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Abstract  

Polonium-210 in phosphoric acid has been recognized as a significant source of alpha contamination of processed Si-wafers for memory devices of computer. In the present work, a convenient method was developed for the determination of trace210Po in phosphoric acid of high purity. For the determination,209Po was used as a yield tracer. The present method consists of (1) addition of the tracer to 5 ml aliquot of phosphoric acid sample, (2) pH adjustment (to 2) of the sample solution to make up electrolytic solution, (3) electrodeposition for the simultaneous achievement of Po separation and preparation of counting source on stainless-steel disc, and (4) alpha-ray spectrometry. By the developed method, more than 95% of Po was separated from phosphoric acid sample onto counting disc. The minimum detectable radioactivity of210Po in 5 ml of phosphoric acid was about 0.03 mBq by counting the electrodeposited alpha-activity for 10 days under a counting efficiency of ≈30%.

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Abstract  

Elemental concentrations in Japanese medaka and mosquitofish collected from uncontaminated rivers in Kumamoto, Japan were analyzed by instrumental neutron activation analysis with k 0 standardization method to know the background levels. A statistical analysis indicated the difference in metal concentrations among rivers and species. Background levels of elemental concentrations in some aquatic insect larvae were analyzed and metal concentrations were different among species, though they were collected at the same point. Enrichment factors of heavy metals in insect larvae were in the order of 103−104 suggesting effectiveness of insect larvae as bioindicator.

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Abstract  

Instrumental neutron activation analysis was applied to the determination of trace impurity elements in a silicon single crystal. Impurity concentrations in polysilicon melt were compared with those in a single crystal. Impurity concentrations in artificial quartz were also compared with those in natural quartz. Segregation coefficients in Au, Ir and Sb were determined at different concentrations. The segregation coefficient of an element in a silicon single crystal is constant over a critical concentration, it becomes larger gradually under the critical one, and at last it becomes larger than 1.

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Abstract

Fluorous multi-phase bromination reaction of alkenes could be successfully transformed to a continuous microflow system in which a fluorous polyether, Galden® HT135, is employed as a recyclable molecular bromine support. This microflow bromination of alkenes could be carried out without any temperature control or an inert gas atmosphere. The circulatory continuous microflow reaction system for bromination of cyclohexene was created which gave 8.3 g (85%) of dibromocyclohexane after continuous operation for 6 h.

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Abstract  

Neutron activation analysis was applied to the determination of trace impurity elements in a silicon ingot. Detection limits of 36 elements were calculated semi — empirically and compared with minimum concentrations detected in a silicon single crystal. The sources of the impurities were estimated from element concentrations detected in polycrystalline silicon and a quartz crucible. Segregation coefficients were determined from the concentration curves in a single crystal and discussed by comparing with reported values.

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Abstract  

A highly sensitive determination of fluorine in standard rocks by photon activation using the19F(,n)18F reaction combined with pyrohydrolysis for the separation of18F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and18F is also produced from Na via23Na(,n)18F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF3 precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 g/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: H. Hori, K. Kadono, K. Fukuda, H. Inoue, T. Shirai, and E. Fluck

Abstract  

/Pyropheophytinato a/ iron/III/ chloride [Fe/Pyropheo-a/Cl] and /pyropheophytinato b/ iron/III/ chloride [Fe/Pyropheo-b/Cl] have been prepared and characterized by Mössbauer spectroscopy. The Mössbauer parameters of the iron/III/pyropheophytins are similar to those of iron/III/ porphyrins. A comparison of the quadrupole splittings for the iron/III/ pyropheophytins with those for the iron/III/ pheophytins suggests that the deviations of the cyclopentenone ring and the saturated pyrrole ring from the macrocyclic plane become smaller with the removal of the methoxycarbonyl group.

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