Carbon-14 dating by liquid scintillation method with CO2 absorbed

This work examines the ages of sambaquis through their deposits of malacological material. Its main objective is to implement a methodology to determine 14C in carbonate by its acid etching breakdown, releasing CO2 absorbed in Carbo-Sorb®, forming carbamate, determined by liquid scintillation. The methodology consisted of absorbing an average of 0.60 g of carbon in 10 mL of Carbo-Sorb® and 10 mL more of Permafluor® as scintillation cocktail. A Packard TR-LSC 3170 liquid scintillation spectrometer was used and an elapsed time of 1,000 minutes was employed. Using glass vials, the background radiation was an average of 3.99 ± 0.16 cpm, the detection limit was 3.77 x 10-4Bq/gC, and the age reached under these conditions was 22,400 BP. The sambaqui samples used for dating were collected in archaeological sites located in the embayment of the Guanabara Bay, in the Municipality of Guapimirim, State of Rio de Janeiro: Sambaquis from Sernambetiba, Imenezes, Rio das Pedrinhas, Amorins and Arapuan The sambaquis ages varied from 2,110 ± 250 BP to 3,690 ± 280 BP when using the CO2 absorption method.