Acrylic paint formulation and additive composition by means of solvent extraction and Py-GC/MS

Although acrylic paint properties and compositions have been widely studied, there remains a lack of information regarding their additives. This is mostly because they are present in such trace amounts that their detection is challenging even when using the advanced analytical tools available nowadays. Additionally, details of paint formulations, including the types of additives used, are kept secret by the manufacturers and constantly changed as requirements for paint performance. Understanding the nature of paint formulations and the additive composition is highly important to comprehending paint degradation processes over time.
This study reports on a novel comprehensive approach to characterize and identify different types of acrylic paint additives, widely used in modern and contemporary art. An analytical procedure based on the off-line combination of solvent extraction and Pyrolysis – Gas Chromatography / Mass Spectrometry (Py-GC/MS) was developed. For this purpose, different acrylic paints containing either inorganic or synthetic organic pigments from different brands, i.e., Winsor & Newton® and Schmincke®, were selected. Ultrasound-assisted extraction of paints was carried out with a selection of different organic solvents. The extracted additives were then analysed by Py-GC/MS in double shot mode for the thermal desorption and pyrolysis of polymers, without and with tetramethylammonium hydroxide (TMAH) for thermally assisted hydrolysis and methylation (THM-GC/MS).