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  • Author or Editor: S. Meloni x
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Abstract  

Two methods have been developed for the determination of platinum group elements (PGEs) and gold in four geological reference materials: one using radiochemical neutron activation analysis and the other using nickel sulphide fire assay, followed by instrumental neutron activation analysis. The results from ten multiplicate measurements have been discussed in terms of precision and accuracy. The average precision for both methods is about 5%. Comparing the reported data with existing values in the literature, the accuracy of the proposed methods is good agreement in most cases. Detection limits in the range 0.001–0.015 ng have been derived for both methods under the operational conditions.

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Abstract  

The paper describes a destructive neutron activation procedure for the determination of all platinum group elements (PGE). Only a few steps are required after irradiation, namely sample dissolution, osmium and ruthenium separation by solvent extraction, anion exchange separation of remaining noble metals and counting. The chemical yield is evaluated. The method has been used for the determination of noble metals in a large variety of standard reference materials, mainly of geological and technological origin. The results, given as the average of four independent analyses are reported and discussed. Average precision for the whole procedure is usually below 8% and sensitivities are adequate to meet the analysis requirements of terrestrial PGE- and Au-poor materials.

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Abstract  

The paper describes a destructive neutron activation procedure especially set up for the determination of low levels of iridium. Only a few steps are required after irradiation, namely sample dissolution, noble metals adsorption on an ion-exchange column, removal of interfering radionuclides and counting. Successively iridium is removed from the column and the chemical yield evaluated. The method has been used for the determination of iridium in a large variety of standard reference materials, including materials of geological, biological and technological origin, with iridium levels ranging from about 0.005 to 18 ng/g. Results, given as the average of three or more independent analyses, and relative standard deviations, are reported and discussed. Average precision is about 8%, and the sensitivity is 0.004 ng.

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Abstract  

The dietetic contribution of some bioelements, namely sodium, potassium, chromium, manganese, copper, zinc, bromine and lanthanum from rice grains was investigated by destructive neutron activation analysis. Three different species of rice grains, all grown in the Po river valley, were studied on account of different industrial treatments they had been submitted to. Radiochemical separations were carried out by means of inorganic adsorbers such as hydrated antimony pentoxide, metallic cadmium, tin dioxide and manganese dioxide. Results are presented and discussed. Precision and accuracy of the method is discussed as well. A depletion of the mineral content of the rice grains related to the different industrial treatments was established together with an enrichment of bromine in the treated grains.

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Abstract  

Marble samples from major Italian quarries and from the Como Cathedral were analyzed for their trace element content, which is indicative of their provenance. Ca, Sc, Cr, Mn, Fe, Co, Rb, Sb, Cs, Ba, La, Ce, Sm, Eu, Gd, Ho, Tm, Yb, Lu, Hf, Th and U elements were determined by neutron activation analysis. Results as well as their precision and accuracy are presented and discussed. Data treatment has allowed to characterize the marble quarries on the basis of their trace element content, to identify the provenance of the marble used in the Como Cathedral and to show differences in the element distribution of new and weathered marble samples from the same quarry.

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Abstract  

Recently excavated roman amphorae were submitted to instrumental neutron activation analysis for the determination of Ca, Sc, Cr, Fe, Co, Sb, Ba, La, Ce, Eu, Yb, Lu, Hf and Th. Data reduction was carried out by identifying first the elements useful for discrimination purposes and then by submitting the data to cluster analysis. Amphorae are parted in two groups which are related to different provenance areas.

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Abstract  

Obsidians from occurrences located in Armenia have been analysed using neutron activation analysis, both instrumental and epithermal, in order to enhance the knowledge of characteristics of potential sources of raw material exploited during prehistory. An alternative characterization technique, the fission-track dating method, was also applied. Results contribute to increase the data-set for provenance studies of prehistoric obsidian artifacts in the Mediterranean and adjacent regions.

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Abstract  

Part of a research program on cultural heritage aimed to elucidate the production of ceramic artifacts in Roman Pavia is devoted to the localization of the possible sources of raw materials (claypits) as well as to the technological production processes. Clay samples were collected in two different areas nearby Pavia, Lomellina and Oltrepo. Some of these samples were also fired at 950 °C. Archaeological ceramic samples, mostly bricks and tiles of Roman age, were obtained from excavations of Roman settlings close to Pavia. All samples were submitted to instrumental neutron activation analysis for the determination of Ca, Fe and a number of trace elements. Results indicate (1) fired and raw clay samples keep the same elemental fingerprint so that only raw samples data can be used in archaeometric studies; (2) some parameters based on rare earth elements are useful to discriminate the clay samples from the two investigated areas; (3) clay discrimination is confirmed also by discriminant analysis; and (4) the insertion of the elemental composition data of the ceramic artifacts in the statistical treatment allows one to assign the artifacts to one of the investigated areas and confirms that, at Roman times, the production of ceramic building materials was mostly based on the use of local prime matter.

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Abstract  

The interactions between titanium dioxide, niobium pentoxide and tantalum pentoxide and 55 elements have been studied by batch experiments in nitric acid. The variation of the distribution ccefficients with nitric acid concentration is presented and discussed. The adsorption mechanism for some ions has also been investigated. Column experiments have been carried out to check the practical use of the investigated oxides in radiochemical separations. A99mTc generator based on the use of TiO2 is also presented.

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Abstract  

A neutron activation analysis method for the determination of uranium in natural fresh waters is described. The method is based on a preconcentration step by precipitation of the metal oxinate on a phenolphtalein bed followed by instrumental neutron activation analysis. Preliminary investigations with239U radiotracer were carried cut to set up the best working conditions and to evaluate the chemical yield. The whole procedure has been applied to the determination of uranium in river water.

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