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Allyl-ß-CD was synthesized and used as the chiral functional monomer to prepare chiral organic polymer monolithic columns in capillary HPLC. First, the enantioselectivity of the prepared allyl-ß-CD modified organic polymer monolithic capillary columns was investigated. Then, the influences of enantioseparation conditions of chiral drugs were further explored. Finally, the recognition mechanism was studied by molecular docking with AutoDock. Complete enantioseparations of four chiral drugs as well as partial enantioseparations of eight chiral drugs have been achieved. Results showed that the RSD values for run-to-run, day-to-day, and column-to-column variations ranged from 1.2% to 4.6%, 1.4% to 4.7%, and 2.0% to 6.1%, respectively. The enantioselectivity factor rather than resolution is correlated with the binding free energy difference between enantiomers with allyl-ß-CD. Furthermore, the abundant ether bonds, hydroxyl groups, and hydrophobic cavities in cyclodextrin are responsible for the enantioseparation ability of the chiral monolithic capillary columns.

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This study introduces a feasible approach for utilizing a conventional High-Performance Liquid Chromatography (HPLC) instrument at the capillary scale (1 - 10 µL/min). The development of an active flow splitter and an adapted UV-visible (UV-vis) detection cell are described. The system employs an Arduino Uno board to monitor a flow sensor and control a stepper motor that automates a split valve to achieve capillary-scale flow rates from a conventional pump. A capillary UV-vis cell compatible with conventional detectors, featuring an optical path length with a volume of 14 nL, was developed to address the detection challenges at this scale and minimize extra column band broadening. The system performance was assessed by a lab-packed LC capillary column with 0.25 mm x 15 cm dimensions packed with 3.0 µm C18 particles. Model compounds, particularly polycyclic aromatic hydrocarbons (PAHs), were employed to assess the functionality of all developed components in terms of theoretical plates, resolution, and band broadening. The proposed system is a profitable, reliable, and cost-effective tool for miniaturized liquid chromatography.

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Within this review, we thoroughly explored supercritical fluid chromatography (SFC) columns used across > 3000 papers published from the first study carried out under SFC conditions in 1962 to the end of 2022. We focused on the open tubular capillary, packed capillary, and packed columns, their chemistries, dimensions, and trends in used stationary phases with correlation to their specific interactions, advantages, drawbacks, used instrumentation, and application field. Since the 1990s, packed columns with liquid chromatography and SFC-dedicated stationary phases for chiral and achiral separation are predominantly used. These stationary phases are based on silica support modified with a wide range of chemical moieties. Moreover, numerous unconventional stationary phases were evaluated, including porous graphitic carbon, titania, zirconia, alumina, liquid crystals, and ionic liquids. The applications of unconventional stationary phases are described in detail as they bring essential findings required for further development of the supercritical fluid chromatography technique.

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The presented review is devoted to methods for determining the component composition of the studied catalytic reactions, natural gas and its processed products using gas chromatography columns prepared on the basis of poly(1-trimethylsilyl-1-propyne) polymer (PTMSP). Methods of polymer modification are proposed in order to change the polarity and selectivity of separation of compounds of different chemical nature. The influence of the film thickness of the PTMSP stationary phase on the separation parameters and the loading capacity of the columns used is noted. Examples of the use of packed and capillary columns in solving various problems by gas chromatography are shown. The detection limits are determined and the repeatability for the analyzed compounds are calculated.

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For the first time, highly porous hypercrosslinked polystyrene layer was synthesized within a gas chromatography capillary column and successfully deposited onto the capillary walls generating porous layer open-tubular capillary column. Elaborated three steps synthetic procedure provides tightly bonded porous polymeric layer and ensues complete elimination of particle shedding and the needs for particle traps. Due to highly developed surface area, porous layer open-tubular column provides strong solute retention that is useful for the separation of various volatile solvents and light gas compounds including ethane, ethylene, ethyne. Aqueous injections will not harm the column.

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This study ascertained the viability of a portable liquid chromatograph, operating at low microliter per minute flow, for the analysis of seized drugs at remote sites as well as in laboratory settings. Synthetic cathinones were screened using dual capillary columns in series, C8 and biphenyl, with on-column ultraviolet detection at 255 and 275 nm. The relative retention times of the two columns in series and their peak area absorbance ratio were used to determine if the 16 synthetic cathinones investigated could be uniquely identified in these conditions. Based on these parameters all of the analytes could be distinguished. Representative mixtures of synthetic cathinones were used to determine the repeatability, linearity, and limits of detection of the method. This cost effective and green instrumentation has the potential to satisfy minimum international guidelines for the analysis of seized drugs.

