Dosage de traces d'hafnium dans l'aluminium par activation neutronique

Three methods are proposed for the assay of traces of hafnium in aluminium metal by neutron activation analysis. In the first method, the isotope ^179mHf (T = 19 s), produced is counted after anionic resin exchange-separation in sulfuric acid medium. The two other methods, which are non-destructive, are based on the formation of ^180mHf (T = 5,5 h) and ^179mHf (T = 19 s). The latter method comprises an instrumental separation.     

Determinations de traces dans les semi-conducteurs par activation neutronique

Résumé On décrit la détermination de traces dans le germanium, le silicium et le sélénium. En appliquant des techniques gamma spectrométriques, précédées ou non de séparations chimiques il est possible de doser les éléments suivants dans (1) germanium: As, Cu, Au, Ga, Zn, Hg, Cr, Sn, Sb, Co, In, Ni, Ir, Se, Sc, Ag, Ta, Hf et U; (2) silicium: P, Au, Sb, Ga, Fe, K, Cr, Mo, Sn, As, Co, In, Zn, Cu, W, Ta, Na, Eu, Sm, La, Sc et T1; (3) sélénium: Cl, Br, I, P, S, Te, Na, K, Cr, Fe, Co, Cu, Zn, Ga, Sc, Ag, Cd, La, W, Au et Tl. Les concentrations et ou limites de détections varient de quelques parties par million à 10⁻³ parties par milliard.     

Dosage du molybdene et du tungstene dans les plantes par activation neutronique

A method for the determination of molybdenum and tungsten in plant material using neutron activation analysis was developed. The considered reaction are: $$\begin{gathered} {}^{98}Mo(n,\gamma )^{99} Mo \hfill \\ {}^{186}W(n,\gamma )^{187} W \hfill \\ \end{gathered} $$ The separation for tungsten and molybdenum was carried out using anion exchange separation (Dowex 1×10; 200–400 mesh). Irradiation was carried out in a swimming pool reactor at a thermal flux of about 1–2×10¹³ n·cm^?2·sec^?1 for 15 hours. The samples and standard were allowed to cool for 5–6 hours before chemical processing. the high concentration of calcium in plants (up to 40 mg/g dry material), the use of hydrofluoric acid for a good absorption and quantitative recovery of tungsten led us to dissolve the samples with Ht?H₂O₂ mixtures containing boric acid to prevent the precipitation of fluorides.     

Dosage de traces de zirconium dans les materiaux a la base d'aluminium par spectrographie

Sans résumé

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Determination of Traces of Zirconium in Aluminium Based Material Bestimmung von Zirkoniumspuren in Al-haltigen Materialien

     

Dosage de quelques impuretés dans le gallium par activation neutronique

Neutron activation is suggested for the determination of Pt, Au, Hg, Sc, Zn and Sn in high purity gallium. Pt, Hg and Au are reduced to metals, gallium is extracted and then Sc, Zn, and Sn are separated on Dowex 1×8 ion exhanger. All components except Sn are determined by substoichiometric methods in the form of chelate complexes. Sn is extracted with oxine into chloroform, and the chemical yield measured by spectrophotometry.      

Dosage de traces de fer total dans les vins

Résumé Le dosage électrophotocolorimétrique des traces de fer total dans les vins au moyen de l'orthophénanthroline a été peu étudié jusqu'à présent. Sous un titre général le mémoire expose les conclusions auxquelles ont abouti diverses recherches consacrées à l'étude du dosage en question. L'application raisonnée de la méthode deBencze a permis d'établir une technique d'évaluation photocolorimétrique du fer dans les vins et les jus de fruits. Intéressante par sa simplicité et sa rapidité d'exécution, la technique en question indique le moyen de doser cet élément directement dans les liquides obtenus à partir des vins, suivant le procédé du traitement oxydatif au perhydrol. Ce traitement a permis de revaloriser le dosage du fer au point de vue de la rapidité par rapport à la minéralisation sèche, sans apporter en même temps des complications dans les manipulations analytiques et sans affecter la sensibilité et la précision de la réaction colorimétrique.

