Phases In GC Research Articles

Exploring the synergistic effects of goethite intercalated coal in the presence of humic acids for enhanced growth of Sinapis alba

BackgroundIron oxide mineral–humic complexes serve as a reservoir of bioavailable Fe for plants, releasing metal ligands and providing Fe–humic complexes directly usable by plant Fe-uptake mechanisms. In this study, we synthesized and characterized goethite α-FeOOH (G) nanoparticles (NPs) intercalated in coal (GC) to estimate the bioactivity effect of humic acids (HA). The synthesized GC NPs were characterized by X-ray diffraction, scanning electron microscopy (SEM), Mössbauer spectroscopy, N2 adsorption–desorption Brunauer–Emmett–Teller (BET) specific surface area, zeta potential, hydrodynamic particle diameter, iron ions release, and a phytoassay method of root elongation using the higher plant Sinapis alba.ResultsX-ray diffraction revealed that G was the primary phase in both GC and GC–HA complexes. Mössbauer spectroscopy analysis identified a goethite-doped Fe2+-in the GC samples. The intercalation of G into the coal matrix increased the specific surface area of GC, enhancing its HA sorption capacity. In addition, GC–HA demonstrated superior plant growth stimulation compared to HA and GC alone, indicating its role in colloidal stability. In contrast to GC, GC–HA exhibited a more consistent and time-dependent release of Fe3+ and Fe2+. This sustained Fe release from GC–HA, coupled with the formation of Fe3+ and more bioavailable (soluble) Fe2+ humic complexes is a promising result in terms of iron nanofertilizers production.ConclusionsThe use of goethite nanoparticles intercalated within a coal matrix and subsequently complexed with HA contributes to prolonged phytoactivity by employing slowly released nutrient additives within the coal mesoporous matrix.Graphical

An Amphiphilic Star-Shaped Polymer (Star-PEG-PCL2) used as a Stationary Phase for GC.

A star-shaped polymer (Star-PEG-PCL2) was synthesized with PCL and PEG and used as a stationary phase for gas chromatography. The statically coated Star-PEG-PCL2 column exhibited an efficiency of 2260 plates/m determined by naphthalene at 120 °C and moderate polarity. The Star-PEG-PCL2 column showed high resolution performance for isomers of a wide ranging polarity, including methylnaphthalenes, halogenated benzenes, nitrobenzene, phenols, and anilines, and displayed dual-nature selectivity for a mixture of 17 analytes. Also, the Star-PEG-PCL2 column exhibited good separation performance and column inertness for Grob test mixture and a series of cis-/trans-isomers. In addition, it exhibited advantageous separation performance over the commercial HP-35 and PEG-20M columns for chloroaniline and bromoaniline isomers through its unique three-dimensional framework. In conclusion, it has good potential as a new stationary phase for separating a variety of analytes because of its special structure and excellent separation performance.

Chromatographic parameters: Characteristic parameters of solute retention – an insightful description of column properties

Previously introduced characteristic parameters of solute retention – the solute characteristic temperature (Tchar) and thermal constant (θ) in GC as well as the characteristic solvent composition (ϕchar) and the composition-constant (Φ) in LC – are described herein from a single perspective. Unlike conventional thermodynamic parameters, e.g., entropy and enthalpy of solute evaporation from stationary phase in GC that do not have a direct chromatographic meaning, the characteristic parameters do. Thus, Tchar and ϕchar are the column temperature and the solvent composition in GC and LC, respectively, at which the solute retention factor (k) is equal to 1. Quantities θ and Φ in GC and LC, respectively, are analogous to the time-constant in scientific and technical fields. Thus, e.g., Φ is the increase in the solvent composition leading to e-fold reduction (e ≈ 2.72) in k. Properties of characteristic parameters illustrating intuitive nature and simplicity of based on them concepts and equations are described.

