Phases For Capillary Gas Chromatography Research Articles

Benzimidazolium ionic liquid functionalized star-polycaprolactone stationary phase for capillary gas chromatography

In this work, an innovative ionic liquid functionalized star-shaped polymer is synthesized by coupling star-polycaprolactone with benzimidazolium (star-PCL-Bim), and statically coated into a capillary column for gas chromatographic (GC) separations. The fabricated star-PCL-Bim capillary column with moderate-polar nature reveals a high column efficiency of 3598 plates/m for n-dodecane at 120 °C, and advantageous distinguishing ability ( R > 1.5) for 9 aromatic isomer mixtures and 12 cis-/ trans -isomers. Its excellent resolving capacity can be credited to the architecture of star-PCL-Bim, the PCL arms, and π-electron-rich benzimidazolium cations, and it results in a quite different retention behavior of star-PCL-Bim from that of star-PCL and commercial HP-35 columns, with “dual-nature” selectivity in separating a mixture including 29 compounds. These favorable chromatographic characteristics demonstrate the great application potential of this material in GC, and provide a prospective strategy to obtain high-performance stationary phases.

A new organic soluble cucurbit[7]uril-truxene derivative as stationary phase for gas chromatographic separation of some challenging isomers

The insolubility of parent cucurbit[n]uril or substituted-cucurbit[n]uril derivatives in organic solvents has always been a key factor restricting the column efficiency and selectivity of capillary gas chromatography column based on cucurbit[n]uril. In this work, a novel organic soluble cucurbit [7]uril-truxene derivative (Q [7]-Tr) was synthesized by Heck coupling reaction between the mono-iodinated hexahexyl-truxene and 4-vinylbenzyloxy-Q [7]. A capillary gas chromatographic column was prepared by static method with this derivative as stationary phase. The column exhibited moderate polarity and an efficiency of 5857 plates/m using n-dodecane as analyte at 120 °C, indicating the highest column efficiency of all the based-cucurbit[n]uril columns published. The Q [7]-Tr column showed high resolutions for a wide range of analytes with different polarities and better separated selectivity towards tough isomers such as aromatic amines isomers and xylene isomers compared to commercial HP-5, DB-35, Stabilwax and Q [7]-based columns. Moreover, the new column exhibited high thermal stability up to 320 °C and excellent repeatability, demonstrating a great potential as a new stationary phase in capillary gas chromatography.

The Preparation of Novel Amino Acid Imidazole Ionic Liquids and Their Application as Stationary Phase for Capillary Gas Chromatographic Separations

AbstractIn this paper, two new amino acid imidazole ionic liquids IL‐3 and IL‐4 were synthesized for the first time, and their separation performance as the stationary phase for capillary gas chromatography (GC) was tested. The statically coated IL‐3 and IL‐4 capillary columns exhibited moderate to high polarity, and achieved the column efficiency of 2242 plates/m and 2487 plates/m respectively determined by n‐octanol at 120 °C. Importantly, the IL‐3 and IL‐4 columns exhibited excellent separation capability for analytes with varying polarity, including n‐alkanes, arenes, esters, alcohols, bromoalkanes, halogenobenzenes, and halogenated anilines. In addition, the IL‐3 and IL‐4 columns presented high selectivity and separation capability for positional, structural and cis‐/trans‐isomers. In particular, they showed high separation performance of the chloroaniline, bromaniline, iodoaniline and xylidine isomers as an important environmental pollutant. The IL‐3 and IL‐4 columns displayed advantageous resolving capability over the commercial HP‐35 column for aromatic amine isomers, and the separation performance of IL‐4 with long carbon chain was better than that of IL‐3. Moreover, it was applied to determine isomer impurities in real samples, and showing huge potential in GC applications. This work demonstrates the potential of the amino acid imidazole ionic liquids as a new type of stationary phase in GC separations.