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Tocochromanols consisting of tocopherols and tocotrienols, is collectively known as vitamin E. Similarity in their structures, physical and chemical properties rendered the tocochromanols to be subject of chromatography interest. Supercritical fluid chromatography is a highly efficient tool for the separation and analysis of tocochromanols. Separation and analysis of tocochromanols using supercritical fluid chromatography had been carried out in the past using capillary or packed columns. Each of these techniques offer their own advantages and drawbacks. Besides being used for analysis, packed column supercritical fluid chromatography found applications as a purification and content enrichment tool. Emergence of new equipment and stationary phase technologies in recent years also helped in making supercritical fluid chromatography a highly efficient tool for the separation and analysis of tocochromanols. This paper gives an insight into the use of capillary and packed columns in supercritical fluid chromatography for the separation and/or analysis of tocochromanols. The types of stationary phase used, as well as chromatographic conditions are also discussed.

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Capillary ultrahigh-pressure liquid chromatography (cUHPLC) is essential for in-depth characterization of complex biomolecule mixtures by LC-MS. We developed a simple and fast method called FlashPack for custom packing of capillary columns of 50-100 cm length with sub- 2 µm sorbent particles. FlashPack uses high sorbent concentrations of 500-1,000 mg/ml for packing at relatively low pressure of 100 bar. Column blocking by sorbent aggregation is avoided during the packing by gentle mechanical tapping of the capillary proximal end by a slowly rotating magnet bar. Utilizing a standard 100-bar pressure bomb, Flashpack allows for production of 15-25 cm cUHPLC columns within a few minutes and of 50 cm cUHPLC columns in less than an hour. Columns exhibit excellent reproducibility of back-pressure, retention time, and resolution (CV 8.7%). FlashPack cUHPLC columns are inexpensive, robust and deliver performance comparable to commercially available cUHPLC columns. The FlashPack method is versatile and enables production of cUHPLC columns using a variety of sorbent materials.

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A highly ordered chiral mesoporous silica-coated capillary column has been used for high-resolution gas chromatographic separations. The column has excellent selectivity, not only for the separation of isomers, polycyclic aromatic hydrocarbons, linear alkanes, long chain alkanes, Grob's test mixture and aromatic hydrocarbons, but also for the resolution of different classes of chiral compounds. Additionally, the column exhibits high column efficiency, excellent temperature resistance, and analysis times are short. This is the first report of a highly ordered chiral inorganic mesoporous silica used in separation science.

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The urban heat island (UHI) effect has been a great threat to human habitation, and how to mitigate this problem has been a global concern over decades. This paper addresses the cooling effect of a novel permeable pavement called evaporation-enhancing permeable pavement, which has capillary columns in aggregate and a liner at the bottom. To explore the efficiency of mitigating the UHI, bench-scale permeable pavement units with capillary columns were developed and compared with conventional permeable pavement. Criteria of capillary capacities of the column, evaporation rates, and surface temperature of the pavements were monitored under simulated rainfall and Shanghai local weather conditions. Results show the capillary column was important in increasing evaporation by lifting water from the bottom to the surface, and the evaporation-enhancing permeable pavement was cooler than a conventional permeable pavement by as much as 9.4°C during the experimental period. Moreover, the cooling effect of the former pavement could persist more than seven days under the condition of no further rainfall. Statistical analysis result reveals that evaporation-enhancing permeable pavement can mitigate the UHI effect significantly more than a conventional permeable pavement.

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In this work, an open-tubular capillary liquid-phase column was prepared by modifying chain polymer on the inner surface of capillary and chemical bonding of metal organic frameworks, NH2 -UiO-66, to the brushes of chain polymer (poly(glycidyl methacrylate)). Besides advantages of facial preparation and good permeability, the chain polymer effectively increases the modification amount of NH2 -UiO-66 nanoparticles to increase the phase ratio of open-tubular capillary column and enhance the interactions with analytes. The results of scanning electron microscope energy-dispersive X-ray spectra indicated that NH2 -UiO-66 nanoparticles were successfully bonded to the chain polymer. Because of the hydrophobic interaction and hydrogen bonding interaction between the analytes and the ligand of NH2 -UiO-66, different analytes were well separated on the NH2 -UiO-66-modified poly(glycidyl methacrylate) capillary (1.12 m × 25 µm id × 365 µm od) with the high absolute column efficiency reaching 121 477 plates, benefiting from an open-tubular column and low mass transfer resistance provided by polymer brush and metal-organic framework crystal. The relative standard deviations of the retention time for run-to-run, day-to-day, and column-to-column (n = 3) runs are below 4.28%, exhibiting good repeatability. Finally, the column was successfully applied to separation of flavonoids in licorice.

