Separation techniques for the analysis of artists' acrylic emulsion paints.

Emulsion paints are complex chemical systems. The main problems in their characterization are related to the similarities in polymer composition and to the presence of many different types of additives. Thus high resolution separations, sensitivity, and response specificity are required to identify simultaneously the polymer matrix and the minor components. Especially surfactants and pigments are thought to affect significantly the properties of the paint layers during ageing and their identification is the first step in evaluating the behaviour of these products in working conditions. Representative samples of acrylic emulsion paints for artists have been investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and size exclusion chromatography-Fourier transform infrared spectroscopy (SEC-FTIR), and the results have been compared. All the analysed samples were bound in ethyl acrylate-methyl methacrylate, poly(EA-co-MMA), or n-butyl acrylate-methyl methacrylate, poly(nBA-co-MMA), copolymers. Two types of nonionic surfactants, ethoxylated fatty alcohols and alkylaryl polyethoxylates, commonly used as emulsifiers and dispersive agents have been identified, together with a number of organic pigments.