Some problems concerning the use of automated radiochemical separation systems in destructive neutron activation analysis

The present state of a long term program is reviewed. It was started to elaborate a remote controlled automated radiochemical processing system for the neutron activation analysis of biological materials. The system is based on wet ashing of the sample, followed by reactive desorption of some volatile components. The distillation residue is passed through a series of columns filled with selective ion screening materials to remove the matrix activity. The solution is thus “stripped” from the interfering radioions, and it is processed to single-elements through group separations using ion-exchange chromatographic techniques. Some special problems concerning this system are treated. (a) General aspects of the construction of a (semi)automated radiochemical processing system are discussed; (b) Comparison is made between various technical realizations of the same basic concept; (c) Some problems concerning the “reconstruction” of an already published processing system are outlined.     

Synthesis, spectroscopic and thermal studies of the copper(II) aspartame chloride complex

Aspartame adduct of copper(II) chloride Cu(Asp)₂Cl₂·2H₂O (Asp=aspartame) is synthesized and characterized by elemental analysis, FT IR, UV/vis, ESR spectroscopies, TG, DTG, DTA measurements and molecular mechanics calculations. Aqueous solution of the green solid absorbs strongly at 774 and 367 nm. According to the FT IR spectra, the aspartame moiety coordinates to the copper(II) ion via its carboxylate ends, whereas the ammonium terminal groups give rise to hydrogen bonding network with the water, the chloride ions or neighboring carboxylate groups. The results suggest tetragonally distorted octahedral environment of the copper ions.     

Rh complexes of 1-(2,4,6-triisopropylphenyl-)3-methyl-1H-phosphole: preparation and use as catalysts in the hydroformylation of styrene

In the series of 1-(2,4,6-trialkylphenyl-)3-methyl-1H-phospholes (1a–c) that are to a certain extent of aromaticity, only the isopropyl substituted one (1a) entered into reaction with dimeric (pentamethylcyclopentadienyl)rhodium dichloride to afford Rh(III) complex (2a) in a reversible manner. After a careful workup, (2a) could be prepared and characterized whose stereostructure was elucidated by B3LYP/3–21G*, B3LYP/6–31G* and LANL2DZ calculations. Complex (2a) as a preformed catalyst, as well as the Rh(acac)(CO)₂ + 2(1a) in situ catalytic system were useful in the hydroformylation of styrene and gave the branched aldehyde in regioselectivities of 65–96%.     

Mössbauer study of iron reduction in hematite containing mineral originated from Aswan area in Egypt

Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.     

Some trace elements in the waters,marine organisms and sediments of the Adriatic by neutron activation analysis

A number of investigations of trace elements in the waters, organisms and sediments of the Adriatic, using neutron activation analysis with radiochemical, separations are reported. These include studies of Hg in mussels from the Northern Adriatic, of Hg and Se in edible animals from the Rijeka region, and of seven elements (As, Cd, Cu, Hg, Mn, Se and Zn) in marine invertebrates from the Slovene coast. Additionally, plankton, sediment cores and water samples were taken from a grid of stations covering the whole Adriatic and analyzed for 6 to 11 of the trace elements As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Sb and Zn (Hg only in water). Generally, levels found were not indicative of pollution as compared with oceanic samples, but some evidence of locally increased levels was found, especially for Hg. The levels of eleven trace elements in three marine Intercomparison samples prepared by the IAEA Monaco Laboratory are also presented.     

Unexpected ring transformation to pyrrolo[3.2-b]pyridine derivatives. Fused azolium salts. 22

2-Arylsulfanyl and 2-benzylsulfanylpyridinium N-arylimides (2) easily prepared from 3-aryltetrazolopyridinium salts (1) with aryl and benzylthiolates, respectively, reacted with various dipolarophiles yielding cycloadducts that underwent transformation to give tetrahydropyrrolo[3,2-b]pyridines (5, 6, and 8) in good yields. A similar rearrangement (formation of 15) was also observed in the case of parent derivatives being unsubstituted in position 2 (12). The abscence of any significant solvent effect, comparison of the sulfur and non-sulfur analogues, as well as the stereoselective nature of the observed ring transformation seem to support a sigmatropic mechanism. Structure elucidation of the products has been carried out by single-crystal X-ray diffraction and (1)H NMR experiments.     

Filiation structurale des phases de´rive´es de BaFeF5

Au sein d'un re´seau de type BaFeF₅ des chai?nes d'octae`dres fluore´sa`sommets communs peuvent disparai?tre en donnant naissance a des canaux dont l'occupation partielle ou totale par des files de cations Sr²⁺ et de couples d'anions F^?, conduit respectivement aux phases Sr₃(FeF₆)₂ ou Sr₅T₃F₁₉ (T = Cr, Co, Ga). Une discussion cristallochimique permet d'expliquer l'existence d'un domaine de solutions solides au sein du diagramme ternaire SrF₂BaF₂FeF₃.     

Nuclear Techniques in the Elucidation of Chemical Structure

The paper offers three applications of nuclear methods in the research of chemical structure. First, progress in positron annihilation spectroscopy is illustrated by a positron beamline study, which obtained results that are not available through conventional experiments. The positron beam was used for the study of Langmuir-Blodgett (LB) films containing 4-58 layers of arachidic acid and its salts. These measurements have shown that this emerging technique is capable of characterizing even such elusive systems. Second, the potential of Mössbauer spectroscopy to answer current challenges of solid state chemistry are shown in a study on perovskites of recent interest. ¹⁵¹Eu Mössbauer spectroscopy was used to study the effect of Pr substitution in EuBa₂Cu₃O_7-. It was shown that the introduction of Pr into the rare earth site as well as into the Ba site results in the appearance of extra electrons both in the copper oxide planes and at the 4f shell of Eu cations. The observed effects were explained by the hole filling effect of Pr. Finally, a survey is presented on the recently developed techniques for nuclear resonant scattering of synchrotron radiation, an exciting and very rapidly developing extension to conventional Mössbauer spectroscopy. An interesting new result is that nuclear inelastic scattering experiments performed on solutions of ⁵⁷Fe complexes show contribution from vibrations rather than from diffusion to the inelastic spectra.     

Phase Analysis of the Binary System of Cryolite (Na3AlF6) and Sodium Metasilicate (Na2SiO3)

The phase analysis of cryolite (Na₃AlF₆) and sodium metasilicate (Na₂SiO₃) was performed by thermal analysis. The eutectic system with a region of two immiscible substances at a concentration of Na₂SiO₃ between 42.8 and 46.3 mol‐% was identified and the eutectic temperature determined to (886±2) °C. Based on the results of mass‐loss measurements, it was assumed that the introduced Na₂SiO₃ reacts with Na₃AlF₆ due to the formation of some nonvolatile stable compounds. The stable reaction products were identified by X‐ray diffraction analysis and IR spectroscopy of the spontaneously cooled samples, which established the formation of NaF and stable amorphous aluminosilicate compounds.