Stationary Phases In Gas-liquid Chromatography Research Articles

SYNTHESIS, PROPERTIES, AND APPLICATIONS OF SUPRAMOLECULAR LIQUID CRYSTAL MATERIALS AND ACRYLAMIDE PORPHYRIN POLYMERS

A review of the work in the field of design, study of properties, and application of liquid crystal materials and acrylamide porphyrin polymers, performed at the Department of Chemistry and Technology of High-molecular Compounds, in the laboratory of Supramolecular and liquid crystal systems and in the laboratory of Polymer materials of the Research Institute of Macroheterocyclic compounds of the Ivanovo State University of Chemical Technology over the past 10 years, is presented. Synthetic methods were developed, mesogenic compounds and mixed liquid crystal compositions based on classical and supramolecular mesogens doped with additives containing polar, amphiprotic and chiral groups were obtained and studied. The mechanisms of chiral transport in the mesophase were studied. The results on the use of liquid crystals as light and heat stabilizers of polymeric materials are presented. Stationary phases for gas-liquid chromatography based on supramolecular mesogens, macroheterocyclic compounds with high structural selectivity with respect to various isomers were developed. Methods have been developed for the synthesis of water-soluble porphyrin polymers and porphyrin-containing hydrogels based on acrylamide and synthetic porphyrin monomers, realizable both under thermal heating and under microwave radiation. It is shown that a change in the ratio and nature of the components, as well as the polymerization conditions in the synthesis of porphyrin polymers provides targeted control of the properties of the resulting compounds. The molecular-mass and spectral characteristics of the obtained polymers, their surface morphology and sorption properties of porphyrin-containing acrylamide hydrogels are investigated. For citation: Burmistrov V.A., Aleksandriiskii V.V., Novikov I.V., Pechnikova N.L., Shilov I.V., Lyubimtsev A.V., Ageeva T.A., Koifman O.I. Synthesis, properties, and applications of supramolecular liquid crystal materials and acrylamide porphyrin polymers. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 7. P. 31-51. DOI: 10.6060/ivkkt.20236607. 6832j.

Nematic Mesogen with 1,3,4-Oxadiazole Unit as Stationary Phase in Gas-Liquid Chromatography

This paper is the first that deals with the new synthesis of nematic liquid crystal titled bis-[5-yl-phenylbenzidine-4`-butyloxyphenly-2-yl-1,3,4-oxadiazole] and secondly discusses research on materials that can be used in stationary phase by using (GLC) as a type of chromatography. The usage of bis-[5-yl-phenylbenzidine-4`-butyloxyphenly-2-yl-1,3,4-oxadiazole]nematic phase has resulted in a lot of superb separations of a lot of poly aromatic hydrocarbons. The retention time change in an unusual way with temperature, appearance a significant increase at the normal liquid transmission point; as expected, that impact is reduced with further planar compounds. FT-IR and 1HNMR were used to characterize the synthesized chemical structure, and POM and DSC were used to investigate the liquid crystalline characteristics.

IONIC LIQUID STATIONARY PHASES IN GAS CHROMATOGRAPHY: FUNDAMENTALS, RECENT ADVANCES, AND PERSPECTIVES

Since their original discovery in 1914, ionic liquids (IL) have been widely examined and explored in chemistry due to their unique physical and chemical properties. Ionic liquids are collectively known as organic salts and have melting points of 100 °C or under. The molten salts most employed in analytical chemistry, including gas chromatography (GC), consist of an organic cation paired with an organic or inorganic anion. This class of materials exhibits negligible vapor pressure and may have their properties (e.g.thermal stability and selectivity) structurally tuned by imparting different moieties to the cation/anion. Currently, there are an estimated 1018possible combinations of IL. In this context, the prospection of highly selective IL-based stationary phases for gas-liquid chromatography has enabled high peak capacity and efficient separations of many critical pairs in complex samples. In this review, we present and discuss fundamental characteristics of ionic liquids and introduce important solvation models for gas-liquid systems. In addition, recent advances and applications of IL in conventional and multidimensional gas chromatography are outlined.

