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Authors: Begoña Quintana 1, María Zurrón 1, David Borrego-Alonso 1, Nuria Navarro 2, Eduardo García-Toraño 2
Affiliation: 1 Universidad de Salamanca, Spain, 2 CIEMAT, Spain.
14C dating of actual marine records as shells gives an essential insight in the CO2 Ocean intake, which has a crucial impact on the greenhouse effect and, therefore, in the global climate change. Shells are mainly composed by carbonates, which requires a chemical carbon extraction process that synthetizes benzene, highly immiscible, when low-level-background liquid scintillation counting (LSC) is used to determine 14C. However, 14C standard solutions are not easily available. At that point, a primary radiometric method as CIEMAT/NIST solve this drawback and, at the same time, gives us the advantage of avoiding the use of a secondary standard.
In this work, the CIEMAT/NIST method has been upgraded to deal with this type of samples, which requires to be measured Butyl-PBD as primary scintillator in benzene solution. The theoretical efficiency calculation made by the last version EFFY8 software has been performed for the specific sample vial composition, including now in EFFY8 the new solute as well as primary and secondary scintillators. The method has been successfully tuned in the [100, 0.01] Bq 14C activity range using an ultra-low-level background LSC device, model Quantulus 1220TM by Perkin Elmer. Validation has been performed in the CIEMAT metrology laboratory.
