Amber, or fossilized plant resin, has most commonly been used as jewelry and as a source for preserved organisms throughout history. More recently, structural analysis of amber and copal (less mature amber) has gained importance in archaeological and botanical research. Nuclear magnetic resonance (NMR) spectroscopy has been the most successful technique in classifying ambers into different categories based on their structure without altering their chemical makeup. More specifically, solid-state carbon-13 NMR spectroscopy has served as an important technique to categorize amber and copal into five main groups corresponding to their geographic location of origin. Solution-state carbon-13 NMR analysis, which provides more distinct peaks than solid-state NMR spectroscopy, has not previously been used for structural analysis of amber. In this study, 12 amber and copal samples soluble in deuterated chloroform (CDCl<sub>3</sub>) were used to determine distinctive structural characteristics for Groups A, B, D, and E. Group C was omitted from this study due to the inability to acquire quality spectra.  While solution-state carbon-13 NMR analysis of the 12 amber and copal samples in this study confirmed the existence of specific structural trends that characterize Groups A, B, D, and E, this study also revealed that there is more spectral variation within each group than apparent from solid-state studies.

Analysis of fossilized resin (amber) by carbon-13 nuclear magnetic resonance spectroscopy in solution: A worldwide survey

2019 Spring National Meeting

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