Calcium isotopes exchange

Russell WA, Papanastassiou DA (1978a) Calcium isotope fractionation in ion-exchange chromatography. Anal Chem 50 1151-1153... 

Figure 6 Oxygen-isotopic compositions of individual minerals in CAIs from the CO chondrites Y-81020, Colony, Kainsaz and Ornans. Primary minerals in CAIs from the least metamoprhosed CO chondrites Y-81020 (type 3.0) and Colony (3.0) are uniformly 0-enriched, whereas CAIs from Kainsaz (3.2) and Omans (3.3) tend to show oxygen isotopic heterogeneity with spinel and high-calcium pyroxene enriched in 0 and melilite and secondary nepheline depleted in 0. Based on these observations, Wasson et al (2001) inferred that oxygen isotope exchange took place during thermal metamorphism and alteration in an asteroid (data from Itoh et al, 2000 Wasson et al, 2001).

The temperature dependence of equilibrium isotope exchange in the calcite-water system has been intensively studied since Urey (1947) first suggested that the paleotemperature of the ancient oceans could be estimated by the 0-isotope distribution between seawater and the calcium carbonate precipitated from it. Urey et al. (1951) argued that O-isotope equilibrium between seawater and CaC03 was likely and support for this idea has come from the close agreement between the CaC03-H20 isotopic fractionation observed in natural systems and those derived from both thermodynamic calculations and laboratory experiments (e.g. Epstein et al., 1951, 1953 Emiliani, 1955 O Neil et al., 1969 O Neil et al., 1975). 

The investigation of isotopic separations in systems with cyclic polyethers has been carried out up to now for the elements lithium, calcium and sodium, in particular. Among these elements, the enrichment of Li is of essential importance for the production of tritium and that of the heavy calcium isotopes for medical labeling experiments. An enrichment aspect does not exist for the monoisotopic element sodium. Investigations with the radioactive nuclides Na and Na are obviously of interest for fundamental investigations because these isotopes can be easily and precisely measured by their y-activity. Except for uranium, most of the investigations on other chemical exchange systems with metal ions are also based on measurements with lithium and calcium, respectively. 

Heumann, K. G., Schiefer, H.-P., Spiess, W. Enrichment of Heavy Calcium Isotopes by Ion Exchanger Resins with Cyclopolyethers as Anchor Groups, in Stable Isotopes, Schmidt, H.-L., Forstel, H., Heinzinger, K. (eds.), Elsevier, Amsterdam 1982... 

The method was tested by Kobayashi, Fujii, and Okamoto in 1982 for the separation of X = calcium isotopes on a cation-exchange column with Y = lithium ions. The heavier calcium isotopes, " Ca, " Ca, and " Ca, were enriched at the... 

Hendry, G., Wydrzynski, T. (2003) 0 Isotope Exchange Measurements Reveal that Calcium Is Involved in the Binding of One Substrate-Water Molecule to the Oxygen-evolving Complex in Photosystem II. Biochemistry 42 6209-6217. 

The first carbonate/water paleotemperature scale was based on the fact that the isotopic composition of oxygen from calcium carbonate differs fi-om that of the water and depends on the temperature when the carbonate in question is precipitated under equilibrium conditions. This difference arises from an isotope-exchange reaction that can be represented by the... 

Weaver, C. and Heaney, R. (1991) Isotopic exchange of ingested calcium between labeled sources. Evidence that ingested calcium does not form a common absorptive pool. Calcif. Tissue Int., 49, 244-247. 

To determine how the degree of exchange between an extrinsic isotope and the intrinsic calcium in the food or meal is affected by the method of incorporating the isotope, the calcium source itself or foods fed with it. 

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