Journal of Chromatography A, 1093 (2005) 177–194 Study of Burseraceae resins used in binding media and varnishes from artworks by gas chromatography–mass spectrometry and pyrolysis-gas chromatography–mass spectrometry Juana De la Cruz-Ca ˜ nizares a , Mar´ ıa-Teresa Dom´ enech-Carb´ o a,∗ , Jos´ e-Vicente Gimeno-Adelantado b , Rufino Mateo-Castro b , Francisco Bosch-Reig b a Department of Conservation and Restoration of Cultural Heritage, Conservation Heritage Institute, Polytechnical University of Valencia, Camino de Vera 14, 46022 Valencia, Spain b Department of Analytical Chemistry, University of Valencia, Dr. Moliner s/n, 46100 Burjassot, Valencia, Spain Received 8 February 2005; received in revised form 6 July 2005; accepted 14 July 2005 Available online 8 September 2005 Abstract In the present work, a study attempting to characterize the Manila elemi and Mexican copal resins from the Burseraceae family, which are used as components of varnishes and binding media of artworks, has been carried out. A new GC–MS method involving the use of methyl chloroformate as derivatisation reagent has been proposed. A second method which uses pyrolysis-GC–MS and hexamethyldisilazane as derivatization reagent has also been applied. Characterization of the main components of the mono-, sesqui- and triterpenoid fractions occurring in the raw materials has been achieved. Both - and -amyrin have been established as the major triterpenoid compounds occurring in these resins together with hop-22(29)-en-3-ol, found only in the Mexican copal. Artificially aged samples of Manila elemi and Mexican copal have also been analysed in order to study the stability of the triterpenoid components of the resins and their possible use as marker molecules. The results obtained indicate that these molecules, in particular, - and -amyrin undergo oxidation processes during both artificial and natural ageing. Nevertheless, hop-22(29)-en-3-ol could be selected as marker compound for Mexican copal. The proposed methods of analysis have been applied to real paint samples extracted from paintings in which Mexican copal was present as the main component of an “oleoresin” binding medium to assess their ability for identifying this product when used in artworks. Satisfactory identification of this resin is obtained by means of GC–MS whereas Py-GC–MS provides, in general, weaker signals for the components of the resin. Additionally, the influence of the pigments present in real samples on the resin ageing process has been considered. © 2005 Elsevier B.V. All rights reserved. Keywords: Gas chromatography; Mass spectrometry; Pyrolysis; Methyl chloroformate; Hexamethyldisilazane; Burseraceae resin; Manila elemi; Canarium luzonicum; Mexican copal; Bursera cuneata; Artwork 1. Introduction Triterpenic resins have been traditionally used as the main components of pictorial varnishes and binding media and, accordingly, the analysis of these natural products has claimed considerable attention in the field of cultural heritage in recent years. Among them, elemi, generic term applied to a ∗ Corresponding author. Tel.: +34 96 3877310; fax: +34 96 3877319. E-mail address: tdomenec@crbc.upv.es (M.-T. Dom´ enech-Carb´ o). large number of resins from the Burseraceae family, has been used as component of varnishes, where other terpenoid prod- ucts are included, to modify their consistency. These resins have been included in a number of recipes for preparing var- nishes from the 19th century [1]. Over the 20th century elemi resin was added to waxes in relining processes (Dutch Pro- cess) for increasing the tackiness [2–4]. Moreover, elemi resin is frequently included in recipes of varnishes for toys, furni- ture, wagons and carriages, metals and swords, violin and musical instruments, gildings, etc. [5]. 0021-9673/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2005.07.058