MULTIFUNCTIONAL CrxCa(10-x)Al30Si60 GLASSES, ELECTRICAL CONDUCTIVITY AND THERMOLUMINESCENCE

The SiO2 glasses embedded with Cr3+ ions are notable for solid state optical resource, which are useful in various opto-electronic and semiconducting applications. However, the available thermoluminescent resource, which include different electronic and semiconducting materials, need some refinement in their structure, luminescence, and electronic properties towards development of advanced glass resource. In this vision, CrxCa(10-x)Al30Si60 glassy materials have planned for synthesis and testing. The GT, and GC phase transition points, and thermal stability (~1.2639) of test samples are identified. Structural vibrations are identified with the help of FT-IR spectra. The order of electrical conductivity (~1.657x10-4 ohm-1 cm-1), and A.E. (~0.3669 eV) of test samples reveal their electrical strength. The symmetry (~ 0.576%) factor, frequency (1.1172 X 1020 S -1) factor, and A.E. (0.682 eV) of the test samples are recorded under 30 kGy irradiation. Overall, the results, which include structure, electrical and luminescence of the test samples suggest the materials might be useful electrically conductive and thermal stimulated light resource.

Incorporation of Imidazolium Ionic Liquids in GC Stationary Phases via the Sol–Gel Process

Room-temperature ionic liquids (RTILs) have proven to be efficient polar or highly polar stationary phases for GC. Nevertheless, the thermal stability of monocationic RTILs limits their use in high-temperature GC. To improve the thermal stability, an RTIL based on a 1-methylimidazolium derivative was anchored in a three-dimensional network using the sol–gel process. Three different strategies were compared: using the derivative pure, in combination with a polymer or copolymerised with diethoxydimethylsilane. This last method allowed for the preparation of hybrid stationary phases with satisfactory efficiency (3500 plates per meter determined by the injection of n-tetradecane at 80 °C, k = 8.19) and very good thermal stability up to 340 °C using the NTf2 counter ion. The stationary phases demonstrated a good ability to separate positional isomers and polycyclic aromatic hydrocarbons. Polarity and molecular interactions with analytes were characterized by calculating the Rohrschneider–McReynolds constants and Abraham system constants. A classification of the polarity of the new stationary phases relative to 44 stationary phases, including commercial and non-commercial ones, was performed based on the RTILs using principal component analysis. Finally, the maximal operating temperature of these new stationary phases was compared with those of the most thermally stable conventional or RTIL-based stationary phases, demonstrating that the sol–gel process is an efficient way to enhance the thermal stability of GC stationary phases.

Chiral Inorganic mesoporous materials used as the stationary phase in GC

AbstractMesoporous materials are promising functional materials due to their properties, such as a large surface area, tunable pore size, structure and morphology. Chiral mesoporous silica is an indispensable part of mesoporous materials. Considering that chirality is rare in inorganic mesoporous materials, there are very few reports on chiral inorganic mesoporous silica for chromatographic separations. In this work, we report the use of chiral inorganic mesoporous silica based on the template of myristyl chloride‐l‐valine sodium as the stationary phase for enantioselective separation in gas chromatography. Thirteen chiral compounds were resolved on a fabricated column using dynamic coating, including chiral alcohols, epoxides and amino acid derivatives. In addition, n‐alkanes, n‐alcohols and aromatic hydrocarbons have also been separated.

In situ fabrication of microporous organic network coated capillary column for high resolution gas chromatographic separation of hydrocarbons.

Microporous organic networks (MONs) are a new class of porous materials synthesized via Sonogashira coupling reactions between organic building blocks. Here we report an in situ synthesis approach to fabricate MONs coated capillary column for high resolution GC separation of hydrocarbons. The McReynolds constant evaluation reveals the MONs coated capillary is a non-polar column. The MONs coated capillary column shows good resolution for GC separation of diverse important industrial hydrocarbons such as linear and branched alkanes, alkylbenzenes, pinene isomers, ethylbenzene and styrene, cyclohexane and benzene. The MONs coated capillary column gave a high column efficiency of 1542 plates per meter for hexane and good precision for replicate separations of the selected hydrocarbons with the RSDs of 0.2-0.3, 1.5-3.1, and 1.9-3.3% for retention time, peak height and peak area, respectively. The MONs coated capillary also offered better resolution than commercial Inert Cap-1 and Inert Cap-5 capillary columns for hexane and heptane isomers. These results reveal the potential of MONs as novel stationary phases in GC.

