Multielement analysis of concrete from nuclear reactors by INAA,ICP-MS and ICP-AES

There is a need to know, before dismantling nuclear plants, how the induced radioactivity is distributed in concrete. Computer codes are used to predict such a distribution, by applying input data like, among others, the chemical composition of the material. Biological shield concretes with particularly high boron or barium concentrations had to be analyzed. Instrumental neutron activation analysis is not able to determine all elements, thus, additional techniques are required, like ICP-MS and ICP-AES. The respective performances of these techniques are discussed. For INAA, the thermal neutron self-shielding was empirically corrected by using comparisons between thermal neutron activation (TNAA), epithermal and fast neutron activation (ENAA), ICP-AES and ICP-MS measurements.     

A polycationic dendrimer as noncovalent support for anionic organometallic complexes

Polycationic dendrimer 1 forms a well-defined, stoichiometric assembly with eight anionic metal complexes; this assembly is successfully applied as a Lewis acidic catalyst which performs comparably to the unsupported metal complex.     

Infrared spectroscopy of gas-phase Cr+ coordination complexes: determination of binding sites and electronic states

Infrared spectra were recorded for a series of gas-phase Cr+ complexes using infrared multiphoton dissociation (IRMPD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The functionalized aromatic ligands (acetophenone, anisole, aniline, and dimethyl aniline) offer a choice of either aromatic ring-pi or n-donor-base binding sites. Use of the FELIX free electron laser light source allowed convenient, rapid scanning of the chemically informative wavelength range from approximately 500 to 1800 cm(-1), which in many cases characterized the preferred site of metal binding, as well as the electronic spin state of the complex. Mono-complex ions, Cr+(ligand), for anisole, aniline, and dimethyl aniline and bis-complex ions, Cr+(ligand)(2), for anisole, aniline, and acetophenone were produced by ligand attachment to laser-desorbed Cr+ ions in the FT-ICR cell. The photodissociation yields plotted as a function of wavelength were interpreted as approximations to the infrared absorption spectra and were compared with computed spectra of different possible geometries and spin states. Clear-cut diagnostic features in the spectra of the acetophenone, anisole, and aniline complexes showed the sites of Cr+ attachment to be the carbonyl oxygen site for acetophenone (bis-complex) and the ring-pi site for anisole and aniline (both mono- and bis-complexes). The bis-complexes of aniline and anisole are low-spin (probably doublet) states, while the mono-complexes of these same ligands are high-spin (sextet) states. The dimethyl aniline complex gave a cluttered spectrum in poor agreement with calculations, which may reflect a mixture of binding-site isomers in this case.     

Infrared spectroscopy of neutral C7H7 isomers: benzyl and tropyl

The gas-phase infrared absorption spectra of neutral benzyl and tropyl, isomers of formula C7H7, have been measured in the 400-1800 cm-1 spectral region. In addition, a quantum chemical calculation has been performed to model the infrared spectra. For the benzyl radical, the theory shows satisfactory overlap with the experiment, although vibrations involving the CH2 group might be anharmonic. The tropyl radical, which is subject to the Jahn-Teller effect, seems well modeled for the out-of-plane vibrational modes, but less so for the in-plane vibrational modes.     

A fast,sensitive determination of doxorubicin in rat plasma by solid-phase extraction and reversed-phase ion-pair chromatography

A very selective method is described for the determination of doxorubicin in rat plasma. Doxorubicin is extracted from the plasma on a pretreated octadecyl silane column and eluted with phosphate buffer pH 2.6/methanol (25/75, v/v) containing sodium 1-heptanesulfonate as ion-pairing agent. The extraction procedure is suitable for samples which contain doxorubicin encapsulated in liposomes if Triton X-100 is added. A portion of the evaporated eluate is used for high-performance reversed-phase chromatography with the same eluent and a fluorescence detector. Daunorubicin is used as internal standard. Extraction of doxorubicin from plasma is quantitative. The calibration graph is linear for 0.2-100 μg l^?1 doxorubicin with a limit of detection of 0.2 μg l^?1 for 0.5 ml of plasma. The relative standard error of estimate of the calibration was typically 3%.     

