Inner Wall Of Capillary Research Articles

The screening of lipase inhibitors based on the metal-organic framework Zeolitic Imidazolate Framework-8-immobilized enzyme microreactor

An online capillary electrophoresis method based-lipase immobilized enzyme microreactor was developed for lipase kinetic study and inhibitor screening from compounds from natural products. Zeolitic Imidazolate Framework-8 (ZIF-8) has the advantages of large pore size, mild synthesis conditions and good biocompatibility. Lipase was immobilized on the inner wall of capillary with the help of the metal-organic framework ZIF-8. The results of electron microscopy showed that lipase could be aggregated and fixed on the inner wall of capillary by ZIF-8. After the experimental conditions including electrophoretic separation and enzymatic reaction were optimized, the baseline separation of substrate p-nitrophenyl acetate (pNPA) and product p-nitrophenol (pNP) was achieved within 3 min. The immobilized enzyme microreactor showed good repeatability and stability, and the determined Michaelis-Menten constant (Km) of lipase was 2.75 mM, which was lower than the kinetic constant determined in off-line reaction, indicating that the immobilized enzyme had a high affinity with the substrate. In addition, the IC50 value of the positive control compound orlistat on lipase inhibition was 7.26 nM, which was consistent with the literature. Then the inhibitory activity of 10 compounds from natural products on lipase was evaluated by the ZIF-8-IMER. Among them, 7 compounds including baicalein, luteolin, epicatechin gallic acid, and chlorogenic acid, had a certain inhibitory effect on lipase. The molecular docking technology proved the interaction between the enzyme and the screened inhibitor, which provides a new method for the screening of lipase inhibitors.

Synthesis of spherical three-dimensional covalent organic frameworks and in-situ preparation of capillaries coated with them for capillary electrochromatographic separation

Covalent organic frameworks (COFs) are divided into two-dimensional (2D) and three-dimensional (3D) structures according to the connection dimension of covalent bonds. 3D COFs have smaller pore size and larger surface area, which would facilitate the separation of small organic molecules with similar structures and properties in capillary electrochromatographic (CEC) separation. However, the application of 3D COFs in CEC is still in its early stages. Thus, 3D COFs (3D-IL-COF-1 and 3D-IL-COF-2) were synthesis by a new synthesis method in this work. The related characterization results confirmed that spherical 3D-IL-COFs formed by the accumulation of small polyhedral particles were successfully synthesized. Then, 3D-IL-COFs were introduced into the inner wall of capillary by in-situ growth method to prepare the 3D COFs coated capillaries for the first time. The electrochromatographic separation performance of the 3D-IL-COFs coated capillaries was investigated using the 3D-IL-COF-1 coated capillary as the model. The results indicate that the 3D-IL-COF-1 coated capillary with uniform coating exhibits a broad-spectrum separation capacity not only for acidic, basic and neutral analytes but also for neutral isomers, which shows that 3D-IL-COFs becomes an attractive potential stationary phase for electrochromatographic separation.

Surface Channeling of Charged and Neutral Beams in Capillary Guides

In this review work, the passage of charged and neutral beams through dielectric capillary guides is described from a uniform point of view of beams channeling in capillaries. The motion of beams into the hollow channels formed by the inner walls of capillaries is mainly determined by multiple small-angle scattering (reflection) and can be described in the approximation of surface channeling. It is shown that the surface interaction potential in the case of micro- and nano-capillaries is actually conditioned by the curvature of the reflecting surface. After presenting the analysis of previously performed studies on X-rays propagation into capillaries, which is valid for thermal neutrons, too, the surface channeling formalism is also developed for charged particle beams, in particular, moving in curved cylindrical capillaries. Alternative theories explaining experimental results on the beams passage through capillaries are based on simple thermodynamic estimates, on various diffusion models, and on the results of direct numerical simulations as well. Our work is the first attempt to explain the effective guiding of a charged beam by a capillary from the general standpoint of quantum mechanics, which made it possible to analytically explore the interaction potential for surface channeling. It is established that, depending on the characteristics of a projectile and a dielectric forming the channel, the interaction potential can be either repulsive or attractive; the limiting values of the potential function for the corresponding cases are determined. It has been demonstrated that the surface channeling behaviour can help in explaining the efficient capillary guiding for radiations and beams.

