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  • Author or Editor: F. Girardi x
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Abstract  

The development and applications of activation analysis in the period 1945–1980 are reviewed. In analysing the number of publications reported with time three periods can be distinguished: (a) A first period of slow development, up to 1960, in which the technique showed its very high sensitivity and demonstrated the importance of trace elements; (b) A second period of fast development (1960–1970) in which all aspects of the technique were developed; (c) A third period (after 1970) in which development occurred at a rate approximately equal to the average development rate of analytical chemistry, in terms of the number of publications reported. The present trends shows only minor developments in the methodology, while a good a potential for new and original applications is evident. The importance of a good scientific knowledge of the specific areas of applications is considered necessary to properly frame the analytical activities.

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Abstract  

A destructive method for the measurement of impurities in high purity zinc by neutron activation analysis is described. It essentially uses organic resins and inorganic exchangers for the separations. Sensitivities at the ppb level are obtained for a high number of elements.

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Abstract  

A new method is presented to remove sodium interferences from neutron-activated materials. The method is based on passage of the samples, dissolved in a concentrated acid solution on a column of hydrated antimony pentoxide (HAP). The retention is quantitative with a maximum capacity of 31 mg Na/g HAP. Only tantalum, in addition to sodium, was retained by HAP out of the 60 elements tested. The method should find applications in neutron activation analysis, particularly of biological materials. Applications are also foreseen in other analytical techniques, such as emission spectroscopy and flame spectrophotometry, where high sodium concentrations in the sample can be a source of interference.

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Résumé  

Cet article traite de l'utilisation d'échangeurs minéraux dans l'analyse destructive de matériaux de grande pureté, en particulier pour la détermination systématique d'un grand nombre d'éléments. On indique brièvement des améliorations récentes dans la méthode permettant d'évaleur mathématiquement les modes de séparation radiochimique à l'aide des échangeurs minéraux. On décrit les modes de séparation dans le cas du dosage des impuretés dans de l'aluminium et du zinc de haute pureté. Les résultats pour plusieurs échantillons de zinc obtenus par purifications successives sont donnés, ces résultats mettent en évidence l'évolution de la distribution des différentes impuretés. On présente aussi les résultats obtenus dans le cas d'un échantillon de zinc choisi comme étalon.

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Abstract  

The retention of different radio-ions on columns of eleven ionic precipitates from different acid media was studied, in view of possible applications for radiochemical separations. The results of about 2,000 adsorption experiments, carried out in a standardized way, are presented schematically in periodic tables.

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Abstract  

The behaviour of 66 radio-ions towards 11 exchangers and 11 solutions under standardized experimental conditions has been evaluated and classified in order to have the possibility of a rapid assessment of radiochemical separation procedures. Two systems of utilizing the bulk of data obtained have been devised and employed. The first is based on the use of a deck of cards similar to those used for fast retrieval of bibliographic information, in which the behaviour of ions is coded by means of punched holes; the second is based on the treatment of the data by means of an electronic computer. The operational modes of the two systems and examples of their practical applications are presented.

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Abstract  

The presence of large quantities of32P in neutron activated biological specimens is often a limiting factor in the direct application of γ-ray spectroscopy. A technique for the selective removal of phosphates in neutron activated specimens is described. The technique is based on the adsorption of phosphates on chromatographic grade alumina. The adsorption selectivity was studied by determining the behaviour of 49 ions when submitted to the procedure for phosphate removal. A few applications are reported as examples.

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Abstract  

A method of neutron activation analysis is described for the quantitative determination of phosporus in nucleic acids, nucleotides and glucose-6-phosphate in amounts of 0.1 to 200 μg, without any chemical separation. This technique may be usefully applied to the measurement of the phosporus content in organic materials and biochemical preparations. The procedure involves a short neutron activation in a nuclear reactor and measurement of the Cerenkov radiation emitted by the irradiated capsule after a suitable decay period. Possible interferences due to other induced radionuclides are discussed.

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Abstract  

Cerenkov counting efficiencies for a large number of radionuclides formed by (n, γ) reactions and used in the field of activation analysis have been obtained by two different experimental procedures. A comparison between the Cerenkov counting technique and scintillation low-resolution gamma-ray spectrometry is also presented. Results are summarized in tables and briefly discussed.

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Abstract  

Three different computer systems for gamma-spectrometric data-handling have been developed at the Joint Nuclear Research Center of Ispra. The systems are: (1) batchwise treatment of the data with a large computer, (2) time-shared teleprocessing by means of a centralised computer, (3) use of a small computer at the laboratory site. The paper describes both hardware and software of the three systems with emphasis on their practical use and on advantages and disadvantages in routine application. A partial analysis of the running costs of the systems is also presented.

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