1Department of Anthropology, University of Georgia, 2Center for Applied Isotope Studies, University of Georgia, 3Department of Anthropology, University of Central Florida, 4Department of Anatomy, Histology, and Anthropology, Vilnius University
April 16, 2020 , Platinum Ballroom
As the sensitivity of isotope ratio mass spectrometers (IRMS) increases and smaller amounts of sample are required for analysis, the need for homogenous samples increases. Here we compare bone collagen and carbonate sample replicate homogeneity prepared by mortar and pestle with and without liquid nitrogen, glass rod, and nothing. We compared stable isotope ratio variance and mean among preparation methods of collagen replicates from a single individual, which were analyzed on an EA-IRMS (n=12). Carbonate from a second individual was analyzed on a Gas Bench-IRMS with preconcentration (Precon, n=12) and Gas Bench-IRMS (n=6). There were no significant differences in carbon or nitrogen isotope ratio variance (p=0.28 and p=0.38), but there were significant differences in carbon and nitrogen isotope ratio means (p=5.25e-5 and p=6.68e-4) for EA-IRMS. There were no significant differences in carbon variance for Precon or Gas Bench-IRMS (p=0.24 and p=0.28), but there were significant differences in carbon ratio means (p=8.57e-8 and p=1.25e-4). There were significant differences in stable oxygen isotope ratio variance for Precon and Gas Bench-IRMS (p=2.2e-16 and p=6.22e-10). Although there were significant differences in mean carbon and nitrogen ratios for all IRMS in this study, these differences fall within the range of error for the machine and may not be caused by preparation method. Differences in oxygen isotope ratio variance indicate that replicates where nothing was done were not homogenous. These results suggest that any method of homogenization is sufficient for isotopic analysis of bone.