This forensic research focuses on developing identification methods that can provide quick, cost effective, non-destructive analysis using portable instrumentation. These capabilities would be invaluable to first responders, military, and security officials to establish an evidentiary link between a suspect and a reference in cases of HMEs, IEDs, arson and environmental contamination. Modern methods for quick identification of the fuels and oxidant sources used in manufacturing HMEs, include Fourier Transform Infrared (FT-IR) and Raman spectroscopy. Visual confirmation alone, however, is not strong enough to discriminate chemicals with nearly identical spectra, which occurs when analyzing sample within the same class. This research focuses on coupling the chemical identification abilities of spectroscopic techniques with the strength of chemometrics such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) for qualitative discrimination and classification of common fuel sources and inorganic salts used as oxidants. Additional quantification research was performed to determine limits of detection for adulterated fuels and oxidant mixtures using partial least squares regression (PLS-R). We have demonstrated that spectroscopic techniques combined with chemometrics can discern highly correlated spectra that are not possible to discriminate by visualizing the spectroscopic information alone