K. E. Polunin

Effect of component ratio of binary organic solvent on sorption of phenols by silica

Chromatography is employed to measure the adsorption constants of hydroxybenzenes on SiO2 in a low-concentration region at varied compositions of a binary organic solvent (n-hexane-ethyl acetate). It is shown that the Henry constants vary depending on the polar-to-nonpolar component ratio in the binary solvent and the number and position of hydroxyl groups in phenol molecules. It is found that the absolute values of changes Δ(ΔG) in the free energy considerably increase as the content of ethyl acetate in the mixtures diminishes, with the ratios between the Δ(ΔG) values of ortho-, meta-, and para-isomers remaining practically unchanged. The data obtained can be used to optimize the processes of the adsorption separation of mixed polyphenols and the isolation of natural phenolic compounds on a preparative scale.

The effect of modification on the physicochemical characteristics of shungite

The influence of thermo- and mechanochemical modification of mineral shungite-III (Karelia, Russia) on its chemical composition and physicochemical properties has been studied. A method has been proposed for the mechanochemical modification of shungite, which yields a finely dispersed sorbent with a specific surface area of 70.6 m2/g, a total pore volume of 0.336 cm3/g, and a carbon concentration of higher than 75%. The comparative analysis of the thermolysis of the mineral and modified shungites in air has revealed a difference between the thermal stabilities of the samples. Almost all of the carbon of modified finely dispersed shungite combusts below 500°C, whereas the decomposition of mineral shungite starts above 600°C and only 60% of carbon combusts at 800°C.

Soft ionization mass spectrometry for studying desorption of bioactive compounds from a shungite surface

Ionized products of desorption of biologically active amino compounds (1,1-dimethylhydrazine, diglycine, tyrosine, and tryptophan) from the surface of a modified mineral (shungite-III, Karelia) have been investigated by laser desorption/ionization mass spectrometry methods (MALDI and SALDI). The composition of the ionized products of laser desorption of amino acids from the surface of nanodispersed shungite is almost independent of carbon content in shungite. The comparative analysis of ionized organic compounds desorbed from the surfaces of shungite and carbon black has led to the suggestion that the decomposition and surface transformation of 1,1-dimethylhydrazine molecules mainly occur on the inorganic components of shungite.

Physicochemical Grounds for Application of Schungite for Neutralization of 1,1-Dimethylhydrazine in Wastewater

Chromatography–mass spectrometry and MALDI mass spectrometry have been used to study the interaction of 1,1-dimethylhydrazine and products of its oxidation with the surface of mineral schungite in aqueous solutions. A comparative analysis has been performed for organic compounds contained in initial and equilibrium 1,1-dimethylhydrazine solutions brought in contact with schungite, as well as compounds desorbed from the modified surfaces of the mineral and its inorganic components. The analysis has revealed the efficiency of schungite as a low-cost and environmentally friendly sorbent capable of catalyzing the profound oxidation of 1,1-dimethylhydrazine and products of its transformation to nontoxic low-molecularmass substances. Environmentally safe methods have been proposed for the regeneration of used schungite.

Preparation of a new sorption material based on modified shungite

A method of modification of mineral shungite (shungite-III) material was proposed that made possible a nanodispersive porous sorbent with the carbon content exceeding 75% and the pore size of 19 nm. The effect of the physicochemical modification of shungite on its composition and sorption properties was studied.

Modeling of dynamic separation of hydroxystilbene mixtures in centrifugal chromatography

The separation dynamics of mixtures of trans-stilbene hydroxyl derivatives (4-hydroxystilbene, 4,4′-dihydroxystilbene, α,α′-diethyl-4,4′-dihydroxystilbene (diethylstilbestrol), and 3,5,4′-trihyxrodystilbene (resveratrol)) is studied by the centrifugal (recycling) chromatography method. An algorithm of numerical modeling of the hydroxystilbene concentration front motion under conditions of a preparative thin-layer chromatography on chromatron is proposed. The correspondence of theoretical and experimental results is shown.

Adsorption of stilbenoids on silica

TLC, HPLC, and statistical methods are used to study the adsorption of stilbenoids from organic solvents on SiO2 in a wide range of concentrations. The dependence of adsorption of trans-stilbene hydroxy and methoxy derivatives on the nature of functional groups, their amount and position in the molecular structure, and also on the concentration and proton-acceptor properties of the polar component of the binary organic solvent is found. It is shown that experimental isotherms of stilbenoid adsorption on aerosil from the mixture of n-hexane and ethyl acetate are well approximated by the Freundlich equation. The adsorption of stilbenoids and phenols on SiO2 is compared. It is found that adsorption properties of phenols and hydroxystilbenes with a similar number of OH groups are practically similar.

Effect of Chemical Composition of Shungite Material on Its Sorption Properties

The influence of composition of shungite material on its sorption properties in respect to biologically active compounds with different functionality is studied using mass spectrometry methods. It is shown that the concentration of the organic component in shungite weakly affects the composition of the ionized products of laser desorption of phenol, benzoic acids, and amines from its surface.

Interaction of diphenylpolyenes with SiO2 surface under conditions of liquid chromatography

Thin-layer and high-performance liquid chromatography methods have been employed to study the interaction of diphenylpolyenes with the surfaces of SiO2 (silica gel) and SiO2-C18 in organic and aqueous media. Electronic absorption spectra of diphenylpolyenes have been measured in different solvents, and the constants of their chromatographic retention on the solid phase surface have been determined. The interaction of diphenylpolyenes with SiO2 surface in a binary organic solvent and with SiO2-C18 surface in a water-organic solvent has been shown to intensify in the series cis-1,2-diphenylethylene < trans-1,2-diphenylethylene < trans-1,4-diphenyl-1,3-butadiene < trans-1,6-diphenyl-1,3,5-hexatriene. The retention constants of diphenylpolyenes have been revealed to depend on the geometry and configuration of their molecules, the length of an olefin fragment, and the nature and polarity of an eluent.

Thermal resistance of composites based on nanodispersed aluminum

Thermolysis of low and high molecular aliphatic carboxylated compounds in composite systems based on nanosized aluminum were studied by the thermal desorption mass spectrometry. The conditions for maximal separation of the thermolysis products and their composition were determined. The kinetic parameters of thermal desorption and thermal degradation of the modifiers were calculated. Differences in the thermal stabilities of the polymer composites based on nanosized aluminum and different modifiers (carboxylated divinyl and divinyl nitrile oligomers) were presented.