Radiocarbon Laboratory at the National Autonomous University of Mexico: First Set of Samples and New ¹⁴C Internal Reference Material

Abstract

ABSTRACT. This contribution reports the first set of samples and the creation of an internal reference material at the recently opened Radiocarbon Laboratory at the National Autonomous University of Mexico (UNAM). Samples for the initial measurements were selected from archaeological and dating projects on Teotihuacán, one of the largest and best-studied Mesoamerican urban and ceremonial centers. The 14 C dates were compared to results obtained by 2 other laboratories in order to assess the results obtained at UNAM and validate the adopted methodology. As part of the quality assurance protocol, an internal reference material was created that consists of charred wood from the Teotihuacán site with a 14 C activity in the value range expected for samples from Mesoamerican archaeological sites. Results from 7 analyses have a mean of 1750 ± 16 BP (80.43 ± 0.16 pMC).

Thermal history of the Acoculco geothermal system, eastern Mexico: Insights from numerical modeling and radiocarbon dating

“…Four soil samples and one charcoal sample were dated at the Laboratorio Universitario de Radiocarbono, Universidad Nacional Autónoma de México (UNAM) by liquid scintillation spectrometry, following standard procedures reported in detail in Beramendi-Orosco et al (2006). Sample descriptions and provenance are provided in Table 3.…”

Dendrochronological Potential of Fraxinus uhdei and Its Use as Bioindicator of Fossil CO2 Emissions Deduced from Radiocarbon Concentrations in Tree Rings

“…Prior to analysis, samples were transformed to benzene (1.5 mL) in a vacuum synthesis line and mixed with 0.5 mL of scintillation cocktail (2,5-diphenyloxazole [PPO] + 1,4-Bis(5-phenyl-2-oxazolyl)benzene [POPOP] dissolved in dead spectrophotometric-grade benzene) in 3-mL Teflon ® vials. Analysis was performed in a Quantulus™ 1220 ultra-low level liquid scintillation spectrometer as detailed elsewhere (Beramendi-Orosco et al 2006). Each sample was analyzed for 2500 min, distributed in 50 cycles, alternating sample vials with oxalic acid SRM 4990C standard and background vials.…”

Method validation for the determination of fraction of modern (F¹⁴C) in wood samples using conventional method

“…Conventional method for benzene synthesis was used (Barker, 1953;Tamers, 1975). This method was widely applied in large number of laboratories and by many scientists (Beramendi-Orosco et al, 2006;Mazeika et al, 2008). The standard method consists of the following essential steps (Edler, 2009; ASTM, 2011): 1) lithium carbide production, 2) acetylene production, 3) trimerization of acetylene to transform it to benzene.…”