Ionic liquids as stationary phase in GC: An innovation for improving food, environmental and petrochemical analysis

Ionic liquids as stationary phase in GC: An innovation for improving food, environmental and petrochemical analysis

Investigation of poly[oligo(ethylene glycol)diacrylates] as potential stationary phases in GC.

Poly[oligo(ethylene glycol)diacrylate]s were investigated as potential candidates for application as stationary phases in capillary gas chromatography. Depending on the molar mass of the monomer, up to three different phase transitions were observed in calorimetric scans of the polymers. Two transitions have been identified as the glass transition and melting of crystallites while the nature of the third effect remains unknown. The new stationary phases demonstrate a good separating ability and selectivity in the viscous-elastic state, i.e. at temperatures above the glass transition and melting points. The new polymeric stationary phases possess selectivity similar to conventional PEG columns but provide better thermal stability than conventional PEG stationary phases.

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].

Mammalian target of rapamycin complex 1 signalling is essential for germinal centre reaction.

The mammalian target of rapamycin (mTOR) is a serine-threonine kinase that has been shown to be essential for the differentiation and function of various immune cells. Earlier in vitro studies showed that mTOR signalling regulates B-cell biology by supporting their activation and proliferation. However, how mTOR signalling temporally regulates in vivo germinal centre B (GCB) cell development and differentiation into short-lived plasma cells, long-lived plasma cells and memory cells is still not well understood. In this study, we used a combined conditional/inducible knock-out system to investigate the temporal regulation of mTOR complex 1 (mTORC1) in the GCB cell response to acute lymphocytic choriomeningitis virus infection by deleting Raptor, a main component of mTORC1, specifically in B cells in pre- and late GC phase. Early Raptor deficiency strongly inhibited GCB cell proliferation and differentiation and plasma cell differentiation. Nevertheless, late GC Raptor deficiency caused only decreases in the size of memory B cells and long-lived plasma cells through poor maintenance of GCB cells, but it did not change their differentiation. Collectively, our data revealed that mTORC1 signalling supports GCB cell responses at both early and late GC phases during viral infection but does not regulate GCB cell differentiation into memory B cells and plasma cells at the late GC stage.

Neisseria gonorrhoeae infects the human endocervix by activating non-muscle myosin II-mediated epithelial exfoliation.

Colonization and disruption of the epithelium is a major infection mechanism of mucosal pathogens. The epithelium counteracts infection by exfoliating damaged cells while maintaining the mucosal barrier function. The sexually transmitted bacterium Neisseria gonorrhoeae (GC) infects the female reproductive tract primarily from the endocervix, causing gonorrhea. However, the mechanism by which GC overcome the mucosal barrier remains elusive. Using a new human tissue model, we demonstrate that GC can penetrate into the human endocervix by inducing the exfoliation of columnar epithelial cells. We found that GC colonization causes endocervical epithelial cells to shed. The shedding results from the disassembly of the apical junctions that seal the epithelial barrier. Apical junction disruption and epithelial exfoliation increase GC penetration into the endocervical epithelium without reducing bacterial adherence to and invasion into epithelial cells. Both epithelial exfoliation and junction disruption require the activation and accumulation of non-muscle myosin II (NMII) at the apical surface and GC adherent sites. GC inoculation activates NMII by elevating the levels of the cytoplasmic Ca2+ and NMII regulatory light chain phosphorylation. Piliation of GC promotes, but the expression of a GC opacity-associated protein variant, OpaH that binds to the host surface proteins CEACAMs, inhibits GC-induced NMII activation and reorganization and Ca2+ flux. The inhibitory effects of OpaH lead to reductions in junction disruption, epithelial exfoliation, and GC penetration. Therefore, GC phase variation can modulate infection in the human endocervix by manipulating the activity of NMII and epithelial exfoliation.

Estimating Thermodynamic Stability Relationship of Polymorphs of Sofosbuvir

The polymorphism of sofosbuvir has been investigated. Three polymorphs have been identified and characterized by X-ray powder diffraction (XRPD) and thermal analysis. Form A and Form B were determined as enantiotropic systems according to the Heat of Fusion Rule. The melting data and isobaric heat capacities of both polymorph have been determined calorimetrically, and the solubility data of each polymorph in water at different temperatures have been determined. With these data, the transition temperature (Ttr) was then estimated using solubility extrapolation method, heat of transition (ΔHtr) method, melting data method, and configurational free energy (Gc) phase diagram method. The values of Ttr were found to be 93.29, 90.59, and 108.37 °C for the first three methods, respectively. In the Gc phase diagram method case, Ttr was found to be 109.25 °C when eq 19 was used compared to 109.28 °C when eq 20 was used.

