Electrochemical synthesis of niobium compounds in anodic dissolution of ferroniobium in methanol

Anodic dissolution of ferroniobium in anhydrous methanol in the presence of sodium methylate was studied. The possibility of recovering pure hexamethoxyniobate from the electrolyzate and its conversion into niobium methylate with an iron content not exceeding 0.01% was analyzed.     

Effect of Water Vapor on Chromatographic Characteristics of the Cyclodextrin-Containing Stationary Liquid Phase in Capillary Gas Chromatography

The effects of the presence of water vapor in the carrier gas and the temperature on the retention of achiral and chiral compounds, enantioselectivity, and performance of an open-tubular column with a cyclodextrin-containing phase were studied. The use of a carrier gas containing water vapor in the determination of optically active isomers, such as camphor, slightly increases the retention factor. A substantial improvement of performance characteristics of the column was found: for hydroxy compounds, the column performance increased by two to three times and the peak symmetry improved by more than twice.     

Electrical and galvanomagnetic effects in new sodium-doped fullerene composites

The Hall effect, magnetoresistance, the temperature dependence of the electrical resistance, and the current-voltage characteristics of new C₆₀-based carbon-carbon composites were studied in magnetic fields of up to 28 kOe at temperatures T = 1.8–336 K. Sodium-doped samples were used. It is shown that there is weak localization of charge carriers and strong electron-electron interactions. Superconductivity occurs in the range T ≤ 15 K. A mixed current may exist at higher temperatures. Cooper pairs are assumed to form due to the interaction of the conduction electrons with the π-electron system of a C₆₀ molecule.     

Specific structural features and thermal resistance of shungite carbon to graphitization

A Raman scattering study is reported of the structural changes in natural glassy carbon in shungite I induced by a thermal treatment within the 500–2700 °C range in an inert atmosphere. It has been found that thermal treatment results in an insignificant increase of the graphite phase content in the bulk of the samples, whereas in the near-surface regions graphitization of the shungite glassy carbon can be more pronounced. The observed resistance of the shungite to graphitization can be explained within a structural model in which the shungite glassy carbon consists of closely packed nanostructures representing hollow multi-layered globules enveloped in random-network carbon. Fiz. Tverd. Tela (St. Petersburg) 41, 1412–1415 (August 1999)     

Electromigration methods in the determination of synthetic food dyes

Conditions were optimized for separating synthetic food dyes E 102, E 110, E 122, E 124, E 128, E 129, and E 133 by two-dimensional thin-layer chromatography (TLC) on Sorbfil plates using the mobile phase methanol-2-propanol-ethyl acetate-water (1: 1: 2: 2) in both the first (high-performance TLC) and second (electroosmotic TLC) directions. Conditions were selected for separating E 122, E 124, and E 133 by capillary zone electrophoresis; a borate buffer solution with pH 9.2 containing 10 vol % of acetonitrile was used. The time of separation was 16 min.     

Dependence of the relative retention of organic compounds on the nature and pressure of the carrier gas and on the thickness of the PEG-20M film in the capillary column

The effects of the carrier gas nature and pressure on the relative retention values of organic compounds were studied using a series of capillary columns differing in the film thickness of the polar stationary phase (PEG-20M). Relative retention depends linearly on the carrier gas pressure. This dependence becomes more pronounced in the following order of carrier gases: helium < nitrogen < carbon dioxide. The limiting relative retention at a carrier gas pressure approaching zero rather than relative retention values measured experimentally (relative retention time, Kovats retention index,etc.) is an invariant characteristic of a compound subjected to chromatography. For the carrier gases studied, the limiting retention values almost does not depend on the nature of the carrier gas used. The limiting indicating the complex absorption-adsorption nature of these parameters. Dissolution of a carrier gas in the stationary liquid phase has an effect on the relative retention. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2177–2186, December, 1997.     

Application of a Mixed Adsorbent for Flow TLC

JPC – Journal of Planar Chromatography – Modern TLC -     

Crystal hydrates: an investigation of the use of crystal hydrates as stationary phases in gas chromatography

Summary The use of crystallohydrates, crystallohydrate solutions and melts as stationary phases in gas chromatography has been proposed. Crystallohydrates have been shown to display high selectivity in the separation of polar organic compounds when use is made of water vapours as the mobile phase. Some aspects of gas-liquid chromatography in water vapours and with the stationary phase comprising crystallohydrates have been studied, and the preliminary results obtained point to the desirability of further progress in this field.Presented at the 14th International Symposium on Chromatography London, September, 1982