In situ fabrication of layered double hydroxide film immobilizing gold nanoparticles in capillary microreactor for efficient catalytic carbonylation of glycerol

• Layered double hydroxides crystallite were in situ fabricated on inner wall of capillary. • Thickness and morphology of LDH film on inner-wall of capillary was finely controlled. • Au NPs were immobilized on layered double hydroxides film. • Au/LDH film showed good catalytic activity in carbonylation of glycerol with urea. • The productivity of glycerol carbonate reached 3.78 g•h −1 •g −1 on Au/LDH catalytic film. Microreactor is capable of intensifying catalytic reaction processes. The fabricating of catalytic film inside microchannels for catalytic reaction remains a challenge. Here we report a facile method for in situ fabrication of layered double hydroxide (LDH) film immobilizing gold nanoparticles in capillary microreactor. Through adjusting the reaction condition of in situ hydrothermal crystallization process and flow deposition process inside microchannel, film thickness, film morphology and Au loading of Au/LDH coating can be finely controlled. Such Au/LDH film inside microchannel exhibited good performance in catalytic carbonylation of glycerol with urea. The yield of glycerol carbonate reached 31.9% at flow rate of 10 µl/min, residence time of 6.62 min and reaction temperature of 413 K under atmospheric pressure. The maximum productivity of 3.78 g∙h −1 ⋅g −1 was obtained at flow rate of 40 µl/min and residence time of 1.65 min under same reaction temperature and pressure. Continuously running the microreactor for 30 h proved the high stability of this catalytic film inside microchannels. This approach could be extended to fabricate other diatomic and triatomic metal LDH films immobilizing metal nanoparticles inside microchannels for heterogeneous catalysis.

Facile synthesis and immobilization of functionalized covalent organic framework-1 for electrochromatographic separation

Inspired by the outstanding functions of 3-aminopropyltriethoxysilane (APTES), which can be used for functionalization of both covalent organic frameworks (COFs) and substrate surfaces, herein, a proof-of-concept demonstration was carried out by one-step synthesis and immobilization of COF-1 in capillary. COF-1 was grown on the inner wall of capillary using APTES, which played a triple role of catalyst, stabilizer, and connecting arm during the process. The immobilization of COF-1 on silicon surface was confirmed by scanning electron microscopy. Moreover, COF-1 modified capillary (COF-1@capillary) column exhibited excellent performance in the electrochromatographic separation of amino acids. High resolution and separation efficiency (225,378 plates/m for 4-methylbiphenyl) were successfully achieved. Separation of methylbenzene, styrene, ethylbenzene, chlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, 4-methylbiphenyl, naphthalene, and 4-vinylbipheny in the electro-driven mode confirmed the successful growth of COF-1 on the inner wall of capillary. The developed facile method for the immobilization of COF-1 may pave the way for further application prospects of boron-based COFs.

Room-temperature growth of covalent organic frameworks as the stationary phase for open-tubular capillary electrochromatography.

