Innovative stable isotope and high-resolution mass spectrometry approaches for provenancing organic materials in paintings and archaeological artefacts

Abstract

Through a Collaborative Doctoral Partnership between the National Gallery and the University of Bristol, this thesis describes the development of novel mass spectrometry (MS) techniques for the analysis of organic materials in cultural heritage. Compound-specific isotope analysis (CSIA), widely used for provenancing archaeological organic residues, was applied, for the first time, for source investigation of organic painting materials. This was achieved by coupling a thermal separation probe (TSP) to a gas chromatograph-combustion-isotope ratio MS (GC-C-IRMS), significantly reducing the sample sizes typically required for this technique. Through complementary use of a GC-quadrupole time of flight-MS (GC-QToF-MS) coupled to the TSP, the method was verified through comparison to established protocols for lipid residue analysis in archaeological vessels. Consequently, it was used to investigate the source of lipid-based binders in paint replicas; providing the first-ever application of CSIA to painting samples, and suggesting that CSIA could differentiate between linseed oil, egg yolk, and walnut or poppyseed oil binders.
Subsequently, the thesis illustrates the application of the new techniques for source-determination of proteinaceous painting materials; specifically how stable isotopic signatures of protein pyrolytic products enable differentiation between terrestrial and aquatic animal glues. Complementary accurate mass information was supplied by high-resolution MS (HRMS), permitting structure elucidation of fragment ions and of unknown protein pyrolysis markers. Lastly, the developed techniques were employed to investigate the origin of cochineal lake pigments, indicating that Mexican, Polish, and Armenian cochineals may be distinguished through the isotopic signature of their main colourant.
In summary, this thesis demonstrates that CSIA, through the newly developed methods, may be utilised to investigate a wide range of painting materials. Furthermore, it illustrates the power of the novel HRMS approach, as a complementary or stand-alone technique, and details the potential of these new developments for overcoming current analytical challenges faced by heritage science.

Date of Award	17 Jun 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Richard P Evershed (Supervisor), Ian D Bull (Supervisor), Lucy J E Cramp (Supervisor), David Peggie (Supervisor) & Catherine Higgitt (Supervisor)