An analytical approach based on X-ray diffraction, Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry to characterize Egyptian embalming materials

Abstract

An analytical approach based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) was used to characterize Egyptian embalming materials from the University of Florence's (Italy) Natural History Museum.FTIR was used as a fast fingerprinting tool due to its ability to characterize inorganic compounds and to highlight different classes of organic materials. GC/MS following alkaline hydrolysis, solvent extraction, and trimethylsilylation was used to determine the molecular nature of organic materials and their degradation products.The results show that the embalming materials consisted of complex mixtures of natural products as well as transformation products due both to natural ageing and human interventions. FTIR analyses, along with evidence of organic materials, enabled us to identify the presence of calcium oxalates, phosphates and carbonates, while XRD patterns confirmed the crystalline nature of both phosphates and oxalates. On the basis of the GC/MS identification of specific profiles of long-chain fatty acids, long-chain alcohols and alkanes, polycyclic terpene hydrocarbons and diterpenes, and triterpenes, we found that the balms of the mummies mainly consisted of beeswax, pine pitch and mastic resin. Ricinoleic acid suggests that castor oil was used as an ingredient in the mummification balm in three of the samples. The combination of results allowed the identification of the organic and inorganic composition of the residue of embalming material sampled from the skulls to be achieved and also permitted us to exclude the presence of possible products used during past restoration cure.