Stationary Phase For Chromatographic Separation Research Articles

Enantioseparations by Gas Chromatography Using Porous Organic Cages as Stationary Phase.

The resolution of chiral compounds into optically pure enantiomers is very important in various fields, such as pharmaceutical, chemical, agricultural, and food industries. Chiral gas chromatography (GC) is one of the efficient methods for enantioseparations of volatile compounds. In recent years, porous materials as stationary phases for chromatographic separations have achieved increasing attention. Porous organic cages (POCs) represent an emerging class of porous materials, which are assembled by discrete organic molecules with shape-persistent and permanent cavities through weak intermolecular forces. This chapter describes several chiral POCs as chiral stationary phases for GC enantioseparations of racemic compounds.

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry.

Porous organic frameworks (POFs), a general term for covalent‐organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state‐of‐the‐art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in “turn‐off” or “turn‐on” fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

Surface-modified three-dimensional graphene nanosheets as a stationary phase for chromatographic separation of chiral drugs

Carbon-based stationary phases for chromatographic separation have been commercially available since the 1980s. Porous graphitic carbon liquid chromatography columns are known to be highly resistant to aggressive mobile phases and extreme pH values of solvents and eluents, an important advantage compared to conventional silica-based alternatives. In our work, we demonstrate a new variant of carbon-based stationary phases for liquid chromatography, specifically developed for chiral separation. Mesoporous three-dimensional graphene nanosheets (3D GNS), functionalized with tetracyanoethylene oxide (TCNEO) and (S)-(+)-2-pyrrolidinemethanol, demonstrate pharmaceutical-grade chiral separation of model ibuprofen and thalidomide racemic mixtures when used as Chiral Stationary Phases (CSPs), with performance parameters comparable to currently commercially available CSPs. Simple covalent attachment of functionalization groups to the surface of mesoporous three-dimensional graphene nanosheets makes these carbon-based CSPs chemically stable and up to an order of magnitude less expensive than standard silica-based analogues.

Simultaneous HPTLC Estimation of Berberine and Curcumin in Gruhadhoomadi Churna

Gruhadhoomadi churna has been traditionally used to reduce inflammation, burning sensation and swelling in case of gout and arthritis. A simple, precise, specific, accurate high performance thin layer chromatography method was developed for simultaneous estimation of berberine and curcumin form gruhadhoomadi churna. Thin layer chromatographic aluminium plates pre-coated with silica gel 60F254 were used as the stationary phase for chromatographic separation of the drugs. n-Propanol:water:glacial acetic acid (8:1:1 v/v/v) was selected as the mobile phase and analysis was carried out in the absorbance mode at iso-absorptive wavelength of 358 nm. This method exhibited good resolution for both drugs with retention factor 0.32±0.03 and 0.77±0.03 for berberine and curcumin, respectively. Regression analysis data indicated good linear relationship for the calibration plots for berberine and curcumin in the range of 200-600 and 400-1200 ng/spot and the regression coefficients were 0.9904 and 0.9934, respectively. The method was validated according to the International Conference on Harmonisation guidelines for accuracy, precision, limit of detection, linearity, limit of quantification, robustness and specificity. In conclusion, the developed method was rapid, simple, reliable and specific for the identification and quantification of berberine and curcumin.

Novel Mixed‐Mode Stationary Phases for Chromatographic Separation of Complex Mixtures of Decomposed Lignin

AbstractElectrochemical degradation of lignin results in a large number of unknown products, formed by both oxidative and reductive decomposition pathways, which have previously been studied by direct mass spectrometry experiments without prior liquid chromatography separation, revealing the presence of many isobaric molecules. In this study, novel phosphonium‐based ionic liquid stationary phases were synthesized and applied in conjunction with high resolution mass spectrometry, to further increase the resolving power of the analytical methodology. The new stationary phases exhibited a wide range of interaction mechanisms in comparison to reversed‐phase materials, and the preliminary results of this proof‐of‐concept study illustrated class‐specific isolation and separation of the major chemical classes of the lignin breakdown products members into very specific retention time windows. For the investigated electrochemically decomposed lignin, the separations revealed predominantly aldehydes and alcohols, and also confirmed the presence of a significant number of isobars.

Graphene oxide-SiO2 hybrid nanostructure as coating material for capillary electrochromatography.

