Fourier-Transform Infrared Spectroscopy (FTIR)
FTIR uses infrared spectroscopy to create an absorbance signature of organic compounds, including those recovered from archaeological sites. These signatures, or spectra, may then be compared with both commercial and private libraries of the spectra from known material to identify the unknown organic compound. Over the past several decades, the FTIR has been used to identify contaminants in manufacturing environments, for material quality control, and as a forensic tool for law enforcement agencies. PaleoResearch Institute is now among a handful of facilities in the world who are using the FTIR to identify archaeological food remains and organic components in sediments from archaeological sites. We have examined ceramics, nutting stones, and fill from fire features and have found the FTIR to be a practical, economic tool to identify di- and tri-glycerides from meat fats, nut oils, maize, and a variety of plants.
What questions can FTIR answer?
What foods were cooked in this vessel?
Fats, lipids and other residues are released from the vessel or sediment with a solvent (usually a high purity chloroform/methanol mixture). Fats are identifiable to plant or animal categories, as in lipid analysis, but frequently the spectra match specific plants in our database. Matches are based on the wave number, and to a degree, amplitude of the infrared absorbance.
What was processed with this tool?
Nut oils and residue from grinding and abrading surfaces can be extracted and compared to our libraries, frequently permitting the identification of the specific plant processed and sometimes the specific part of the plant processed.
What was processed in this feature?
Sediments and charcoal from cooking features, fire-cracked rock and sediments from living surfaces can be analyzed to identify feature use or use areas within a feature.
The sample should be taken from fill that includes cultural material, i.e., burned remains (but not the fuel layer). We have examined feature fills from several locations. For instance, a pit in northwestern Colorado yielded evidence of meat fat in the form of matches with mono- and diglycerides from meat.