Poly(9,9'-spirobifluorene-manganese porphyrin): a new catalytic material for oxidation of alkenes by iodobenzene diacetate and iodosylbenzene

Anodic oxidation of tetraspirobifluorene-manganese porphyrin lead to the coating of the working electrode by insoluble electroactive poly(9,9'-spirobifluorene-manganese porphyrin) films for which electrochemical behaviour and physicochemical properties are described; these polymeric materials are able to catalyze the heterogeneous epoxidation of styrene with iodobenzene diacetate and iodosylbenzene.     

Spontaneously formed trans-anethol/water/alcohol emulsions: mechanism of formation and stability

We studied the spontaneous emulsification and droplet growth mechanism in trans-anethol/water/ethanol solutions, also known as the beverage ouzo, using dynamic light scattering spectroscopy. This simple ternary mixture is a generic example of a system that forms microemulsions spontaneously when brought into the two-phase region. The volume fraction of the dispersed phase was found to profoundly affect the growth rates of the droplets, which is a new finding that has not been predicted by the Lifshitz-Slyozov-Wagner theory. Time-dependent measurements show that the droplet growth is governed by Ostwald ripening (OR), and no coalescence was observed. Furthermore, the OR rates increase with increasing oil concentration at low alcohol content. We attribute this behavior to enhanced droplet-droplet interactions. At high ethanol concentrations, we found that the measured rates decreased as the oil concentration increased. The OR growth mechanism completely correlates with changes in droplet size. The kinetics of droplet growth shows that the ripening has a saturation limit at a droplet radius of about 1.5 mum. Thus, formed emulsions remain stable for months.     

Covalently bonded platinum(II) complexes of alpha-amino acids and peptides as a potential tool for protein labeling

Arylplatinum(II) complexes have been covalently bonded to the N and C termini and to the alpha-carbon of various amino acid derivatives. These organometallic-functionalized amino acid compounds can be converted into the corresponding free amino acids under both basic and acidic conditions; this demonstrates the excellent stability properties of these biomolecules. Due to the NMR activity displayed by the 195Pt nucleus (natural abundance 33.8%, I = 1/2) these compounds are functional bio-markers. Furthermore, the ability of the arylplatinum functional group to bind SO2 gas, selectively and reversibly as indicated by changes in the spectroscopic properties (1H, 13C, 195Pt NMR and UV spectra) of these compounds, allows for the potential use of these complexes as in vitro biosensors.     

Les Phases Na5NbO5 et Na5TaO5 Structure Cristalline de Na5NbO5

Na₅Nb0₅ and Na₅Ta0₅ Phases. Crystal Structure of Na₅NbO₅ New ternary oxides of formulas Na₅NbO₅ and Na₅TaO₅ have been prepared. They crystallize in the monoclinic system (space group C2/c). The crystal structure of Na₅NbO₅ has been determined. It derives from a NaCl-type structure by ordering of the cations and of the oxygen vacancies in the anionic sublattice, the corresponding formula being Na_5/6Nb_1/6O_5/6□_1/6. Sodium and niobium have a distorted square-pyramidal surrounding.     

Ferrocenyltrithiocarbonates : I. Direct access from α-ferrocenylcarbinols by a SNi mechanism. Absolute x-ray structure determination of (R)-ferrocenylmethylmethane S-methyl-trithiocarbonate

¹⁰³Rh Chemical shifts of a variety of mono- and di-nuclear rhodium carbonyl complexes are reported together with the modifications to the probe and decoupler unit of a JEOL PS-100 PFT spectrometer which enable these ¹⁰³Rh-decoupled ¹³C NMR measurements to be made. These data are discussed in conjunction with ¹³C NMR data on other rhodium carbonyls.