GC-MS characterisation of paint varnishes

This paper presents an analytical procedure based on gas chromatography separation and mass spectrometric identification, which allows the determination of natural resins, waxes and lipids in the same microsample -1 mg . By this way, the chemical characterization of dammar and mastic resins, used on their own and also in mixture with wax and oils in paint varnishes, is achieved. The triterpenoid composition of raw commercial resins was compared with that of samples collected from reference varnish layers prepared at Opificio delle Pietre Dure Florence, Italy : a profound change in the varnish chemical composition was found after only 6 months exposure to daylight. The identified terpenoid compounds which resulted more stable to oxidation and polymerization are pentacyclic triterpenoids, such as a- and b-amyrone and 28-norolean-17-en-3-one. The presence of these compounds in varnish samples from the Madonna col Bambino by Coppo da Marcovaldo end of 13th century , currently being rest...