Novel, Selective Calix[6]Arene - Polyethylene Glycol (C6A-PEG) Stationary Phase for Capillary Gas Chromatography (GC)

A novel calix[6] arene polymer stationary phase (C6A-PEG) is reported that combines the π-electron-rich cavity of calix[6] arene (C6A) with polyethylene glycol (PEG) units for gas chromatography (GC). Thermogravimetric analysis revealed a 5% weight loss of C6A-PEG at 318 °C, and its static-coated capillary column showed high efficiency of 2924 plates/m (k = 3.48) determined by 1-octanol at 120 °C. As a result, the moderate polar C6A-PEG column showed clearly advantageous performance for the Grob reagent and a mixture of 25 analytes with high selectivity for hydrogen-bonded acids. Also, it exhibited high resolving performance for various isomer mixtures, in particular high-resolution performance (R > 2.2) for the challenging toluidine and dimethylaniline systems with distinct advantages compared to the C6A and PEG columns (R < 1.5 for some pairs). This work demonstrates the potential of calixarene-based polymers as novel stationary phases for gas chromatographic analysis.

Benzimidazolium Ionic‐Liquid‐Functionalized Star‐shaped Copolymer Stationary Phase for Capillary Gas Chromatography

AbstractIn this work, a novel star‐shaped copolymer functionalized by benzimidazolium ionic liquid (Star‐PEG‐PCL2‐2Bim) was synthesized and applied as stationary phase in capillary gas chromatography (GC). After static coating, the Star‐PEG‐PCL2‐2Bim column exhibited a column efficiency of 2655 plates/m and moderate polarity. The Star‐PEG‐PCL2‐2Bim column showed preferential retention and high resolving capability for hydrogen‐bonded and aromatic analytes, showing advantages over the ordinary polysiloxane phase. Impressively, it attained high resolution for the isomer mixtures of halogenated benzene, nitrobenzene, phenol and benzaldehydes with good peak shapes. The advantageous separation performance shows the good potential of the Star‐PEG‐PCL2‐2Bim stationary phase for GC analysis.

A new stationary phase for capillary gas chromatography based on amphiphilic triblock copolymer – Benzimidazolium ionic liquid

In this work, a novel amphiphilic triblock copolymer bonded with benzimidazolium ionic liquid (TCP-Bim) was designed, synthesized, and employed as stationary phase for capillary gas chromatography (GC) column. This innovative column exhibited moderate polarity and an efficiency of 3280 plates/m, showing high resolutions for a wide range of analytes, with marked capabilities towards isomer separations, and different retention behaviors and separation performances respect to TCP or commercial HP-35 and PEG-20 M columns. The TCP-Bim stationary phase has exhibited in some cases unmatched separation capabilities, like, for example, in the case of separation of chloroaniline and bromoaniline. Its column performances have been compared with TCP and other commercial columns analyzing from apolar to polar compounds, showing in every case outstanding capability which clearly indicate that TCP-Bim can be considered a very interesting candidate as a new type of stationary phase in GC.

Performance and selectivity of amphiphilic pillar[5]arene as stationary phase for capillary gas chromatography

Pillar[n]arenes possess highly symmetrical and rigid pillar-shaped architecture with π-electron rich cavity that afford their reliable host-guest recognition interactions towards matched guests. In this work, a novel amphiphilic pillar[5]arene (P5A-C10-2NH2) was designed, synthesized and employed as the stationary phase for capillary gas chromatography. To date, they have not been reported in the field of chromatography. The P5A-C10-2NH2 capillary column (10 m × 0.25 mm i.d.) was prepared by static coating method. Its capillary column exhibited moderate polarity and column efficiency of 2265 plates/m determined by naphthalene at 120 °C. As evidenced, the P5A-C10-2NH2 column achieved advantageous separation performance for a mixture of 24 analytes of diverse types and exhibited different chromatographic selectivity from two pillar[5]arene derivatives columns and commercial HP-35 column with 35%-phenyl-methylpolysiloxane. Moreover, the P5A-C10-2NH2 column baseline resolved more than a dozen positional and cis-trans isomers. Furthermore, the separation mechanism of P5A-C10-2NH2 column was discussed by quantum chemical calculations. In addition, the P5A-C10-2NH2 column had high thermal stability and excellent separation repeatability 0.01–0.04% for run-to-run, 0.03–0.17% for day-to-day and 3.2–3.9% for column-to-column. The special amphiphilic structure and high resolution for various analytes reveal the good potential of pillararenes as a new class of stationary phases for chromatographic analyses. Moreover, the TPG column achieved improved thermal stability over the GIL column and excellent repeatability.

Surface-confined guanidinium ionic liquid as a new type of stationary phase for hydrophilic interaction liquid chromatography.