ChemInform Abstract: Hydrogen Bonding. Part 14. The Characterization of Some N-Substituted Amides as Solvents: Comparison with Gas-Liquid Chromatography Stationary Phases.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Determination of solute partition behavior with room-temperature ionic liquid based micellar gas–liquid chromatography stationary phases using the pseudophase model

The use of micelles in ionic liquid based gas-chromatography stationary phases was evaluated using equations derived for a “three-phase” model. This model allows the determination of all three partition coefficients involved in the system, and elucidates the micellar contribution to retention and selectivity. Four types of micellar-ionic liquid columns were examined in this study: 1-butyl-3-methylimidazolium chloride with sodium dodecylsulfate or dioctyl sulfosuccinate, and 1-butyl-3-methylimidazolium hexafluorophosphate with polyoxyethylene-100-stearyl ether or polyoxyethylene-23-lauryl ether. The partition coefficients were measured for a wide range of probe molecules capable of a variety of types and magnitudes of interactions. In general, most probe molecules preferentially partitioned to the micellar pseudophase over the bulk ionic liquid component of the stationary phase. Therefore, addition of surfactant to the stationary phase usually resulted in greater solute retention. It is also shown that the selectivity of the stationary phase is significantly altered by the presence of micelles, either by enhancing or lessening the separation. The effects of surfactant on the interaction parameters of the stationary phase are determined using the Abraham solvation parameter model. The addition of sodium dodecylsulfate and dioctyl sulfosuccinate to 1-butyl-3-methylimidazolium chloride stationary phases generally increased the phase's hydrogen bond basicity and increased the level of dispersion interaction. Polyoxyethylene-100-stearyl ether and polyoxyethylene-23-lauryl ether surfactants, however, enhanced the π–π/n–π, polarizability/dipolarity, and hydrogen bond basicity interactions of 1-butyl-3-methylimidazolium hexafluorophosphate to a greater degree than the ionic surfactants with 1-butyl-3-methylimidazolium chloride. However, these nonionic surfactants appeared to hinder the ability of the stationary phase to interact with solutes via dispersion forces. Therefore, it is possible to effectively predict which analytes will be most highly retained by these micellar-ionic liquid stationary phases.

Specific Surface of a Stationary Phase in Gas-Liquid Chromatography

A model of the surface of a stationary phase in gas-liquid chromatography based on the statistic theory of macromolecules was considered. Quantitative relationships between the capacity of a liquid adsorbent and its molecular structure were determined.

Immobilized Ionic Liquids as High-Selectivity/High-Temperature/High-Stability Gas Chromatography Stationary Phases

Ionic liquids (ILs) are a class of nonmolecular solvents in which the cation/anion combination can be easily tuned to provide desired chemical and physical properties. When used as stationary phases in gas-liquid chromatography, ionic liquids exhibit dual nature retention selectivity. That is, they are able to separate polar molecules such as a polar stationary phase and nonpolar molecules such as a nonpolar stationary phase. However, issues such as optimization of the wetting ability of the ionic liquid on fused-silica capillaries, the maximum operating temperatures of the stationary phases, and nonuniform film thickness on the wall of the capillary at high temperatures have limited their use in gas chromatography. As described in this paper, these limitations are overcome by cross-linking a new class of ionic liquid monomers by free radical reactions to provide a more durable and robust stationary phase. By lightly cross-linking the ionic liquid stationary phase using a small amount of free radical initiator, high-efficiency capillary columns were produced that are able to endure high temperatures with little column bleed. Two types of cross-linked IL stationary phases are developed. A partially cross-linked stationary phase allows for high-efficiency separations up to temperatures of approximately 280 degrees C. However, by creating a more highly cross-linked stationary phase of geminal dicationic ILs, exclusively, an increase in efficiency is observed at high temperatures allowing for its use over 350 degrees C. In addition, through the use of solvation thermodynamics and interaction parameters, it was shown that the cross-linking/immobilization of the ionic liquid does not affect the selectivity of the stationary phase thereby preserving its dual nature retention behavior.

