Bulk Explosive Investigation: Chemical Analyses of Fuel-Oxidizer Explosive Mixtures Commonly Used in Criminal Actions

Explosives are widely utilized across various legal activities, including military operations, law enforcement, mining, and construction. Unfortunately, they are also involved in illegal acts such as terrorism, robbery and vandalism. The analysis of explosives and post-explosion residues plays a crucial role in forensic chemistry, aiding investigations into explosive-related crimes. This analysis aims to identify the explosive involved in criminal action. It aids in determining the cause of the explosion, assessing potential clandestine facilities, establishing authorship, and identifying trends for criminal purposes. One type of explosive widely used, not only in Brazil but also worldwide, is fuel-oxidizer mixtures, such as black powder, explosive emulsions, and mixtures based on chlorate and/or perchlorate salts. These explosives are composed of substances with significantly different chemical natures. As a result, their complete identification generally requires the application of various analytical techniques. For this purpose, in addition to direct analyses of the mixtures, they often involve procedures for separating their components and analyzing each of them using appropriate analytical techniques. This separation is typically achieved through simple solvent extractions, often using water and organic solvents. The aqueous and organic extracts, along with any insoluble fractions, are then analyzed, as outlined in this study. This work presents a simple workflow for sample preparation and analysis of bulk fuel-oxidizer explosive mixtures, which are frequently encountered in criminal activities globally, including in Brazil. The workflow employs various analytical techniques, including Gas Chromatography-Mass Spectrometry (GC-MS), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Ion Chromatography (IC), Laser-Induced Breakdown Spectroscopy (LIBS), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM/EDS), and X-ray Diffraction (XRD). This procedure provides a practical guide for forensic laboratories, enhancing their ability to analyze commonly encountered explosive samples with precision and reliability.