Abstract Most of the carbonate samples have a basic well-defined pretreatment protocol for 14 C-AMS dating, but particularities of specific organisms have to be treated with care. This is the case of stromatolite samples, in which carbonate is formed by biogenesis and also has a porous structure that could contain recent organic material as a contaminant. In this work, we analyzed the differences in the radiocarbon content by using organic matter removals before chemical treatment with HCl: sodium hypochlorite (NaOCl) a 0.7M solution with pH ∼11, and hydrogen peroxide (H 2 O 2 ) an 8.8M solution with pH ∼5. These treatments were chosen because they are the most used in stromatolite samples for geochemical analysis. To compare the impact of the organic matter removal treatments in stromatolite samples we also processed them as regular carbonate samples for radiocarbon analysis, with no organic matter removal (control samples). X-ray diffraction and X-ray fluorescence have been used to obtain mineral and elemental characterization, respectively. H 2 O 2 could not influence the results of Mg-calcite concentrate samples. The use of NaOCl appears to have been effective in preserving more material than H 2 O 2 independent of the mineralogical composition of the stromatolite layers. The F 14 C results after HCl etching for Mg-calcite concentrated samples were similar to those without etching suggesting that the HCl etching does not impact the results in this case. The organic matter removal is more important than the etching procedure for stromatolite samples. NaOCl is more indicated to be used as chemical pretreatment for radiocarbon analysis purposes independent of the mineral matrix of samples.

M I Oliveira

C Carvalho

D Tremmel

C Silveira

A A Brito

F M Oliveira

V N Moreira

K Macario

L Bastos

M Moreira

R T Lopes

Radiocarbon

RADIOCARBON 的目的是发表关于 14C 和其他宇宙成因同位素的所有方面的技术和解释性文章。此外，我们还提供已发布和未发布日期的区域汇编以及解释性文本。除了三年一次的国际放射性碳会议论文集外，我们还偶尔出版关注特定主题的特刊。

The journal Radiocarbon aims to publish technical and interpretive articles on all aspects of 14C and other cosmogenic isotopes. Additionally, we provide regional compilations and interpretive texts, both published and unpublished. Besides the proceedings of the International Radiocarbon Conference, which occurs every three years, we occasionally publish special issues focused on specific topics.

《Radiocarbon》期刊旨在发表关于14C及其他宇宙成因同位素的技术性和解释性文章。此外，我们还提供已发布和未发布的区域汇编及解释性文本。除了每三年一次的国际放射性碳会议论文集外，我们还偶尔出版关注特定主题的特刊。

Category	Quartile
地球科学	3
地球科学, 地球化学与地球物理	3

Biogenic carbonate samples: Preliminary tests on chemical protocols for radiocarbon analysis

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Journal Info

Category	Quartile
GEOCHEMISTRY & GEOPHYSICS	2