Graphene oxide (GO) has been considered as a promising stationary phase for chromatographic separation. However, the very strong adsorption of the analytes on the GO surface lead to the severe peak tailing, which in turn resulting in decreased separation performance. In this work, GO and silica nanoparticles hybrid nanostructures (GO/SiO2 NPs@column) were coated onto the capillary inner wall by passing the mixture of GO and silica sol through the capillary column. The successful of coating of GO/SiO2 NPs onto the capillary wall was confirmed by SEM and electroosmotic flow mobilities test. By partially covering the GO surface with silica nanoparticles, the peak tailing was decreased greatly while the unique high shape selectivity arises from the surface of remained GO was kept. Consequently, compared with the column modified with GO (GO@column), the column modified with GO and silica nanoparticles through layer-by-layer method (GO-SiO2 NPs@column), or the column modified with silica nanoparticles (SiO2 NPs@column), GO/SiO2 NPs@column possessed highest resolutions. The GO/SiO2 NPs@column was applied to separate egg white and both acidic and basic proteins as well as three glycoisoforms of ovalbumin were separated in a single run within 36 min. The intra-day, inter-day, and column-to-column reproducibilities were evaluated by calculating the RSDs of the retention of naphthalene and biphenyl in open-tubular capillary electrochromatography. The RSD values were found to be less than 7.1%.

Simultaneous Estimation of Aloe Emodin and Emodin from Rheum emodi, Cassia alata and Aloes by HPTLC.

A simple, precise, specific, accurate high performance thin layer chromatography method was developed for simultaneous estimation of aloe emodin and emodin from medicinal plants like Rheum emodi (Rhubarb), Barbados aloes (dried juice of Aloe barbadensis leaf) and Cassia alata (Candle bush). Thin layer chromatographic aluminum plates pre-coated with silica gel 60 F254 was used as the stationary phase for chromatographic separation of the drugs. Toluene:ethyl acetate:formic acid (10:2:1 v/v/v) was selected as mobile phase and analysis was carried out in absorbance mode at iso-absorptive wavelength of 263 nm. This method shows good resolution for both drugs with retention factor 0.37±0.03 and 0.55±0.03 for aloe emodin and emodin, respectively. The regression analysis data indicated good linear relationship for the calibration plots for aloe emodin and emodin in the range of 300 - 800 ng/spot and 150 - 400 ng/spot and regression coefficient was 0.9993 and 0.9994, respectively. Validation of the method was performed according to International Conference on Harmonisation guidelines for following parameters: Accuracy, precision, limit of detection, linearity, limit of quantification, robustness and specificity. In conclusion, the developed method was found to be rapid, simple, reliable and specific for the identification and quantitation of these anthraquinones in medicinal plants and marketed formulations.

Advances in cucurbituril bonded stationary phases for chromatographic separation

Cucurbit [n] urils (CB [n]), a kind of host molecules of the fourth generation supramolecule followed crown ethers, cyclodextrins and calixarenes in supramolecular chemistry, are macrocyclic ligands and consist of several glycoluril units. Their special molecular recognition based on unique separation selectivity and stability have gained great interest in supramolecular chemistry and chromatography. Hereby, we give a review of research progresses of cucurbit [n] urils structural features, its homologues and derivatives and their applications in chromatographic stationary phase.

Synthesis and characterization of periodic mesoporous organosilicas with uniform spherical core–shell structure used as a stationary phase

Micrometer-size periodic mesoporous organosilicas (PMOs) with a uniform spherical core–shell structure were prepared, and their application as a stationary phase for chromatographic separation was demonstrated in this study. The structure and morphology of this new material was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nitrogen sorption measurements. The results showed that the materials exhibited a spherical morphology, core–shell structure and mesostructure. This new material was tested as a potential stationary phase for HPLC because of its combination of a core–shell structure and PMOs. The new material showed high column efficiency for fast separation of aromatic hydrocarbon compounds.

Research developments for the applications of carbon nanotubes in separation science

As a novel nanomaterial, carbon nanotubes (CNTs) have been extensively applied in many fields such as material, catalysis, adsorption and separation, etc. The applications of CNTs in separation science, such as in solid phase extraction (SPE), solid phase microextraction (SPME) and membrane extraction, and as stationary phase for chromatographic separation and capillary electrophoresis (CE) are reviewed in the paper.

Highly Stable Surface Functionalization of Microgas Chromatography Columns Using Layer-by-Layer Self-Assembly of Silica Nanoparticles

A controllable and high-yield surface functionalization of silicon microchannels using layer-by-layer (LbL) self-assembly of SiO2 nanoparticles (SNPs) is presented. The application of SNPs (45 nm average diameter) coating as a stationary phase for chromatographic separation is also demonstrated with surface functionalization using chloroalkylsilanes. This method facilitates a simple, low-cost, and parallel processing scheme that also provides homogeneous and stable nanoparticle-based stationary phases with ease of control over the coating thickness. The SNP-functionalized microfabricated columns with either single capillary channels (1 m long, 150 μm wide, 240 μm deep) or very narrow multicapillary channels (25 cm long, 30 μm wide, 240 μm deep, 16 parallel channels) successfully separated a multicomponent gas mixture with a wide range of boiling points with high reproducibility.

