Multispectral investigation of natural resins

Abstract

Resins have been used as remedies since ancient times and various embalming resins have been identified in recent years. In Europe, Mumia vera aegyptiaca, a resinous substance from ancient Egyptian mummies, was even sold in pharmacies as a tonic until the early 20th century. It is difficult to examine the composition of these archeological samples in detail as the well-established analytical techniques, that is, gas chromatography-mass spectrometry or liquid chromatography coupled with tandem mass spectrometry, are destructive and therefore do not allow the analysis of valuable archeological samples. Hence, there is an urgent need for alternative, nondestructive methods for the identification of resin residues. This study aims to explore and compare the use of five spectroscopic methods as an alternative to established analytical procedures. For that, 15 resin samples of known origin and three samples from an Egyptian market were studied. While laser induced-breakdown spectroscopy and terahertz time-domain spectroscopy provide only limited information for resin classification, nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy can be used to classify the resin samples more accurately. Furthermore, photoluminescence/photoluminescence excitation spectroscopy shows a promising potential in combination with its general advantages, such as cost-efficiency, nondestructive nature, and fast data acquisition.