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Graphene oxide functionalized silica microspheres (GO@SiO2 ) were synthesized based on condensation reaction between amino from aminosilica particles and carboxyl groups from GO. Reduction of GO@SiO2 with hydrazinium hydroxide generated graphene modified silica particles (G@SiO2 ). GO@SiO2 and G@SiO2 packed capillary columns for capillary electrochromatography were thereafter fabricated by pressure slurry packing with single-particle frits. GO of 0.3 mg/mL in dispersion solution for GO@SiO2 synthesis was considered as a compromise between retaining and column efficiency whereas GO@SiO2 of 20 mg/mL in slurries for column packing was chosen for a homogenous and tight bed. Optimum mobile phases were acquired considering both electroosmotic flow and resolution at an applied voltage of -6 kV as the following: acetonitrile/phosphate buffer (10 mM, pH 7.0), 75:25 (v/v) for polycyclic aromatic hydrocarbons and 50:50 (v/v) for aromatic compounds. A comparison was made between electrochromatographic performances for three PAHs (naphthalene, fluorene and phenanthrene) and three aromatic compounds of various polarities (toluene, aniline and phenol) on bare aminosilica, GO@SiO2 and G@SiO2 packed columns, which proved the contribution of alone or combinational actions of solvophobic effect and π-π electron stacking as well as hydrogen bonds to retaining behaviors by GO@SiO2 and G@SiO2 . Well over-run, over-day and over-column precisions (retention time: 0.3-1.4, 1.1-3.8 and 2.8-5.2%, respectively; peak area: 2.6-6.5, 4.8-8.3 and 6.5-12.6%, respectively) of GO@SiO2 packed columns were a powerful proof for good reproducibility. Analytical characteristics of GO@SiO2 packed capillary columns in CEC analysis of fresh water were evaluated with respect to linearity (R2 = 0.9961-0.9989) over the range 0.1 to 100 mg/L and detection limits of 9.5 for naphthalene, 12.6 for fluorene and 16.2 µg/L for phenanthrene. Further application to fresh water increased the visibility of the proposed material, where good spike recoveries in the range 89-96% were offered.

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This review focuses on the preparation of organic polymer-based monolithic stationary phases and their application in the separation of biomolecules, including antibodies, intact proteins and protein isoforms, oligonucleotides, and protein digests. Column and material properties, and the optimization of the macropore structure towards kinetic performance are also discussed. State-of-the-art liquid chromatography-mass spectrometry biomolecule separations are reviewed and practical aspects such as ion-pairing agent selection and carryover are presented. Finally, advances in comprehensive two-dimensional LC separations using monolithic columns, in particular ion-exchange×reversed-phase and reversed-phase×reversed-phase LC separations conducted at high and low pH, are shown.

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Chromatography techniques based on chiral stationary phases are widely used for the separation of enantiomers. In particular, gas chromatography has developed rapidly in recent years due to its merits such as fast analysis speed, lower consumption of stationary phases and analytes, higher column efficiency, making it a better choice for chiral separation in diverse industries. This article summarizes recent progress of novel chiral stationary phases based on cyclofructan derivatives and chiral porous materials including chiral metal-organic frameworks, chiral porous organic frameworks, chiral inorganic mesoporous materials, and chiral porous organic cages in gas chromatography, covering original research papers published since 2010. The chiral recognition properties and mechanisms of separation toward enantiomers are also introduced.

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In recent years protein therapeutics have seen increasing use in the therapeutic arena. As with traditional small molecule drug substances, one is obligated to ensure purity and stability of the various dosage forms. With these higher molecular weight therapeutics a common approach for analytical characterization is enzymatic digestion followed by gradient elution liquid chromatography with mass spectrometry detection to create a peptide map (bottom-up protein analysis). Due to the difficult to separate mixtures frequently encountered, there is the need for advanced chromatographic systems featuring increased resolution and/or peak capacity that can be operated in the gradient elution format. Presently we describe an extreme ultra-pressure liquid chromatography (XUPLC) system that has been implemented as an in-house add-on to a commercial ultra-pressure chromatography system. This add-on allows operation at the 38 Kspi range, accommodates the use of capillary columns in excess of one meter packed with sub-2 µm particles and can be operated in the gradient elution format. To evaluate the utility of this system, rat growth hormone was used as a model protein and was exposed to light (λ 254 nm) to create a stress environment. When enzymatic digests of control and stressed protein were analyzed with the XUPLC system using MS detection, greater than 92% peptide coverage was achieved, including the identification some peptides where pre-oxidation of Met residues had occurred, as well as chemistry specifically related to the photolysis of protein disulfide linkages. When the same samples were analyzed by commercial UPLC and compared to the XUPLC results, the utility of the increased peak capacity available with the XUPLC was apparent as previously co-eluting peaks were now well resolved. In particular one specific degradation route was identified where a pair of isobaric cis/trans diastereomerically related peptides were well resolved by XUPLC while they were unresolved by UPLC. Clearly the use of this system operating at the higher pressure regime with long capillary columns is and will be useful in continued investigations of protein stability, especially in cases where only subtle differences in the amino acid residues have occurred during degradation.

