Resinite

For the first time, molecular evidence of the structural role played by succinic acid within the macromolecular structure of Class Ia and Class Id resinites is presented. Using a novel gas chromatographic methodology, communol (Class Ia) and ozol (Class Id) moieties within the polylabdane matrix are shown to be cross-linked with succinic acid. Samples were analysed using pyrolysis-gas chromatography-mass spectrometry with in situ HMDS derivatisation, using a thermal separation probe to perform the pyrolysis and sample introduction. The relatively slow rate of heating and prolonged pyrolysis of resinites using this new methodology, combined with the use of a mild derivatization reagent, allowed communol pyrolysates from Class Ia resinite and ozol pyrolysates from Class Id resinite to elute with unbroken succinyl ester cross-linkages. These results provide direct molecular evidence that the key role of succinic acid within Class Ia and Class Id resinite is to cross-link the macromolecular structure. In the Class Id resinite, the methodology also allowed the detection succinyl ester linkages between ozol pyrolysates and dehydroabietol, thus, demonstrating that non-polymerized diterpenes contribute structurally to the macromolecular structure of Class Id resinite.

ABSTRACT Class Ib resinites are the most common subclass of amber and are found throughout the world. They have a macromolecular structure based on co-polymerized communic acid, communol and biformenes. Because this class of resinite does not contain succinic acid, crosslinking of the polymer through esterification of communol moieties has never been theorized. Analysis of Class Ib resinites from Grassy Lake and Cedar Lake in western Canada was performed using pyrolysis-gas chromatography-mass spectrometry with in situ hexamethyldisilazane derivatization, using a thermal separation probe to perform the pyrolysis and sample introduction. This has allowed larger, more complex fragments to be released from the polymer matrix than previously possible using instantaneous pyrolysis methodologies. The results show for the first time that Class Ib resinite can undergo self-crosslinking between the communol and communic acid moieties in the polylabdane matrix. The chromatographic results also show that a portion of the monoterpenes and non-polymerizable diterpenes in the resinite are bound to the polymer matrix and not fully occluded as was previously theorized. Fourier transform infrared (FTIR) spectra of the resinites are presented and a more accurate spectral interpretation is proposed, based on the chromatographic results.