Reproducible tritium generation in electrochemical cells employing palladium cathodes with high deuterium loading

Reproducible tritium generation well above background has been observed in tightly closed D₂SO₄-containing cells in four out of four Pd wire cathodes of one type. Tritium analysis was performed before and after each experiment on the Pd, the electrolyte and the gas in the head space. No tritium generation was observed in four identical Pd cathodes in H₂SO₄ cells operated at the same time under the same conditions. A cyclic loading-unloading regime with low current densities, rather than the usual continuous constant current regime, was employed to attain D/Pd and H/Pd loadings of 1±0.05 reproducibly. D/Pd loadings greater than 0.8±0.05 appear to be necessary to generate tritium. The largest amount of tritium, generated in 7 days of continuous electrolysis, was 2.1 × 10¹¹ tritium atoms, compared with a background of 4 × 10⁹ tritium atoms. The concentration of tritium and its axial distribution in the Pd were determined and concentrations of up to 9 × 10¹⁰ atoms/g Pd were found compared with a maximum background of 5 × 10⁸ atoms g⁻¹. The T/D ratio in the Pd is about 100 times larger than in the electrolyte or gas and indicates that tritium generation occurs in the Pd interior rather than at its surface. No tritium generation was observed in two other types of Pd electrodes in D₂SO₄, despite the attainment of D/Pd ratios near 1:1. Thus high D/Pd ratios appear to be a necessary but not sufficient condition for tritium generation in D₂SO₄ electrolysis.     

Selection of the sample composition for the selective preconcentration of some platinum group metal ions by Donnan dialysis

The possibility of selective preconcentration of platinum group metal ions by Donnan dialysis was investigated. The effect of sample matrix (glycine) on self diffusion of the following platinum group metal ions Pt(IV), Pd(II), Rh(III), Ir(III) and Ir(IV) was determined. To separate a sample from the receiver electrolyte (0.5M NH₄Cl), anion or cation-exchange membrane were used. Excellent selective preconcentration of Pd(II) in the sample and Ir(III) in the receiver solution was achieved. Experiments performed enable to draw some conclusion on the charge sign of glycinepalladium complexes.     

Kinetic Study of Metals Sorption on a Resin Modified with Tetrakis(carboxyphenyl)Porphyrin

 The sorption of metal ions (e.g. Cd²⁺, Cu²⁺, Ni²⁺ and Pb²⁺) from aqueous solution on the anion exchange resin Amberlite IRA-904 modified with tetrakis(4-carboxyphenyl)porphyrin (TCPP) was studied in batch equilibrium experiments. The influence of operating variables such as initial pH and contact time between solution and the resin on the equilibrium parameters was measured. The selectivity order of investigated metal ions was evaluated as follows: Pb²⁺ > Ni²⁺ > Cu²⁺ > Cd²⁺. The matrix cations, such as Mg²⁺ and Ca²⁺, exhibit very low affinity for TCPP-modified resin. The rate uptake of the sorption procedure is predominantly controlled by film diffusion. The best retention kinetic was observed for lead where half the saturation of the TCPP-modified sorbent was achieved in less than 5 min. Author for correspondence. E-mail: kryspyrz@chem.uw.edu.pl Received November 20, 2002; accepted January 26, 2003 Published online May 5, 2003     

Far-infrared spectra of lanthanide complexes with 8-hydroxyquinoline

Summary Vibrational spectra of lanthanide oxines have been measured in the far-infrared region. In addition, the similar yttrium complex was investigated for further experimental evidence for the proposed band assignments. The most important metal-oxygen and metal-nitrogen bond vibrations have been attributed to absorptions between 390–350 cm^–1 and 210–170 cm^–1, respectively.

