Calcium trace data

The investigation of body fluids with respect to nutrient (essential) elements and toxic elements -which are challenging topics for analytical chemistry - include the determination of concentrations at the trace and ultratrace level. However, isotope variation and isotope effects (especially of lighter elements such as hydrogen, carbon, nitrogen, oxygen but also of iron and calcium) have also been studied.22 23 The most frequently applied mass spectrometric technique for the analysis of body fluids today, which fulfils all requirements and also results in accurate and precise data, is ICP-MS. 

Approximate contents of 14 minor and trace elements in oils produced from three coals by the catalytic hydrogenation process of Gulf Research and Development Co. were determined by emission spectroscopy. The results were compared with corresponding data for the original coals and the solid residues from the process. The contents of ash, sulfur, vanadium, lead, and copper are near or below the limits specified for an oil to be fired directly in a gas turbine while sodium and probably calcium are too high. Titanium appears to be somewhat enriched in the oils analyzed relative to other elements, suggesting its presence in organo-metallic complexes. 

Natural carbonate minerals do not form from pure solutions where the only components are water, calcium, and the carbonic acid system species. Because of the general phenomenon known as coprecipitation, at least trace amounts of all components present in the solution from which a carbonate mineral forms can be incorporated into the solid. Natural carbonates contain such coprecipitates in concentrations ranging from trace (e.g., heavy metals), to minor (e.g., Sr), to major (e.g., Mg). When the concentration of the coprecipitate reaches major (>1%) concentrations, it can significantly alter the chemical properties of the carbonate mineral, such as its solubility. The most important example of this mineral property in marine sediments is the magnesian calcites, which commonly contain in excess of 12 mole % Mg. The fact that natural carbonate minerals contain coprecipitates whose concentrations reflect the composition of the solution and conditions, such as temperature, under which their formation took place, means that there is potentially a large amount of information which can be obtained from the study of carbonate mineral composition. This type of information allied with stable isotope ratio data, which are influenced by many of the same environmental factors, has become a major area of study in carbonate geochemistry. 

On a brighter side, the model of Kretz (1982) for the partitioning of cations between calcite and dolomite has shown impressive correlations between observational data and predicted partition coefficients (see Table 3.2). He proposes, based on the earlier work of Jacobsen and Usdowski (1976), that different partition coefficients exist for a trace cation at Mg and Ca sites in dolomite, which are principally influenced by the size differences between the trace cation and calcium or magnesium. He has made a number of predictions of metal ion partition coefficients in dolomite. It will be interesting to see if future work bears them out. 

The effect of other electrolytes is also of interest. Addition of divalent cations, e.g., in the form of calcium and magnesium chloride salts, results in precipitation of the anionic vesicles, which is also observed for micelles in water. There is, however, a significant trend within the alkali metal cations, e.g., from Na+ to Rb+. The larger rubidium ion has a promotional effect on the formation of vesicles, and indeed with Cs+, vesicles are already formed on the addition of trace amounts of salt. The relevant data are shown in Fig. 19.8. 

In our studies, the model substance (montmorillonite) was a calcium bentonite (Istenmezeje, Hungary), the characteristic features of which are given here. X-ray diffraction (intensity of the basal reflection) and thermoanalytical (weight loss upon heating) data show 91% montmorillonite content. The other constituents are 5% calcite, 3% kaolinite, 1% x-ray amorphous silicates, and a trace of quartz. The amorphous phase is silicate particles, which are not crystalline for... 

Figure 13 Trace-element ratios in IDPs. Data from synehrotron X-ray fluoreseenee analyses are plotted on three element diagrams. Element ratios are normalized to bulk Cl abundances (element/Fe)sampie/(element/Fe)ci also denoted element/Fe/CL Cl eomposition lies at the point element/Fe/CI = 1 on eaeh plot. Averages, assuming data are normally distributed (open squares) and assuming the data are log normally distributed (open diamonds), are also shown. Plots (a)-(c) exhibit the behavior of some more refractory elements chromium, calcium, and titanium with respect to nickel, while (d) and (e) show the behavior of zine (relatively volatile) with respect to nickel (relatively refractory) and selenium (relatively volatile) (source Kehm et aL, 2002).

In every model for the composition of the upper-continental crust, major-element data are derived from averages of the composition of surface exposures (Table 1). Several surface-exposure studies have also provided estimates of the average composition of a number of trace elements (Table 2). For soluble elements that are fractionated during the weathering process (e.g., sodium, calcium, strontium, barium, etc.), this is the only way in which a reliable estimate of their abundances can be obtained. 

In a number of cases, data taken from earlier experiments were misrepresented in purporting to show effects in completely different circumstances, e.g. the traces showing changes in intracellular calcium concentration of pulmonary artery cells in response to ryanodyne and hypoxia were used again but claimed to show membrane potential changes in cerebral arterial myocytes induced by IP3 and heparin. 

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