Identification of Postblast Residues by DART-High Resolution Mass Spectrometry Combined with Multivariate Statistical Analysis of the Kendrick Mass Defect

Abstract

The coupling of an atmospheric pressure ionization source (Direct Analysis in Real Time, DART) and a high-resolution mass spectrometer (Orbitrap) has enabled the rapid and efficient analysis of a variety of energetic formulations. This approach was used to generate mass spectra for 83 plastic explosives and polymer samples in less than 2 min per sample. To manually interpret and identify all of the constituent polymers and other interesting features in the acquired mass spectra is a tedious and time-consuming challenge. Instead, a methodology based on the systematic calculation of Kendrick mass defects (KMDs) was developed and implemented. Its application allowed the identification of the polymeric support present in each energetic formulation. The presence of polyisobutylene in PG2 has been confirmed thanks to this approach, and a mixture of polyisobutylene, polybutadiene, and polystyrene has been confirmed in the Semtex 10 formulation. The developed methodology has also permitted the observation of changes that occur to the polymeric composition of these formulations after a blast. It appears that the most adequate way to describe post blast polymer samples is that they are less oxygenated and, above all, more unsaturated than the original starting material. These conclusions were deduced with the aid of principal component analysis, which served to establish the main factors that differentiate the samples.