Introduction
Smokeless powders (Figure 1) are often used in improvised explosive devices. The formulations for smokeless powders vary between manufacturers and between brands from a given manufacturer; ingredients include energetics, stabilizers, plasticizers and deterrents. Both chemical composition and morphology are important in characterizing smokeless powders.
Chemical analysis of smokeless powders can provide valuable forensic evidence. Observation with the SEM can reveal morphological information to help with identification. Here we show how SEM-EDS analysis can be used to identify inorganic components, and how the AccuTOF-DART mass spectrometer can rapidly identify the organic components and provide a chemical fingerprint that can be used to identify individual powder particles.
Experimental
The AccuTOF™ mass spectrometer was operated in positive-ion mode. Polyethylene glycol (PEG-600) was measured as a reference standard within each data file, but separate from the smokeless powder particle measurements. Individual particles sampled with vacuum tweezers were positioned in the DART gas stream for analysis (Figure 2). Disposable vacuum tweezers were constructed by passing a glass capillary through an Eppendorf pipette tip and inserting the pipette tip into a rubber hose connected to a low-vacuum pump. Data were acquired by using JEOL Mass Center software and mass spectra were processed by TSSPro3 software (Shrader Software Solutions, Detroit, MI).
The DART ion source was operated with a gas heater temperature setting of ≤200°C to avoid damaging or detonating the smokeless powder particles. Individual samples could be analyzed within seconds. As long as the gas heater temperature did not exceed 200°C, the samples were not consumed and could be examined or reanalyzed at a later time.