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Summary There has been little study of the electrophotocolorometric determination of the total iron content of wines by means of orthophenanthroline. Under a general title, the paper gives the general conclusions reached as a result of various studies of this determination. An intelligent application of theBencze method has resulted in a photocolorimetric evaluation of iron in wines and fruit juices. Characterized by simplicity and rapidity, this technique provides a means of determining this element directly in the liquids obtained from wines after oxidative treatment with perhydrol. This procedure compares, favorably with respect to speed with mineralization by the dry method, but is free from the complications in the analytical manipulations and there is no adverse effect on the sensitivity and the precision of the colorimetric reaction.

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Zusammenfassung Die elektrokolorimetrische Bestimmung der geringen Gesamtmengen an Eisen in Wein mit Hilfe von o-Phenanthrolin wurde bisher nur wenig untersucht. Die beim Studium dieses Verfahrens gesammelten Erfahrungen werden in Form eines allgemeinen Überblicks mitgeteilt. Die Anwendung der Methode vonBencze führte zur Ausarbeitung einer Arbeitsvorschrift zur kolorimetrischen Bestimmung des Eisens in Wein und Fruchtsäften. Diese ist wegen der Einfachheit und Geschwindigkeit ihrer Durchführung von praktischem Interesse. In der durch Oxydation des Weines mit Wasserstoffperoxyd erhaltenen Lösung kann das Eisen unmittelbar bestimmt werden. Diese Art des Aufschlusses ist besser geeignet als die trockene Veraschung, ohne die Empfindlichkeit oder die Genauigkeit der Farbreaktion zu beeinträchtigen.

     

Etude du dosage de 30 elements par activation dans les protons de 11 MeV

We have irradiated 30 elements with 11 MeV protons and we present here: (1) The specific activities for the main radioisotopes produced by (p, n) or (p, α) reactions (on main γ rays except the 511 keV). (2) The main γ energies of these radioisotopes (at ±0.3 keV) when they have not been accurately measured previously. (3) The limits of detection or the lowest amounts measured in samples of Al, Ag or Co. From these preliminary results it can be deduced that 11 MeV protons offer new possibilities in the field of activation analysis.      

Dosage des impuretes dans le zinc de haute purete par activation aux neutrons

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.     

Dosage du plutonium dans les alliages plutonium aluminium par fluorescence-x

An X-ray fluorescence method is described for the determination of plutonium in Pu-Al alloys. In order to obtain satisfactory reproducibility, the alloy is first dissolved in a nitric acid-mercury (II) nitrate mixture. The Lα emission of plutonium is measured, to eliminate matrix effects, an internal standard with a wavelength near that of the Pu emission is used. Equipment and sample preparation are described. Extension of the method to other determinations is discussed.     

Dosage du carbone dans quelques metaux purs par irradiation dans les photons γ

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.      

Détermination de traces de mercure dans les systèmes biologiques par activation de neutrons

Résumé Une méthode simple et rapide de détermination de traces de mercure est présentée utilisant l'activation de neutrons. Le mercure 197 sous forme de complexe (HgCl₄ ^2–) est retenu sur une résine échangeuse d'anion qui est comptée directement. La méthode est appliquée à des milieux biologiques très divers. Les échantillons contiennent des quantités de mercure allant de 10 p. p. b. à 200 p. p. m. La déviation standard dans ces cas est de ± 10%.

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Determination of traces of mercury in biological material by neutron activation

Summary A simple and rapid technique for the trace analysis of mercury by neutron activation is presented. The activated mercury, as an HgCl₄ ^2– complex, is retained on an anion exchange resin which is counted directly. Results obtained for biological samples containing 10 p. p. b. to 200 p. p. m. are given. In this range, results had a ± 10% standard deviation.

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Zusammenfassung Ein einfaches und rasches Verfahren zur Bestimmung von Spuren Quecksilber durch Neutronenaktivierung wurde beschrieben. Das aktivierte Quecksilber wird als HgCl₄ ^2– an einem Anionenaustauscherharz adsorbiert und seine Aktivität direkt gemessen. Biologische Proben mit 10 ppb bis 200 ppm Hg wurden analysiert. In diesem Bereich betrug die Standardabweichung ± 10%.

     

Dosage des Traces d'Arsenic par Voltametrie et Redissolution Cathodique dans les Solutions Industrielles de ZnSO4

Abstract

A method is described for the determination of traces of arsenic in industrial ZnSO₄ solutions for electrolysis by cathodic stripping voltammetry. The limit of detection is of the order of 1 ppb.     