Guanidinium-based ionic liquids possess lower toxicity and greater designability than commonly used species and have presented good performances in liquid-phase extraction and stationary phase for capillary gas chromatography. In the present work, a novel type of surface-confined guanidinium ionic liquid stationary phase was developed by bonding a hexaalkylguanidinium ionic liquid N,N,N',N'-tetramethyl-N",N"-diallylguanidinium bromide onto the surface of 3-mercaptopropyl modified silica. The obtained surface-confined guanidinium ionic liquid silica materials were characterized by elemental analysis, infrared spectroscopy and thermogravimetric analysis, and then packed as a high-performance liquid chromatography column for the evaluation of chromatographic retention behavior. Typical polar compounds were used to evaluate the separation performances, and the changes of retention with water content in mobile phase further suggested the hydrophilic interaction liquid chromatography retention mechanism. Moreover, the effect of different chromatographic factors (salt concentration, mobile phase pH, and column temperature) on retention was investigated with a series of compounds as test solutes to gain insights into the retention mechanism. The results indicated that the surface-confined guanidinium ionic liquid stationary phase exhibited a hydrophilic interaction liquid chromatography/anion-exchange mixed-mode retention behavior and possessed promising potential in separating a wide range of compounds as an alternative stationary phase for high-performance liquid chromatography.

Separation performance of the copolymer and homopolymer of aliphatic polycarbonate diols as the stationary phases for capillary gas chromatography

This work presents the investigation of two aliphatic polycarbonate diols (CAPC and HAPC) as the stationary phases for capillary gas chromatography (GC). The CAPC and HAPC capillary columns showed moderate polarity and high column efficiency of 3704 – 4545 plates/m measured by n-octanol and naphthalene at 120 °C. It was found that despite their similar chemical compositions, CAPC and HAPC differ largely in their selectivity towards the isomers of alkanes, methylpyridines and xylenes. As demonstrated, the CAPC column exhibits advantageous comprehensive performance over the HAPC column and the commercial PEG column. Particularly, the CAPC column exhibits higher resolving performance towards the isomers indicated above and the Grob mixture than the HAPC column. Also, it shows distinct advantages over the PEG column in separating the Grob mixture, the isomers of diethylbenzenes and cymenes, and practical analysis of chemical products and the essential oil from the leaves of Rhododendron dauricum L. Additionally, the CAPC column has excellent repeatability and reproducibility on analyte retention times with the relative standard deviation (RSD) values in the range of 0.05% – 0.08% for run-to-run, 0.12% – 0.19% for day-to-day and 2.6% – 4.9% for column-to-column, respectively. Its applications to purity test of chemical products and GC–MS analysis of the essential oil demonstrate its promising future for practical GC analyses.

Stationary Phases for Capillary Gas Chromatography Obtained on the Basis of Hypercrosslinked Polystyrenes

Capillary columns with previously or in situ synthesized super-crosslinked polystyrene phases are prepared. It has been shown that columns with stationary phases based on presynthesized hypercrosslinked polystyrenes, spherical monodisperse particles, or “nano-sponges,” despite their microporous structure, show insufficient kinetic efficiency and selectivity in the separation of light hydrocarbons. Higher kinetic efficiency was observed in columns where the hypercrosslinked polystyrene phase was synthesized directly in the column, although the porosity structure of this phase remains unknown. All columns with hypercrosslinked polystyrene stationary phase have good thermal stability, with no observed chemical destruction and physical aging at temperatures up to 250°C.

A New Stationary Phase for Capillary Gas Chromatography: Calix[4]resorcinarene Functionalized with Imidazolium Cationic Units

In this work, a novel calix[4]resorcinarene-based ionic liquid (C4RA-2IL) was synthesized, structurally characterized, and statically coated on capillary column as stationary phase for capillary gas chromatography (GC). The column efficiency of the C4RA-2IL column is 3345 plates m−1, which are determined by n-dodecane at 120 °C. Based on its McReynolds constants, the C4RA-2IL column showed moderate polarity. Particularly, the C4RA-2IL column show high separation performance for a wide range of analytes and some difficult separation of meta/para-isomers. Moreover, it exhibited excellent selectivity for critical aromatic isomers of chloroaniline, bromaniline, iodoaniline, toluidine and xylidine isomers and shows advantageous separation capability over the commercial polysiloxane stationary phase. This work presents a promising future of calixarene-based ionic liquid as a new type of stationary phase in GC separations.

