Forensic analysis of automotive paints by Raman spectroscopy

Abstract

In this work, the possible contribution of Raman spectroscopy in forensic science is evaluated, more specifically for the analysis of automotive paint samples. Spectra from paint flakes as well as from cross sections were examined, in order to identify not only the pigments but also binders and extenders in all paint layers. Moreover, the possibility of distinguishing paint samples from different cars was evaluated to assess the use of vibrational spectroscopic techniques in the investigation of a hit-and-run accident.The presence of rutile and extenders, such as calcite and barium sulphate, could be demonstrated by their characteristic Raman bands. However, the identification of the binder by Raman spectroscopy was hampered: only with additional information from IR analysis could most of the bands in the spectrum be assigned to molecular vibrations of the binders. In contrast, organic pigments, having very distinctive and well-resolved characteristic bands, could easily be identified by comparing the spectra from the basecoat of the sample with spectra from a reference database. Because of these characteristic bands, the basecoat seems to provide the best spectra to distinguish paint samples. Moreover, some paints can also be distinguished by the absence or presence of the bands from calcium carbonate and barium sulphate in the primer surfacer. When recording spectra from paint flakes, Raman bands from the spectra of the clearcoat as well as from the basecoat are obtained.

Raman spectroscopy of synthetic organic pigments used in 20th century works of art

“…10 In art and archaeology, where -up to now -Raman microscopy is more regularly applied for inorganic pigments or natural organic lake colours and dyestuffs, 11 -14 it performed surprisingly well for modern organic colourants in first experiments, especially for azo pigments. 15 -17 The objective of this study was to deepen our knowledge about the capabilities and limitations of Raman microscopy for the identification of synthetic organic pigments in minute paint samples.…”

Uso de la espectroscopia Raman en el análisis de fragmentos de pintura automotriz como evidencia forense

“…Espectro de pintura automotriz La figura 6 presenta el espectro de una de las muestras de pintura analizadas y los picos característicos del metacrilato, uno de los aditivos de la pintura automotriz (De Gelder et al, 2005). Es posible observar similitudes en los picos, tanto en su posición como en su relación de intensidad, por tanto, se puede corroborar la presencia de metacrilato.…”

Raman spectroscopy and its applications

“…Otras áreas incluyen la identificación de cabellos, fibras, virutas de pinturas y tintas [27][28][29][30][31].…”