Examination of Firearms Review: 2007 to 2010 - Interpol

PIXE, respectively, determine the total elemental composition of the paint matrix
to include the pigment and binder via backscatter imaging, and then subtract the
carbon and oxygen content of the pigments from the whole in order to calculate
the contribution from the binder alone. The authors cite that the advantage of
this approach is the ability to analyze the same area of detail within one
experimental set-up scheme.
EDXRF was also used in conjunction with digital imaging and chemometrics to
determine the weatherproofing classification level and durability of 17 varnishes
and 10 paints subjected to accelerated weathering tests as part of a quality
assurance test plan.[164]
A portable XRD/XRF instrument design was discussed by Pifferi et al. for
nondestructive analysis. Its features include the ability to acquire data using both
techniques simultaneously for qualitative and quantitative work in a nondestructive
mode.[165] Nakai and coauthors have published results of
experiments conducted on the capability of SEM/EDS when coupled with a
transition edge sensor (TES) microcalorimeter to analyze white automotive
paint.[166] Samples were prepared as would be typical for SEM analysis in that
chips were embedded in a resin, polished to reveal the layer structure at the
surface of the mold, and coated with carbon. Acceleration voltages were the
same for both the TES and traditional solid state detector (SSD) at 15 KeV.
Beam currents were also comparable. Data acquisition time for the TES was
300 live seconds as compared to 100 seconds for the SSD. The authors report
that the TES detector as used in this work was able to resolve titanium
interferences on the barium signal in the white primer layer, which also contained
a detectable signal for sulfur. It was reported that this detection system also
provided a better estimate of the ratio of lead to tin in the electrocoat layer.
Additional research regarding elemental analysis of paint layers utilized direct
sampling of acrylics for analysis by graphite furnace atomic absorption
spectrometry (GFAAS), as well as the detection of bromine in industrial paints by
inductively coupled plasma–mass spectrometry (ICP-MS), where it can exist as a
flame retardant.[167;168]
Lastly, the use of LIBS to monitor application of paints and coatings to metal
substrates has been reported on by Kim et al.[169] In this report, a compact
LIBS system was described for use in identifying eleven different yellow OEM
paints that were developed to be undifferentiated by the human eye. In this
manner, different applications would all appear to be of a uniform color. In this
example, the color was the yellow recognized as belonging to the Caterpillar, Inc.
heavy-machinery company. The ability to differentiate between urethane, epoxy,
and alkyd formulations provided resolution in two cases of paint failure, which
were able to be readily diagnosed at field sites using this technology.
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