Analysis of Modern and Ancient Artifacts for the Presence of Corn Beer; Dynamic Headspace Testing of Pottery Sherds from

  • PDF / 676,521 Bytes
  • 10 Pages / 612 x 792 pts (letter) Page_size
  • 70 Downloads / 184 Views




Analysis of Modern and Ancient Artifacts for the Presence of Corn Beer; Dynamic Headspace Testing of Pottery Sherds from Mexico and New Mexico Theodore Borek1, Curtis Mowry1, and Glenna Dean2 1 Materials Characterization, Sandia National Laboratories, 1515 Eubank Blvd. SE, MS 0886, Albuquerque, NM, 87123 2 Archeobotanical Services, PO Box 658, 21581 Hwy 84, Abiquiu, NM, 87510 Abstract A large volume-headspace apparatus that permits the heating of pottery fragments for direct analysis by gas chromatography/mass spectrometry (GC/MS) is described here. A series of fermented-corn beverages were produced in modern clay pots and the pots were analyzed to develop organic-species profiles for comparison with fragments of ancient pottery. Brewing pots from the Tarahumara of northern Mexico, a tribe that produces a corn-based fermented beverage, were also examined for volatile residues and the organic-species profiles were generated. Finally, organic species were generated from ancient potsherds from an archeological site and compared with the modern spectra. The datasets yielded similar organic species, many of which were identified by computer matching of the resulting mass spectra with the NIST mass spectral library. Additional analyses are now underway to highlight patterns of organic species common to all the spectra. This presentation demonstrates the utility of thermal desorption coupled with GC/MS for detecting fermentation residues in the fabric of unglazed archaeological ceramics after centuries of burial. Introduction This work was instigated by an inquiry to perform a spot analysis for furfural on pottery sherds.1 Since the spot test involves the use of hydrochloric acid, and we did not want use this potentially destructive test on historical specimens, an alternative analytical scheme that utilized dynamic large-volume headspace sampling was proposed. Dynamic large-volume headspace sampling with gas chromatographic separation with mass spectrometric identification, as used in our laboratory, is a technique that permits the collection of trace organic species from materials that are undergoing thermal treatment in an inert atmosphere. We have developed this technique because: 1. It does not utilize solvents; there is no need to be concerned with selectivity, dilution, or loss of analytes. 2. Ultimate temperature may be selected to minimize thermal stress on articles tested. 3. If necessary, further testing on the same article may be performed without too much concern for this method altering nonvolatile residues. 4. It is nondestructive to the article examined at the temperatures used here. A test specimen is placed in a heating apparatus that has been previously demonstrated to be free of organic species. The test specimen is then slowly heated in a flowing stream of filtered ultrahigh purity nitrogen, and the offgases collected using a cryogenically cooled, 3-trap environmental air sampling system (Entech Instruments, Simi Valley, CA). This system

removes most of the water and carbon dioxide from