Vibrational spectroscopy with chromatographic methods in molecular analyses of Moravian amber samples (Czech Republic)

• Studlovite and valchovite molecular compositions are presented for the first time.
• Baltic amber and archaeological samples from Kralice na Hané were also analysed.
• Marker molecules and PCA were used for the classification of ambers.
• Studlovite (Eocene) was classified as amber of Class 2 type.
• Valchovite (Upper Cretaceous) was classified as amber of Class 1b type.

New information on the molecular composition of valchovite (from Boskovice Furrow, Czech Republic) and studlovite (Študlov, near Valašské Klobouky, South-east Moravia, Czech Republic) were obtained using gas chromatography, attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), and Fourier transformed Raman spectroscopy. ATR-FTIR was coupled to principal component analysis and used for the classification of ambers according to their composition. The archaeological amber originating from a Lusatian Urnfield settlement of the Hallstatt period (Kralice na Hané, near Prostějov, Czech Republic), together with Baltic amber (Denmark), were used to demonstrate that two principal components suffice to classify the samples into distinct groups. Valchovite (Upper Cretaceous) and studlovite (Eocene) did not show compounds and features typical for Baltic amber, but only nonspecific or non-identifiable compounds that are remnants of the original terpenoids. However, although the results of the analytical records did not indicate a more specific plant source, studlovite was classified as belonging to amber classification Class 2, and valchovite, to Class 1b. The results confirmed the higher degree of maturation of studlovite in comparison with older valchovite and the close spectral resemblance between ambers of different ages emphasises the importance of alterations and post-depositional conditions on the character of the resulting amber. Succinic acid, determined as its dimethyl ester, and the ‘Baltic shoulder’, the well-known markers in ambers of Baltic origin, as well as softening point, or the ratio I1645/I1450 in the FT-Raman spectra, showed that the archaeological samples were derived from Baltic amber, confirming the view that the territory of Moravia was a trading or market center for this material on its way to southern and southeastern Europe.