Covalent organic frameworks (COFs) are a class of porous materials with high surface area, high porosity, good stability and tunable structure that have been widely used in the separation area. In this work, we have proposed the in situ synthesis of a novel COF composed of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (Tz) and 1,4-dihydroxyterephthalaldehyde (Da) onto the capillary inner surface for electrochromatographic separation. Fourier transform infrared (FT-IR) spectroscopy, elemental analysis (EA) and scanning electron microscopy (SEM) have facilitated the characterization of the prepared capillary columns. The COF (TzDa) modified OT-CEC column exhibited satisfactory separation selectivity towards neutral compounds (such as chlorobenzenes and alkylbenzenes), acidic and basic compounds (such as phenols and anilines), food additives (vanillin and its analogues) and small biomolecules (such as amino acids and polypeptides). Furthermore, the TzDa modified capillary was quite stable and reproducible. The relative standard deviations for retention times of the test analytes (alkylbenzenes) were as follows: for intra-day (n = 3) runs (≤1.74%), inter-day (n = 3) runs (≤2.25%) and between columns (n = 3) (≤4.83%). This new type of COF-based stationary phase has tremendous potential in separation science.

In situ fabrication of 3D COF-300 in a capillary for separation of aromatic compounds by open-tubular capillary electrochromatography

Two-dimensional (2D) COFs have been successfully applied for various applications, such as capillary electrochromatography (CEC). Compared with 2D COFs, three-dimensional (3D) COFs have higher surface area and lower density, which should have superior potential as the separation medium in CEC. However, the 3D COFs on the inner wall of capillary is hard to fabricate in situ. Up to date, the application of 3D COFs in open-tubular capillary electrochromatography (OT-CEC) is still considered a challenge. For the first timethe COF-300-coated capillary was prepared by in situ growth (COF-300 was made from terephthalaldehyde and tetra-(4-anilyl)-methane) on OT-CEC. Benzene, methylbenzene, styrene, ethylbenzene, naphthalene, 1-methylnaphthalene, and propylbenzene were used to evaluate the performance of the COF-300-coated capillary by OT-CEC. For three consecutive runs, the intraday relative standard deviations (RSDs) of migration time and peak areas were 0.1-0.4% and 2.5-8.3%, respectively. The interday RSDs of migration time and peak areas were 0.2-0.5% and 1.0-10.8%, respectively. Five groups of aromatic co mpounds were used to further study the separation mechanism, which indicated that hydrophobic interaction and size selection interaction are the main factors. It should be noted that the COF-300-coated capillary can be used for more than 140 runs with no observable changes ofthe separation efficiency. Graphical abstract The 3D COF-300-coated capillary was prepared by in situ growth for OT-CEC. Six groups of aromatic compounds were separated by 3D COF-300-coated capillary. Size selection and hydrophobic interaction affect the migration time of analytes.

A novel diazoresin/polystyrene-poly(ethylene oxide) covalent capillary coating for the analysis of proteins by capillary electrophoresis

A novel method for the preparation of covalently linked capillary coatings of polystyrene-poly (ethylene oxide) (PS-PEO) was demonstrated by using photosensitive diazoresin (DR) as coupling agents. Layer by layer (LBL) self-assembly membrane of DR and PS-PEO based on hydrogen bonding firstly was fabricated on the inner wall of capillary, then with the treatment of UV light through the unique photochemistry reaction of DR, the hydrogen bonding was converted into covalent bonding. The covalently bonded coatings have the ability of inhibiting protein adsorption on the inner surface of capillary, and thus a baseline separation of Lysozyme (Lys), cytochrome c (Cyt-c), bovine serum albumin (BSA), ribonuclease A (RNase A) and myoglobin (Mb) was achieved by using capillary electrophoresis (CE). Compared with bare capillary or non-covalently bonded DR/PS-PEO coatings, the covalently linked DR/PS-PEO capillary coatings improved the CE separation performance for proteins; what’s more, it exhibited good stability and repeatability. This method can provide a green and easy way to make the covalently coated capillaries for CE, replacing of the old way which using highly toxic and moisture sensitive silane coupling agent by DR in the covalent coating preparation.

