Way to Distinguish Car Paint Traces Based on Epoxy Primer Layers Analysis by Pyrolysis-Gas Chromatography-Mass Spectrometry

摘要

Fragments of paint coat or paint smears are very often transferred onto the clothing of a hit-and-run accident victim. Identification of paint samples requires examination of their polymer binders by pyrolysis-gas chromatography-mass spectrometry method (Py-GC-MS). Previously, Py-GC-MS has been successfully applied in our laboratory to the analysis of a polymer binder of clear coat layers (top layer of the paint coats). The aim of this research was to analyse the "bottom" side of the paint chip - the epoxy paint layer. Paint samples were analysed at least three times without derivatisation at 750°C, or after derivatisation in two steps at 400°C and 750°C using tetramethylammonium hydroxide (TMAH). It was observed that derivatisation increased the number and the quantity ratios of the pyrolysis products and enabled differentiation between the samples of similar chemical composition. It was found that Py-GC-MS allows for successful comparison of paint samples based on clear coat layer and primer layer analyses.