1,721,044 research outputs found
Il tenore di Calcio nei materiali geologici e biologici: un metodo preciso per la sua determinazione mediante analisi per attivazione neutronica strumentale
No full textNeutron activation analysis: a powerful tool for assay of rare-earth elements in terrestrial materials
No full textNeutron activation analysis methods for determination of rare-earth elements in different matrices have been developed at the University of Pavia using the 250 Kw TRIGA Mark II reactor. A critical review of both instrumental and destructive methods is presented, as well as the indication of the best working conditions for irradiation, counting and radiochemical separations. The optimized procedures were utilized in the determination of rare-earth elements in standard reference materials of both mineral and biological origin. The adopted radiochemical procedure is based on the separation of the rare-earth element group by fluoride precipitation.
Results, given as the average of six independent determinations and relative standard deviations, are reported and discussed. Precision of the methods can be deduced from the reproducibility of data, whereas accuracy is evaluated by comparison with existing values in the literature. Sensitivity limits under the described operational conditions are also reported, as are trends and correlations among data
Trace element distribution in soils and waste sludges: implications for agricultural purposes
No full textNeutron activation analysis: a powerful tool for rare-earth elements of assay in terrestrial materials
No full textRare-earth elements in the NBS Standard Reference Materials Spinach, Orchard Leaves, Pine Needles and Bovine Liver
No full textA highly sensitive radiochemical neutron activation method for the determination of all rare-earth elements (REE) in NBS biological reference materials is described. The materials are irradiated, dissolved in HF/HC1 solutions, mixed with scandium and REE carriers (except La, Pr, Nd, Dy, Er), and the resulting solutions evaporated to dryness. The residues are dissolved in HC1 and the REE precipitated as fluorides on addition of HF/NH4F solutions. The REE fluorides were collected, dissolved in a nitric/boric acid solution and the radioactivity of the resulting solutions determined by gamma spectrometry. The concentrations of REE in the NBS SRM Spinach, Orchard Leaves, Pine Needles, and Bovine Liver were found to be in the ng/g to fig/g range. The relative standard deviations are ~8%. The results agreed, within experimental errors, with literature values. The distribution patterns of REE in the NBS materials relative to chondritic meteorites resemble the patterns for geological materials
An accurate procedure for the determination of low levels of Iridium in standard reference materials by neutron activation analysis
No full textArchaeometric investigations by neutron activation analysis: the provenance of obsidian, marble and clay artefacts
No full textValutazione della rappresentatività di campioni di interesse archeologico mediante analisi per attivazione neutronica: applicazione a materiale ceramico
No full textAn accurate procedure for the determination of low levels of Iridium in Standard Reference Materials by neutron activation analysis
No full textThe 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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