Dependence of the efficiency of a multicapillary column on the liquid phase loading method

One of the main approaches employed to reach fast chromatographic separation is based on using columns containing up to 1000 capillaries with the diameter size down to 10-100 microm. The efficiency of such columns depends on the dispersion of the capillary radius and on the way of the liquid-film loading. We present general equations describing these effects. Specifically, we show theoretically and experimentally that the separation efficiency can be improved by using the loading methods specially designed in order to take into account correlation between the film thickness and capillary radius.     

Mechanism of the liquid-phase oxidation of diethyl sulfide catalyzed by heteropoly acids

It has been established that in the oxidation of diethyl sulfide by¹⁸O₂ in CH₃C¹⁶O₂H–H₂ ¹⁶O solution at 369 K catalyzed by heteropoly acids, sulfoxide and sulfone with 44–54%¹⁸O enrichment are formed. The process is accompanied by isotope exchange of molecular oxygen.

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, ¹⁸O₂ CH₃C¹⁶O₂H–H₂ ¹⁶O 369 ¹⁸O 44–54%, .

     

Voltammetric identification of motor oils using an “electronic tongue”

The possibility of the voltammetric identification of motor oils using a chemometric method of the principal component analysis and voltammograms of metal ions and organic markers (Cu(II), Pb(II), o- and p-aromatic nitro compounds) on carbon paste electrodes containing analytes as binders.     

Quantitative analysis of physical factors that determine the behavior of activity coefficients of electrolytes

The development of theoretical ideas on the cause and the mechanism of the change of activity coefficients is the main aim of the investigation. The model describing the interaction of hydrated ions in electrolytes is proposed. In the model the electrostatic forces between ions and change of the energy of the hydrate shell in the process of ion convergence determine ions distribution in solution. The significant factor is the dependence of dielectric permittivity on the concentration of the electrolyte and on the distance to ion. The statistical approach developed allows one to calculate the influence of principal physical factors and, on this basis, to explain the nature of curves describing the activity coefficients. The results of simulation have been tested on a large number of experimental data.     

Multicapillary columns with a porous layer based on the divinylbenzene copolymer

A method for preparing a multicapillary column with a porous layer based on the styrene-divinylbenzene copolymer has been developed. The column makes it possible to quickly separate C₁–C₄ hydrocarbons and oxygen-containing compounds. The main chromatographic properties of the columns were studied.     

Investigation of structure and properties of divinylbenzene-styrene copolymer films

A method for preparation of divinylbenzene-styrene copolymer porous layer on the inner wall of a fused silica capillary was developed. Capillary gas chromatography was used to investigate the sorption capacity of copolymer film toward substances of various classes.     

Differentiation of Different Sorts of Sugars by the CAPoNeF Method

The proposed method as CAPoNeF (Comparative Analysis of Positive and Negative Fluctuations) allows to “read” any trendless sequence quantitatively irrespective of the imposed model and treatment errors that inevitably accompany random sequence. This method will have a wide possibility because of its generality and simplicity in possible applications. In particular, the proposed strategy makes it possible to detect weak signals in the time electrochemical series caused by the presence of random micro-impurities in the studied solutions as objects of analysis. On the example of the current-voltage time series of sugar syrups of various manufacturers, the possibility of identifying numerical parameters is shown. Hidden in the noise, analytical signals can be used to express the similarity or difference between sugars from different manufacturers.     

Spherical 7-Designs in 2 n -Dimensional Euclidean Space

We consider a finite subgroup _n of the group O(N) of orthogonal matrices, where N = 2 ⁿ , n = 1, 2 .... This group was defined in [7]. We use it in this paper to construct spherical designs in 2 ⁿ -dimensional Euclidean space R ^N . We prove that representations of the group _n on spaces of harmonic polynomials of degrees 1, 2 and 3 are irreducible. This and the earlier results [1–3] imply that the orbit _n,2 x ^t of any initial point x on the sphere S _{N – 1} is a 7-design in the Euclidean space of dimension 2 ⁿ .     

Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .