On the use of in-situ spectroscopic techniques for the study of the provenance of historic ivories

Ivory trafficking is a multifaceted problem that has long endangered the fate of African and Asian elephants. In field investigations, it is essential to conduct ivory inspections in a nondestructive manner to prevent the inclusion of noncompliant materials. In this research, a practical approach to identify Asian and African elephants’ ivories was developed using an integrated methodology of art history, vibrational spectroscopy, and chemometrics. Spectra were acquired by an FT-IR spectrometer and a fiber optics reflectance spectrometer (FORS) in the Vis-NIR region. The discriminant methods were calibrated with spectra acquired from Asian and African elephant ivory tusks and applied to historic ivory objects (n = 78) of uncertain origin. Models based on the chemometric methods Principal Component Analysis (PCA) and Partial Least Squares -Discriminant Analysis (PLS-DA) were able to successfully classify ivory objects into Asian and African ivory, with an estimated true prediction rate (TPR) of 99 % both for African and Asian ivory samples. This study demonstrated the potential of FT-IR spectroscopy and FORS with chemometric methods as suitable tools for ivory investigations, aiding to the existing set of ivory trafficking prevention methods.