Stationary Phases In Gas Chromatography Research Articles

Selectivity of hexaphenylbenzene-based hydrocarbon stationary phase with propeller-like conformation for aromatic and aliphatic isomers

Herein we report a propeller-like hexaphenylbenzene-based hydrocarbon material (denoted as BT) as the stationary phase for capillary gas chromatography (GC). The statically-coated BT capillary column showed a high column efficiency of 4340 plates m−1 and weak polarity. Owing to its unique conformation, π-electron toroidal delocalization and intrinsic microporosity, the BT stationary phase exhibited interesting selectivity for aromatic compounds over alkanes. Compared with the graphene (G) column, the BT column showed much prolonged retention and high selectivity for aromatic isomers, especially methylnaphthalenes, dimethylnaphthalenes and phenanthrene/anthracene, mainly because of its propeller-like conformation with rich intercalation effects. Moreover, it exhibited good column repeatability (intra-day, inter-day) and reproducibility (between-column) with RSD values on the retention times less than 0.08% for intra-day, 0.32% for inter-day and 3.8% for between-column, respectively. Also, it showed good potential for determination of minor isomer impurities in real samples. To the best of our knowledge, this work presents the first example of employing an neat aromatic hydrocarbon material as the GC stationary phase with high selectivity for analytes of a wide ranging polarity.

Experimental Investigation and Modeling of Activity Coefficient at Infinite Dilution of Solutes Using Dicationic Solvent Based on Pyrrolidinium as a New Stationary Phase in Gas Chromatography

Activity coefficients at infinite dilution, γ ∞ i, were calculated for 12 solutes, with organic solutes including linear alcohols (methanol, ethanol, propanol), linear alkanes (heptane, octane), benzene, toluene, cyclohexane, 1, 2-dichloroethane, trichloroethylene, acetonitrile and carbon tetrachloride. The values of γ ∞ i were determined via either thermodynamic or artificial neural network modelling at different temperatures. A comparison between extracted results from these two methods confirmed that experimental and predicted results are roughly the same. The accuracy of predicted results proves this model is fully compatible with a wide range of solutes, and it can readily be used as an alternative to conventional gas-liquid chromatography for the measurements of activity coefficient at infinite dilution.

Graphene-Based Materials Used in as Stationary Phase for Chromatography: A Mini Review

Graphene has fascinated the scientific community since its discovery. Graphene is a one atom thick planer sheet. Graphene exhibited great potential to be application in analytical chemistry due to its exceptional properties. Chromatography is a versatile, powerful separation and analysis technique. In this article, an overview of graphene and graphene-based materials used in stationary phase for gas chromatography, liquid chromatography and ion chromatography is presented. Detail separation fabrication methods and separation mechanisms, characteristic of graphene-based materials column was discussed in this article.

Evaluating the solvation properties of metal-containing ionic liquids using the solvation parameter model.

Ionic liquids (IL) have been utilized as gas chromatography stationary phases due to their high thermal stability, negligible vapor pressure, wide liquid range, and the ability to solvate a range of analytes. In this study, the solvation properties of eight room temperature ILs containing various transition and rare earth metal centers [e.g., Mn(II), Co(II), Ni(II), Nd(III), Gd(III), and Dy(III)] are characterized using the Abraham solvation parameter model. These metal-containing ILs (MCILs) consist of the trihexyl(tetradecyl)phosphonium cation and functionalized acetylacetonate ligands chelated to various metals. They are used in this study as gas chromatographic stationary phases to investigate the effect of the metal centers on the separation selectivities for various analytes. In addition, two MCILs comprised of tetrachloromanganate and tris(trifluoromethylphenylacetylaceto)manganate anions were used to study the effect of chelating ligands on the selectivity of the stationary phases. Depending on the metal center and chelating ligand, significant differences in solvation properties were observed. MCILs containing Ni(II) and Mn(II) metal centers exhibited higher retention factors and higher peak asymmetry factors for amines (e.g., aniline and pyridine). Alcohols (e.g., phenol, p-cresol, 1-octanol, and 1-decanol) were strongly retained on the MCIL stationary phase containing Mn(II) and Dy(III) metal centers. This study presents a comprehensive evaluation into how the solvation properties of ILs can be varied by incorporating transition and rare earth metal centers into their structural make-up. In addition, it provides insight into how these new classes of ILs can be used for solute-specific gas chromatographic separations. Graphical abstract The solvation properties of eight metal-containing ionic liquids (MCILs) comprised of transition and rare-earth metal centers are evaluated for the first time using gas chromatography. The results reveal that metals comprising the MCILs provide unique separation selectivities for various analytes and that these materials can be exploited as stationary phases in solute-specific gas chromatographic separations.

