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Completed Project

Chemical Characterization of Amber from Arkansas

Sonia Santos ’21 Linnea Martin ’21 and Professors Sarjit Kaur and Edith Stout (Chemistry)

Ambers are produced over millions of years of resin fossilization and are composed of a mixture of terpenoid compounds. Terpenes, a general category for organic compounds found in nature, can be broken into subcategories of mono-, sesqui-, di-, and triterpenes. Terpene composition of ambers can be determined through the analytical technique gas chromatography-mass spectrometry (GC-MS). Infrared spectroscopy (IR) is also helpful in comparing spectra to an in-house database of IR spectra of ambers of known geological origin studied previously. Through chemical analysis of amber, insight is gained regarding the botanical source as well as the geographic distribution and evolution of tree species. In this study, these two analytical techniques, IR and GC-MS were used to analyze, characterize, and compare terpenes found in four geological Arkansas amber samples. Three of the four samples had similar IR scans, showing characteristic peaks for ambers and are closely related. The other amber sample, while showing some organic fossil-like peaks, very likely contained a silicate contamination and precluded a comparison to the other ambers.  Based on GC-MS, mono-, sesqui-, and triterpenes were present and, therefore, all four samples are designated triterpene ambers. It is unusual to find triterpene ambers in the Arkansas region as most triterpenes (C30) found in ambers come from trees in the dipterocarpaceae species which are prevalent in Southeast Asia and India. On the average, all four samples are similar based on the chemical composition of sesquiterpenes and triterpenes, after allowing for some difference expected due to extraction of organic components and contamination of the one amber.  Further evaluation of the GCMS data is in process for a more detailed comparison of the major components in each amber sample.