GC-MS characterization of paint varnishes

This paper presents an analytical procedure based on gas chromatography sep aration and mass spectrometric identification, which allows the determinati on 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 a chieved. The triterpenoid composition of raw commercial resins was compared with that of samples collected from reference varnish layers prepared at O pificio delle Pietre Dure (Florence, Italy): a profound change in the varni sh 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 <alpha>- and bet a -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 tend of 13th century), currently being restored at Opificio delle Pietre Dure (Flo rence, Italy), enabled us to identify dammar and mastic resins. (C) 2000 El sevier Science B.V. All rights reserved.