Investigating the combined capability of confocal Raman microscopy and direct analysis in real time-mass spectrometry (DART-MS) for the analysis of intact explosives

Abstract

The identification of organic and inorganic components used to produce homemade explosives (HMEs) remains a challenge for forensic analysts due to their diverse physicochemical properties that require different instrumentation. This study aims to explore the combined use of direct analysis in real time-mass spectrometry (DART-MS) and Raman microscopy to provide a rapid and reliable analysis of a variety of intact explosives with minimal sample preparation, including 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), seven inorganic oxidizing salts, and five smokeless powder constituents. While both techniques were well-suited for the analysis of TNT and PETN, DART-MS had the advantage of being more sensitive compared to Raman spectroscopy for the identification of the organic components contained in smokeless powder. Even though the identification of ammonium-based salts using DART-MS could be achieved, the analysis of low-volatility compounds, such as the inorganic oxidizing salts, was more straightforward with Raman microscopy and did not require sample preparation. This study demonstrates the benefits and limitations of combining Raman microscopy and DART-MS for the analysis of intact explosives and precursors. Using this combined approach enabled the rapid identification of various organic and inorganic explosives and precursors with minimal sample preparation.