Preparation and evaluation of open‐tubular capillary column combining a metal–organic framework and a brush‐shaped polymer for liquid chromatography

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.     

开管毛细管色谱柱的制备及其在蛋白质组学研究中的应用进展

近年来随着生命科学等领域的深入发展,人们对微量样本分离分析的需求越来越高,液相色谱系统的微量化受到了更多的关注。由于开管毛细管色谱柱具有较低的反向压力,可通过采用更长的色谱柱提高柱效,从而实现对复杂生物样本的高效分离,因而成为液相色谱柱新的发展方向。本文对开管毛细管色谱柱的制备方法及应用进展进行了综述。     

芯片液相色谱技术进展

微型化是现代分析仪器发展的重要趋势.微型化液相色谱仪器在提供与常规尺度液相色谱相同甚至更高分离效率的同时,可以有效减少溶剂和样品的消耗;在液相色谱-质谱联用中,低流速进样可以有效提高质谱离子源的离子化效率,提高质谱检测效率;对于极微量样品的分离,微型化的液相色谱可以有效减少样品稀释;液相色谱的微型化还有利于液相色谱仪器...     

毛细管离子色谱分析系统研究进展

离子色谱是目前分析离子型样品的成熟技术,其水相工作介质的特点相对于液相色谱更适合于生物样品的分析。毛细管离子色谱(CIC)由于其节省样品的特点在生物分析方面的优势更为明显。CIC大体上可分为开管型、填充柱型和整体柱型3种类型。本文以填充型CIC几大关键部件技术发展为主线,综述了近年来CIC的研究进展。     

The application of immobilized liquids for open tubular liquid chromatography

Summary The applicability of immobilized silicone phases, as reversed phase retentive layers in 5–25μm fused silica capillaries for open tubular liquid chromatography (OTLC) has been investigated. Various types of silicone phases have been tested, of which vinyl containing gums show the most promising features, to create a stable retentive layer in fused silica capillaries. Diffusion coefficients of solutes in the immobilized silicone phases were determined by static measurement and found to be in the order of 5–27 · 10⁻¹² m²/s. These relatively small diffusion coefficients form the main drawback of the immobilized silicone phases, because this seriously hinders the use of thick layers of the stationary phase which is preferred in OTLC to avoid mass overload.     

Open tubular capillary column of 50 μm internal diameter with a very high separation efficiency for the separation of peptides in CEC and LC

A specially designed long open tubular capillary column (50 μm internal diameter and 112 cm effective length) was prepared by fabrication of a thin three‐component co‐polymer layer on the inner surface of silica capillary. A pretreated silica capillary was reacted with 4‐(chloromethyl)phenyl isocyanate in the presence of dibutyltin dichloride as catalyst followed by sodium diethyl dithiocarbamate. Then a thin polymer layer was made on the inner surface of capillary by reversible addition‐fragmentation transfer polymerization of styrene, N‐phenylacrylamide, and methacrylic acid. A carefully adjusted formulation of reaction mixture and elaborated procedures were adopted to secure formation of the co‐polymer layer of enhanced separation performance. The co‐polymer immobilized open tubular capillary column was used for the separation of a synthetic mixture of five peptides and excellent separation efficiency (over 1.7 million per column) was obtained in the capillary electrochromatography mode. Such excellent separation efficiencies of ca. 1 m column have not been obtained in the isocratic elution mode so far. The column was also used for separation of the peptides in the liquid chromatography mode to show very good separation efficiency (average 286 700 per column).     

On-line multidimensional chromatography using packed capillary liquid chromatography and capillary gas chromatography

The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix.     

Open tubular columns: The influence of changing the liquid phase film thickness on column efficiency

Summary The factors characterizing the influence of the variation of the liquid phase film thickness on the mass transfer terms in the Golay equations describing the performance of open tubular columns are investigated and numerical values are given.Paper dedicated to Professor S. R. Lipsky on his sixtieth birthday.     

Open tubular columns prepared with very thick liquid phase film I. Theoretical basis

The influence of the liquid phase film thickness in open-tubular (capillary) columns on the individual resistance-to-mass-transfer terms and on the overall column efficiency is examined from the theoretical point of view. Methods for the calculation of the diffusion coefficients are discussed.     

Practical applications of open tubes in liquid chromatography

The practical applications of open tubes in liquid chromatography as separation columns and as reactors for post column derivatization are discussed. With present technology, the potential efficiency of open tubular columns cannot be fully exploited. As reactors in post column derivatization, these tubes offer many advantages if knitted or stitched to enhance radial mass transfer. The application of open tubes with diameters between 0.12 mm and 0.6 mm as reactors in the selective and sensitive detection of amino acids is demonstrated.     

The application of porous silica layers in open tubular columns for liquid chromatography

Summary Two methods to realize a porous retentive silica layer on the inner wall of 10–25 μm fused silica capillaries for OTLC, etching and precipitation of silica from solution, have been investigated. Etching of the fused silica capillaries with 1M KOH, creates an activated surface, but the capacity of the silica layer is too small to serve as retentive layer in OTLC. Better prospects are offered by the precipitation of silica from a solution of polyethoxysiloxane, dynamically coated on the inner wall of the fused silica capillary. It appears to be possible to deposite a porous silica layer up to 0.8 μm thick (in a 25 μm capillary) by this method, which seems to be suitable for liquid-solid an dynamically generated liquid-liquid chromatography in open tubular columns. The performance of these columns are demonstrated by means of efficient separations of test mixtures using on-column fluorescence detection.     

