Determination of elemental and organic carbon on damaged stone monuments

An analytical methodology was developed for the discrimination and evaluati on of the different types of carbon matter, particularly carbonate, element al and organic carbon, present on monuments and historical buildings, due t o interaction between materials and atmospheric pollution. With this aim sa mples of black patinas were analysed by a procedure consisting of three dif ferent steps. Total, noncarbonate and elemental carbon were measured by com bustion-chromatographic CO2 determination: C-t was obtained by burning the bulk samples (step 1), while C-nc and C-e were quantified after elimination of C-c with acid treatment (step 2) and elimination of C-o by means of alt ernate attacks, followed by centrifugation, with concentrate acid and base solutions at high temperature and pressure (step 3); the carbonate carbon a nd the organic carbon were then calculated. Furthermore, for a complete sam ple characterization, oxalate, acetate, formate and the main anion contents were detected by ion chromatography. The methodology was also tested on st andard samples containing the same carbon species as the black crusts. The results obtained indicate that this approach satisfactorily distinguishes b etween elemental and organic carbon and allows reliable elemental carbon de termination at the ppm level in black damage crust samples from historic mo numents and buildings. (C) 2000 Elsevier Science Ltd. All rights reserved.