MIL-53-based homochiral metal-organic framework as a stationary phase for open-tubular capillary electrochromatography

Homochiral metal-organic frameworks(MOFs)have attracted considerable attention in many fields of research,such as chiral catalysis and chiral chromatography.However,only few homochiral MOFs can be effectively used in capillary electrochromatography(CEC)and their performances are far from adequate.In this study,we successfully synthesized achiral nanocrystalline MIL-53.A facile post-synthetic modification strategy was then implemented to functionalize the product,yielding a homochiral MOF:L-His-NH-MIL-53.This MOF was then employed as a chiral coating in open-tubular CEC mode(OT-CEC),and,as such,it exhibited high enantioselectivities for several racemic drugs.The homochiral MOF and the fabricated capillary coating were systematically characterized using transmission electron microscopy,scanning electron microscopy(with energy-dispersive X-ray spectrometry),Fourier-transform infrared spectroscopy,X-ray diffractometry,thermogravimetric analysis,circular dichroism spectroscopy,Brunauer-Emmett-Teller surface area measurements,and X-ray photoelectron spectroscopy.This study is expected to provide a new strategy for the design and establishment of MOF-based chiral OT-CEC systems.

Recent applications and chiral separation development based on stationary phases in open tubular capillary electrochromatography(2019–2022)

Capillary electrochromatography(CEC)plays a significant role in chiral separation via the double separation principle,partition coefficient difference between the two phases,and electroosmotic flow-driven separation.Given the distinct properties of the inner wall stationary phase(SP),the separation ability of each SP differs from one another.Particularly,it provides large room for promising applications of open tubular capillary electrochromatography(OT-CEC).We divided the OT-CEC SPs developed over the past four years into six types:ionic liquids,nanoparticle materials,microporous materials,biomaterials,non-nanopolymers,and others,to mainly introduce their characteristics in chiral drug separation.There also added a few classic SPs that occurred within ten years as supplements to enrich the features of each SP.Additionally,we discuss their applications in metabolomics,food,cosmetics,environment,and biology as analytes in addition to chiral drugs.OT-CEC plays an increasingly significant role in chiral separation and may promote the development of capillary electrophoresis(CE)combined with other instruments in recent years,such as CE with mass spectrometry(CE/MS)and CE with ultraviolet light detector(CE/UV).

A benzenesulfonic acid-modified organic polymer monolithic column with reversed-phase/hydrophilic bifunctional selectivity for capillary electrochromatography

Here,a styrene-based polymer monolithic column poly(VBS-co-TAT-co-AHM)with reversed-phase/hydrophilic interaction liquid chromatography(RPLC/HILIC)bifunctional separation mode was success-fully prepared for capillary electrochromatography by the in situ polymerization of sodium p-styrene sulfonate(VBS)with cross-linkers 3-(acryloyloxy)-2-hydroxypropyl methacrylate(AHM)and 1,3,5-triacryloylhexahydro-1,3,5-triazine(TAT).The preparation conditions of the monolith were optimized.The morphology and formation of the poly(VBS-co-TAT-co-AHM)monolith were confirmed by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).The separation perfor-mances of the monolith were evaluated systematically.It should be noted that the incorporation of VBS functional monomer can provideπ-πinteractions,hydrophilic interactions,and ion-exchange in-teractions.Hence,the prepared poly(VBS-co-TAT-co-AHM)monolith can achieve efficient separation of thiourea compounds,benzene series,phenol compounds,aniline compounds and sulfonamides in RPLC or HILIC separation mode.The largest theoretical plate number for N,N0-dimethylthiourea reached 1.7×10^(5)plates/m.In addition,the poly(VBS-co-TAT-co-AHM)monolithic column showed excellent reproducibility and stability.This novel monolithic column has great application value and potential in capillary electrochromatography(CEC).

Capillary Electrochromatography Using C_8 Open Tubular Column Prepared by Sol-Gel Technique

Open tubthar C8 columns were prepared by sol-gel technology and used in the electrochromatographic separations.

Separation of Peptides by Pressurized Capillary Electrochromatography

A novel gradient pressurized capillary electrochromatography (pCEC) instrument was developed to separate peptides. Two gradient elution modes, hydrophobic and hydrophilic interaction mode in pCEC, were performed on this instrument. Baseline separation of six peptides was obtained on two gradient modes with C18 column and strong cationic exchange column respectively. The effects of mixer volume and total flow rate of pumps on resolution were also discussed.

