Authors:A. Bilewicz, R. Dybczynski, and J. Narbutt
Selectivity of hydrous titanium dioxide as an ion exchanger for alkali metal and tetraalkylammonium ions, has been studied using radioactive indicators:22Na and137Cs. The equilibrium distribution of trace amounts of sodium and cesium ions between the exchanger and aqueous solutions containing macroamounts of other univalent cations was studied over the temperature range of 15 to 80°C. The selectivity sequence in slightly acidic and neutral solutions is as follows: (CH3)4N+<Li+<Na+<K+<Rb+<Cs+, whilst in alkaline solutions it is partly reversed. From the values of selectivity coefficients and the calculated values of thermodynamic functions one can infer that whilst hydrated ions are exchanged from acidic and neutral solutions, from alkaline solutions partly dehydrated ions enter the exchanger phase. The existence of ion-sieve effects for the univalent cations studied was observed, and the presence of at least two kinds of hydroxyl functional groups of different acidities is postulated. Ion exchange reactions of alkali metal cations on hydrous titanium dioxide, as well as the selectivity sequences observed have been interpreted on the basis of EISENMAN theory.
Authors:R. Dybczyński, M. Wasek, and H. Maleszewska
A highly accurate and precise procedure deserving the name of definitive method has been devised for the determination of copper in biological materials. The method is based on combination of neutron activation and very selective and quantitative post-irradiation separation of copper from other radionuclides by extraction chromatography, using columns with LIX 70 on Bio-Beads SM-1, followed by gamma-ray spectrometric measurement. All potential sources of errors were carefully examined and eliminated or appropriate corrections were introduced into the procedure. The method contains several warning mechanisms safeguarding against making gross errors. Limit of detection for rather short irradiation time (tir
1 h) (which enables radiochemical work without sophisticated shielding) amounts to 15 g/kg. Results for copper concentration in several NBS, IAEA and other certified reference materials are presented and a new recommended value for IAEA's Milk Powder (A-11) is proposed.
Authors:R. Dybczyński, H. Maleszewska, and M. Wasek
Distribution coefficients of 14 elements between LIX 70 in toluene and aqueous 1M NaNO3 solution containing varying concentrations of HCl or suitable buffer, respectively, were determined by batch equilibration. It was shown that very selective separation of Cu from other elements can be achieved on columns with LIX 70 supported on Bio-Beads SM-1. Highly accurate and precise method for the determination of trace amounts of Cu in biological materials was devised by combining NAA with extraction chromatography. Results of copper determination in NBS 1570 /Spinach/, IAEA H-4 /Animal muscle/ and IAEA V-8 /Rye flour/ are presented.
The contribution of different analytical techniques to the results of a recent IAEA intercomparison (A-11) of the determination
of the inorganic constituents of a milk powder sample is discussed. In all, 43 laboratories from 24 countries reported results
on 40 elements, “recommended” concentrations for 14 elements were established. NAA was the most important of the 9 techniques
used in this run, it contributed 40% of all the results and all the results for 7 elements. Accuracy and precision of NAA
proved to be good compared to those of other methods.
Authors:B. Danko, R. Dybczyński, and Z. Samczyński
A new method has been developed aimed at determining traces of lanthanides in the materials of biological origin by NAA. The
chemical procedure that involves both, selective and quantitative pre-irradiation isolation of the elements of interest and
post-irradiation separation of lanthanides into two groups has been employed. The method is based on classical column ion-exchange
and extraction chromatography. In the pre-irradiation step all the accompanying elements are eliminated and the quantitatively
isolated lanthanides fraction is free from highly activating macro components, as well as from other trace elements, including
uranium, which is the source of spectral and nuclear interferences. After neutron irradiation, the lanthanide fraction is
divided into two sub-fractions, taking advantage of the different anion-exchange affinities of individual lanthanide complexes
with EDTA towards strongly basic anion-exchanger. This provides the favorable gamma-ray spectrometric measurement conditions
enabling reliable determination of 13 elements.
Authors:S. Sterliński, H. Maleszewska, and R. Dybczyński
Trace amounts of Ir, Au, Cu, Pd and Pt were determined in rhodium metal by instrumental neutron activation analysis with Ge(Li)
spectrometry as well as by the radiochemical version of the method. The latter was based on a specially developed procedure
of the dissolution of Rh, followed by group separation with the aid of ion exchange chromatography. The results obtained by
destructive and non-destructive methods are critically discussed and compared. Special attention was paid to self-shielding
effect and an accurate method of the correction of this effect is presented.
Authors:A. Bilewicz, R. Dybczynski, and J. Narbutt
The adsorption of transition metal cations on hydrated titanium dioxide in complexing ammonia and amine solutions has been studied as a function of ammonia (amine) concentration. The relationships between the distribution coefficients and ammonia concentration as well as the effects of various amines on sorption of transition metals indicate that a coordinate bond is formed between the metal ions and the hydroxy groups of the sorbent. The distribution coefficients of silver(I) and cobalt(III), which form strong ammonia complexes in aqueous solutions, decrease with increasing concentration of ammonia already at concentrations exceeding 10–3. mol·dm–3. Cations of zinc, manganese and mercury which form much weakerammonia complexes do not exhibit any effect of ammonia concentration in the whole range investigated. In the case of sorption of macroamounts of ammonia or amine complexes of silver, the molecular sieve effect plays an important role. The differences in the affinity of hydrated titanium dioxide for ammonia solvates of various transition metal ions can serve as a tool for effective separation of these ions in ammonia solutions.
Authors:R. Dybczyński, S. Sterliński, and C. Golian
Trace amounts of lanthanum in spectrally pure praseodymium oxide have been determined by four independent methods: (1) non-destructive
Ge(Li) spectrometry, (2) spectrometry of slow γ-γ coincidences, (3) radiochemical separation of140La from macro amounts of142Pr and other interfering activities (mainly192,194Ir and152,154Eu) with∼100% yield, by several ion-exchange steps followed by NaI(Tl) spectrometry, (4) method of standard additions using
the same procedure as in method (3). Near the detection limit only the two last methods gave accurate results.
Authors:B. Danko, H. Polkowska-Motrenko, and R. Dybczyński
The influence of irradiation conditions on the results of Co determination in plant samples by radiochemical neutron activation analysis (RNAA), after the conventional and microwave assisted wet digestion, has been investigated. Nine CRMs of botanical origin were examined. The study has demonstrated that the effectiveness of mineralization depended significantly on the kind of sample and the irradiation conditions. When analyzed CRMs were subjected to long-term irradiation in a high neutron flux, the mineralization using the microwave technique was necessary to obtain the correct results of Co determination in some of the plant samples. It has been proved that microwave digestion in a mixture of HNO3+H2O2+HF should be a standard method of wet ashing, independent on matrix and irradiation conditions.