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In recent years, micro/nano-scaled separation technique has attracted increasing attention due to its inherent advantages. The porous layer open tubular ( PLOT) capillary column is an important microcolumn form. Comparied to wide-bore PLOT capillary columns ( inner diameter >25 μm ) , the PLOT capillary columns with a narrow inner diameter yield higher separation efficiency and lower reagent consumption. In this paper, the preparation methods for porous layer open tubular capillary columns with narrow inner diameter, less than or equal to 25 μm, are reviewed. Detection techniques combined with mass spectrometry and their applications in liquid chromatography are also disussed.

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Cholesteryl methacrylate has been used to obtain hypercrosslinked poly(cholesteryl methacrylate-co-4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic stationary phase for capillary liquid chromatography. Different contents of cholesteryl methacrylate and toluene in polymerization mixture have been tested to obtain chromatographic performance. The best column has been prepared using 7% of cholesteryl methacrylate and 1% of toluene in polymerization mixture. Such a monolithic material exhibited a surface area of 452m2/g (BET). The column efficiency of about 63 000 plates/m (H=15µm) was achieved for benzene. The polystyrene column with cholesteryl methacrylate providing an additional functional group gave the highest efficiency compared to known poly(4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) and poly(cholesteryl methacrylate-co-trimethylolpropane trimethacrylate) monolithic columns. All of the above capillary columns were used for the separations of small molecules, such as alkylbenzenes, o-terphenyl/triphenylene, parabens, and proteins in reversed-phase liquid chromatography mode. The relative standard deviation of day-to-day reproducibility of hypercrosslinked poly(cholesteryl methacrylate-co-4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic columns were between 12.39-15.95% for retention factors and 10-24% for plate heights, respectively.

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The enantiomeric composition of several chiral markers in lavender essential oil was studied by flow modulated comprehensive two-dimensional gas chromatography operated in the reverse flow mode and hyphenated to flame ionization and quadrupole mass spectrometric detection. Two capillary column series were used in this study, 2,3-di-O-ethyl-6-O-tert-butyldimethylsilyl-ß-cyclodextrin or 2,3,6-tri-O-methyl-ß-cyclodextrin, as the chiral column in the first dimension and α polyethylene glycol column in the second dimension. Combining the chromatographic data obtained on these column series, the enantiomeric and excess ratios for α-pinene, ß-pinene, camphor, lavandulol, borneol, and terpinen-4-ol were determined. This maybe a possible route to assess the authenticity of lavender essential oil.

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A novel method for the analysis of benzimidazole residues in water samples by capillary electrochromatography-UV detection (290nm), using laboratory-made packed columns is presented. Capillaries (25cm packed length×75µm inner diameter, 34cm total length, 25.5cm effective capillary length) were packed with C18 particles (5µm, non-encapped) following a high pressure packing procedure and using a compact steel unit designed for packing capillary columns. Acetone was employed as solvent to carry the particles through the capillary and pack it under a pressure of 42MPa. Outlet and inlet frits were made by sintering the particles of the stationary phase by heating the packed material with a nichrome ribbon connected to a 7V AC power supply. With the aim of achieving a good analytical performance, the variables that affected the separation were studied, using a mobile phase composition of 60:40 (v/v) acetonitrile/water containing ammonium acetate (1mM, pH 6.5), a separation voltage of 25kV and a temperature of 25°C. In addition, a combined hydrodynamic-electrokinetic injection mode was considered and samples were injected for 75s under a voltage of 12.5kV and a pressure of 11.5bar. Finally, the determination of benzimidazoles in water samples was accomplished by capillary electrochromatography using dispersive liquid-liquid microextraction as sample treatment. Variables affecting the extraction efficiency were optimized, using chloroform and ethanol as extraction and disperser solvents, respectively. This method was applied to different water samples, obtaining satisfactory results in terms of linearity (R2≥0.990), repeatability (RSD≤1.2%), reproducibility (RSD≤2.2%) and trueness (R≥87.7%). Detection and quantification limits were lower than 2.8µgL-1 and 9.3µgL-1, respectively.

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Slurry packing capillary columns for ultrahigh pressure liquid chromatography is complicated by many interdependent experimental variables. Previous results have suggested that combination of high slurry concentration and sonication during packing would create homogeneous bed microstructures and yield highly efficient capillary columns. Herein, the effect of sonication while packing very high slurry concentrations is presented. A series of six, 1m×75µm internal diameter columns were packed with 200mg/mL slurries of 2.02µm bridged-ethyl hybrid silica particles. Three of the columns underwent sonication during packing and yielded highly efficient separations with reduced plate heights as low as 1.05.

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