In situ synthesis of a spherical covalent organic framework as a stationary phase for capillary electrochromatography

Covalent organic frameworks(COFs)are a novel type of crystalline porous organic polymer materials recently developed.It has several advantages in chromatographic separation field,such as high thermal stability,porosity,structural regularity,and large specific surface area.Here,a novel spherical COF 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde(BPTA)was developed as an electrochromatographic stationary phase for capillary electrochromatography separation.The COF TAPB-BPTA modified capillary column was fabricated via a facile in situ growth method at room temperature.The characterization results of scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectroscopy,and X-ray diffraction(XRD)confirmed that COF TAPB-BPTA were successfully modified onto the capillary inner surface.The electrochromatography separation performance of the COF TAPB-BPTA modified capillary was investigated.The prepared column demonstrated outstanding separation performance toward alkylbenzenes,phenols,and chlorobenzenes compounds.Furthermore,the baseline separations of non-steroidal anti-inflammatory drugs(NSAIDs)and parabens with good efficiency and high resolution were achieved.Also,the prepared column possessed satisfactory precision of the intra-day runs(n=5),inter-day runs(n=3),and parallel columns(n=3),and the relative standard deviations(RSDs)of the retention times of tested alkylbenzenes were all less than 2.58%.Thus,this new COF-based stationary phase shows tremendous application potential in chromatographic separation field.

The Synthesis and Characterization of β-cyclodextrin Derivated Pancreatin Used as Chiral Selector in Capillary Electrochromatography

The preparation of capillary electrochromatography column for chiral separation with β-cyclodextrin derivatized Pancreatin was imvestigated, which had three steps, synthesis of β-cyclodextrin derivated pancreatin, the modification of the capillary internal surface and the covalent binding of β-cyclodextrin derivated pancreatin on the capillary internal wall. β-cyclodextrin derivated pancreatin was synthesized using β-cyclodextrin and protein in the presence of ethylene glycol diglycidyl ether （EGDE） in boric acid buffer at pH = 8.7. Amino group was coated on the internal surface of the silica capillary by sot-gel technology using triethoxylmethylsiloxane and （ 3-aminopropyl ） trimethoxysiloxane. Covalent binding of β-cyclodextrin derivated pancreatin was performed by glataraldehyde. Chlorpheniramine, phenylalanine and troopine were separated baseline by β-cyclodetrin derivated pancreatin in capillary electrochromatography.

Determination of N-Methylcarbamate Pesticides in Vegetables by Solid-phase Extraction and Pressurized Capillary Electrochromatography

Capillary electrochromatography （CEC） is a hybrid technique that couples the good selectivity of high-performance liquid chromatography （HPLC） and the high separation efficiency of capillary electrophoresis （CE）. Both charged and uncharged compounds can be separated effectively using CEC. In some cases, however, the bubbles that generated in the capillary column in pure CEC performed on commercial CE instruments will cause unstable current and even disrupt the separation when the concentration of buffer is very high. By applying pressure on the electrochromatographic separation via a micro-HPLC pump, pressurized capillary electrochromatography （ pCEC ） combines two driving factors of the electroosmotic flow （EOF） and the pressure flow, thereby increasing the speed and the selectivity of separation and suppressing the bubble formation. Moreover,

Preparation and Characterization of β-Cyclodextrin Derivatized Ovalbumin Used as Chiral Selector in Pressure Capillary Electrochromatography

Synthesis and properties of β-cyclodextrin derivatized ovalbumin used as chiral selector were investigated, β-cyclodextrin derivatized ovalbumin was synthesized using β-cyclodextrin and ovalbumin in the presence of ethylene glycol diglycidyl ether in boric acid buffer at pH value 8.7 at 37℃. Amino group was coated on the internal surface of the silica capillary by sol-gel technology with triethoxylmethylsiloxane and （3-aminopropyl）trimethoxysiloxane. Covalent binding of g-cyclodextrin derivatized ovalbumin was performed by glutaraldehyde. Enantiomers of chlorpheniramine, phenylalanine and atropine were separated by pressure capillary electrochromatography column coated with β-cyclodextrin derivatized ovalbumin.