Physical Ionic Liquid/Polysiloxane Mixtures for Tuning the Polarity and the Selectivity of the Polysiloxane Stationary Phase for GC Analysis

Two novel room-temperature ionic liquids (RTILs), a mono-cationic (tetra-n-octylammonium) and a dicationic (bis-methylpiperidinium-butylidene) room-temperature ionic liquid with the bis[(trifluoromethyl)sulfonyl]imide anion, were individually mixed with OV-1701 polysiloxane to tune the selectivity and the polarity of stationary phases for GC. The interaction properties of the stationary phases were investigated on the basis of polarity calculations and the linear solvation energy relationship. The incorporation of the monocationic RTIL in the OV-1701 increased the dipolarity/polarizability capacities (s) and the hydrogen-bond basicity ability (a) allowing the separation of the m-chloroaniline/p-chloroaniline isomers and the m-xylene/p-xylene isomers which are not usually separated on polysiloxane stationary phase. The mixed stationary phases exhibited a greater selectivity than the OV-1701 phase for the majority of the aromatic compounds tested, demonstrating a kind of synergistic effect of the combination of polysiloxane and RTIL. The addition of RTIL proved to be an original method to modulate the polarity and the selectivity of the stationary phase of intermediate polarity in order to prepare stationary phases dedicated for specific separation with good durability (more than 20 months and more than 1,000 injections) and without any loss of thermal stability.

Three Nematogen Azobenzene-Based Stationary Phases for Capillary GC: Synthesis and Comparative Study

In this paper, three laterally substituted liquid crystals termed LCC1, LCC3 and LCC4 were synthesized. Characterization of these substances was carried out by 1H NMR and 13C NMR; they possess similar core and differ in their lateral substituents. Their thermal stability was conducted by thermogravimetric analysis and showed decomposition beginning at 212, 233 and 264 °C related to LCC1, LCC3 and LCC4, respectively. Thermal properties were determined by differential scanning calorimetry, thermomicroscopy and inverse gas chromatography. The three novel compounds exhibited a nematic mesophase at a defined range of temperatures, which varied from 81 to 55 °C. Lengthening of the lateral substituent seemed to affect the nematic range by decreasing it. Fused-silica capillary columns (30 m × 0.32 mm) were employed for the analytical study. Numerous mixtures of components of various properties were injected. Particular attention was given to the selectivity towards the close-boiling isomers. These investigations indicated that lateral attached groups had considerable effect on the thermal and chromatographic properties of the liquid crystal compounds. These interesting results may guide in improving the development of new type of liquid crystals with desired properties for a widespread application.

Analysis Of The Enantiomers Ratio Of Citronellal From Indonesian Citronella Oil Using Enantioselective Gas Chromatography

Citronellal 97,3% has been isolated from Java citronella oil (Cymbopogon winterianus) from Yogyakarta Indonesia by fractional distillation under reduced pressure (5 cmHg, 110-120 oC). Citronellal has two optical isomerics that can be separated by capillary column of chiral GC phase. Enantioselective capillary GC with heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin (β-DEX-225) as stationary phase has been used for analysis of the enantiomers ratio of citronellal. The analysis of enantiomer ratio showed that citronellal contain of 88.21% ee of (R)-(+)-citronellal. Physical properties of isolated citronellal showed that the compound was (+) enantiomer. Structure identification of citronellal was carried out by GC-MS, IR, and 1H NMR, resulted identical fragment and spectra with standard citronellal. Theoretical study with semiempirical-AM1 method showed that energy of (R)-(+)-citronellal on the β-DEX 225 was lower than its (S)-(-)-citronellal.

