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The preparation, certification, and characterization of two new biological certified reference materials for inorganic trace analysis have been presented. They are based on two different varieties of tobacco leaves, namely, Oriental Basma Tobacco Leaves (INCT-OBTL-5), grown in Greece, and Polish Virginia Tobacco Leaves (INCT-PVTL-6), grown in Poland. Certification of the materials was based on the statistical evaluation of results obtained in a worldwide interlaboratory comparison, in which 87 laboratories from 18 countries participated, providing 2568 laboratory averages on nearly 80 elements. It was possible to establish the certified values of concentration for many elements in the new materials, that is, 37 in INCT-OBTL-5 and 36 in INCT-PVTL-6, including several toxic ones like As, Cd, Hg, Pb, and so forth. The share and the role of instrumental analytical techniques used in the process of certification of the new CRMs are discussed.

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Abstract.The article describes studies on the separation of uranium from acid pregnant leach solutions obtained from Polish uranium ores: dictyonema shales and sandstone rocks. Ion exchange chromatography was applied for uranium sorption, using commercially available, strongly basic anion exchanger, Dowex 1. In model experiments, the infl uence of degree of crosslinking of Dowex 1 on the effi ciency of uranium extraction was investigated. The effect of H 2 SO 4 concentration on the breakthrough curve of uranyl ions for the Dowex 1 resins, of different crosslinking: X4, X8 and X10, was examined. Unexpectedly high increase of exchange capacity of uranium was observed in case of Dowex 1X10. This gives potential opportunity of improving the effectiveness of uranium recovery process. Applying column packed with Dowex 1X10, 'yellow cake' with ca. 92% yield and high purity of recovered uranium was obtained. A block diagram of the procedure for uranium and lanthanides extraction from acidic leach liquor has been proposed.