Investigation by solid-phase micro-extraction and gas chromatography/mass spectrometry of organic films on stone monuments

Abstract

Deposition of organic chemicals on historical buildings is a well-known phenomenon. Such material originates from airborne pollution, from human activity, and from natural sources, and it tends to accumulate over long times on the surfaces in the form of a black film which covers considerable portions of the monument surface. Analysis is generally performed on grams of particulate, removed with obvious serious detriment to the monument itself; this material is then conventionally extracted with solvents and analyzed by gas chromatography/mass spectrometry (GC/MS). We propose here a new analytical strategy which takes advantage of the dry solid-phase micro-extraction headspace technique coupled with GC/MS. For this purpose, we used samples of no more than 100 mg of powdered material for each measurement. The black crusts coating the stone surfaces of ancient monuments, dating back to the 13-17th centuries and located in small towns, between high mountains and far away from urban (polluted) environments, have been analyzed. Despite their locations, organic chemicals connected with human activity from our contemporary age, hydrocarbons, PAHs, oxy-PAHs, and herbicides have been revealed. In addition fatty acid residues, probably due to microorganism growths, as well as a large number of mono-and sesquiterpenes reasonably arising from local natural sources, have been detected. The technique we describe, which has been used for the first time in a cultural heritage context, is rapid and not detrimental to the piece of art. The chromatograms thus obtained are characterized by a low background level and a high signal to noise ratio. Copyright # 1999 John Wiley & Sons, Ltd. Received 11 March 1999; Accepted 14 March 1999A significant part of our cultural heritage is made of stone, and most of it is constituted by buildings and outdoor exposed monuments. They inexorably suffer from ageing and decay processes, which are mainly due both to atmospheric phenomena and to the activities of human beings; particularly in recent times, atmospheric pollution threatens even their very existence. In our contemporary age, we are almost accustomed to seeing their grey surfaces, which turn to black especially in the chiselled parts or those protected from the direct impact of rain. The monument surface, in fact, acts as a repository of organic chemicals, which originate from airborne pollution and human activity in general, from aerosols and plant vapours, from natural fires, from growth of microorganisms and, finally, from the ageing of a possible chemical treatment used by the artist who originally polished the stone surface.1 The wet and dry organic deposition is apparent as a black crust and, besides being responsible for its unpleasant aspect and primarily for the monument decay, from a different point of view is also a chemical record of the history of the monument itself and of the geographic area where it is located.The combined action on a carbonate surface of the many physical and chemical agents, such as temperature, sun irradi...

Investigation by solid‐phase microextraction and gas chromatography/mass spectrometry of trail pheromones in ants

“…Quite recently, we became acquainted with dry headspace SPME by applying it to the GC/MS analysis of VOCs of anthropic and natural origin 9. In this communication we present our results on the glandular secretions employed for chemical communication in the complex organization of ant societies.…”