Quantification of vehicle paint components containing polystyrene using pyrolysis-gas chromatography/mass spectrometry

Qualitative analysis of complicated paint samples from traffic accident cases can usually be dealt with by Fourier Transform Infrared Spectroscopy (FTIR) or Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS); however, the collection of quantitative evidence is still difficult, especially for solid and cured polymers, due to multiple factors involved. Polystyrene, one of the commonly used ingredients in paint recipes, is quantified by pyrolysis-GC/MS which offers satisfactory performance with low sample consumption and high sensitivity. Not only are the characteristics of PS during the various pyrolyzing process discussed, but also the matrix effects on quantification are evaluated for better identification of paint sources. We design a method based on the unique pyrolysis characteristics of polystyrene, in which styrene is the major pyrolysis product at nearly 750°C, to identify and quantify paint samples of different sources with limited quantities and high similarities. Validation of this method is accomplished by joining international proficiency tests twice successfully meeting the requirements, indicating that the method is useful and feasible in examining vehicle paint traces with the convenience and practicability of combining with other analytical techniques for forensic purposes.