An innovative multi-analytical strategy to assess the presence of fossil hydrocarbons in a mummification balm

Abstract

This research work focuses on the detection of radiocarbon contamination, for instance bitumen, in a mummification balm prior to its radiocarbon dating. A new analytical methodology combining ATR-FT-IR (Attenuated Total Reflexion - Fourier Transform Infrared Spectroscopy), TLC (Thin Layer Chromatography), is developed in order to allow a straightforward identification of contaminants directly from the excavation site and monitor the sampling prior to radiocarbon dating. The mummy of Padiimenipet, currently held at the Louvre Museum, was chosen to build the methodology as previous work relying on GC–MS (Gas Chromatography – Mass Spectrometry) identified bitumen in this balm. Radiocarbon dating of multiple aliquots of the sample by AMS (Accelerator Mass Spectrometry) confirmed the presence of fossil compounds and their important heterogeneity. ATR-FTIR approaches allowed a preliminary characterization, with identification of the main chemical families from the balm and notably hydrocarbons. TLC, used in normal phase and using methanol as eluent, confirmed in a very efficient way the presence of hydrocarbons in the sample and such technique could easily be used in situ to select samples devoid of these compounds, possibly fossil. GC–MS analysis requiring specific SPE (solid phase extraction) concentration confirmed the presence of bitumen but is not designed to offer an easily implemented diagnosis. Consequently, the combined use of ATR-FTIR and TLC could be used in the future as a new on-site methodology to perform a screening of organic samples before radiocarbon dating and identify fossil contamination.