High-Stability Ionic Liquids. A New Class of Stationary Phases for Gas Chromatography

Room-temperature ionic liquids are a class of non-molecular ionic solvents with low melting points. Their properties have the potential to be especially useful as stationary phases in gas-liquid chromatography (GLC). A series of common ionic liquids were evaluated as GLC stationary phases. It was found that many of these ionic liquids suffer from low thermal stability and possess unfavorable retention behavior for some classes of molecules. Two new ionic liquids were engineered and synthesized to overcome these drawbacks. The two new ionic liquids (1-benzyl-3-methylimidazolium trifluoromethanesulfonate and 1-(4-methoxyphenyl)-3-methylimidazolium trifluoromethanesulfonate) are based on "bulky" imidazolium cations with trifluoromethanesulfonate anions. Their solvation characteristics were evaluated using the Abraham solvation parameter model and correlations made between the structure of the cation and the degree to which the ionic liquids retain certain analytes. The new ionic liquids have good thermal stability up to 260 degrees C, provide symmetrical peak shapes, and because of their broad range of solvation-type interactions, exhibit dual-nature selectivity behavior. In addition, the ionic liquid stationary phases provided different retention behavior for many analytes compared to a commercial methylphenyl polysiloxane GLC stationary phase. This difference in selectivity is due to the unique solvation characteristics of the ionic liquids and makes them very useful as dualnature GLC stationary phases.

Optimization of separation on the basis of unifac parameters and evaluation of the composition of the stationary phase in gas-liquid chromatography

An algorithm for the optimisation of separation in gas-liquid chromatography based on varying the composition of the stationary phase and the column temperature is presented using the critical parameter Rs≥0.75 (σRs→max). The stationary phase composition, on the basis of retention parameters expressed in terms of vapour pressure and activity coefficient has been derived. Determination of the composition of the stationary liquid was carried out by defining the noture of solute-solvent interactions using group additive value contributions to the activity coefficients. Predicting values on experimentally determined parameters reduced calculation errors by a factor 2 to 3.

Comparison of two azobenzene liquid crystal stationary phases in open tubular column gas chromatography

Comparative applications of two liquid crystals used as stationary phases in gas-liquid chromatography were investigated using different kinds of solutes. These liquid crystal molecules are: 4-(4-trans-pentylcyclohexanecarboxyloxy)-2′-methoxy-4′-(4-trans-pentylcyclohexanecarboxyloxy)-azobenzene (LC1) and 4-(4-trans-pentylcyclohexanecarboxyloxy)-2′-butoxy-3′-methyl-(4-butoxybenzoyloxy)-azobenzene (LC2). Their thermal properties were established with differential scanning calorimetry (DSC). The chromatographic separation abilities of LC1 and LC2 were studied using capillary glass columns. Interesting analytical performances were obtained in different fields: isomeric separation of alkanes, aromatics, polyaromatics, volatile aromatic compounds and cis- and trans-isomers. Comparison between LC1 and LC2 is presented. Elution properties of LC1 and LC2 showed some differences. LC2 exhibited a higher separation efficiency especially for alkanes, light aromatics and polyaromatics, and the elution orders of some solutes were reversed compared with LC1. Then, the two liquid crystals are efficient before and after solid-solid or solid-nematic transitions. Nevertheless, they present higher plate numbers in the nematic state. Nice separations of volatile aromatic compounds are obtained by the two liquid crystals.

Glycerol as a new dissolution medium for α-, β- and γ-cyclodextrins for preparing stereoselective stationary phases for gas-liquid chromatography

Glycerol was applied as the dissolution medium for α, β- and γ-cyclodextrins and its gas-liquid chromatographic performance was compared with that of formamide. Various stationary glycerol-based chiral phases for classical gas-liquid chromatography were examined. The columns containing glycerol appeared relatively stable in comparison with those prepared with formamide. Glycerol-based phases functioned over the temperature ranged 80–100°C for about 400 h without any changes indicating losses of glycerol or activity. Owing to the lower stability of cyclodextrin complexes in glycerol medium relative to those in formamide, and the fact that glycerol-based columns allow operation ca. 40°C higher, many separations which were previously unreported at higher temperatures were achieved. The model compounds tested were (+/−)-α-pinene, cis/trans-decalin, cis/trans-anethole, cis/trans-isosafrol, cis/trans-isoeugenol, (+/−)-camphor, (+/−)-fenchone, (+/−)-isomenthone, (+/−)-isoponocampheol, (+/−)-borneol and (+/−)-isoborneol.

