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Development and application of analytical tools to investigate composition
and ageing processes of modern oil-based paint materials


HPLC-ESI-Q-ToF analysis of alkyd paint


Modern oil paint, industrially produced and sold in tubes as ready-made, diffused amongst artists since the end of the XX century. Modern oil paints present significant compositional differences with traditional natural oil paints. The introduction in the commercial paint formulations used in artworks of low cost lipid sources, surfactants, stabilizers and thinners necessary for long term stability and industrial workability is demonstrated to cause challenging conservation problems. Alkyds paints are oil-modified polyesters synthesized from polyols, aromatic polybasic acids and different weight percentages of oil/fatty acids, and have been commonly used as binders in artist paints and coating since the 1940s. Preservation of artworks containing modern oil-based industrial paints requires the availability of suitable analytical tools and a better knowledge of degradation pathways of modern oil-based paints.
A new analytical approach based on the integration of three different mass spectrometric techniques was developed and used for the characterization of plant oils, modern oil paint, commercial alkyd paints, and industrial alkyd resins, before, during and after laboratory ageing treatments.
• Gas chromatography-mass spectrometry was successfully applied for the determination of the fatty acid profile and aromatic fractions of the resins after hydrolysis;
• High performance liquid chromatography coupled with electrospray ionization mass spectrometry with a tandem quadrupole-time-of-flight mass spectrometry allowed us to characterize triglycerides, diglycerides and the pentaerythritol and phthalic acid esters when present;
• Flow Injection analysis was used as a rapid method to evaluate the presence of possible additives such as synthetic polymers.
This approach was applied to evaluate the chemical modifications of plant oils, oil paints and alkyd resins during artificial ageing. The combined analytical approach was successfully applied for the characterization of paint samples collected from case-studies.

Published papers
• Jacopo La Nasa, Ilaria Degano, Elisa Ghelardi, Francesca Modugno, Maria Perla Colombini, “Core shell stationary phases for a novel separation of triglycerides in plant oils by high performance liquid chromatography with electrospray-quadrupole-time of flight mass spectrometer”, Journal of Chromatography A, 2013, vol. 1308, p 114-124
• Jacopo La Nasa, Ilaria Degano, Francesca Modugno, Maria Perla Colombini, “Alkyd paints in art: characterization using integrated mass spectrometry”, Analytica Chimica Acta, 2013, vol. 797, p 64–80
• Jacopo La Nasa, Ilaria Degano, Francesca Modugno, Maria Perla Colombini, “Effects of acetic acid vapour on the ageing of alkyd paint layers: multi-analytical approach for the evaluation of the degradation processes”, Polymer Degradation and Stability, 2014, vol. 105, p 257-264
• Jacopo La Nasa, Ilaria Degano, Francesca Modugno, Maria Perla Colombini, “Industrial alkyd resins: characterization of pentaerythritol and phthalic acid esters using integrated mass spectrometry”, Rapid Communication in Mass Spectrometry, 2014, in press


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