Using gas chromatography, we studied the influence of the nature of substituents in the β-cyclodextrin (CD) molecule on the sorption properties and the possibility of complex formation with the macrocycle of 26 organic compounds (hydrocarbons and alcohols) in binary sorbents based on the smectic–nematic supramolecular liquid crystal 4-(3-hydroxypropyloxy)-4'-formylazobenzene (HPOFAB) and four derivatives β-CD. It has been established that the nature of the substituents in the β-CD molecule significantly affects the manifestation of solvation interactions between LC and macrocyclic additive and, as a consequence, the mesomorphic, sorption, and selective properties of the studied composite sorbents.

A gas chromatographic study of the adsorption of vapors of organic compounds with different polarities on a carbon adsorbent with a bilayer based on a liquid crystal of the “double dovetail” type and unsubstituted β-cyclodextrin is performed. The thermodynamic characteristics of adsorption are determined from the temperature dependences of the Henry constants of adsorption. Comparison of the obtained thermodynamic characteristics of adsorption on an adsorbent with a monolayer of a liquid crystal and a liquid crystal–cyclodextrin bilayer is performed. It is shown that the modified with a bilayer adsorbent possesses moderate selectivity to weakly polar optical isomers under the conditions of gas adsorption chromatography.

The study of the adsorption and selective properties of the composite surface-layer adsorbent SiO2/MIL-100(Cr) was performed using the inverse gas chromatography method. The composite was prepared on the basis of silicon dioxide and MIL-100(Cr) – benzene-1,3,5-tricarboxylate Cr(III), which is a mesoporous metal-organic coordination polymer (MOCP). The textural characteristics of the original MIL-100(Cr) and the composite with it were determined using the method of low-temperature nitrogen adsorption/desorption. A sharp decrease in the specific surface area of the composite compared to the synthesized MOCP was established, which is explained by the low mass content of the latter (15 %) relative to the silica support. Based on experimental data, the thermodynamic characteristics of the adsorption of various hydrocarbons and chlorinated methane derivatives on a surface-layer adsorbent were calculated. An analysis of the specific retention volumes and thermodynamic characteristics of adsorption demonstrated that the composite adsorbent exhibits a mixed adsorption mechanism. Depending on the nature of the adsorbate and the shape and size of its molecule, various types of intermolecular interactions appear, and a sieve effect was also observed. Using cyclohexane as an example, the possibility of the passage of its molecules only into the pores of one type of framework due to the discrepancy between the dimensions of the pore window was demonstrated. It is proposed to consider the interaction of adsorbate molecules with the porous structure of MIL-100(Cr) in the framework of “guest-host” complex formation by analogy with macrocyclic compounds. Surface layer adsorbent SiO2/MIL-100(Cr) exhibited selective properties towards isomeric alkanes and arenes. Separation factor for isomeric octanes at 160 ℃ was 1.4 for the 2,3,4-trimethylpentane/2,2,4-trimethylpentane pair and 1.5 for the 2,3-dimethylhexane/2,2,4-trimethylpentane pair. In the case of xylene isomers, the highest separation factor was observed for o- and m-xylenes (αo/m = 1.2).

The sorption and selective properties of a mixed stationary phase based on an ionic liquid (1-butyl-3-methylimidazolium bromide) and partially methylated β-cyclodextrin are studied by reversed-phase gas chromatography. The thermodynamic characteristics of sorption are determined for 30 volatile organic compounds from different classes. The effect of the size, shape, and polarity of the molecules on the strength of the formed sorbate–macrocycle associates is shown. It is found that the studied stationary phase possesses para-metha -selectivity and enantioselectivity.

In this paper, we report on the fabrication of a new material SiO2@MIL-101(Cr), which synthesis is based on the metal-organic framework MIL-101(Cr) and the silica support Chromosorb W. The obtained surface-layer sorbent was analyzed by powder X-ray diffraction analysis, Raman spectroscopy and porosity measurement. The retention regularities and the thermodynamic characteristics of the sorption of volatile organic compounds from the gas phase were studied for the packed column with the surface-layer sorbent SiO2@MIL-101(Cr). The results indicated that the adsorbent-adsorbate interaction in the mesoporous structure of SiO2@MIL-101(Cr) depends not only on the dispersion attractive forces but also on π-π-stacking and specific interactions with hydroxyl groups and metal cations' open coordination sites on the pore surface. In this work, we gave examples of gas chromatograms of isomers of alkanes, arenes, and chlorine derivatives of methane on a packed column with the obtained sorbent. Examples of gas chromatograms of isomers of alkanes, arenes, and chlorine derivatives of methane on a packed column with the obtained sorbent are presented.