Application of substituted liquid crystals as stationary phases in gas-liquid chromatography for the separation of mono-and dimethyl naphthalenes

Thirteen mono- and dilaterally substituted liquid crystalline compounds were investigated for their gas chromatographic behaviour as stationary phases for the separation of mono- and dimethylnaphthalenes. A normal packed column system was used. These compounds offered a good separation for some pairs of methylnaphthalenes.

P-Alkoxy- andp-alkylbenzoates of α, a'-bi-p-hydroxytoluene. New series of liquid-crystalline compounds

Abstract Six p-alkoxy and eight p-alkylbenzoates of 1,2-(p-hydroxyphenyl)ethane were synthesized for potential use as stationary phases in gas-liquid chromatography. All the p-alkoxy derivatives were nematic. The first five members of the alkyl series were nematic and the rest exhibited both smectic and nematic character. Most possess the desired combination of a wide liquid-crystalline temperature range and a high mesomorphic-isotropic transition temperature. The nematic-isotropic transition temperatures and entropies show the usual alternations characteristic of a high-melting series.

Hydrogen bonding. Part 14. The characterisation of some N-substituted amides as solvents: comparison with gas–liquid chromatography stationary phases

Equations previously used for the characterisation of GLC stationary phases have been found to be equally suitable for the characterisation of common solvents. Thus equation (a) has been applied to solubility data for series of solutes on N-formylmorpholine (NFM), N-methylpyrrolidinone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylace amide (DMA).SP =c+r·R2+s·π2*+a·α2H+b·β2H+I· log L16(a)In equation (a), SP can be log V°G or log L for a series of solutes on a given solvent where V°G is the specific retention volume and L is the Ostwald solubility coefficient. The solte parameters are R2, a polarisability parameter; π2*, the solute dipolarity; α2H, the solute hydrogen-bond acidity; β2H, the solute hydrogen-bond basicity; and log L16 where L16 is the solute Ostwald solubility coefficient on n-hexadecane at 298 K.It is shown that at 298 K all four amides have about the same dipolarity, as judged by the s-constant, and have nearly the same hydrogen-bond basicity, as judged by the a·α2H term: all have zero hydrogen-bond acidity so that b= 0 in equation (a). Comparison can be made between results for NFM and NMP at 393 K and results for some GLC stationary phases. The two amides are less dipolar than tricyano(ethoxy) propane and diethyleneglycol succinate, about the same as Zonyl E-7®and Carbowax®, and more dipolar than poly(phenyl ether). The amides, however, have rather more hydrogen-bond basicity than any of the above five GLC phases. It is suggeted that equation (a) can be used as the basis of method for characterising condensed phases, such that common solvents as well as GLC stationary phases can be included within the scope of the method.

Proposed substitution of apolane-87 for squalane as a nonpolar reference phase in gas chromatography

Squalane is the standard, nonpolar reference phase used in schemes to characterize the solvent strength and selectivity of stationary phases in gas-liquid chromatography. A commentary, supported by additional experimental evidence, is provided to indicate a lack of suitability for this purpose. Primary objections to its use as a reference phase are its high volatility, compositional variations due to the presence of impurities, susceptibility to oxidative degradation, poor film forming and stabilizing properties, and retention properties that are strongly influenced by the character and treatment of the support used to prepare column packings. Because similar problems were not observed, or were much less significant, for the synthetic hydrocarbon Apolane-87, its use as a reference phase is to be preferred. Reference values for retention indexes, gas—liquid partition coefficients, and partial molal Gibbs free energies of solution for a series of solvent-selectivity test solutes are provided for both phases.

