Direct temperature mass spectrometric study on the depth-dependent compositional gradients of aged triterpenoid varnishes

Theodorakopoulos, Charis, Boon, Jaap and Zafiropulos, Vassilis (2009) Direct temperature mass spectrometric study on the depth-dependent compositional gradients of aged triterpenoid varnishes. International Journal of Mass Spectrometry, 284 (1-3). pp. 98-107. ISSN 1387-3806

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Abstract

The depth profiles of aged dammar and mastic films, which were uncovered by optimized KrF excimer laser ablation (248 nm, 25 ns), were examined by direct temperature-resolved mass spectrometry (DTMS). The results establish the generation of depth-dependent compositional gradients in triterpenoid resins as a consequence of aging, for the first time on the molecular level. Electron ionization DTMS total ion currents show that the required temperature to volatilize the polar compounds and the relative amount of pyrolysis products of the high molecular weight condensed fraction is reduced when the upper layer of varying thickness of the films had been removed by the laser. The relative abundance of characteristic ion fragments of known oxidized triterpenoid compounds gradually decreased with depth. In contrast, the ion fragments of original resin molecules became more abundant with depth. The mass spectra of the bulk of the films resembled that of the control samples, which were not subjected to aging. Multivariant factor discriminant analysis quantified the oxidative gradients and showed that a depth of 15 μm from the surface of the aged films is the threshold between highly and much less deteriorated material.

Item Type:	Article
Additional Information:	Special Issue on Art and Cultural Heritage.
Uncontrolled Keywords:	laser ablation, gradient, direct temperature-resolved mass spectrometry, multivariant factor discriminant analysis
Subjects:	F100 Chemistry W100 Fine Art
Department:	Faculties > Arts, Design and Social Sciences > Arts
Depositing User:	Ay Okpokam
Date Deposited:	10 Oct 2013 10:38
Last Modified:	12 Oct 2019 19:42
URI:	http://nrl.northumbria.ac.uk/id/eprint/13860

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