Evaluation of Raman spectroscopy and application of chemometric methods for the differentiation of contemporary ivory specimens I: elephant and mammalian species

Abstract

Specimens of mammoth, African and Asian ivory dentine, and other mammalian species were examined using Fourier-Transform (FT), conventional dispersive (confocal) and remote-sensing portable Raman spectroscopy, all with near-infrared laser excitation (1064 and 785 nm). FT-Raman spectroscopy produced the best quality spectra for differentiation purposes and the application of a fibre probe coupled to a portable Raman spectrometer has also been demonstrated and proposed for the in situ characterization of suspected contraband ivories at airports. In addition to the visual comparison of spectral features, chemometric methods are used to discriminate between African and Asian elephant dentine by analyzing normalized integrated band areas in ten selected wavenumber regions. Principal component analysis separates the spectra of both species into two well-defined groups based upon their organic and inorganic composition. By means of stepwise discriminant analysis almost 98% of the spectra are correctly classified to their species group memberships.

Application of portable Raman spectroscopy and benchtop spatially offset Raman spectroscopy to interrogate concealed biomaterials

“…The vibrational modes of Raman spectra of ivory comprising these inorganic and organic components have been reported previously. [2] In order for Raman spectroscopy to be deployed into 'live' environments, it must meet a number of well-understood objectives and of major importance is the speed of analysis. Analysis: from data capture, to answer that can be understood and used by a customs official, needs to be completed in seconds.…”

Raman spectroscopy at the beginning of the twenty‐first century

“…This nice piece of research shows in a clear and convincing way how Raman spectroscopy can be employed as a powerful tool for structural and taxonomic studies in the field of marine biology. Edwards et al 44 describe the discrimination between specimens of mammoth, African and Asian ivory dentine and other mammalian species by analysing normalized integrated Raman band regions by means of chemometric methods. There, the authors compared the Raman results obtained with Fouriertransform (FT), conventional dispersive (confocal), and remote-sensing portable Raman spectrometers, all with nearinfrared laser excitation.…”

The Goodmanham plane: Raman spectroscopic analysis of a Roman ivory artefact

“…For comparison purposes, several specimens of modern ivory were studied from documented museum collections, including African elephant (Loxodonta africana), Asian elephant (Elephas maximus), sperm whale (Physter catedon), hippopotamus (Hippopotamus amphibius), walrus (Odonbenus rosmarus), narwhal tusk, warthog tusk and mammoth (Mammuthus primigenus). 13,21,22 Raman spectroscopy FT-Raman spectra were obtained using a Bruker IFS66 instrument with FRA106 Raman module attachment and Nd 3C /YAG laser excitation at 1064 nm. Although, normally, specimens were supported vertically in the sample compartment and held with a spring-loaded security device for 180°i llumination and collection, since several of the archaeological specimens were especially fragile, a special horizontal sample table with overhead laser focusing and collection optics was used here.…”