Molecularly Imprinted Polymer for Theophylline Retention and Molecular Recognition Properties in Capillary Electrochromatography

Molecular imprinting of theophylline in poly (methacrylic acid- ethylene dimethacrylate) as CEC stationary phases was synthesized by an in situ photo-initiated polymerization reaction. The effect of electrolyte pH on xanthine derivatives and the stability of MIP column performance were investigated. the relative standard deviation (D RS) of migration time of five consecutive runs on MIP column was in the range of 2.2%–3.1%. The reproducibility of migration time column to column of M(A) was in the range of 3.8%–4.9%. The highest column efficiency was more than 140 000 plates per meter. The MIP capillaries had showed better selective for theophylline, which comparing with the reference column. The urine sample was separated by spiked 5×10?4 mol·L?1 theophylline. Key words capillary electrochromatography - molecular imprinting polymers - theophylline CLC number O 657.8 Foundation item: Supported by the National Nature Science Foundation of China (20375028) and the Research Fund for the National High Technology Development “863” of China (2002AA2Z2004)Biography: Cai Ling-shuang (1968-), female, Associate professor, Ph. D, research direction: separation science.

Development of Amine Capillary Column Applied to the Analysis of Basic Compounds by Electrochromatography

An amine capillary column was developed in a fused-silica capillary as stationary phase and applied to separation of basic compounds by capillary electrochromatography (CEC). The functionalized capillary was prepared by inmobilization of 3-Aminopropyl)triethoxysilane (APTES). The CEC conditions including APTES and buffer concentration, pH and applied voltage were investigated to obtain the optimal CEC system for the separation of three anesthetics as basic test molecules. The capillary column provided an efficiency of up to 20,000 plates/m. Lidocaine, ketamine and xilacine were baseline separated under the running conditions with 10 mM Na2HPO4 pH 9.0 as BGE. The applied voltage was 5 kV temperature was set at 25oC and UV detection was performed. The resolutions were 4.97 and 1.53 for ketamine, lidocaine and xilacine, respectively. The column used in CEC mode showed better separation of the anesthetics compared with those used in the capillary zone mode. The comparison with reversed stationary phases used in HPLC in terms of resolution (Rs), sensitivity (LOD), efficiency (N), precision (RSD), asymmetry (T) was also performed. This study provided an alternative way for the CEC separation of basic compounds and demonstrated the improvement in the chromatographic parameters.

Advances in capillary electro-chromatography

Capillary electrochromatography (CEC) is a micro-scale separation technique which is a hybrid between capillary electrophoresis (CE) and liquid chromatography (LC). CEC can be performed in packed, monolithic and open-tubular columns. In recent three years (from 2016 to 2018), enormous attention for CEC has been the development of novel stationary phases. This review mainly covers the development of novel stationary phases for open-tubular and monolithic columns. In particular, some biomaterials attracted increasing interest. There are no significant breakthroughs in technology and principles in CEC. The typical CEC applications, especially chiral separations are described.

Advances in Capillary Chromatography

Capillary columns are used in both capillary liquid chromatography and capillary electrochromatography. The design for capillary liquid chromatography is discussed in comparison with capillary gas chromatography. The difference of diffusion coefficient in gas and liquid phase is a key role. The study for obtaining a high performance capillary liquid chromatography is discussed. Capillary electrochromatography is recently interesting for its instinct ability to realize a high performance chromatography. Capillary electrochromatography with and without pressurized flow is reviewed briefly. Instrumentation for capillary electrochromatography with pressurized flow is discussed. The port of splitting, and gradient elution of both solution and potential are described. The new findings of both the variation of column resistance and capacity factor according to the value of applied electric voltage are also discussed.

基于碳点的色谱分离材料研究进展

色谱分离的核心是色谱柱,色谱柱的灵魂是色谱分离材料,色谱分离材料的种类和性质直接决定色谱的分离模式和分离性能。碳点作为一类新型的零维碳纳米材料,自2004年被首次报道以来,凭借其广泛的原料来源、低毒性、易于功能化、优异的生物相容性和抗光漂白性等独特性能,已广泛应用于生物成像、发光二极管、传感、催化等领域,并呈现出蓬勃的生机。同时,碳点还具有设计性强、粒径大小适中等优势,将其引入色谱分离新材料中开发高选择性的色谱固定相具有重要意义。本文首先简要回顾了碳点的分类、合成策略、发展历程,然后聚焦于色谱分离材料领域,系统综述了近年来碳点在液相色谱固定相(含亲水色谱、反相色谱、混合色谱、手性色谱等)、气相色谱固定相和毛细管电色谱固定相方面的最新研究进展,特别强调了各类固定相的制备方法及其应用,并对碳点在色谱分离材料领域的发展前景和未来努力方向进行了分析和展望,期望为基于碳点的色谱分离新材料的理性设计及应用提供一些参考。