Evaluation of ionic liquid gas chromatography stationary phases for the separation of polychlorinated biphenyls

The feasibility of six ionic liquid- (IL-) based stationary phases for the analysis of environmentally important polychlorinated biphenyls (PCBs) by gas chromatography combined with either electron capture micro-detector (GC-micro-ECD) or quadrupole mass spectrometry (GC–MS, for confirmation) have been evaluated. These IL-based columns showed a separation mechanism different from that observed for other commercial phases, such a low bleed high temperature 8% phenyl (equiv.) polycarborane-siloxane suggested shape-selective phase for non-ortho and mono-ortho-CBs, HT-8, or a polar poly(ethylene glycol), resulting in a different elution order of the 69 investigated PCBs. However, no all phases provided equality satisfactory resolutions for the most environmentally relevant congeners, the 12 toxic and the 7 priority PCBs. From this point of view, the best results were obtained with the SLB-IL76 and SLB-IL59 phases, which showed a number of coelutions for these specific congeners only slightly higher to that observed on HT-8. Interestingly, the SLB-IL59 phase was the only one among the evaluated phases allowing a complete resolution of the most toxic non-ortho substituted congeners # 77, 126 and 169 from all other PCBs investigated. SLB-IL76 and SLB-IL59 also demonstrated a superior chromatographic performance concerning peak symetry, retention time stability and column bleeding, compared to the other four IL-based columns evaluated. Altogether, results obtained for the analysis of pure standards illustrated the potential of, in particular, SLB-IL 59 as an alternative phase for confirmation of the identity of PCBs typically detected in environmental matrices that coeluted on conventional non-polar phases in use for this type of determination. However, the long-term stability and quantitative behaviour of these stationary phases during the analysis of real samples still need to be addressed.

Sorption, thermodynamic, and selective properties of camphor-substituted copper(II) tetrapyrazinoporphyrazine as a stationary phase for gas chromatography

The surface of a Chromaton N-AW diatomite adsorbent was modified with copper(II) tetra(1',7',7'-trimethylbicyclo[2.2.1]heptano-[2',3'-b]-pyrazino)porphyrazine. Adsorption of vapors of 20 organic compounds on the surface of the modified adsorbent was studied by inverse gas chromatography. Electron-donor isomers of methylpyridine and dimethylpyridine, isomers of weakly polar xylenes and cresols, aliphatic alcohols, and other hydrocarbons capable of showing various types of intermolecular interactions with the complex of camphor-substituted tetrapyrazinoporphyrazine with copper(II) were chosen as adsorbates. Specific retention volumes of adsorbates, heat and adsorption entropy, and Gibbs adsorption energy were calculated. The effects of temperature and chemical nature of the adsorbates on the thermodynamic characteristics of sorption are discussed. Factors of separation of closely-boiling hydrocarbons are calculated. It has been found experimentally that the macroheterocycle-based adsorbent shows high selectivity to closely-boiling compounds of various types, unattainable for the unmodified adsorbent.

Evaluation of Gas Chromatography Stationary Phases Based on Morpholinium Ionic Liquids by McReynolds Constants and Activity Coefficients at Infinite Dilution.

