The use of microwave digestion method for the determination of chemical forms of sodium and chloride ions in seashell structures

Takenaka, Miyuki; Ikeda, Masafumi; Terada, Shinichi

doi:10.1039/a809486a

Cited by 4 publications

(3 citation statements)

References 10 publications

(8 reference statements)

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“…The diameters of the pores are up to 10 m. The nonchalky layers seem to have smooth surfaces and higher densities. 11 EDS analysis indicates that the chemical composition of the oyster shell is mainly composed of C, O, and Ca, as expected. The stoichiometric amount of C, O, and Ca is equivalent to calcium carbonate ͑CaCO 3 ͒.…”

Section: Resultssupporting

confidence: 79%

Electrolyte Conductivity Through the Shell of the Eastern Oyster Using a Four-Electrode Measurement

Yoon¹,

Mount

Hansen

et al. 2009

J. Electrochem. Soc.

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The bioceramic shell of the Eastern oyster was investigated to determine its physical and chemical compositions. Resistance and electrolyte conductivity measurements through the shell using a four-electrode cell configuration were made. The scanning electron microscopy/energy-dispersive spectroscopy analysis of oyster shell cross sections revealed that this multilayered biocomposite material is composed of numerous incongruent “chalky” and “nonchalky” layers, each containing similar chemical elements but having different overall chemical compositions and porosities, with the chalky layers being quite porous and voluminous, whereas the nonchalky layers appear to be nonporous, more dense, and compact. The electrolyte conductivity within the pores of the shell was dependent on the ionic concentration of the electrolyte, suggesting that the tortuosity across the shell material via the various chalky and nonchalky layers has an effect on the transport of ions. Rather, consideration of the data in terms of the space charge model indicates that the surface charges within the porous biocomposite facilitate the conduction of ions, much like a ceramic membrane. These findings suggest that the oyster shell may function not only as a protective physical structure, but also as a ceramic membrane allowing for the exchange of ions from the external environment.

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Section: Resultssupporting

confidence: 79%

Electrolyte Conductivity Through the Shell of the Eastern Oyster Using a Four-Electrode Measurement

Yoon¹,

Mount

Hansen

et al. 2009

J. Electrochem. Soc.

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“…The density separation of marine carbonates was first described by Takenaka et al (1999) who applied it to the separation of calcite and aragonite from bimodal species (containing both aragonite and calcite) as a preparation step for the determination of the chemical forms of Na and Cl ions in marine shell structures. Later, Henderson et al (2000Henderson et al ( , 2001 used it for the separation of carbonate minerals of marine origin during U-series dating of beach slopes and platforms.…”

Section: Carbonate Density Separation (Cards): a New Approachmentioning

confidence: 99%

Improved AMS¹⁴C Dating of Shell Carbonates Using High-Precision X-Ray Diffraction and a Novel Density Separation Protocol (Cards)

2010

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ABSTRACT. One critical variable in the successful application of radiocarbon dating is the effective removal of carbonaceous contaminants. In the case of marine carbonates, contamination appears usually in the form of secondary low-magnesium calcite, the stable polymorph of calcium carbonate and byproduct of the post-mortem recrystallization or replacement of the autochthonous phase, originally in the form of high-magnesium calcite or aragonite. Depending on the nature of the depositional environment, the secondary phase may be contemporary in age with the original shell carbonate and may have even been derived from it by dissolution-recrystallization processes, or can be an exogenous contaminant of younger or older age. The limited ability of current pretreatment protocols to detect and remove the secondary mineralogical phases prior to dating carbonates has been one of the reasons marine shell and coral 14 C determinations are often difficult to validate in terms of their reliability. We have developed a new pretreatment protocol designed to achieve greater reliability and accuracy in the dating of this material. The method entails 2 steps. The first one involves the improved detection and quantification of secondary calcite in aragonite using X-ray diffraction, at a precision of ~0.1% and ~0.8%, respectively. Next, where this is required, a novel density separation step using non-toxic heavy liquids (CarDS) is applied to the diagenetic sample. This enables the clear separation of calcite and aragonite, with only the latter kept for dating. We have applied the new steps, screening and separation, on standard and archaeological examples and our initial results suggest that it is successful and reproducible. In this paper, we describe the method and initial results.

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“…While density fractionation has never been reported as a 14 C pretreatment method for shells, it has been used for marine sediments (Henderson et al 2001) and shells (Takenaka et al 1999) in other applications. A similar approach has been taken for fractionating bone osteones by density (Bell et al 2001;Shin 2007) The present method has been applied to ancient molluscan shells that have potentially undergone recrystallization so that their 14 C ages may be determined more accurately than before.…”

Section: Introductionmentioning

confidence: 99%

A New Radiocarbon Pretreatment Method for Molluscan Shell Using Density Fractionation of Carbonates in Bromoform

et al. 2010

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ABSTRACT. Coastal archaeological sites that lack organic remains for radiocarbon dating are often abundant sources of molluscan shells. As a substitute for materials such as bone and charcoal, shells can be analyzed with 14 C dating to determine a site's age. Despite their being convenient, non-mobile archaeological artifacts, molluscan shells are plagued by several issues, including carbonate remodeling, in which aragonite in shells is converted to calcite as predicted by thermodynamics. We present here a carbonate density separation technique that addresses the issue of carbonate remodeling. Using a density fractionation with bromoform, aragonite concentrations are enriched in shells that have undergone significant remodeling. The technique has been applied to archaeological shells and has returned dates that are younger than those previously determined for the same shells.

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The use of microwave digestion method for the determination of chemical forms of sodium and chloride ions in seashell structures

Cited by 4 publications

References 10 publications

Electrolyte Conductivity Through the Shell of the Eastern Oyster Using a Four-Electrode Measurement

Electrolyte Conductivity Through the Shell of the Eastern Oyster Using a Four-Electrode Measurement

Improved AMS¹⁴C Dating of Shell Carbonates Using High-Precision X-Ray Diffraction and a Novel Density Separation Protocol (Cards)

A New Radiocarbon Pretreatment Method for Molluscan Shell Using Density Fractionation of Carbonates in Bromoform

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The use of microwave digestion method for the determination of chemical forms of sodium and chloride ions in seashell structures

Cited by 4 publications

References 10 publications

Electrolyte Conductivity Through the Shell of the Eastern Oyster Using a Four-Electrode Measurement

Electrolyte Conductivity Through the Shell of the Eastern Oyster Using a Four-Electrode Measurement

Improved AMS14C Dating of Shell Carbonates Using High-Precision X-Ray Diffraction and a Novel Density Separation Protocol (Cards)

A New Radiocarbon Pretreatment Method for Molluscan Shell Using Density Fractionation of Carbonates in Bromoform

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Improved AMS¹⁴C Dating of Shell Carbonates Using High-Precision X-Ray Diffraction and a Novel Density Separation Protocol (Cards)