Examination of Firearms Review: 2007 to 2010 - Interpol

application of the technique to works of art.[193-197] Further, the Journal of
Raman Spectroscopy has a special issue entitled “Raman Spectrometry in Art
and Archaeology III,” Volume 89, number 4, December 2007, pertinent articles
from which have been included in this review.
One focus of recent Raman studies was surface enhanced Raman spectroscopy
(SERS). Chen and coauthors reviewed the technique to include the principle,
instrumentation, and its use in art and archaeology.[198] Wustholz et al. studied
the utility of SERS to analyze dyes. They highlight recent work and future
challenges.[199] In their work, Whitney and coworkers applied the technique to
red dyes and their mixtures, and Brosseau et al. reported the first SERS study of
multiple artists’ materials, including organic pigments (both synthetic and
natural).[200-202] Van Elslande and coauthors also applied the technique to
organic pigments.[203] Lau et al. applied the technique in a different way by
analyzing natural resins.[204] As opposed to normal Raman, SERS was able to
overcome interference from fluorescence in extremely small natural resin
samples.
Multivariate statistics was also found to be useful for Raman studies. In two
separate publications, Nevin et al. utilized Raman and PCA to analyze
proteinaceous binding media, a material which is typically problematic for Raman
analysis.[205;206]
Organic pigments were the focus of multiple Raman publications during this
review period. Lutzenburger and Stege noted that there are approximately 100
synthetic organic pigments used in artists’ paints today.[207] A comprehensive
and efficient sampling and analysis strategy was suggested, with attention to the
practical strengths and limitations of the technique. Case studies were
discussed, and for the organic pigments identified, the history of their use was
also discussed. These authors collaborated with Schulte and others to study
synthetic pigment identification by using both dispersive and FT-Raman on 23
pigments.[208] Different excitation wavelengths were required to avoid
fluorescence and heating of the artifacts. In many cases it was possible to
identify both organic pigments and the main inorganic pigments or fillers.
Discrimination power varied within different pigment classes and complementary
chromatographic methods were recommended. Papliaka and coauthors used
Raman and FTIR in combination to characterize the materials of a contemporary
painting and to investigate the stability of synthetic pigments in a widely used
contemporary binding medium for conservation purposes.[209] Red organic
colorants were the focus of Schmidt’s and Trentelman’s study, and yellow
organic pigments were analyzed by Ropret et al. and Colombini and Kaifas.[210-
212] In the latter study, the authors also looked at orange organic pigments, as
well as pigments found in automotive paints.
Correia and coauthors took a different approach by examining inorganic
pigments and extenders and, in combination with other analytical techniques,
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