Thin-layer chromatography with high-boiling mobile phases.1. Investigation of the flow of the high-boiling mobile phases

This paper considers some aspects of a new TLC technique using a molten mobile phase which is solid under ambient conditions. The flow of high-boiling mobile phase at elevated temperature in thin-layer chromatography has been investigated and it is shown that the equation Z_f² = kt is not applicable to migration of the high boiling mobile phase front. The flow stability of the high-boiling mobile phase is noted. It is suggested on the basis of studies of concentration profiles of the solidified mobile phases by scanning photometers that the shape of the mobile phase concentration profile be taken into account in calculation of R_f Values.     

Application of capillary gas chromatography for physico-chemical measurements particularly considering the influence of adsorption on the liquid phase-tube wall interface

Summary Utilization of capillary chromatography for the quantitative definition of the thermodynamic values of the solute/liquid phase interaction is shown. A method is given to define the pure values of the distribution coefficients of volatile compounds in a gas-liquid phase system with the use of an intermediate standard for which adsorption interaction can be neglected. It is shown that the definition of the heats of solution of polar solutes in a cross-linked liquid phase leads to higher values if adsorption interaction is not taken into account.     

Use of low volatility mobile phases in electroosmotic thin-layer chromatography

A variant of electroosmotic thin-layer chromatography is suggested with the use of low volatility compounds as mobile phases aimed at drastically decreasing the evaporation of the mobile phase and improving the reproducibility of the method. The linear movement velocity of zones of separated compounds is experimentally shown to increase 2-12-fold in electroosmotic chromatography (compared to similar values in traditional TLC). The separation efficiency is also considerably increased.     

A new method of thin-layer chromatography with controlled vapor phase

A new version of thin-layer chromatography with controlled vapor phase is described. It has no analogues in planar and liquid chromatography. The method is based on a dynamic change in the physicochemical properties of a chromatographic system as a result of the contact of the plate bearing analytes with a vapor phase of certain composition created in the chromatographic chamber. The active vapor phase is created either by pumping a gas through the chromatographic chamber or by introducing a solvent vapor from another part of the chamber. The composition and properties of the mobile phase are controlled immediately in the course of separation by means of absorption or adsorption of one or another gas with the mobile or stationary phase. By the examples of benzoic acids and nitroaniline isomers in the presence of carbon oxide and vapors of acetic acid, ammonia, and ethanol, it was shown that this procedure utilizes the difference in the protolytic and solvation properties of adsorbates for changing the adsorption equilibrium and the selectivity and efficiency of separation.     

Molecular Recognition in Solutions of Rod‐Like Copolymers with Two Different Sequences

Segregation in a solution of rigid copolymeric molecules with two different sequences leading to co‐existence of two smectic mesophases has been studied. Thermodynamic characteristics of these mesophases and their equilibrium compositions were found in the frame of two discrete models. It was shown that the degree of ordering in the mesophase depends on the sequence of units in the identical molecules forming this mesophase. The concentration of “mismatched” molecules in the mesophase (the purity of mesophase) is determined both by the composition and the sequence of such molecules. It was shown, that a difference in the sequences can be sufficient to cause phase separation.

     

Gas–Adsorption Chromatography of Reactive Compounds on Open-Tubular Columns with Poly(trimethylsilylpropyne)

The possibility of using a new poly(trimethylsilylpropyne) adsorbent for the separation of volatile inorganic hydrides and chlorinated organic compounds in capillary gas chromatography has been studied. Excellent separation properties of columns with the proposed adsorbent have been demonstrated.     

Study of a New Version of Classical Thin-Layer Chromatography with a Closed Adsorbent Layer

JPC – Journal of Planar Chromatography – Modern TLC -     

Electrochemical synthesis of sodium hexamethoxyniobate

Anodic dissolution of niobium in anhydrous methanol in the presence of sodium methylate was studied. A method for recovery of niobium methylate from sodium hexamethoxyniobate by the reaction with ammonium chloride was developed.