Revealing ivory origin: a novel ATR-FTIR spectroscopic and chemometric approach to distinguish Asian and African variants

Abstract

In wildlife seizure proceedings, it is essential to accurately identify and differentiate between seized Asian and African elephant ivory and their carved products. This differentiation is necessary for effectively tracking the ivory trade, which will assist in combating illegal ivory trafficking. However, distinguishing similar types of samples from closely related species poses a challenging task, as they share similar chemical compositions. Therefore, the present study aimed to differentiate Asian and African elephant ivory samples, collected from ten individuals of each species. To achieve this objective, a rapid and cost-effective ATR-FTIR spectroscopy combined with chemometrics was employed. The spectra of the ivory samples were visually compared and subsequently subjected to chemometric analysis. The PCA model differentiated Asian and African elephant ivory samples into two distinct clusters, achieving an accuracy of 95%. Furthermore, the PLS-DA model successfully classified the ivory samples into two distinct categories with 100% accuracy. To validate the performance of the developed PLS-DA model, both cross-validation and external validation were conducted, yielding a classification accuracy of 100%. A blind test was also conducted to assess the prediction accuracy of the PLS-DA model, which also achieved 100% prediction accuracy. Additionally, the PLS-DA model effectively differentiated ivory from bone samples. The findings of this study highlighted the effectiveness of employing ATR-FTIR spectroscopy combined with PLS-DA tool to differentiate ivory samples sourced from Asian and African elephants. The present approach is effective even for the samples that have lost their morphological characteristics or consist of powdered ivory traces recovered from crime scenes.