Nondestructive Analysis of Mummification Balms in Ancient Egypt Based on EPR of Vanadyl and Organic Radical Markers of Bitumen

The black matter employed in the funeral context by ancient Egyptians is a complex mixture of plant-based compounds with variable amounts of bitumen. Asphaltene, the most resistant component of bitumen, contains vanadyl porphyrins and carbonaceous radicals, which can be used as paramagnetic probes t...

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Bibliographic Details
Published in:Analytical chemistry (Washington) 2020-12, Vol.92 (23), p.15445-15453
Main Authors: Dutoit, Charles E, Binet, Laurent, Fujii, Hitomi, Lattuati-Derieux, Agnes, Gourier, Didier
Format: Article
Language:English
Subjects:
Asphaltenes
Bitumens
Chemistry
Egypt, Ancient
Egyptian civilization
Electron paramagnetic resonance
Electron spin resonance
Electron Spin Resonance Spectroscopy
Embalming
Hydrocarbons - chemistry
Mummies
Nondestructive testing
Porphyrins
Probes
Radicals
Sample preparation
Superhigh frequencies
Vanadates - chemistry
Vanadyl porphyrins
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Summary:The black matter employed in the funeral context by ancient Egyptians is a complex mixture of plant-based compounds with variable amounts of bitumen. Asphaltene, the most resistant component of bitumen, contains vanadyl porphyrins and carbonaceous radicals, which can be used as paramagnetic probes to investigate embalming materials without sample preparation. Electron paramagnetic resonance (EPR) at the X-band, combining in-phase and out-of-phase detection schemes, provides new information in a nondestructive way about the presence, the origin, and the evolution of bitumen in these complex materials. It is found that the relative EPR intensity of radicals and vanadyl porphyrins is sensitive to the origin of the bitumen. The presence of nonporphyrinic vanadyl complexes in historical samples is likely due to the complexation of VO2+ ions by carboxylic functions at the interface between bitumen and other biological components of the embalming matter. The absence of such oxygenated vanadyl complex in natural bitumen and in one case of historical human mummy acquired by a museum in the 19th century reveals a possible, nondocumented, ancient restoration of this mummy by pure bitumen. The linear correlation between in-phase and out-of-phase EPR intensities of radicals and vanadyl porphyrins in balms and in natural bitumen reveals a nanostructuration of radicals and vanadyl porphyrin complexes, which was not affected by the preparation of the balm. This points to the remarkable chemical stability of paramagnetic probes in historical bitumen in ancient Egypt.
ISSN:0003-2700
1520-6882
DOI:10.1021/acs.analchem.0c03116