Biomimetic cell-cell adhesion capillary electrophoresis for studying Gu-4 antagonistic interaction between cell membrane receptor and ligands

We report a new method: biomimetic cell-cell adhesion capillary electrophoresis (BCCACE) to screen drugs targeting interactions between cell membrane receptors and ligands under an environment close to physiological conditions, in which the cell membrane receptors/ligands can maintain their natural conformations and bioactivity without being isolated and purified. Firstly, we screened twenty-one lactose derivatives by cell-immobilized capillary electrophoresis and obtained Gu-4 with the best activity (K = 3.58 ± 0.22 × 104) targeting macrophage antigen-1 (Mac-1). Then, BCCACE was performed as follows: HEK 293 cells overexpressed with receptor (intercellular adhesion molecules-1, ICAM-1) were cultured and immobilized on the inner wall of capillaries as stationary phase, which simulated the endothelial cells lining on the inner surface of blood vessels. HEK 293 cells overexpressed with ligand Mac-1 as samples were used to simulate the neutrophils cells in blood vessels. And Gu-4 added into the running buffer solution as the antagonist was used to simulate the drug in blood. The results showed that Gu-4 (40 μM) could selectively inhibit cell-cell adhesion by targeting the interaction between Mac-1 and ICAM-1. Finally, the pharmaceutical efficacy assays of Gu-4 at cellular and animal levels were carried out using the concentration of 40 μM and the dose of 20 mg kg−1 respectively, which showed the anti-cancer metastasis activity of Gu-4 and the validity of the method. This method simulated a complete three-dimensional vascular model, which can easily obtain the suitable blood concentration of drugs. This system simulated the interaction between leukocytes and vascular endothelial cells in the bloodstream antagonized by drugs, and obtained the effective concentration of the antagonist. It can be used as an accuracy and efficient drug screening method and will be expected to become a new method to screen drugs targeting cell-cell adhesion.

Self-assembled covalent capillary coating of diazoresin/sodium polystyrene sulfonate for analysis of proteins by capillary electrophoresis

Covalently linked capillary coating of sodium polystyrene sulfonate (PSS) is prepared using the layer by layer self-assembly technique combined with photochemistry reactions. PSS coating based on ionic bonding was first assembled on the inner wall of capillary by using photosensitive diazoresin (DR) as the coupling agent, and then the ionic bonding was converted into covalent bonding after treatment with UV light through a unique photochemistry reaction of DR. DR/PSS covalent coating resisted protein adsorption on the inner surface of the capillary, and thus a baseline separation of various proteins (Lys, Cyt-c, BSA and RNase A) was achieved in a short time by capillary electrophoresis (CE). Compared with bare capillary and uncrosslinked DR/PSS coating, the covalent coating has good stability and reproducibility. Because of the replacement of highly toxic and moisture-sensitive silane coupling agent by DR in the covalent coating preparation, this method may provide a green and easy way to make the covalently coated capillaries for CE.

Polydopamine-assisted immobilization of a zinc(II)-derived metal-organic cage as a stationary phase for open-tubular capillary electrochromatography.

A capillary column was modified with a soluble zinc(II)-derived metal-organic cage (MOC) [Zn2L] as the stationary phase to obtain a new coating layer for use in open-tubular capillary electrochromatography. The inner surface of the capillary was first coated with a layer of polydopamine. Then, a solution of the MOC in dichloromethane was introduced into the capillary upon which it is bonded both covalently and non-covalently. The resulting coating layer on the capillary was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The results demonstrated the successful formation of the [Zn2L] modified open-tubular column. The column showed good separation performance towards neutral compounds (such as methylbenzene, ethylbenzene, n-propylbenzene and n-butylbenzene), acidic drugs (such as ibuprofen, ketoprofen, flurbiprofen and diclofenac sodium), food additives (such as parabens, vanillin and related phenolic compounds) and small biomolecules (such as nucleosides and nucleotide bases) by π-interaction and hydrophobic interaction. It also exhibited good precision, the relative standard deviations of the retention time for intra-day, inter-day runs and column-to-column being <1.6%, 2.8%, and 4.0%, respectively. Graphical abstract Schematic presentation of the open-tubular column modified with zinc(II)-derived metal-organic cage by polydopamine-assisted strategy onto the inner wall of capillary for electrochromatographic separations.

