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For the enrichment or the simple recovery of caesium from river and sea waters, selective inorganic exchangers were considered. Ammonium hesacyanocobalt ferrate (NCFC) was chosen because it can be used in strongly acidic solutions (with the exception of concentrated sulphuric acid), Cacsium is fully retained by the NCFC chromatographic column and can then be recovered by dissolution in hot sulphuric acid. The solution is then diluted and analysed, either directly or following caesiuni separation, by atomicabsorption spectrometry.To check the reliability of the analytical procedure, a series of cxperirnents were carried out in which the possible interfering species were added to the aqueous caesium solution prior to analysis. The well known ionic interference in flame atomisation processes caused by magnesium, calcium, strontium and metals was investigated by electrothermal atomisation measurements. The experimental data showed that this effect does not occur even when these elements are present in concentrations of the order of thousands of parts per million. However, strong interferences from iron and cobalt were observed.Keywords: Electvothevmal atomic-absovption spectvometvy; caesiwm detevmination ; cobalt and ivon intevfevemes ; spectval intev fevence ; caesium envichmentNuclear activities, such as electricity production by nuclear power plants, involve the occasional release of small amounts of radionuclides into the environment. Among the possible diffusion paths of such discharges rivers often play a role of paramount importance. Studies on the distribution of radionuclides between river water and the suspended solid materials or sediments can be carried out using radioactive tracer techniques, but they also require analytical methods suitable for the characterisation of the different components of the system. The caesium concentration in these matrices is very low, so that, in addition to a sensitive analytical method, it was necessary to make use of an enrichment technique to bring the caesium concentration within the scope of the analytical method.Atomic-absorption spectrometry was selected as the analytical method because of its sensitivity, speed and ease of operation.For the enrichment or even for the simple recovery of caesium from different solutions, selective inorganic exchangers were considered. Ammonium hexacyanocobalt ferratel (NCFC) was chosen because it can be employed in strongly acidic solutions (with the exception of concentrated sulphuric acid2). The use of NCFC is particularly advantageous for the recovery of caesium from solutions obtained on acid dissolution of mineral or biological materials.Caesium is fully retained by a chromatographic column of NCFC and can then be recovered by dissolution of the NCFC in hot 12 M sulphuric acid. The solution is then evaporated to form a paste, cooled and distilled water is added. When columns of NCFC supported in silica gel are used, the dissolution of the NCFC is made with hot 18 M sulphuric acid with continuous stirring. The solution contains an...

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Commercial graphite tubes (Massmann type) generally have a cylindrical shape and only a portion of the internal volume is available for absorption, owing to the geometry of the focused light beam. The aim of this work was to find the best geometry of the atomisation chamber to exploit the absorbing power of the optical system.Starting from the geometry of the light beam of an atomic-absorption spectrophotometer (Pye Unicam SP1900), the size and geometry of the tube have been defined. The temperature distribution along the axis of the tube, the diffusion of the atomic vapour from the centre to the ends of the tube and the residence time of the atoms within the tube were studied to determine their influence on the analytical sensitivity.As theoretical calculations demonstrated that the improved tube should give an appreciable enhancement of the sensitivity, a graphite tube was constructed according to this new geometry. The experimental results obtained with different elements confirmed the expected improvement in the analytical performance.