Open tubular columns and non-porous packings in copolymer HPLC analysis

Summary The separation of poly(styrene-co-acrylonitrile) is presented in open tubular stainless steel columns and columns packed with non-porous glass beads. Furthermore separation on a short silica packed column proved to be better than on a similar longer column. A definition of the term high performance precipitation liquid chromatography is suggested for gradient elution with sample injection into a starting eluent which is a nonsolvent for the copolymer under investigation. The choice of a suitable solvent-nonsolvent combination is of essential importance.     

The optimization of capacity and efficiency when coupling fused silica open tubular columns in gas chromatography

Summary There are a number of parameters which have to be chosen depending on the analysis being done in gas chromatography. While the choice of stationary phase material is based on the solutes to be separated, the thickness is dependent on the concentration and the volatility of the components to be analyzed. This study undertakes a coupled column phase ratio optimization by connecting a short piece of a particular column prior to a normal length of an analytical column. Various columns of different dimensions (phase ratio), but of the same stationary phase material (methyl silicone), are coupled together by a deactivated glass press-fit connector, and the efficiency and capacity are measured. The coupling of fused silica open tubular columns is optimized in efficiency by matching or decreasing the phase ratio of successive columns. Capacity optimization is accomplished by increasing the phase ratio of consecutive columns. Capacity and efficiency optimization are opposing each other; therefore, if some efficiency can be sacrificed a substantial increase in capacity is possible.     

A weak cation-exchange phase for the separation of biogenic amines by open tubular liquid chromatography

Summary The preparation and performance of a weak cation-exchange stationary phase for Open Tubular Liquid Chromatography (OT-LC) was investigated. The stationary phase was prepared in 5.4 μm I.D. fused silica capillaries byin situ photopolymerization of a mixture of silicon acrylate and acrylic acid. The influence of pH, counter ion concentration and organic modifier concentration of the mobile phase on the retention was studied with catecholamines as test solutes using LIF detection. Other biological amines like amino acids, small peptides and nucleic acid derivatives could be separated on this stationary phase as well. The kinetic performance of the stationary phase was studied with several cations and neutral solutes.     

窄内径多孔层开管柱的制备及在液相色谱中的应用

近年来,微纳分离技术由于其内在的优势而受到越来越多的关注.多孔层开管柱是一种重要的微分离柱形式,与粗内径的多孔层开管柱(>25μm)相比,窄内径的多孔层开管柱具有更高的分离效率和更低的试剂消耗量.本文综述了内径≤25μm的窄内径多孔层开管毛细管柱的制备方法、与质谱检测联用技术以及在液相色谱中的应用研究进展,对其发展前景进行了展望.     

Applications of a miniaturized fluorimetric photodiode array detector for capillary liquid chromatography

A high sensitivity, multichannel fluorescence detector with small volume has been developed for capillary column liquid chromatography. Using an intensified linear photodiode array to monitor fluorescence emission, several important mixtures exhibiting native fluorescence have been examined following high efficiency separation on a capillary column. By correlating mass spectral, fluorescence spectral, and retention time data, information of potential utility in the structural elucidation of aromatic molecules contained in complex mixtures can be obtained. Examples include the separation and spectral examination of the polyaromatic compounds in samples of both biological and environmental interest.     

The analysis of lubricating oil additives by supercritical fluid chromatography with packed and open tubular capillary columns

Lubricating oil additives have been analyzed by supercritical fluid chromatography on open tubular and packed capillary columns. Carbon dioxide and modified carbon dioxide were used as mobile phases and detection was accomplished by flame ionization and micro UV. Rapid and efficient analysis of the lubricating oil additives was demonstrated.     

Preparation and evaluation of 3 m open tubular capillary columns with a zwitterionic polymeric porous layer for liquid chromatography

A 3 m zwitterionic polymeric porous layer open tubular column (3 m × 25 μm id × 375 μm od) with a polymeric porous layer thickness of 4 μm was fabricated by the copolymerization of [2‐(methacryloyloxy)ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide and N,N’‐methylenebis(acrylamide). The effects of the diameter of the capillary, reaction temperature, and polymerization time on the preparation of the open tubular column were investigated. Characterized by scanning electron microscopy, the zwitterionic layer was observed to be rough and throughout the fused‐silica capillary homogenously, which increased the phase ratio. The separation of neutral, basic, and acidic compounds demonstrates the strong hydrophilicity of the poly[2‐(methacryloyloxy)ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide coating. In addition, the poly[2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide porous layer open tubular column was applied for the analysis of flavonoids from the rootstalk of licorice, revealing the potential in separating complex samples. The relative standard deviation of retention time for run‐to‐run (n = 5), day‐to‐day (n = 3), and column‐to‐column (n = 3) of toluene, N,N‐dimethylformamide, formamide, and thiourea were below 1.2%, exhibiting good repeatability.