In this work, four ionic liquids (ILs) based on the N-alkyl-N-methylmorpholinium cation ([Mor1,R], in which R = 2, 4, 8, or 10) and bis(trifluoromethanesulfonyl)imide anion were synthesized. Using GLC, a number of parameters describing the sorption properties of the investigated ILs were determined. The values of Kovats indices, McReynolds constants, and activity coefficients at infinite dilution were the basis for the evaluation of intermolecular interactions. The effect of the chain length of the alkyl substituent in the cation, which was used to modify their polarity, has been discussed. Comparison of the characteristics of the investigated IL-based stationary phases with commercially available ones allowed for the statement that the investigated ILs were more polar. The tested ILs had a relatively high polarity. Increasing the length of the alkyl chain in the morpholinium ring reduced polarity. ILs based on the morpholinium cation were tunable in a wide range of their polarity.

Examination of Selectivities of Thermally Stable Geminal Dicationic Ionic Liquids by Structural Modification

Dicationic ionic liquids (ILs) are widely used as gas chromatography (GC) stationary phases as they show higher thermal stabilities, variety of polarities, and unique selectivities towards certain compounds. An important aspect contributing to them is that they show multiple solvation interactions compared to the traditional GC stationary phases. Dicationic ILs are considered as combination of three structural moieties: (1) cationic head groups; (2) a linkage chain; and (3) the counter anions. Modifications in these structural moieties can alter the chromatographic properties of IL stationary phases. In this study, a series of nine thermally stable IL stationary phases were synthesized by the combination of five different cations, two different linkage chains, and two different anions. Different test mixtures composed of a variety of compounds having different functional groups and polarities were analyzed on these columns. A comparison of the separation patterns of these different compounds on nine different IL columns provided some insights about the effects of structural modifications on the selectivities and polarities of dicationic ILs.

New stationary phases for gas chromatography based on polymers with intrinsic porosity

Norbornene polymers with intrinsic porosity were investigated as candidates for polymeric stationary phases in capillary GC. Kinetic and thermodynamic characteristics of the stationary phases were evaluated and turned out that only polymer with vicinal distribution of trimethylsilyl groups (polymer II) provided properties making it potential candidate for application in capillary GC. Columns with stationary phase based on polymer II demonstrated unique selectivity, moderate thermostability and efficiency better than previously studied columns with stationary phase based on poly[(1-trimethylsilyl)-1-propine].

Characterization of a dicationic imidazolium-based ionic liquid as a gas chromatography stationary phase

Here we report the characteristics of a new synthesized ionic liquid, 1,9-di(N-naphthalen-2-ylimidazolium)nonane bis[(trifluoromethyl)sulfonyl]imide ([C9(2NPTim)2][(NTf2)2]), as a stationary phase by inverse gas chromatography. The McReynolds constants demonstrated that the [C9(2NPTim)2][(NTf2)2] had an average polarity of 667 and polarity number P.N.=75, suggesting its polar nature. The solvation properties of the new stationary phase were determined by the calculation of Abraham solvation system constants, whereby the results showed that its major interactions with the analytes included H-bond basicity (a), dipole–dipole (s) and dispersive (l) interactions. The activity coefficients (γ∞) and selectivities (SIJ∞) at infinite dilution were also determined for various polar and nonpolar organic solutes at different temperatures. The separation performance of the [C9(2NPTim)2][(NTf2)2] stationary phase was evaluated by GC separations of different analytes, including normal alkanes and aromatic compounds. The TGA results showed that the stationary phase had high thermal stability up to 420°C.