Anomalies observed earlier in the gas chromatographic indices of retention (RIs) of polar compounds (e.g., dimethylformamide) in nonpolar capillary columns are confirmed for packed columns. The anomalies consist of minima in the temperature dependences of retention indices, RI(T), or, in other words, a change in the sign of the dRI/dT derivatives. Such anomalies, especially at a low contents of the stationary phase and temperatures of separation, are additionally confirmed via the recurrent approximation of the retention volumes, VN(Т + 10 K) = aVN(T) + b, where Т is the column temperature. Two consistent ways of interpreting the revealed effects are used. One is based on considering the reversible increase in the polarity of the nonpolar stationary phase in the chromatographic zone, caused by the polar adsorbate in it. The other includes assessing the contributions from adsorption of the adsorbates at the phase boundaries. Both explain the anomalies in RIs, mainly at low temperatures of separation and contents of the stationary phase. A third possible reason (dimerization of the polar adsorbate) is excluded, due to the negligible difference between the contributions from the adsorption of polar dimethylformamide and nonpolar n-heptane. The role of adsorption at the phase boundaries in packed columns is confirmed by estimating the corresponding contributions from adsorption and the increase in the adsorbate retention indices at low contents of the phase on a solid support.

The retention regularities and the thermodynamic characteristics of the sorption of volatile organic compounds from the gas phase were studied for the chromatography columns packed with composite sorbents based on the MIL-53(Al) metal-organic framework and polydiphenyldimethylsiloxane (PPMS). It was shown that with an increase in the content of MIL-53(Al) in the binary sorbent to 73 wt %, retention is predominantly associated with adsorption in the microporous structure of MIL-53(Al) rather than dissolution in the PFMS film. It has been shown that the adsorbate–adsorbent interaction in the orthorhombic channels of MIL-53(Al) depends to a greater extent on the dispersion attractive forces than the dipole–dipole and specific interactions.

The features of the monolayer structure of supramolecular liquid crystals (LC) and "supramolecular LC - beta-cyclodextrin" bilayers placed on a flat carbon surface are presented. The application possibility of these materials in gas-adsorption chromatography is discussed. It is shown that self-organizing ordered planar structures of these modifiers on the adsorbent-carrier carbon surface provide high meta-/para-and ortho-/para-selectivity as well as enantioselectivity to non polar and polar optical isomers.

СвНИИНПИстория развития хроматографии в Самаре тесно связана с именем М.С.Вигдергауза -выдающегося ученого, теоретика и практика, чьи работы во многом изменили представление о возможностях этого направления аналитической химии.Первая часть настоящего исторического обзора охватывает около трех десятилетий, с конца 1950-х до начала 1990-х годов, когда самарская (в то время -куйбышевская) научная школа хроматографии прошла путь от зарождения до зрелого периода, отмеченного целым рядом значительных и ярких достижений

The sorption and selective properties of a composite sorbent based on the supramolecular liquid crystal 4-(3-hydroxypropyloxy)-4'-formylazobenzene (HPOFAB) and partially methylated β-cyclodextrin heptakis-(2,6-di-O-methyl)-β-cyclodextrin (Me2,6-β-CD) have been studied by inverse gas chromatography. The standard thermodynamic functions of sorption on the smectic A phase of the sorbent for 29 volatile organic compounds of different classes were determined and compared with similar functions obtained on a column with “pure” HPOFAB. The reasons for the increase in the retention of all studied compounds (except for the optical isomers of butanediol-2,3) when Me2,6-β-CD (10 wt. %) added to HPOFAB are discussed. It was found that the mixed SA phase of the binary sorbent in conditions of gas-liquid chromatography has moderate values of structural selectivity and enantioselectivity to both low-polar terpene hydrocarbons and polar optical isomers (butanediols-2,3).

A quantum-chemical semi-empirical PM3 and Gaussian 09 method has been used to evaluate the structure of a monolayer of alpha- and beta-cyclodextrins on a carbon surface. The adsorption energies for various types of packing of cyclodextrin molecules in a dense monolayer have been calculated. It has been established that the monolayers with the "sideway" orientation of the cyclodextrin molecules to the carbon surface are most energetically favorable.

The inclusion of volatile organic compounds of various classes in the permethylated β‐cyclodextrin in an oligomeric solution of polyethylene glycol was investigated by inverse gas–liquid chromatography methods and by a stereochemical approach. It was established that the “guest–host” complexation process is influenced by the geometrical structure of the guest molecules, their chirality, and entropy factors.

The isomer-selective properties of the carbon adsorbent Carbopack Y modified by successively applied immiscible monolayers of 4-n-octyloxy-4’-cyanobiphenyl mesogen and β-cyclodextrin have been studied. It has been shown that the bilayer modified adsorbent has a high selectivity to structural and optical isomers under the conditions of the gas-adsorption chromatography. Thermodynamic justification of the selectivity and its temperature dependence has been given. Compensation temperatures for the reversal of the isomer conversion from the chromatographic column have been calculated.

Direct headspace gas chromatographic analysis with flame ionization and mass spectrometric detection was used to identify and quantify volatile organic compounds (VOCs) in the headspace of the medicinal plant material of Common Tansy (Tanacetum vulgare L.) and preparations of its oil and tablet dry extract. All the main components of the headspace of medicinal plant raw material of Tansy are present in the headspace of phytopreparations. The retention indices of VOCs \(\left( {I_{i}^{T}} \right)\) were determined for the linear programmed temperature of a column with a 5% diphenyl–95% dimethylpolysiloxane stationary phase and the relative peak areas (Arl,i) in the chromatogram are determined. It is shown that the specific chromatographic profiles of VOCs, which represent the set of values of \(I_{i}^{T}\) and Arl,i, for Tansy samples from different regions of Russia are similar.