Analysis of Drugs and Explosives using Terahertz and Raman Spectroscopy

• Main Author: Burnett, Andrew David
• Published: University of Leeds 2008
• Subjects: 543
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486390

A broadband terahertz time-domain system (THz-TDS) has been developed in order to analyse several drugs-of-abuse and explosives in the terahertz region of the electromagnetic spectrum. Many of the samples analysed, showed numerous spectral features in the terahertz region, which could be used to conclusively identify them; using terahertz spectroscopy. Terahertz spectra are also compared to Raman spectra in the same frequency region. Comparison of these spectra shows that there are often significant spectral differences, . which provides information about the relative activity of the THz and Raman active modes, which in tum can be useful in the identification of the origin of the normal modes. The normal modes of many of the molecules analysed have also been calculated using . both molecular mechanics (MM) and quantum mechanical (QM) codes, in on;ler to predict the terahertz spectra of the compounds, and to gain a fundamental understanding of the origin of the normal modes. Drugs-of-abuse and explosives found in the real world are often impure or diluted, so . real world 'street samples' and plastics explosives have also been analysed to determine the effect of a mixture of adulterants, on the terahertz spectra of a compound and whether· this will prohibit the identification. This data has also been combined with chemometric based techniques such as principal component analysis (PCA) in order to start moving towards a system for the automatic identification of a compound using terahertz spectroscopy. Finally, an analysis of a drug sample through a range of common packaging materials, using THz-TDS, has also been performed in order to determine if drugs-of-abuse can be detected through packaging.