Raman spectroscopy coupled to chemometrics to discriminate provenance and geological age of amber

Abstract

Raman spectroscopy coupled to partial least squares (PLS) was used for the classification of amber samples according to their provenance and geological age. Spectral data were from samples from Czech Republic, Baltic region, and objects dated back from Upper Cretaceous and Cenozoic ages. Intensity ratio of two wavenumbers has been used as indicator of both geological age and provenance amber so far. In this work, an alternative chemometric approach was proposed to select additional intervals of the spectra where discrimination relies. Several metrics (number of misclassifications and permutation test) evaluated the capability of the alternative PLS models to predict future measurements. Results achieved indicated the possibility to assess the geological age and provenance of amber considering an interval of wavenumbers instead of single wavenumbers that could be disturbed by physical effects. Furthermore, differences in the Raman spectra were highlighted by using Variable Importance Projection methodology over PLS model. The proposed methodology clearly distinguished Baltic from Czech Republic amber and resins from Cenozoic period and Upper Cretaceous. This research could represent a breakthrough for amber cultural heritage studies.

Determination of the Reactivity Degree of Various Alkaline Solutions: A Chemometric Investigation

“…In general, Raman spectra have to be preprocessed prior chemometric analysis in order to keep only chemical variances. 37 Figure 3 displays spectra before and after this pretreatment. This preprocessing was selected in order to suppress the baseline shift of the spectra, mainly due to fluorescence effect (Fig.…”

Application of Raman Spectroscopy to Ancient Materials: Models and Results from Archaeometric Analyses

“…An analogous strategy was exploited by Peris-Dìaz et al [41], where Raman spectroscopy, paired to partial least squares (PLS) model, was employed for classifying amber samples in agreement with their provenance and geological age.…”

“…Density plot of the Q 2 Y values account for the full vibrational spectra (d) and the 1100 to 1800 cm −1 range (e). (Reproduced from work in [41] with the permission of Wiley, copyright 2017.) Figure 10.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Their proposed methodolgy clearly distinguished Baltic from Czech Republic amber and resins from the Cenozoic period and Upper Cretaceous. The authors claim their research could represent a breakthrough for amber cultural heritage studies …”