Quelques interferences sur le dosage du plomb dans les eaux alimentaires par spectroscopie d'absorption atomique sans flamme

Interferences in the determination of lead in potable water by graphite-furnace atomic absorption spectrometry are examined. The peak-height signal and the pyrolysis/atomization curves are studied as a function of the nature and concentration of the interferent. Some interferences are caused not by the cation or anion, but by the salt. Magnesium chloride interferes most extensively not only by decreasing the signal but also by changing the pyrolysis curve. Interferences are more pronounced in hydrochloric than in nitric acid medium. Frequently, stabilization of an interfering effect from a defined interferent concentration was observed in nitric acid medium whereas in hydrochloric acid medium the signals continued to change.     

Etude thermodynamique du systeme plomb—selenium par calorimetrie

The enthalpy of formation of PbSe liquid alloys was measured at nine temperatures by direct reaction calorimetry (drop method) for 0 < x_Se < 0.5 and 883 < T < 1365 K. The enthalpy of formation is strongly negative in the whole range investigated. It is not dependent on the temperature when x_Se < 0.3 but increases strongly with temperature when 0.3 < x_Se < 0.5 (ΔC_p,max ?90 J K^?1 mol^?1 at x_Se = 0.5).     

Etude par spectrographie d'absorption infra-rouge de quelques complexes aquoamminés du nickel

Résumé Un essai d'interprétation des spectres d'absorption infra-rouge, entre 200 et 4000 cm^–1, des sels de nickeloaquopentammine et de nickelo-diaquotétrammine a permis d'obtenir un aperçu sur la structure de quelques autres complexes du nickel. En particulier, l'étude du déplacement de la bande de vibration de déformation symétrique de l'ammoniac avec l'espèce chimique a servi à déterminer la pureté de sels de nickelohexammine d'après leurs spectres.

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Summary An interpretative study of the infra red absorption spectra, between 200 and 4000 cm^–1, of the salts of nickeloaquapentammine and of nickelo-diaquatetrammine has given an insight into the structure of several other nickel complexes. In particular, the study of the displacement of the vibration band of symmetric deformation of ammonia with the chemical species has served to determine the purity of salts of nickelohexammine from their spectra.

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Zusammenfassung Der Versuch einer Interpretation der Infrarotabsorptionsspektren von Aquopentamminnickelaten und Diaquotetramminnickelaten zwischen 200 und 4000 cm^–1 gab einen Überblick über die Struktur einiger anderer Nickel-komplexe. Insbesondere diente die Untersuchung der Verschiebung der symmetrischen Schwingungsbande zur Reinheitsbestimmung von Hexammin-nickelaten auf Grund ihrer Spektren.

     

Determination du bore dans le zirconium,par activation au moyen de deutons

The determination of boron in zirconium by activation analysis using the¹⁰B(d, n)¹²C reaction with the chemical separation of¹¹C is described. The method was applied to industrial zirconium samples as zircalloy.

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Collaborateur temporaire de thèse au CEA.     

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.      

Determination du plomb sur la vegetation le long des autoroutes

Abstract

Lead determinations, by pulse polarography, were made in 1971, on plants, trees and vegetables growing near belgian highways. Implications on food toxicology are assessed.     

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.     

Analyse du phosphore dans le silicium par reactions nucleaires

The determination of phosphorus is presented using the³¹P(p, α)²⁸Si reaction. The principle of the method and the instrumentation are discussed as well as the precision, sensitivity and the influence of the target thickness. The method is especially suitable for the investigation of diffusion phenomena. The concentration profiles are shown in silicon samples for various times of pretreatment. The interpretation of the profiles is given.      

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.      

Essais interlaboratoires: dosage du cadmium,du cuivre et du plomb dans l'eau de mer par spectrometrie d'absorption atomique electrothermique: |en|An in terlaboratory study of the determination of cadmium,copper and lead in seawater by electrothermal atomic absorption spectrometry

An in terlaboratory study of the determination of cadmium, copper and lead in seawater by electrothermal atomic absorption spectrometry.The reproducibility of a selective extraction method on Chelex-100 resin in the Ca²⁺ form, described previously, was tested on seawater with and without addition of Cd, Cu and Pb. The metals extracted were determined by electrothermal atomic absorption spectrometry (a.a.s.). The results obtained by the three laboratories participating in these tests prove the validity of the method for the determination of cadmium and copper. The largest dispersion of results, observed for lead, is related to the poorest precision of electrothermal a.a.s. for this element.     

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.     

Effets de surface dans le dosage par activation neutronique du soufre

Surface effects in the determination of sulfur by neutron activation analysis Thermal neutron activation analysis leads to overestimated sulfur contents in some metals. This phenomenon was studied for samples of iron. It is attributed to ineffective chemical etching arising from dissolution of the metal through a surface layer which retains impurities, especially sulfur-35. Significant amounts of this isotope are produced at the surface through the ³⁵Cl(n, γ)³⁵S reaction. Experimental modifications which lead to the correct sulfur concentration are proposed.     

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.     

Etude du comportement thermique des n-alcanes dans des milieux hydrocarbones complexes par analyse calorimetrique differentielle. II. Determination du taux de n-alcanes contenu dans un gazole. Determination du point de trouble

The study of the thermal behavior of n-alkanes in a hydrocarbon matrix has been carried out by means of a Mettler TA 2000 B heat flow differential scanning calorimeter. A quantitative method to determine the composition in n-alkanes contained in a gas oil is described. It is assumed that the determination of the cloud point by means of DSC measurements can be obtained with a good precision.     

Dosage au moyen de particules alpha de l'oxygene dans le plomb et le plomb antimonie

The determination of oxygen in lead and in lead antimony by means of α-activation analysis is described. The separation of fluorine resulting from irradiation of oxygen is performed by extraction with diphenyldichlorosilan in isopropyl ether. In the case of lead antimony alloy, a more complex separation scheme of fluorine from iodine resulting from irradiation of antimony is described.