Examination of Firearms Review: 2007 to 2010 - Interpol

as well as to low concentration organic components of mixtures that contain both
inorganic and organic moieties.
A further forensic application was reported by Szafarska and coauthors in which
ATR-FTIR was used to analyze paint the authors applied to polyester and fabric
matrices. [155] Applying a series of normalization and subtraction steps to the
collected IR data, the authors determined that this approach would be an
acceptable alternative to physically removing paint from a substrate for analysis.
In a study employing the use of synchrotron radiation, eighteen titanium dioxide
(TiO2) pigments in rutile form were examined along with fragments of seven
types of white automotive paints. Results indicated detection of elements such
as niobium, which is indicative of the sulfuric acid preparation method of the TiO2
pigment. Aluminum and silicon could not be effectively excited and therefore
detected with the described high-energy synchrotron radiation X-ray fluorescence
(XRF) analytical scheme. They were, however, observed by SEM/EDS. For the
white automotive paints, detection of trace amounts of heavy elements was used
to discriminate samples that were indistinguishable by color measurement of the
white basecoat.[156]
Uses of Raman spectroscopy with respect to modern forensic applications was
reported by Otieno-Alego.[157] Also, the combined techniques of µ-Raman and
µ-XRF were applied to multilayer paint chips using a single spectrometer.[158]
The use of confocal Raman microscopy to monitor the distribution of melamine in
a polyester-melamine coil coating as well as for depth profiling of these coatings
was reported on by Zhang and coauthors.[159;160] This same group of
researchers also reported on the use of step-scan photoacoustic FTIR for the
latter application.[161]
Lastly, for consideration in potential sourcing of raw materials, researchers in
Pakistan described synthesis of ultramarine blue pigment from kaolin mined in
the Swat valley region of that country. Analysis of the end product was
accomplished using UV-vis, FTIR, and X-ray diffraction (XRD) analysis.[162]
11. Elemental Analysis
Applications in the area of elemental analysis of paint samples included
spectrometric techniques such as particle-induced X-ray emission (PIXE), XRF,
SEM/EDS, XRD, and laser induced breakdown spectroscopy (LIBS). In one
article, PIXE, XRD, and backscatter capabilities associated most commonly with
SEM/EDS applications were used in tandem to simultaneously acquire data on
pigments and binder matrices in paint layers.[163] With this research, the
authors were attempting to resolve the problem of estimating the pigment/binder
ratio present in paint, which is often complicated in SEM/EDS by the presence of
carbon and oxygen in both entities. Their resolution involved a three-step
process: determine the pigment identities and concentrations via micro-XRD and
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