Proteinaceous binding media characterization and age estimation of medieval wall paintings

In this study the nature of the proteinaceous material used as the binder in ancient paintings and the possibility of using amino acid racemization for dating are investigated. Mediaeval wall paintings executed with the tempera technique using proteinaceous media were examined. The characterization was performed by checking samples of paint layers, which were hydrolyzed with hydrochloric acid and cleaned through ion exchange resins. The amino acides were derivatized with acid 2-propanol and trifluoroacetic anhydride to produce amino-esters, which were then analyzed by means of capillary gas chromatography (GC), using chiral tetraamide ligands as stationary phases. The paint media were identified by comparing the GC results with amino acid profiles of standard materials. The amino acid racemization was also investigated. A correlation between the age of the painting and the racemization level of the aspartic acid was found