Cross-section measurements of multilayer automotive paint samples using combined Raman spectroscopy and LIBS

Multilayer automotive paint samples can be important evidence in forensic investigations but due to their inherent complexity it is a challenging task to analyze them. We herein present a method for a comprehensive chemical sample characterization based on the subsequent measurements of paint samples with Raman spectroscopy and laser induced breakdown spectroscopy (LIBS) at the same sampling points along the cross-sections of the paints. The method requires minimal sample preparation because the layers do not have to be separated. In combination with multivariate data analysis (namely k-means) the proposed method provides information both on the distribution of molecular compounds as well as elements which could then be used for the discrimination of different paints. Eight different samples were investigated and individual chemical profiles were found whereby a spatial resolution of close to 10 μm could be demonstrated. Investigation of different samples of the same origin showed similar profiles revealing the reproducibility of the proposed method. We therefore believe that our approach could be a good addition to the methods used so far for the analysis of paint samples.