In-situ growth of a metal organic framework composed of zinc(II), adeninate and biphenyldicarboxylate as a stationary phase for open-tubular capillary electrochromatography.

This work reportson the in-situ growth of a metal organic framework (MOF) composed of zinc(II), adeninate and biphenyldicarboxylate on the inner wall of a capillary, and theuse of this MOF as a stationary phases in open-tubular capillary electrochromatography. The inner wall of a fused-silica capillary was first modified with 3-aminopropyltriethoxysilane to create surface amino sites, and then the MOF was synthesized by in-situ growth. The modified capillary was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results proved the successful growth of the MOF. The resultant open-tubular column showed good separation selectivity towards neutral compounds, acidic and basic compounds including nonsteroidal anti-inflammatory drugs, sulfa drugs and small biomolecules. In addition, the modified column is stable and repeatable. The precisions (expressed as RSDs) of the retention time for intra-day (n= 5) and inter-day (n = 5) separations and between columns (n= 3) are less than 0.5, 1.6 and 4.7%, respectively. Conceivably, this new kind of MOF represents a most useful novel stationary phase in electrochromatographic separations. Graphical abstract Schematic presentation of the open-tubular column modified with bio-MOF-1 by in situ hydrothermal reaction with adeninate, Zn(II) and biphenyldicarboxylate for capillary electrochromatographic separations.

Quantitative Analysis of Artificial Sweeteners by Capillary Electrophoresis with a Dual‐Capillary Design of Molecularly Imprinted Solid‐Phase Extractor

A novel coupling system of capillary electrophoresis (CE) and monolithic molecularly imprinted polymer (MIP) was developed for selective and sensitive determination of sweeteners; sucrose, sucralose, and aspartame, based on an in‐column and open‐tube molecularly imprinted solid‐phase extraction (MISPE) concentrator. The MISPE was fabricated by coating a short layer of MIP material (about 3 mm long) directly at the inlet end of the inner wall of capillaries under the irradiation of light emitting diode (LED). Compared with the conventional methods using hydrodynamic injection by MISPE fiber, the MISPE concentrator provides increase in sensitivity without significant loss of separation efficiency. In this work, LED‐induced in‐multiple capillary MISPE was used for extraction and determination of artificial sweeteners, sucrose, sucralose, and aspartame, from beverage samples. The results of MISPE showed good extraction ability with the enrichment ratios of &gt;150 for sucrose and sucralose, and of &gt;200 for aspartame with acceptable analytical performance. The reproducibility of on‐line MISPE concentrator was 1.6% for sucralose and 2.7% for aspartame under the same fixed set of experimental conditions. The developed multiple MISPE system has been successfully adapted for practical application for commercial soda drink samples.

Evaluation of the Interactions Between Platelets and Alkaloids by Frontal Analysis Capillary Electrophoresis Using Polyvinyl Alcohol-Coated Capillary

Capillary electrophoresis (CE) has been widely used in the study of the interactions between targets (biological macromolecules) and ligands due to its good biocompatibility. However, the separation and analysis of platelets, which play a pivotal role in thrombotic diseases, were limited owing to platelets adhesion in inner wall of capillary during CE analysis. In this paper, polyvinyl alcohol-coated capillaries were simply prepared to prevent the adhesion of platelet. Then, a frontal analysis CE (FACE) method was developed to evaluate the interactions between platelets and eight alkaloids include glaucine, magnoflorine, dehydrocorydaline, palmatine, berberine, isorhynchophylline, rhynchophylline, and brucine. The binding constants and stoichiometries of the interactions were calculated by Scatchard equation for strong and specific interaction, and the non-specific binding equation for weak interaction. The results indicated that glaucine, dehydrocorydaline, and isorhynchophylline showed relatively high affinity interaction with platelets. The developed FACE method may be further applied in the evaluation of interactions between platelets and other small molecular compounds.