Dispersive force parameters as a measure of the polarity of surfactants used as stationary phases in gas-liquid chromatography

The possibility of describing the polarities of compounds by the use of dispersive force parameters is examined. Relationships between the structures of the compounds examined and these parameters are derived. The increments in the parameters for selected structural fragments are also presented.

Determination of surface polarity by heterogeneous gas-solid chromatography

A polarity scale for heterogeneous surfaces is proposed that uses energy distribution functions calculated from chromatographic retention data. The energy required to form a complete monolayer (E/sub mon/, obtained from the energy distribution function, has been chosen as the parameter best suited for describing the heat of adsorption on a heterogeneous surface. E/sub mon/ values for chloroform (proton donor), pyridine (proton acceptor), and dichloromethane (dipole interactor) are used as parameters in the surface polarity scale that is analogous to the Rohrschneider and McReynolds scales that describe the polarity of gas-liquid chromatography stationary phases. Monolayer energies have also been used to construct a surface selectivity triangle. Results are presented for a variety of surfaces differing in the relative number of acidic, basic, and dipolar sites.

A novel group of very long chain polyenoic fatty acids in dipolyunsaturated phosphatidylcholines from vertebrate retina.

Dipolyunsaturated phosphatidylcholines from bovine retina contain a whole series of unusual fatty acids. Methyl esters from these acids are very strongly retained on polar and nonpolar gas-liquid chromatography stationary phases. On thin layers of silica-AgNO3, they separate as tetra-, penta-, and hexaenoic fatty acid methyl esters. After hydrogenation, the three polyunsaturated fractions give the same series of saturated methyl esters, having 20 (or 22)-36 carbon atoms. High pressure liquid chromatography, as well as gas-liquid chromatography, indicates that the new components of the three fractions are even-carbon homologs of well known polyenoic fatty acids of the n-6 and n-3 families, since they behave as series of 20-36-carbon tetraenoic (n-6), pentaenoic (n-3 and n-6), and hexaenoic (n-3) fatty acids. Their occurrence in phospholipid molecules also having docosahexaenoate (22:6) explains the separation of major dipolyunsaturated phosphatidylcholines from retina into dodecaenoic, undecaenoic, and decaenoic fractions after argentation thin layer chromatography. Using high pressure liquid chromatography, the latter are resolved into individual species having 10-12 double bonds and 42-58 carbon atoms. The unusual PCs are thus endowed not only with the highest degree of unsaturation, but with the longest hydrocarbon chains yet reported for vertebrate glycerophospholipids. It is shown that phosphatidylcholines containing the novel fatty acids are highly concentrated in photoreceptor membranes and that they occur in the retina of vertebrates so distant in evolution as fish, birds, and various mammals.

Spectroscopy and the classification of liquid stationary phases in gas-liquid chromatography

A table of data for acidity, basicity, polarity and London potential for stationary phases is given. These provide guidance in choosing a stationary phase for a given task from the 26 substances listed. The indices are calculated from infra-red shifts of 1-chlorobutane and the visible wavelength shifts of l2 when they are dissolved in the stationary phases, from NMR estimates of acidity and basicity and from relative retention data. They replace the less reliable data of Burns and Hawkes. Methods of determining the indices are suggested that require only a gas chromatograph and can be applied by technicians with no specialized understanding of solution parameters. An attempt to add electron donoracceptor indices to the table was unsuccessful. A further table is given of the slopes of the log plots d(logt′)/dC for use in extrapolating from one homologue to another on these stationary phases.

Prediction of retention data by using parameters of intermolecular interaction : I. A model for calculation of non-polar and polar interaction parameters

Two interaction energy parameters, D and ϕ, characterizing the interaction between solute and stationary phase in gas-liquid chromatography have been suggested. In the calculation of these parameters, molecular values like atomic group refractions, dipole moments and Van der Waals radii have been used. Moreover, it has been attempted to consider mutual orientations of the interacting molecules.