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Ferne IR-Spektren von Lanthanidenkomplexen mit 8-Hydroxychinolin

Zusammenfassung Es wurden die Vibrationsspektren von Lanthanid-Oxinen im fernen IR-Bereich gemessen. Zusätzlich wurde der analoge Yttrium-Komplex untersucht, um die Bandenzuordnungen experimentell zu stützen. Die wichtigsten Metall-Sauerstoff- und Metall-Stickstoff-Bindungsschwingungen wurden den Absorptionen zwischen 390–350 cm^–1 und 210–170 cm^–1 zugeordnet.

     

Ion Chromatography with Pulsed Amperometric Detection for Determining Cyanide in Urine and Meconium Samples

The parents’ addictions and eating habits have a significant influence on the child’s growth. The first stool of a newborn baby provides a large amount of information about xenobiotics transmitted by the mother’s body. The analytical technique used in the study is ion chromatography with pulsed amperometric detection (IC-PAD). The biological samples, which were obtained from women staying in a maternity ward and their partners, revealed cyanide concentrations in urine samples spanning 1.30–25.3 μg L⁻¹. Meanwhile, the results of the meconium samples were in the range of 1.54 μg L⁻¹ to 24.9 μg L⁻¹. Under the optimized chromatographic conditions, the IC-PAD system exhibited satisfactory repeatability (R < 3%, n = 3) and good linearity in the range of 1–100 μg L⁻¹. Thus, it proved to be an effective tool for monitoring trace cyanide concentration in a series of human body fluid matrices, including meconium. Based on the literature review, this is the first application of the IC-PAD analytical technique for the determination of cyanide ions in meconium samples.     

Preparation and characterisation of monolayers and Langmuir–Blodgett films of liquid crystal mixed with cubic silsesquioxanes

Polyhedral oligomeric silesquioxanes (POSS) with eight polyether substituents were mixed with the liquid crystal (LC) 4-octyloxy-4′-cyanobiphenyl and spread at the air/water interface. The surface pressure-area and surface potential-area isotherms were recorded for different weight ratios of both components. The obtained results showed that POSS molecules had beneficial influence on LC monolayer improving its stability and rigidity. Moreover, it was found that some LC–POSS mixtures collapse reversibly and form multilayer films on the top of LC monolayer. On the other hand, interfacial dilatational and shear rheology indicated decrease of elasticity of the films after mixing. Brewster angle microscopy revealed multilayer structure of the condensed film and formation of net-like structures in the expanded film. These films were successfully transferred on solid substrates using the Langmuir–Blodgett technique. The scanning electron microscopy images confirmed the film deposition and formation of networks by POSS–LC mixtures. These findings may be useful in the fabrication of electronic devices based on LCs.     

Mechanochemical syntheses as an example of green processes

Presented work describes mechanical treatment as a non-conventional solid-state process for preparation of some functional materials. Mechanochemical syntheses may be alternative as waste-free and ecologically safer methods of preparing pigments, composites, catalysts, biomaterials, which obey main principles of Green Chemistry.     

Protein-induced DNA bending: the role of phosphate neutralisation

An important component of protein–nucleic acid interactions is the formation of salt bridges between cationic amino acid side chains and the anionic phosphate groups of the nucleic acid. We have used molecular mechanics to study the energetic and conformational impact of such interactions. Firstly, crystallographic protein–nucleic acid complexes from the Protein Data Bank were analysed in terms of DNA curvature and the presence of salt bridges. For complexes where the DNA is significantly bent, the contribution of salt bridges to this curvature was modelled by studying the effect of neutralising the appropriate phosphate groups. The number and the distribution of salt bridges vary widely for different DNA binding motifs and appear to have very different effects on DNA. In the case of homeodomain, bZIP and helix–loop–helix proteins, salt bridges induce DNA bending, whereas for prokaryotic helix–turn–helix proteins the number of salt bridges is much smaller and little bending is found. By analysing the components of the DNA deformation energy involved in protein binding we show that salt bridges consistently increase the flexibility of the DNA backbone. Received: 1 September 2000 / Accepted: 5 January 2001 / Published online: 3 May 2001