Discrimination of Automobile Acrylic Clear Coatings by Pyrolysis-GC/MS

In order to improve the discrimination of automobile acrylic clear coatings in trace evidence examination, a method of pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) was established to analyze automobile acrylic clear coatings (i.e. acrylic melamine and acrylic urethane paints), and its applicability in forensic practice was investigated. The repeatability of the method was acceptable. The RSDs of the relative peak area of the three monomers of acrylic urethane paint were no more than 5.3% in one day, or 10.6% in six days. The results show that Py-GC/MS performes better than infrared spectroscopy in discriminating acrylic clear coatings. In the forensic practice of trace evidence, the application of Py-GC/MS depends on the amount of paint sample available, and non-destructive methods should be used before destructive ones.