Thermodynamic and Selective Properties of Diatomite Adsorbent Modified with a Mixture of 4-(2-Hydroxyethoxy)-4'-formylazobenzene–µ-oxodimer of Iron 2,8,12,18-Tetramethyl-3,7,13,17-tetra-n-amylporphin under Inverted Gas Chromatography Conditions

Abstract

The sorption of vapors from the gas phase of a number of compounds on the surface of a wide-pore adsorbent Chromaton N-AW modified with a mixture of 4-(2-hydroxyethoxy)-4′-formylazobenzene–µ‑oxodimer 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphine has been studied by the method of inverted gas chromatography. Electrodonor isomers of methylpyridines and dimethylpyridines, isomers of weakly polar xylenes, and a number of enantiomers have been selected as sorbates. The specific retention volumes of sorbates have been calculated, enthalpy and entropy contributions to the sorption process has been shown, and the analytical properties of the resulting stationary phase have been studied. The effect of temperature and the chemical nature of sorbates on the thermodynamic characteristics of sorption has been discussed. The separation factors of both structural and optical isomers and low-boiling hydrocarbons of various structures have been calculated. The influence of both components of the mixture on the sorption process has been considered: the formation of supramolecular ensembles with specific interactions and possible complex formation with iron µ-oxodimer 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphine. It has been experimentally established that the sorbent based on the proposed mixture of mesogenic 4-(2-hydroxyethoxy)-4′-formylazobenzene and the iron µ-oxodimer 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphine exhibits high selectivity with respect to low-boiling compounds of various nature, which is unattainable for an unmodified adsorbent. It has been concluded that the use of the presented modifiers in gas chromatography makes it possible to study new stationary phases based on similar mixtures using macrocycles of various structures and nature, promising from the point of view of both structural and chiral gas chromatography.