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  • Author or Editor: G. Revel x
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Abstract  

A method is described for the determination of carbon in iron, chromium, nickel, and molybdenum, using the12C (γ, n)11C reaction. The samples are irradiated with the bremstrahlung from a 35 MeV electron beam impinging a platinum target. Two apparatuses for the separation of carbon are described. The11C* activity of the sample is compared with the activities of two graphite standards, counting the positron annihilation gamma rays. The limit of detection is 0.02 μg/g of carbon in high-purity iron.

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Résumé  

L'irradiation neutronique produit à partir du cérium une radioactivité importante, aussi des séparations chimiques sont indispensables. Nous avons mis au point une méthode d'échange d'ions en milieu tartrique, et nous dosons ainsi une vingtaine d'éléments. L'emploi d'un détecteur à jonction Ge−Li permet de simplifier notablement ces séparations.

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Abstract  

The advantages and drawbacks of using instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS) for soil, sediment, plant and water pollution studies are discussed. The experimental procedures used for each method and for each type of sample matrix are described. They were tested on several certified reference materials. The results obtained on these materials showed good agreement for many elements for which the two techniques are suited, and they were complementary for the other elements which are also of environmental interest. An element-by-element assessment is presented to indicate the precautions to be taken and the most convenient technique for each of them.

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Abstract  

This paper presents the experimental results of an investigation upon cellulose treated with tri-n-octylphosphine oxide for the column chromatography method used during the activation analysis of metals. The most interesting results are obtained in the separation of Au−Sb−Tl.

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Abstract  

The distribution coefficients of a number of elements have been determined for Dowex 50X8 and Dowex 1X8 resins in tartric acid medium. These determinations lead to their practical application in activation analysis. A comparison is given with other generally used acidic media.

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Abstract  

A simplified calculation model of the recoil and irradiation enhanced diffusion which occur in neutron activation analysis of metals is proposed. Under usual irradiation conditions, the recoil does not exceed 0.01 μm for n, γ reactions and 2 μm for other reactions; the diffusion does not exceed 1 μm. Examples, in which deep impurity diffusion leading to important analytical errors was put forward, are discussed through this calculation model. In most cases, the observed phenomena are not related to diffusion but to other causes such as unefficient etching of the sample surface.

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Abstract  

A new method of silicon determination in molybdenum by the30Si(n, γ)31Si was developed. All the problems occurring during this analysis: standardization, quantitative dissolution, silicon sorption on vessels, reproducibility of β-counting...were carefully studied and new answers were brought to them. The chemical speratation of silicon was performed with a column of anion exchange resin in HCl-HF-H2O2 solution and a column of alumina at pH 9. Accuracy and reproducibility were controlled on standard samples prepared by fusion of inactive molybdenum and radioactive silicon in a plasma furnace.

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Abstract  

A new chemical separation procedure for the determination of silicon in iron after neutron activation was developed. It uses two separation steps, one on a cation exchange resin in HCl−HF-acetone medium, and the other on alumina at pH 9. The detection limit for silicon was 0.02 μg. This analytical procedure was applied to the control of the zone-melting purification of iron.

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Résumé  

Après une irradiation neutronique de 7 jours dans un flux de 3·1012 n·cm−2·sec−1, une trentaine d'éléments peuvent être dosés sans séparation chimique dans des échantillons d'aluminium de diverses provenances. Les modalités de mesure et de calcul des radioactivités sont précisées et nous indiquons les limites de détection obtenues. Elles sont comprises entre 5·10−2 et 5·10−6 μg/g selon les éléments recherchés. Pour certains d'entre eux (Fe, Zn, Zr) ces limites peuvent être améliorées par une séparation chimique simple.

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