Open-tubular capillary electrochromatography using carboxylatopillar[5]arene as stationary phase.

Pillar[n]arenes have achieved much interest in material chemistry and supramolecular chemistry due to unusual pillar shape structure and high selectivity toward guest. However, pillar[n]arenes have not yet been applied in capillary electrochromatography. This work at first time reports that carboxylatopillar[5]arene is used as a stationary phase in open-tubular capillary electrochromatography. Carboxylatopillar[5]arene not only possess the advantages of pillar[n]arenes but also provide free carboxy groups for immobilizing on the inner wall of capillary column via covalent bonding. The characterization of SEM and FT-IR indicated that carboxylatopillar[5]arene was successfully grafted on the inner wall of capillary. The baseline separation of model analytes including neutral, basic, and acidic compounds, nonsteroidal anti-inflammatory drugs and dansyl-amino acids have been achieved thanks to the electron-rich cavity of carboxylatopillar[5]arene and hydrophobic interactions between the analytes and stationary phase. The intraday, interday, and column-to-column precisions (RSDs) of retention time and peak area for the neutral analytes were all less than 3.34 and 9.65%, respectively. This work indicates that pillar[n]arenes have great potential in capillary electrochromatography as novel stationary phase.

Evaluation of the interaction between hydroxyapatite and bisphosphonate by nonlinear capillary electrochromatography.

Bisphosphonates are a class of chemical compounds used to treat diseases caused by increased bone resorption. Zoledronate is a third-generation bisphosphonate drug. Hydroxyapatite is main mineral constituent of bones, which can be bound by bisphosphonates in vivo. In this work, we report a method of nonlinear capillary electrochromatography for study on the interaction between hydroxyapatite and bisphosphonate. Hydroxyapatite was modified on the inner wall of capillary by a biomimetic-mineralization method. Then nonlinear chromatography was used to fit and analyze the interaction between zoledronate and hydroxyapatite. The association rate constants of zoledronate in hydroxyapatite-modified capillary and bare capillary are 642.3 and 195/M/min, respectively. This indicates that there is strong binding interactions and affinity between zoledronate and hydroxyapatite. Besides, the interaction between zoledronate and hydroxyapatite was confirmed further by ultraviolet spectroscopy. The method of nonlinear capillary electrochromatography provides a fast and effect approach for studying of bone metabolism disease by evaluation of interaction between hydroxyapatite and bisphosphonates.

In situ synthesis of the imine-based covalent organic framework LZU1 on the inner walls of capillaries for electrochromatographic separation of nonsteroidal drugs and amino acids

The covalent organic framework LZU1 (Lan Zhou University-1) is one of the imine-based covalent organic frameworks (COFs) that possesses attractive properties such as structural regularity, stability and good porosity. This work reports on the in-situ synthesis of COF-LZU1 on the inner walls of capillary column for open-tubular capillary electrochromatography (OT-CEC). The fused-silica capillary was first modified with 3-aminopropyltriethoxysilane and glutaraldehyde. Epitaxial growth of COF-LZU1 on the inner walls was accomplished by Schiff base reaction. The formation of COF-LZU1 was confirmed by SEM and FT-IR. The COF-LZU1 coating increases the interactions between analytes and coating, which remarkably improves the CEC separation selectivity of neutral analytes, amino acids and nonsteroidal anti-inflammatory drugs. The COF-LZU1-modified column exhibits good stability and repeatability. The precisions (relative standard deviations) for intra-day, inter-day and column-to column are <1.6%, 5.6% and 6.8%, respectively. Hence, the imine-based COFs represent attractive stationary phase for application in CEC separations.

Novel Zn-based MOFs stationary phase with large pores for capillary electrochromatography.