Dosage direct du paracetamol dans les milieux biologiques par polarographie sinusoidale

(The direct determination of paracetamol in biological fluids by a.c. polarography). Paracetamol can be determined rapidly in biological fluids (blood serum and urine) by a.c. polarography. After elimination of protein by perchloric acid, followed by reaction with nitrous acid in acidic medium, the nitro derivative is measured at pH 10. As little as 4 × 10^-6 M paracetamol (0.6 μg ml^-1) in serum can be determined.     

Determination du fluor dans les milieux aqueux par activation au moyen de photons gamma

An apparatus ensuring identitical irradiation conditions for three samples and a standard of large volumes is reported. The interference caused by the protons originating from the¹⁶O(γ, p)¹⁵N reaction is determined. Results show that the secondary rection¹⁸O(p, n)¹⁸F induced by the protons of the former reaction gives an apparent fluorine content in natural waters of 0.015 μg/g for a maximum gamma photon beam energy of 21 MeV.      

Dosage des impuretes dans le zinc par activation neutronique : Dosage de l'argent et du cobalt dans un zinc raffiné par fusion zonale

A neutron activation method for the determination of cobalt and silver in the microgram range in a matrix of electrolytic zone-refined zinc is described. Silver and cobalt can be separated in a state of high radiochemical purity by means of an anion-exchange resin, silver being eluted by 10 M hydrochloric acid and cobalt by 4 M hydrochloric acid. The standard deviations are, respectively, 0.1 p.p.m. for silver and 0.01 p.p.m. for cobalt for impurity levels of 1 p.p.m. silver and 0.1 p.p.m. cobalt.     

Dosage de sept agents conservateurs dans les denrées alimentaires par chromatographie liquide a haute performance

(Determination of seven food preservatives by high-performance liquid chromatography.) Solvent-programmed h.p.l.c. is applied for the determination of sorbic, benzoic and salicylic acids and p-hydroxybenzoic acid as well as three of its esters, singly or in mixture; quantitative separation takes less than 20 min. Recoveries varied from 90.9 to 99.4% for the concentration range 200–1000 ppm when the method was applied to mayonnaise.     

Analyse par activation neutronique des lanthanides dans les eaux naturelles

A new method of neutron activation analysis of rare earths in natural waters is proposed and applied to thermal and superficial waters. Natural waters samples are irradiated in a liquid state, without preconcentration. The rare earths are separated, after irradiation, from interfering elements by stationary phase chromatography and precipitation. Determination are carried out by gamma spectrometry with a germanium (lithium) detector. The method is applied to quantitative analysis of Dy, Eu, Sm, La, in natural waters, thermal or superficial, coming from Massif Central and Pyrénées (France).      

Application de l’Analuyse par Radioactivation Neutronique et du Calcul Electronique au Dosage non Destructif de Traces de Chlore dans les Silices-alumines

A method applicable for serial determination of traces of chlorine in SiO₂−Al₂O₃ catalysts by neutron activation is described. The results are evaluated by means of a computer. The³⁸Cl activity is subtracted from the activity of the interfering components (⁵⁶Mn,²⁴Na) and this enables a direct γ-spectrometric determination. In praxis ten samples should be irradiated simultaneously and for this reason 3 standards are irradiated together with the samples to correct for the fluxus gradient. The reproducibility of the method is better than 2 per cent for 10–300 mg samples with a Cl content of 10 ppm.      

Dosage par activation neutronique des terres rapes dans des roches uraniferes

The determination of rare earths by activation analysis in uranium containing rocks is disturbed either by fission-produced rare earths, or by neptunium-239 originating from uranium-238. In order to eliminate of these interferences the chemical separation of rare earths from uranium prior to activation should be performed. The purpose of this work was the elaboration of a chemical process to separate rare earths prior to irradiation in a nuclear reactor. The rock sample is fused with sodium borate, then, after addition of hydrochloric acid, the resulting solution is passed through a Dowex 1×8 column. Uranium is retained on the resin and rare earths and scandium are eluted. Aluminium is added as a carrier to the solution and rare earths and scandium are coprecipitated with aluminium hydroxide. This precipitate is irradiated in the nuclear reactor. Gamma spectrometry is used for the determination of each radionuclide. Activities measurements are performed in successive steps during one month. The following elements are determinated: Pr, La, Sm, Nd, Yb, Lu, Ce, Tb, Eu, and Sc. The chemical yield is measured by using scandium as an internal standard.