The selectivity of a polydimethylsiloxane-based triblock copolymer as the stationary phase for capillary gas chromatography

A triblock copolymer (PCL-PDMS-PCL) constructed from polydimethylsiloxane (PDMS) and poly(ε-caprolactone) (PCL) chains was synthesized and used as the stationary phase for capillary gas chromatography (GC).

Ultramicroporous metal-organic frameworks for capillary gas chromatographic separation

Fine-tuning of the SiF62--containing metal-organic frameworks (SIFSIX) through the substitution of metal centers and ligands changed the apertures from 8.3 Å to 3.8 Å, resulting in ultramicropores and notably improving the separation performance of alkane isomers. Herein, we reported SIFSIX-1-Zn, SIFSIX-1-Cu and SIFSIX-3-Zn as representative stationary phases for capillary gas chromatography (GC). The capillary column coated with ultramicroporous SIFSIX-3-Zn efficiently separated the alkane isomers and benzene homologues, which outperformed SIFSIX-1-Zn and SIFSIX-1-Cu. This resulted from size matching between the window of the ultramicroporous SIFSIX-3-Zn and the analytes, which was also supported by McReynolds constants, column efficiency and peak tailing effect. It opened up a new avenue for ultramicroporous materials in the chromatography separation of isomers.

Separation performance of p-nitro-octadecyloxy-calix[8]arene as stationary phases for capillary gas chromatography

Here we report the first example of employing p-nitro-octadecyloxy-calix[8]arene (C8A-NO2) as stationary phase for capillary gas chromatographic (GC) separations. The statically coated C8A-NO2 column provided column efficiencies of 2554 plates/m and showed moderate polarity. Its selectivity and retention behaviour were investigated by a number of mixtures of diverse analytes and their isomers. It was found that the C8A-NO2 column exhibited high resolving capability for aliphatic and aromatic analytes from apolar to polar nature, especially for positional and structural isomers. Among them, advantageous resolving capability over the commercial polysiloxane DB-1701 and DB-17 columns was obtained for chloroaniline and bromoaniline isomers. In addition, the C8A-NO2 column was applied for the determination of isomer impurities in commercial reagents of geraniol, cis-decahydronaphthalene, and trans-decahydronaphthalene.

Chiral order inorganic mesoporous silica used as stationary phase in gas chromatography

Chiral mesoporous materials have widely applications in chiral separation, asymmetric catalysis, and chiral sensing. Chiral order inorganic mesoporous silica (COIMS) is a kind of chiral materials with high order mesoporous structure not containing organic component. Here we report that a COIMS diluted with a polysiloxane OV-1701 was explored as a novel stationary phase for capillary gas chromatography. The COIMS was synthesized from D-phenylalanine chiral source, and its separation properties of the chiral column were investigated. Eight enantiomers including chiral alcohols, dialcohols, esters and amino acid derivative have been resolved on the coated capillary column. In addition, COIMS chiral column also exhibits good selectivity for the separations of linear alkanes and alcohols. This work indicates that the column has the advantages of high temperature resistance and short analysis time, so it has great potential to develop it as a chiral stationary phase at high temperature.

Chirality: An Important Phenomenon Regarding Biosynthesis, Perception, and Authenticity of Flavor Compounds.

Chirality plays an important role in flavor research. This will be outlined using selected examples from the key areas analysis, authenticity assessment, biogenesis, and odor perception. Developments of analytical techniques, in particular the use of chiral stationary phases in capillary gas chromatography, enabled the determination of naturally occurring configurations of chiral volatiles at trace levels. Thus, knowledge of pathways and enzymes involved in the biogenesis of chiral substances was acquired, and enantioselective analysis has become a prominent tool in the authenticity assessment of flavorings. Increasing information is also available on structure-odor relationships of chiral flavor compounds and the influence of their configurations on odor thresholds and odor properties. A substantial extension of these data sets and a further understanding of the role of chirality in the perception of aroma compounds is expected from studies on the enantioselectivity of odorant receptor systems. Developments in these areas will be put into a historical perspective, recent progress will be emphasized, and data gaps will be described.

Separation Performance of Capillary Gas Chromatography Based on Monohydroxycucurbit[7]Uril Incorporated Into Sol-Gels as the Stationary Phase.

