title: Gas chromatographic-mass spectrometric characterisation of plant gums in samples from painted works of art.
abstract: This paper presents an analytical GC-MS procedure to study the chemical composition of plant gums, determining aldoses and uronic acids in one step. The procedure is based on the silylation of aldoses and uronic acids, released from plant gums by microwave assisted hydrolysis, and previously converted into the corresponding diethyl-dithioacetals and diethyl-dithioacetal lactones. Using this method only one peak for each compound is obtained, thus providing simple and highly reproducible chromatograms. The analytical procedure was optimised using reference samples of raw plant gums (arabic, karaya, ghatti, guar, locust bean and tragacanth, cherry, plum and peach gums), commercial watercolours and paint layers prepared according to ancient recipes at the Opificio delle Pietre Dure of Florence (Italy). To identify gum media in samples of unknown composition, a decisional schema for the gum identification and the principal component analysis of the relative sugar percentage contents were employed. The procedure was used to study samples collected from wall paintings from Macedonian tombs (4th-3rd centuries bc) and from the Mycenaean "Palace of Nestor" (13th century bc) in Pylos, Greece. The presence of carbohydrates was ascertained and plant gum binders (fruit and a mixture of tragacanth and fruit tree gums) were identified in some of the samples.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy. ilariab@dcci.unipi.it
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bonaduce
authors.forename: Hariclia
authors.initials: H
authors.lastname: Brecoulaki
authors.forename: Maria Perla
authors.initials: MP
authors.lastname: Colombini
authors.forename: Anna
authors.initials: A
authors.lastname: Lluveras
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Restivo
authors.forename: Erika
authors.initials: E
authors.lastname: Ribechini
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D049690:History, Ancient; D009005:Monosaccharides / Q000032:analysis; D010151:Paintings; D053149:Plant Gums / Q000737:chemistry*; D014574:Uronic Acids / Q000032:analysis
chemical_list: D009005:Monosaccharides; D053149:Plant Gums; D014574:Uronic Acids