Sorption Redistribution of Volatile Organic Substances in a Mixed Gas-Liquid Crystal-Macrocycle-Adsorbent System under Inverse Gas Chromatography Conditions

Abstract

4-[(S)-2-Methyl-3-hydroxypropyloxy]-4'-formylazobenzene, 4-(3-hydroxypropyloxy)-4'-formylazobenzene and µ-oxodimer of iron 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphine were synthesized using known methods. A mixture with a certain concentration of components was prepared from the synthesized compounds. The resulting mixture was used as an impregnation of the wide-porous adsorbent Chromaton N-AW. The degree of impregnation was 10%. The prepared adsorbent was used as a stationary phase for inverse gas-mesophase chromatography. In this work, the sorption redistribution of a number of volatile organic compounds—isomers of methyl and dimethylpyridines, weakly polar xylenes and enantiomers from the gas phase on the prepared adsorbent was studied using inverse gas chromatography. During the experiment, the specific retention volumes of sorbates, characterizing the sorption activity of the prepared stationary phase were calculated. For structural isomers, activity coefficients for the distribution of sorbates in the liquid layer of the liquid crystal were obtained. To confirm the data on the sorption activity of sorbates, the thermodynamic parameters of the dissolution of specific isomers were found. Conclusions were drawn about the influence of enthalpy and entropy factors on the retention ability of sorbates. The influence of structure, isomerism, intermolecular interactions, and the addition of a macrocycle on the sorption properties of sorbates is discussed. Data on the analytical features of sorption were obtained, namely, the maximum values of separation factors for structural and optical isomers and compounds of different structures, but with similar boiling points, were calculated. It was experimentally established that the prepared adsorbent exhibits a fairly high ability to separate close-boiling structural isomers and a moderate ability to separate enantiomers. Emphasis is placed on the maximum value of the separation factor of 3,4- and 3,5-lutidines, which is the highest in value among the previously developed stationary phases of similar structure. In conclusion, the use of the resulting adsorbent in a unified system of chemical analysis is justified.