Multi-dimensional gas chromatography with a planar microfluidic device for the characterization of volatile oxygenated organic compounds

Oxygenated compounds like methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetaldehyde, crotonaldehyde, ethylene oxide, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, and 2-chloromethyl-1,3-dioxolane are commonly encountered in industrial manufacturing processes. Despite the availability of a variety of column stationary phases for chromatographic separation, it is difficult to separate these solutes from their respective matrices using single dimension gas chromatography. Implemented with a planar microfluidic device, conventional two-dimensional gas chromatography and the employment of chromatographic columns using dissimilar separation mechanisms like that of a selective wall-coated open tubular column and an ionic sorbent column have been successfully applied to resolve twelve industrially significant volatile oxygenated compounds in both gas and aqueous matrices. A Large Volume Gas Injection System (LVGIS) was also employed for sample introduction to enhance system automation and precision. By successfully integrating these concepts, in addition to having the capability to separate all twelve components in one single analysis, features associated with multi-dimensional gas chromatography like dual retention time capability, and the ability to quarantine undesired chromatographic contaminants or matrix components in the first dimension column to enhance overall system cleanliness were realized. With this technique, a complete separation for all the compounds mentioned can be carried out in less than 15min. The compounds cited can be analyzed over a range of 250ppm (v/v) to 100ppm (v/v) with a relative standard deviation of less than 5% (n=20) with high degree of reliability.

Microfluidic droplet-array liquid–liquid chromatography based on droplet trapping technique

We describe the first realization of liquid chromatographic separation in a droplet-based microfluidic system and develop a novel mode for microchip-based chromatography named as droplet-array liquid-liquid chromatography. In this system, two arrays of picoliter-scale droplets immobilized on both sidewalls of a microchannel with droplet trapping technique served as the stationary phase in chromatographic separation, while the other immiscible phase flowing in the microchannel served as the mobile phase. The chromatographic separation was achieved on the basis of multiple extraction and elution of analytes between the droplet array stationary phase and the mobile phase. The proof-of-concept study of the droplet-array LC system was performed in the separation of fluoranthene and benzo[b]fluoranthene. Under the optimum conditions, the two analytes were separated within 26 min with separation efficiencies of 112 μm and 119 μm plate height, respectively. The advantages of the present system include simple structure, low driving pressure, and relatively high sample capacity. It can also provide a useful platform for LC theory study and educational purposes by allowing the researchers and students to directly "see" the continuous extraction and elution process of a chromatographic separation.

Self-assembled highly ordered ethane-bridged periodic mesoporous organosilica and its application in HPLC

Monodisperse spherical periodic mesoporous organosilicas (PMOs) with ethane integrated in the framework were synthesized and their application as stationary phase for chromatographic separation is demonstrated. The ethane-PMOs were prepared by condensation of 1,2-bis(triethoxysilyl)ethane (BTSE) in basic condition using octadecyltrimethylammonium chloride (C(18)TMACl) as template and ethanol as co-solvent. The morphology and mesoporous structure of ethane-PMOs were controlled under different concentrations of sodium hydroxide (NaOH) and EtOH. The results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), nitrogen sorption measurement, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis showed that ethane-PMOs have spherical morphology, uniform particle distribution, highly ordered pore structure, high surface area and narrow pore-size distribution. The column packed with these materials exhibits good permeability, high chemical stability and good selectivity of mixtures of aromatic hydrocarbons in normal phase high-performance liquid chromatography (HPLC).

Ionic liquid-modified silica as a new stationary phase for chromatographic separation

A new stationary phase based on silica modified with 1-methyl-3-propylimidazolium chloride was synthesized and characterized in this paper. A derivative of 1-methyl-3-propylimidazolium chloride was used to chemically modify the surface of silica particles to act as the stationary phase for HPLC. The modified particles were characterized by Fourier Transform Infrared (FT-IR), 13C NMR spectroscopy and thermogravimetric analysis (TGA). The surface modification procedure rendered particles with a surface coverage of 0.89 μmol/m2 of alkylimidazolium chloride. Columns packed with the modified silica and blank silica particles were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic compounds as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic and electrostatic interactions.

Thermally responsive chromatographic materials using functional polymers

Functional polymers that respond to small changes in environmental stimuli with large changes in their structure and properties are often called "intelligent" polymers. We have modified material surfaces with such polymers and used them in separation systems. Silica beads were modified with the temperature-responsive polymer poly(N-isopropylacrylamide) (PNIPAAm). PNIPAAm-grafted surfaces exhibited temperature-driven alterations of hydrophilic-hydrophobic surface-properties. Using this feature, PNIPAAm and related temperature-responsive polymers have been used to generate temperature-sensitive stationary phases for chromatographic separations. We attached several different functional polymers, including temperature- and pH-responsive polymers, to silica beads. These temperature-responsive stationary phases are useful in development of separation methods since adjusting the temperature represents an extra tool for optimizing the selectivity. Applications of thermally responsive columns for separations in the HPLC mode are demonstrated.

