Examination of spray paints on plasters by the use of pyrolysis-gas chromatography/mass spectrometry for forensic purposes

The thin layer of spray paint, which creates an inscription, smudge or a drawing on plaster has to be examined in situ. The application of reflectance IR spectroscopy enables one to identify in some cases the spray paint directly on plasters. However, very often the bands of plaster components overlay signals originating from paint, making its identification impossible. In pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) method the influence of inorganic substances on chromatographic results is very small. So, an attempt was made to use this method to spray paints examination. ay paints, available on the Polish market were placed on surfaces of four types of plaster: mineral-based plaster, acrylic copolymer-based plaster, silicate-based plaster and silicone-based plaster. Then they were dried, collected and analysed. It was found that spray paints collected from the plasters can be effectively differentiated in many cases by means of Py-GC/MS based on a specific minor and major compounds content.