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- Author or Editor: K. Sakamoto x
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Abstract
Terrestrial zircon and apatite, as examples of uranium rich refractory minerals, and chromite, also highly refractory but uranium poor, were neutron-irradiated for their133Xe release studies. Uranium determination by133Xe was found not to be successful in these refractory samples, due to incomplete fissiogenic-xenon release at 1600°C as revealed by stepwise heating experiment. The high temperature release peaks appeared at ≾1500°C in these terrestrial minerals studied, but at 1000∼1200°C in reported meteoritic whitlockite and chromite.
Abstract
Substoichiometric isotope dilution analysis for the determination of trace iron has been studied by using synergistic extraction of iron(III) with a substoichiometric amount of 4-isopropyltropolone (Hipt) in the presence of an excess of 3,5-dichlorophenol (DCP) in heptane. Optimum conditions for the substoichiometric extraction of iron(III) in 
g to sub-g levels were examined and the high selectivity for iron(III) toward various metal ions encountered in the analysis of biological materials was confirmed. The present method was applied to a biological reference material (NIES, CRM No.9, sargasso) without any pre-separation and was successfully evaluated. Furthermore, substoichiometric stable isotope dilution mass spectrometry using the present extraction method was also used with the above sample. Applicability and practicability was compared for both substoichiometric methods.
Abstract
Reversed-phase extraction chromatography employing a Daiflon-supported HDEHP column and HCl as eluent was examined for carrier-free separation of167Tm from a photo-irradiated Yb target and also from particle-bombarded Er and Ho targets. The examination was performed with radioassays of radioactive Tm and Yb tracers and57Co-
-induced X-ray analysis of Er and Ho. An example of the separation of about 1 mCi of167Tm from a 100 mg irradiated Yb target enriched in168Yb and a procedure for the final preparation for medical use are described. The YbSO4 precipitation could be combined with this chromatographic separation of167Tm from a more massive Yb target of natural abundance, weighing several tens of grams. A procedure for YbSO4 precipitation is also presented in the Appendix.
Abstract
Thirty samples from a limestone stratum across the Pemian-Triassic (P-Tr) boundary layer in China were analyzed for 30 elements by instrumental neutron activation analysis, wavelength dispersive X-ray fluorescence and ICP-MS, and also for mineral compositions with a powder X-ray diffractometer. The depth profile was found to indicate a sudden change of elemental and mineral compositions across the P-Tr boundary. Also the profile showed severa peaks in elemental concentrations in the lower Permian layered samples as well as in the overlying Triassic strata, which are associated with the change of mineral compositions. Elemental profiles were found to be classified into 4 groups and to give some insights in the geochemical records. Ir is far less abundant (0.1 ppt) compared with that of the K-T boundaries (10 ppb), and the Ir/Co ratio is outside the K-T and Cl chondrite trends. This change of elementary profile is suggestive of the internal causes rather than the external ones such as an asteroid impact for the mass extinction at the P-Tr boundary.
Abstract
Uranium concentrations in three types of inclusions of the Allende (C III), a bulk sample of the Plainview (H5), and a bulk and 5 to 15 density separates of the Huckitta pallasite were determined and discussed by comparing the results from homogenized fission track and/or239Np analyses with the133Xe results. Stepwise heating experiment revealed that the133Xe release from the Plainview is bimordal and incomplete by a simple heating at 1600 °C, and that the133Xe releases in the Huckitta bulk and metallic samples are multitudinous but can be extracted rather completely at 1600–1700 °C. In the Huckitta, uranium-rich phase (∼100 ppb) was in the lightest density fraction of d=2.9–3.3, but the bulk uranium was found to be mostly from the heavy metal-rich fraction of d>4.2.
Abstract
The synthesis of [γ-32P]ATP with high specific radioactivity was investigated by the enzymatic method. We utilized a part of the glycolytic pathway which consists of three reaction steps. First, we examined the maximum radioactivity of H3 32PO4 without the decrease of labeling yield. Next, we examined the minimum amount of reagent without the decrease of labeling yield, because some reagents contain the phosphorus species as impurity. In this paper, we propose the optimum condition for synthesis of [γ-32P]ATP with high specific radioactivity. As our calculation, we will be able to obtain about 220 TBq/mmol specific radioactivity using 1.5 GBq of H3 32PO4.
Abstract
A novel analytical method, the substoichiometric isotope dilution mass spectrometry (SIDMS) has been proposed. This method consists of the substoichiometric separation of the element in question and the subsequent intensity measurement of a stable isotope of the element with a mass spectrometer. In SIDMS, the correction of the mass discrimination of isotope measurement is not necessary and the use of expensive enriched stable isotopes may be avoided. The validity and the usefulness of SIDMS are demonstrated by the substoichiometric extraction of iron(III) with 4-isopropyltropolone and 3,5-dichlorophenol following microwave-induced plasma mass spectrometry.
Abstract
Samples of an andesite (Asama-yama, Japan) and a basalt (Kilauea, Hawaii) were finely fractioned by density and the U distributions among the separates were determined by homogenized fission track method. Groundmass was found to be enriched with U; one half of the andesite U and almost all of the basalt U are accounted for by the groundmass U. Cerium and other REE are correlated with U. In the andesite separates Na is accompanied by these elements, but Fe and Co are rather anticorrelated. Uranium concentrations in the bulk samples and some of the separates were then compared with those determined by133Xe extracted by heating at 1600°C. Fissiogenic133Xe seems to become labile in groundmass, especially of the andesite, during reactor irradiations for 5 h or more. Stepwise heating experiments suggested that133Xe in U-rich groundmass tends to escape at low temperatures and the remaining133Xe is mostly retained in highly refractory sites in phenocryst rather poor in U.
Abstract
INAA, RNAA and IPAA were employed to determine upto 26 trace elements in 32 spices of 18 species and 16 pulses of 8 species originating from different localities. The results are compared with each other and the reported values. The concentration levels, their variations and the correlations of the analysed elements in these samples were also investigated. The variability of concentrations among the samples of different origin are small. The levels and ranges of the concentration are highly variable which are found to be characteristic to each element. High elemental correlations exist in some sets of elements, reflecting characteristics of chemical nature of elements and/or of their physiological functions.
