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  • Author or Editor: H. Bowen x
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Résumé  

Les milieux biologiques étalon pour une analyse élémentaire sont peu nombreux et posent des problèmes d'homogénéité, de conditions reproductibles, de séchage et de stokage. Leur usage a soulevé un certain nombre de problèmes concernant la sureté de certaines techniques analytiques, quelques uns de ces problèmes n'ont toujours pas de solution. Ils sont illustrés en se référant à un échantillon standard de chou, de sang humain, d'hématies et de sérum, lesquels ont été analysés à plusieurs reprises. Des valeurs raisonnablement sures sont maintenant connues pour les 35 éléments suivants dans l'échantillon standard de chou: Al, As, Au, B, Ba, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, F, Fe, Hg, K, La, Mg, Mn, Mo, N, Na, P, Pb, Rb, S, Sb, Sc, Si, Sn, U, V, W, Zn; il reste des incertitudes pour Ag, Ce, Ga, I, Ir, Ni, Se Sm et Ti. Dans le sang, les analyses des 17 éléments suivants sont suffisamment exactes pour permettre l'emploi de ce produit comme un étalon, approximatif. Ba, Br, Ca, Cl, Cu, Fe, I, K, Mg, Na, Ni, P, Pb, Rb, Se et Zn. Cependant il y a de sérieux doutes au sujet de la constante de la concentration de certains de ces éléments selon les individus. A la suite d'une récente étude, l'exactitude des résultats concernant, Ag, As, Co, Cr, F, Hg et Sb est également mise en doute.

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Abstract  

Tin(II) and tin(IV) are absorbed from aqueous solutions by Sephadex G-25 gel, from which they can be eluted by humates or fulvates, with which they interact more strongly. Methyltin species are not absorbed by Sephadex G-25, and so can be separated from inorganic tin. Both inorganic tin and methyltin species in natural waters at pH 7.4 can be quantitatively retained by passing through small columns of Chelex-100 resin: the methyltin species can then be washed off the resin with 4M nitric acid. Trimethyltin chloride113Sn in water scarcely interacts with fulvates, humates, kaolinite or montmorillonite but is absorbed bySphagnum peat. Dimethyltin dichloride-113Sn reacts significantly with all the above materials after 2 hours equilibration. Methyltin trichloride-113Sn interacts weakly in alkaline solutions.

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Abstract  

The separation of uranium/VI/ from solution using tri-n-octylphosphine-oxide /TOPO/ and polyurethane foam has been shown to be efficient and specific. A desorption method has been investigatied which recovers uranium and TOPO in independent fractions.

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Abstract  

While silver can be efficiently collected from biological materials into lead beads by conventional fire assay, reagent blanks make this method unsuitable for determining the metal at concentrations less than 1 ppm. A radiochemical neutron activation analysis method is described which avoids this problem and can give reliable results down to 1 ng g–1. The method has been tested using various reference materials /RM/, and it is concluded that NIES Mussel and Pepperbush are the best characterised RMs for determining traces of silver.

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Abstract  

Tracer110mAg has been used to investigate the speciation of silver in natural waters, which may contain chloride, sulphide or humate ions. Silver chloride or oxide is readily absorbed from waters by many materials, and some may be photochemically reduced to metallic silver. Absorbed silver, silver chloride and silver sulphide may be distinguished by their desorption behaviour. Humates form complexes with silver chloride, silver sulphide and the silver cation, which can be separated from smaller species by gel permeation chromatography.

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Abstract  

Rhodium/III/ solutions react with tin/II/ chloride to form a short-lived yellow complex which is extracted by polyurethane foam. Iridium/IV/ solutions are decolourised by tin/II/ chloride but the metal is poorly extracted by foam. The rhodium/III/ complex is readily desorbed from foam using hydrochloric acid and acetone.

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Abstract  

A rapid non-destructive activation analysis method has been developed for the determination of antimony. A high resolution low energy Ge detector is used to measure the 61.6 keV γ-ray from122mSb (T=4.2 min). Sensitivities and detection limits for biological and environmental samples activated with thermal and epithermal neutrons are listed. The time required for the anlaysis is about 12 min per sample using thermal activation and 22 minutes using epithermal activation analysis.

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Abstract  

Rare earth elements have been determined in Syrian phosphate rocks by two methods: inductively coupled plasma atomic emission spectrometry following a cation separation, and instrumental neutron activation analysis using both short and long irradiation periods. The results from the two methods agree in most cases apart from Ce, Lu, Nd and Sm. Despite the absence of reliable reference materials, we believe the emission spectrometry technique to be the more accurate.

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Abstract  

Radio-tracer experiments have shown that antimony, mercury and zinc interact to form complexes with humic and/or fulvic acids, whose molar masses can be estimated by gel chromatography. Sb(III) and (V) humates are stable in the pH range 7–11, but are largely dissociated below pH 4; humic acid does not reduce Sb(V) to Sb(III) in solution. Mercury forms a strong complex with humic+fulvic acids. Zinc forms complexes with both humic acids and glycine, and the humic acid complex has similar elution behaviour on dextran gel to a fraction from river water equilibrated with65Zn. At least one other form of zinc, in addition to Zn2+, occurs in this river.

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Abstract  

A study was initiated to investigate the chronological deposition of uranium in certain species of trees growing on the site of a former uranium metal processing facility. The Feed Materials Production Center (FMPC) is located in Fernald, Ohio, and for roughly 40 years operated as a large scale uranium processing center. Core samples from several species of trees growing in different locations throughout the site were extracted using a 12.5 mm incremental wood boring drill bit. After extraction, each core sample was cut and packaged into individual sections representing 4 annual growth rings and submitted for instrumental neutron activation analysis (INAA). The reaction 235U(n,f)140Ba→140La+γ was evaluated using high resolution germanium gamma-spectroscopy to detect the 1.596 MeV photon emission from the fission product 140La following a minimum of a 3 week decay. A total of 106 samples representing 7 individual trees of 3 unique species were irradiated. In addition to the tree-core samples, 18 quality control (QC) samples and 18 standard reference material (SRM) Fly Ash samples were irradiated with the core samples for determining neutron flux. The activity in any one sample in a batch was determined by comparison with the amount of natural uranium in the QC standards. No significantly measurable amount of uranium was detected in any of the tree core samples, although 3 tree core samples were in excess of the minimum detectable amount (30 ng).

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