Solubility of copper (I) bromide in aqueous solutions of potassium bromide

The solubilities of cuprous bromide were measured at 24.8°C in aqueous KBr and in aqueous KBr-KNO₃ mixtures. The results have been analyzed to give equilibrium constanns from formation of neutral and negatively charged complexes of CuBr, and sets of virial parameters suitable for calculation of activity coefficients for the complexes.     

The rhodium complex of a tris(bipyridine) ligand—Its electrochemical behaviour and function as mediator for the regeneration of NADH from NAD+

The tris-bipyridine ligand3a and its stoichiometric Rh³⁺ complex have been prepared. Cyclovoltammograms of the complex at pH 7.4 using a glassy carbon disk electrode reveal a strong reduction peak at –620 mV and two weak reduction peaks at more negative voltage. The reduction potential of the new complex is shifted by 300 mV to more positive values as compared to [Rh(bipy)₃]³⁺. There is no reversible reoxidation peak of the Rh(I) complex formed due to the decomplexation of one of the three bipyridine units in the course of the transition Rh(III)Rh(I). The Rh(III) complex of3a was also studied with respect to its function as a possible redox mediator for the electrochemical regeneration of NADH from NAD⁺. The preparative electrolysis of the Rh³⁺ complex of3a in the presence of NAD⁺ yields a selective formation of NADH, whereas NAD dimers were not detected. On the other hand, a significant acceleration of this reaction compared to [Rh(bipy)₃]³⁺ was not observed.     

ANTIVIRAL ACTIVITY OF MEROCYANINE 540

Abstract Simultaneous exposure to the lipophilic dye merocyanine 540 (MC 540) and white light inactivates several enveloped viruses. The same treatment appears to have little or no effect on pluripotent hematopoietic stem cells, mature red cells, and mature leukocytes. At least some components of the clotting system are spared, too. The molecular basis of the virucidal effect of MC 540 and light is not yet completely understood. Based on what is known about the interactions of MC 540 with cells and artificial membranes, it seems likely that MC 540 binds to and damages the viral envelope. MC 540-mediated photosensitization may have implications for the sterilization of bone marrow and blood products, the preparation of vaccines, and selected areas of antiviral therapy.     

Single-column method of ion chromatography for the determination of common cations and some transition metals

A single-column method for the simultaneous determination of common cations and transition metals in real samples is proposed in this paper. Eleven cations (copper, lithium, sodium, ammonium, potassium, cobalt, nickel, magnesium, calcium, strontium and zinc) were separated and analyzed by means of ion chromatography using an isocratic elution with 2.5 mM methane sulfonic acid and 0.8 mM oxalic acid as mobile phase, IonPac SCS1 (250 mm x 4 mm I.D.) as the separation column and non-suppressed conductor detection. Optimized analytical conditions were further validated in terms of accuracy, precision and total uncertainty and the results showed the reliability of the IC method. The relative standard deviations (RSDs) of the retention time and peak area were less than 0.04 and 1.30%, respectively. The coefficients of determination for cations ranged from 0.9988 to 1.000. The method developed was successfully applied to determination of cations in samples of beer and bottled mineral water. The spiked recoveries for the cations were 94-106%. The method was applied to beer and beverage without interferences.     

Activation of Hydrogen Peroxide by Ionic Liquids: Mechanistic Studies and Application in the Epoxidation of Olefins

Imidazolium‐based ionic liquids that contain perrhenate anions are very efficient reaction media for the epoxidation of olefins with H₂O₂ as an oxidant, thus affording cyclooctene in almost quantitative yields. The mechanism of this reaction does not follow the usual pathway through peroxo complexes, as is the case with long‐known molecular transition‐metal catalysts. By using in situ Raman, FTIR, and NMR spectroscopy and DFT calculations, we have shown that the formation of hydrogen bonds between the oxidant and perrhenate activates the oxidant, thereby leading to the transfer of an oxygen atom onto the olefin demonstrating the special features of an ionic liquid as a reaction environment. The influence of the imidazolium cation and the oxidant (aqueous H₂O₂, urea hydrogen peroxide, and tert‐butyl hydrogen peroxide) on the efficiency of the epoxidation of cis‐cyclooctene were examined. Other olefinic substrates were also used in this study and they exhibited good yields of the corresponding epoxides. This report shows the potential of using simple complexes or salts for the activation of hydrogen peroxide, owing to the interactions between the solvent medium and the active complex.     

Vacancy ion-exclusion chromatography of carboxylic acids on a weakly acidic cation-exchange resin

In this preliminary study, a new approach to ion-exclusion chromatography is proposed to overcome the relatively poor conductivity detection response which occurs in ion-exclusion chromatography when acids are added to the eluent in order to improve peak shape. This approach, termed vacancy ion-exclusion chromatography, requires the sample to be used as eluent and a sample of water to be injected onto a weakly acidic cation-exchange column (TSKgel OApak-A). Vacancy peaks for each of the analytes appear at the retention times of these analytes. Highly sensitive conductivity detection is possible and sharp, well-shaped peaks are produced, leading to efficient separations. Retention times were found to be affected by the concentration of the analytes in the eluent, and also by the presence of an organic modifier such as methanol in the eluent. Detection limits for oxalic, formic, acetic, propionic, butyric and valeric acids were 0.1, 0.2, 0.3, 0.3, 0.4 and 0.5 microM, respectively, and linear ranges for some acids extended over two orders of magnitude. Precision values for retention times were 0.21% and for peak areas were <1.90%. The vacancy ion-exclusion chromatography method was found to give detection responses four to 10 times higher than conventional ion-exclusion chromatography using sulfuric acid eluent and two to five times higher than conventional ion-exclusion chromatography using benzoic acid eluent.