Characterization by the solvation parameter model of the retention properties of commercial ionic liquid columns for gas chromatography

For the first time, four commercial ionic liquid columns (SLB-IL59, SLB-IL76, SLB-IL82 and SLB-IL100) for gas chromatography have been comprehensively evaluated in terms of efficiency, polarity and solvation properties. Grob tests and McReynolds constants showed that they were all high-efficiency columns of high polarity, but with low inertness to compounds with hydrogen bonding capabilities. The solvation parameter model was used to characterize the solvation interactions of the four columns in the 80–160°C temperature range. Results revealed that all the ionic liquids studied can be considered moderately hydrogen-bond acid and highly cohesive stationary phases, on which the dominant contributions to retention were the dipolar-type and hydrogen-bond base interactions, while π–π and n–π interactions were barely significant. The SLB-IL59 column provided the best separation of homologs, while the SLB-IL76 and SLB-IL100 columns had the most basic and the most acidic phases, respectively. A principal component analysis for the commonly used stationary phases in capillary GC showed that these commercial ionic liquid columns fill an empty area of the available selectivity space, which clearly enhances the separation capacity of this technique.

Calcination and alkali metal modification of alumina as solid stationary phase in GC

Alumina has unique textural properties and functionalized surface. The single or multi-treatments of alumina with calcination and alkali metal treatment (NaCl) are of prime one importance not only for determining the structure, textural and surface chemistry of the phase but also to understand how modification is related to the changes in these properties and also to the change in its performance as solid stationary phase. Thermodynamic parameters (ΔH, ΔG and ΔS) were determined using n-hexane as a probe in order to show the adsorbate-adsorbent interaction. It was observed that the non-polar solutes could be separated independent of the reactivity and porosity of the alumina surfaces. Alkali metal modification of the calciened alumina is a selective stationary phase for eluting natural gas sample exhibiting good separation.

Properties of columns with several pyridinium and imidazolium ionic liquid stationary phases

Recent advances in the development of new liquid phases (ILs) made it possible to use some classes of ILs as polar stationary liquid phases (SLP). In our days only alkylimidazolium- and alkylphosphonium-based ILs are widely used as polar SLP. In present work some other types of ILs – pyridinium and cyanopropyl/hydroxypropyl imidazolium were investigated as SLP. Columns with efficiencies 2000–2500 plates/m by high-pressure static method were prepared. Polarity and selectivity of these phases were measured. Selectivity was described in terms of intermolecular interactions by using Abraham solvatation parameter model. The set of the regularities between cation structure of ionic liquid and selectivity has been shown. The number and position of methyl groups in ionic liquid pyridinium ring were shown to have the sufficient influence on all type of molecular interactions. Finally the resolutions of test mixture for the several ionic liquid SLP were obtained. For columns with some ionic liquids the dependencies of the height equivalent to a theoretical plate (HETP) and sample loading capacity were obtained and compared with the conventional phases. It was found that the optimal efficiency for the IL columns is attained at lower carrier gas velocities in comparison with traditional phases. Nevetheless sample loading capacity of IL phases is comparable to those of conventional GC phases.

Study of Chiral Ionic Liquid as Stationary Phases for GC

Due to the synthetic flexibility and special enantioselectivity, chiral ionic liquids (CILs) have heightened interest and an increasing number of CILs has been designed and utilized. In this work, CIL named l-1-butyl-3-(2-propionic-1-ether) imidazolium bromide ([BAlaIM]Br) derived from natural amino acids was synthesized, with chiral center at cation moiety. Chiral stationary phases for gas chromatography were then prepared by mixing the CIL with polymeric ionic liquid ([PSOMIM][NTf2], homemade) at different ratios (4:1, 2:1, and 1:1). The column efficiency was measured to be about 3,200 plates m−1 (8 m × 0.25 mm i.d.) when the content of [BAlaIM]Br was 50 % (mass percent) in the mixed stationary phase. All columns were coated via the static coating method using 0.30 % (w/v) of stationary phases dissolved in methanol. The results showed that the CIL contributed to the selectivity of stationary phase toward positional isomers dichlorobenzenes, methylnaphthalenes and pinenes, etc. Meanwhile, [BAlaIM]Br showed better selectivity for enantiomers such as carvones, citronellals, limonenes and camphors. The interactions between chiral selector and enantiomers were also discussed.