Volume 50, Issue 4 (July 2005)

    Forensic Applications of Infrared Chemical Imaging: Multi-Layered Paint Chips

    (Received 30 November 2004; accepted 12 March 2005)

    Published Online: May

    CODEN: JFSOAD

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    Abstract

    This paper examines the potential of infrared chemical (hyperspectral) imaging as a technique for the forensic analysis of automotive paint chips in particular, and multicomponent (e.g., layered) samples in general. Improved sample preparation procedures for the infrared analysis of paint chips are detailed, with the recommendation that where mounting resins are chemically incompatible with the sample, it is better to mount and section the sample in a soft wax from which the sections can be removed and pressed into a KBr disk for transmission analysis. Infrared chemical images of multilayered paint chips have been successfully obtained, with the chief advantage over conventional infrared analysis being that thousands of infrared spectra are collected in a few minutes across the whole sample, at a spatial resolution of around 5 µm. As with conventional infrared spectroscopy, chemical species can be identified from their spectra, but the wealth of information available can be also extracted in a number of different ways that make multicomponent spectral (and hence chemical) comparisons between two samples easy to visualize and understand. In one approach, the infrared chemical images of two paint chips being compared side-by-side can be viewed as a “movie,” in which each frame is an intensity map of the two samples at a given wavenumber (frequency) value. In another approach, the spectra (pixels) in the image files are classified into chemically similar groups, resulting in a “cluster” image that makes it possible to simultaneously compare all of the layers in two paint chips. These methods are applicable to other multicomponent samples, and also to other chemical imaging techniques


    Author Information:

    Reedy, BJ
    Centre for Forensic Science, University of Technology, Sydney, NSW

    Lennard, C
    Forensic Services, Australian Federal Police, Canberra, ACT

    Roux, C
    Centre for Forensic Science, University of Technology, Sydney, NSW

    Flynn, K
    Centre for Forensic Science, University of Technology, Sydney, NSW

    O'Leary, R
    Centre for Forensic Science, University of Technology, Sydney, NSW


    Stock #: JFS2004502

    ISSN: 0022-1198

    DOI: 10.1520/JFS2004502

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    Author
    Title Forensic Applications of Infrared Chemical Imaging: Multi-Layered Paint Chips
    Symposium , 0000-00-00
    Committee E30