A novel monohydroxycucurbit[7]uril-based stationary phase for capillary gas chromatography (GC) has been produced. For this, a capillary column coating was made using a sol–gel technique, incorporating synthesized monohydroxycucurbit[7]uril [(OH)Q[7]] and hydroxy-terminated poly(dimethylsiloxane) (OH-PDMS) into the sol–gel network through hydrolysis and polycondensation and chemical sol–gel grafting to the inner wall of a fused-silica tube. The preparation method may produce a coating with greater integrity, which gives the prepared column a higher separation efficiency and better selectivity toward analytes than a reported stationary phase based on neat cucurbit[n]urils (Q[n]s). The prepared (OH)Q[7]/PDMS column had 3,225 theoretical plates per meter determined using naphthalene at 120°C and exhibited a weakly polar nature. The (OH)Q[7]/PDMS column has high resolution over a broad spectrum of analytes with symmetrical peak shapes and exhibited better separation performance than commercial capillary columns and reported columns based on neat Q[n]s that failed to resolve some critical analytes. Moreover, the column also showed good thermal stability up to 300°C and separation repeatability with relative standard deviation values in the range of 0.01–0.11% for intraday, 0.11–0.32% for interday and 0.29–0.58% for column-to-column. In addition, the energy effect on the retention of analytes on the (OH)Q[7]/PDMS stationary phase was investigated. The results indicated that retention on the column was determined mainly by the enthalpy change. As demonstrated, the proposed coating method can address some disadvantages that exist with the reported Q[n]s columns and combine the full advantages of (OH)Q[7] with the sol–gel coating method while achieving outstanding GC separation performance.

Nanostructured Silver Coating as a Stationary Phase for Capillary Gas Chromatography.

A capillary column coated with nanostructured silver coating was fabricated for gas chromatography. The nanostructured silver coating, about 80–120 nm in thickness, was prepared as the stationary phase via silver mirror reaction, and was characterized by SEM and EDS. The column was evaluated using different types of model analytes, including n-alkanes, n-alcohols, benzenes, and Grob mixture. A baseline separation of ten n-alkanes on the silver column (15 m × 0.20 mm i.d.) was achieved within 3.5 min through the main hydrophobic mechanism. A mixture of six n-alcohols, or another mixture containing three butanol isomers and two octanol isomers, was separated well on the column. The column separated some benzenes containing benzene, toluene, ethylbenzene, p-xylene, o-xylene, styrene, benzaldehyde, and benzyl alcohol. A Grob mixture containing seven analytes was also separated successfully. Based on a multiple retention mechanism such as hydrophobic, dipole-dipole, and dipole-induced dipole interactions, the silver column achieved a good separation of twelve different types of compounds within 2.5 min. The column presented satisfactory separation repeatability with relative standard deviation of retention time between 0.073% and 0.591%. The results indicate that the silver column is promising for gas chromatographic separation.

Cyanopropyl-Cation Ionic Liquids as High Polar Stationary Phases for Capillary Gas Chromatography

The present work was devoted to the investigation of highly polar capillary columns with stationary phases based on ionic liquids (IL) with cyanopropyl-containing cations. Five imidazole and quinolinium cyanopropyl-containing ILs have been studied. Their high polarity has been demonstrated. The measured Abraham selectivity has demonstrated an increase in specific types of interaction comparing to noncyanopropyl analogs. High thermal stability up to 300°C has been shown, especially for dicationic ILs. Examples of separation for one-dimensional and two-dimensional gas chromatography have been shown.

Amphiphilic Star-Shaped Calix[4]resorcinarene as Stationary Phase for Capillary Gas Chromatography

This work describes the separation performance of the amphiphilic star-shaped calix[4]resorcinarene (C4A-CL) as the stationary phase for capillary gas chromatography (GC). The statically coated C4A-CL capillary column exhibited medium polarity and high column efficiency of 3877 plates m−1 determined by naphthalene at 120 °C. Importantly, the C4A-CL column exhibited extremely high resolving capability for aliphatic analytes with varying polarity, including n-alkanes, esters, ketones, alcohols, and bromoalkanes. In addition, the C4A-CL column exhibited high selectivity and resolving capability for positional, structural and cis-/trans-isomers. Among them, the C4A-CL column displayed advantageous resolving capability over the commercial DB-17 column for aromatic amine isomers. Moreover, it was applied for the determination of isomer impurities in real samples, showing good potential in GC applications.