Metal-organic frameworks (MOFs) are attractive stationary phases in the field of separation sciences for their unique properties such as large specific surface areas, high porosity, and diverse structures. However, there are few MOFs, which have ultrahigh porosities and gas uptake capacities. In this work, MOF-180 with exceptional porosity, a cage size of 15 × 23 Å, was grown on inner wall of capillary as a novel stationary phase for open-tubular CEC. It has been demonstrated that the MOF-180-modified capillary column exhibited good performance for separation of acidic, basic, and neutral analytes. As compared with MOF-199-modified column, MOF-180-modified column exhibited specific recognition and size selectivity to the tested compounds. The characteristics observed by SEM and FTIR indicated that MOF-180 was successfully grafted on the inner wall of the capillary. The precisions (RSDs) of retention time, peak area, and W1/2 for methylbenzene, ethylbenzene, n-propylbenzene, chlorobenzene, o-dichlorobenzene, and 1,2,4-trichlorobenzene were 0.50-0.54%, 3.31-4.13%, 0.35-1.61%, 1.73-4.22%, 2.67-4.37%, and 1.60-3.38%, respectively. Besides, the run-to-run, day-to-day, and column-to-column RSDs of EOF were 0.6%, 4.19%, and 4.31%, respectively.

An immobilized carboxyl containing metal-organic framework-5 stationary phase for open-tubular capillary electrochromatography

A novel capillary column with metal-organic framework-5 (MOF-5) as the stationary phase was prepared for open-tubular capillary electrochromatography (OT-CEC). To grow MOF-5, the fused-silica capillary was functionalized firstly using 3-aminopropyltriethoxysilane and glutaraldehyde as covalent linkers; and then MOF-5 would be immobilized on the inner wall of COOH-terminated capillary by epitaxial growth, to produce a MOF-5-modified capillary. The successful growth of MOF-5 has been characterized and confirmed by scanning electron microscopy, X-Ray diffraction and Fourier transform infrared spectra. The influence of pH value and methanol on electroosmotic flow (EOF) of the MOF-5-modified capillary column was investigated. The EOF showed a pH-dependent from anode to cathode. The immobilization of MOF-5 improved the interactions between analytes and layer on inner wall of the capillary. Excellent separations of substituted benzenes and acidic and basic analytes were obtained on the fabricated capillary columns. The MOF-5-modified capillary columns exhibited good repeatability, with relative standard deviations for intra-day, inter-day runs and column-to-column less than 1.87%, 3.53%, and 8.49%, respectively. Our successful application of MOF-5 paved the way for introducing series of dicarboxylate-based isoreticular MOFs to OT-CEC as novel stationary phase.

Growth of metal–organic framework HKUST-1 in capillary using liquid-phase epitaxy for open-tubular capillary electrochromatography and capillary liquid chromatography

Much attention is being paid to applying metal–organic frameworks (MOFs) as stationary phases in chromatography because of their fascinating properties, such as large surface-to-volume ratios, high levels of porosity, and selective adsorption. HKUST-1 is one of the best-studied face-centered-cubic MOF containing nano-sized channels and side pockets for film growth. However, growth of HKUST-1 framework inside capillary column as stationary phase for capillary electrochromatography is a challenge work. In this work, we carry out the growth of HKUST-1 on the inner wall of capillary by using liquid-phase epitaxy process at room temperature. The fabricated HKUST-1@capillary can be successfully used for the separation of substituted benzene including methylbenzene, ethylbenzene, styrene, chlorobenzene, bromobenzene, o-dichlorobenzene, benzene series, phenolic acids, and benzoic acids derivates. High column efficiency of 1.5×105N/m for methylbenzene was achieved. The formation of HKUST-1 grown in the capillary was confirmed and characterized by scanning electron microscopy images, Fourier transform infrared spectra and X-ray diffraction. The column showed long lifetime and excellent stability. The relative standard deviations for intra-day and inter-day repeatability of the HKUST-1@capillary were lower than 7%.