ToF-SIMS and other mass spectrometric imaging techniques allow for the simultaneous and direct characterisation of all the components in explosives like C4, including the explosive active components, additives, binders and contaminants. ToF-SIMS provides rapid identification of both organic and inorganic constituents and their characteristic isotopic abundances with excellent sensitivity. Most importantly, it is well-suited for direct analysis of small explosive particulates collected directly in the field and sent back to the lab.
According to Christine Mahoney from the National Institute of Standards and Technology (NIST) in Maryland, USA, the technique is sensitive enough to detect bits of explosive material scattered in a fingerprint, making it a potentially powerful forensic tool. Using ToF-SIMS in combination with other techniques that visualise the crystal structure of the samples, Mahoney identified and differentiated between commercial C4, military C4 from the United States, and C4 from the UK.
The ultimate goal of the project, though, is not to develop ToF-SIMS as a portable technology to use in the field. Rather, Mahoney is creating a library of precise, standardised reference samples that could be used to test, calibrate and optimise new technologies for detecting explosives in the field.
“We can really nail down the differences in the chemistries between different kinds of explosives,” said Mahoney. The work is being presented at AVS 57th International Symposium & Exhibition in a talk titled “Characterization of Composition C4 Explosives using Time-of-Flight Secondary Ion Mass Sepctrometry (ToF-SIMS) and X-Ray Photoelectron Spectroscopy (XPS)”. The abstract can be viewed at http://www.avssymposium.org/Open/SearchPapers.aspx?PaperNumber=AS2-ThM-9