Adsorption of human serum albumin on to synthesized dye-like polystyrene gel beads

In bioseparation, adsorption of proteins on to various polymer surfaces plays an important role in different fields, particularly in pseudo-affinity chromatography techniques. In this context, this study aims to synthesize cross-linking polystyrene gel beads as packing material in column chromatography for albumin purification. Suitable chemical groups, such as sulfonate and l-cysteine with high affinity towards human serum albumin were introduced on the aromatic ring of the hydrophobic adsorbing polystyrene support. These functional groups were chosen on the basis of the interactions of albumin with their exogenous and endogenous ligands in such manner to confer this material a highly binding ability and enhance its efficacy. Adsorption of human albumin on to these two synthesized adsorbents was performed at 37 °C in physiological pH 7.3 during 20 min of incubation. The adsorbed albumin content at interface allows to establish the adsorption isotherm curves. The adsorption rate on both resins was found to be significantly high and the affinity constants, evaluated by the Langmuir model, were: 7.5×10 5 and 1.45×10 6 M −1 for poly(styrene sodium sulfonate) and poly(styrene cysteine sulfamide), respectively. Thus, the obtained material gel beads could be used advantageously as a dye-like stationary phase in chromatographic separation of albumin instead of other conventional supports.

Creation and characteristics of phosphatidylcholine stationary phases for the chromatographic separation of inorganic anions

New stationary phases for chromatographic separation of anions, obtained by loading liposomes made from dimyristolyphosphatidylcholine (DMPC) onto reversed-phase packed columns (C 18 and C 30) are reported. Mono- and divalent anions were used as model analyte ions and retention data for these species were obtained using the DMPC stationary phases and used to elucidate the separation mechanisms involved in this chromatographic system. The DMPC stationary phases can separate anions by either a solvation-dependent mechanism or an electrostatic ion-exchange mechanism, depending upon the relative magnitudes of the negative electrostatic potential ( Ψ (−)) of the phosphate moiety (P −) and the positive electrostatic potential ( Ψ (+)) of the quaternary ammonium groups (N +) on the headgroup of DMPC. If Ψ (+)> Ψ (−), such as in case where Ψ (−) has been reduced either by binding of eluent cations (e.g., H + or divalent cations) onto the P − group of DMPC or by steric screening when a C 30 reversed-phase material was used to support the DMPC, then the overall electrostatic surface potential (and hence also the effective anion-exchange capacity) was generally large and the anions were separated on the basis of an electrostatic mechanism. However, if Ψ (+) was similar to Ψ (−), such as in the case of using a C 18 reversed-phase support and monovalent cations as eluent cations, then the overall electrostatic surface potential and the effective anion-exchange capacity were very small and the analyte anions were separated on the basis of a solvation-dependent mechanism. The DMPC stationary phases were found to be suitable for the direct determination of iodide and thiocyanate in highly saline water samples, such as seawater samples.

Investigation on the use of UTEVA as a stationary phase for chromatographic separation of actinides on-line to inductively coupled plasma mass spectrometry

Download options Please wait... Article information DOI https://doi.org/10.1039/B007123O Article type Paper Submitted 04 Sep 2000 Accepted 20 Nov 2000 First published 15 Dec 2000 Download Citation J. Anal. At. Spectrom., 2001,16, 26-31 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Investigation on the use of UTEVA as a stationary phase for chromatographic separation of actinides on-line to inductively coupled plasma mass spectrometry L. Perna, M. Betti, J. M. B. Moreno and R. Fuoco, J. Anal. At. Spectrom., 2001, 16, 26 DOI: 10.1039/B007123O To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Lorenzo Perna Maria Betti Josepha Maria Barrero Moreno Roger Fuoco

Novel Sol−Gel-Derived Material for Separation and Optical Sensing of Metal Ions: Propyl-ethylenediamine Triacetate Functionalized Silica

A novel organically modified silica material has been prepared by sol−gel processing. The material incorporates an organic substituent, propyl-ethylenediamine triacetate, which is linked to the silica matrix covalently. This optically transparent material has been characterized by thermogravimetric analysis and infrared spectroscopy. Its binding capability with various metal ions has been examined. The material is porous, and almost all the covalently linked organic substituents are active in the pore space. It can be processed into monoliths or coated as thin films of widely variable shapes. The usefulness of this material as a stationary phase for chromatographic separation of metal ions has been demonstrated. The feasibility of this material as a chemical recognition phase for optical sensing of Cu2+ has also been illustrated. The material is highly stable and highly resistant to leaching of the organic modifier.