Мезоморфные, сорбционные и селективные свойства 4-(4-{4-[2-гидроксиэтилокси]бензоилокси}-фенилдиазенил)бензальдегида как стационарной фазы для газовой хроматографии

Мезоморфные, сорбционные и селективные свойства 4-(4-{4-[2-гидроксиэтилокси]бензоилокси}-фенилдиазенил)бензальдегида как стационарной фазы для газовой хроматографии

Argentation gas chromatography revisited: Separation of light olefin/paraffin mixtures using silver-based ionic liquid stationary phases

Silver ion or argentation chromatography utilizes stationary phases containing silver ions for the separation of unsaturated compounds. In this study, a mixed-ligand silver-based ionic liquid (IL) was evaluated for the first time as a gas chromatographic (GC) stationary phase for the separation of light olefin/paraffin mixtures. The selectivity of the stationary phase toward olefins can be tuned by adjusting the ratio of silver ion and the mixed ligands. The maximum allowable operating temperature of these stationary phases was determined to be between 125°C and 150°C. Nuclear magnetic resonance (NMR) spectroscopy was used to characterize the coordination behavior of the silver-based IL as well as provide an understanding into the retention mechanism of light olefins.

Preparation and evaluation of a novel bonded imidazolium ionic liquid as stationary phase for gas chromatography.

1-Butyl-3-[(3-trimethoxysilyl)propyl]imidazolium chloride ionic liquid was synthesized and chemically modified onto the inner wall of a fused capillary column as a stationary phase for gas chromatography. The 1-butyl-3-[(3-trimethoxysilyl)propyl]imidazolium chloride ionic liquid bonded capillary column was evaluated in detail. The results revealed that the ionic liquid bonded capillary column exhibited high column efficiency of 1.08 × 104 plates/m, and good chromatographic separation selectivity (α) for polar and non-polar substances, and a good thermal stability between room temperature and 400°C. Moreover, the determination of thermodynamic parameters and the linear solvation energy relationship were further carried out. The results indicated that the chromatographic retention of each probe molecule on the ionic liquid bonded stationary phase was an enthalpy-driven process, and the system constants of the linear solvation energy relationship signified that the dispersion interaction, the hydrogen bonding acidity and hydrogen bonding basicity were dominant interactions between probes and stationary phase among five interactions during the chromatographic separation. However, the contribution of each specific interaction for the stationary phase is ranked as the dispersion interaction > the hydrogen bonding basicity > the hydrogen bonding acidity.

A rod-spacer mixed ligands MOF [Mn3(HCOO)2(D-cam)2(DMF)2]n as coating material for gas chromatography capillary column

The interest in metal-organic frameworks (MOFs) is rapidly expanding because of their fascinating architectures and intriguing topologies which allowed for potential applications in gas storage, separation, heterogeneous catalysis, and several other areas. As suitable chromatographic separation media, several MOFs have been employed as stationary phase for gas chromatography and high-performance liquid chromatography. In this work we report the use of a mixed ligands rod-spacer MOF [Mn3(HCOO)2(D-cam)2(DMF)2]n as coating material for capillary column of gas chromatographic separation of a series of biochemical important compounds having linear alkyl hydrocarbon (aldehyde, alcohol and ester), aromatic hydrocarbon with two phenyls (ether, ester and ester with alcohol) and aromatic hydrocarbon (ester, ester with amino and two esters). The mixture of functional ligands, good thermal and chemical stabilities and host-guest interaction sites of the MOF are attributes to the good efficiency in gas chromatographic separation.

Capillary column coated with geminal ionic liquids as stationary phases for gas chromatographic separation

Four geminal ionic liquids (GILs), namely, 1,4-bis(1,1′-butyl-3,3′- methylene- imidazolium)-benzene bis[(trifluoromethyl)sulfonyl]imide (BBMIB-NTf2), 1,4- bis(1,1′-butyl-3,3′-methylene-imidazolium)-benzene tetrafluoroborate (BBMIB-BF4), 1,4- bis(1,1′-butyl-3,3′-methylene-imidazolium)-benzene hexafluophosphate (BBMIB-PF6), and 1,4-bis(1,1′-methyl-3,3′-methylene-imidazolium)-benzene bis[(trifluoromethyl) sulfonyl] imide (BMMIB-NTf2), were synthesized. They were statically coated onto the inner walls of fused-silica capillary columns and used as stationary phases for gas chromatography. The evaluation of BBMIB-NTf2, BBMIB-BF4, BBMIB-PF6, and BMMIB-NTf2 as stationary phases is reported here for the first time. These new stationary phases exhibit efficiencies of at least 2.3 × 103 plates per meter. Abraham solvation parameter model was used to evaluate the solvation characteristics. The system constants indicated that the dipolarity/polarizability and the hydrogen-bond basicity play a major role among five molecular interactions between stationary phases and solute molecules. A fundamental understanding into the solvation characteristics of these GILs can be used as a guide to choosing the appropriate geminal ionic liquids for specific applications in various fields. The chromatographic separation performance was evaluated by a Grob test mixture, n-alkanes, alcohols, and aromatic isomers. Furthermore, the thermal stability was tested. The present results demonstrate that these geminal ionic liquids stationary phases possess excellent chromatographic separation performance and good thermal stability (at least up to 270 °C) and may be applicable as gas chromatography stationary phases for more application.

Preparation of Toluene-Imprinted Homogeneous Microspheres and Determination of Their Molecular Recognition Toward Template Vapor by Inverse Gas Chromatography

A toluene-imprinted polymers (MIPs) homogeneous microsphere was prepared by precipitation polymerization technique using toluene as porogen (also as template) with 4-vinyl pyridine (4-VP) as the functional monomer. Structural characterization was performed by the nitrogen adsorption method and optical microscope utilized for observing particle size of polymers. Retention capability and selectivity for this MIP toward template vapor and its relative compounds were evaluated and the isotherm rebinding capacity of the MIP tested by adopting an inverse gas chromatography method. Results indicated that the toluene-imprinted polymer (MIP3), as a stationary phase in gas chromatography, possessed high retention selectivity toward template vapor, with a retention factor value of 68.42, an imprinting factor value of 7.049, and selectivity factor values of 4.821 and 5.370 for the template relative to benzene and p-xylene, respectively. A model mixture containing toluene, benzene, and p-xylene could be effectively separated, with a resolution of 5.138 for toluene to p-xylene and of 1.762 for toluene to benzene. The isotherm adsorption curve for the MIP3 toward toluene vapor exhibited II type of BET adsorption. Additionally, the toluene-imprinted microspheres showed satisfactory applicability in the removal of toluene from polluted indoor air.

Ni(II) complex of octasubstituted tetraphenylporphine as a stationary phase for gas chromatography

The Ni(II) complex of 5,10,15,20-tetrakis[3[Formula: see text],5[Formula: see text]-di(2[Formula: see text]-methylbutyloxy)phenyl]porphine was synthesized and characterized by 1H NMR, UV-vis spectroscopy and MALDI-TOF mass-spectrometry. The stationary phase on the base of synthesized Ni(II) complex was used for chromatographic separation of isomeric methyl- and dimethylpyridines. The high structural selectivity of this sorbent was explained by giving the results of DFT calculation of pyridine derivatives axial complexes with porphyrin Ni(II) complexes.

Synthesis and characterization of 3,4-di(3-phenoxy-4-fluoro phenyl)-2,5-diphenyl phenyl grafted polysiloxane as stationary phase for gas chromatography

Synthesis and characterization of 3,4-di(3-phenoxy-4-fluoro phenyl)-2,5-diphenyl phenyl grafted polysiloxane as stationary phase for gas chromatography

Separation performance of a large π-conjugated truxene-based dendrimer as stationary phase for gas chromatography

High-resolution performance of a π-conjugated truxene-based dendrimer as the stationary phase for gas chromatographic separations.

MEMS-based column coated with reduced graphene oxide as stationary phase for gas chromatography

Schematic diagram of single-layer stationary phase film (a) and two-step stationary phase film (b).