共价有机框架材料在毛细管电色谱中的应用进展

毛细管电色谱(CEC)因兼具高效液相色谱(HPLC)的高选择性和毛细管电泳(CE)的高分离效率而受到越来越多研究者的关注。在毛细管电色谱中,选择合适的固定相材料对获得优异的分离效果起着十分重要的作用。近年来,多种新型材料如氧化石墨烯、蛋白质、金属有机框架(MOFs)及共价有机框架(COFs)等被作为固定相应用于毛细管电色谱领域以期获得更好的分离性能,同时拓展毛细管电色谱的应用范围。其中,COFs因具有孔隙率高、比表面积大、高稳定性、孔径可调和可设计性强等独特性质,在毛细管电色谱领域显示出了巨大的应用前景。鉴于此,本文对2016-2023年间COFs在毛细管电色谱领域的研究进展进行了综述,包括COFs毛细管电色谱柱的分类和制备方法,以及基于COFs固定相的毛细管电色谱技术在环境内分泌干扰物、农药、芳香族化合物、氨基酸及药物分离领域中的应用及分离机理等内容。最后对发展基于COFs固定相的毛细管电色谱应努力解决的问题和该技术未来的发展方向进行了分析和展望。

多孔有机笼的制备及其用作毛细管电色谱手性固定相

多孔有机笼(POCs)是具有一类内在的、客体可及的空腔的离散分子,是一类独特的微孔材料。本文根据席夫碱反应原理,用(1 R,2R)-二氨基环己烷和3,3′,5,5′-四醛基-4,4′-联苯二酚缩合成一种孔径均匀、高比表面积、热化学稳定性良好的棱柱形手性多孔有机笼(POCs)。采用核磁共振氢谱仪、红外光谱、热重分析和扫描电子显微镜对该材料进行表征。将该材料溶解在二氯甲烷中,用动态涂覆法将溶液均匀地涂覆在石英毛细管内壁上,制成毛细管电色谱柱。结果表明,该手性电色谱柱不仅能拆分氧氟沙星、特罗格尔碱、2-氨基-1-丁醇和1-苯基-1-戊醇4种手性药物,还能拆分o,m,p-甲苯胺和o,m,p-氯苯胺2种位置异构体,说明该手性柱具有良好的手性分离能力。通过研究氧氟沙星、特罗格尔碱、2-氨基-1-丁醇和1-苯基-1-戊醇的最佳拆分条件,得出电压、缓冲溶液浓度和pH值对组分分离度有显著影响,其中,氧氟沙星、特罗格尔碱、2-氨基-1-丁醇的最优分离电压均为15 kV,1-苯基-1-戊醇的最佳分离电压为17 kV;氧氟沙星、特罗格尔碱、2-氨基-1-丁醇、1-苯基-1-戊醇的最佳缓冲液浓度均为0.100 mol/L,pH为7.5。在最佳的分离条件下,该电色谱柱拆分氧氟沙星、特罗格尔碱、2-氨基-1-丁醇和1-苯基-1-戊醇的分离度分别为1.80、3.33、1.69、1.18,都获得了较好的分离效果。可见,POCs是一种良好的手性毛细管电色谱固定相,有一定的手性拆分能力,在色谱分离中具有良好的应用前景。

A chiral metal-organic framework{(HQA)(ZnCl_(2))(2.5H_(2)O)}n for the enantioseparation of chiral amino acids and drugs

Chiral metal-organic frameworks(CMOFs)with enantiomeric subunits have been employed in chiral chemistry.In this study,a CMOF formed from 6-methoxyl-(8S,9R)-cinchonan-9-ol-3-carboxylic acid(HQA)and ZnCl_(2),{(HQA)(ZnCl_(2))(2.5H_(2)O)}n,was constructed as a chiral stationary phase(CSP)via an in situ fabrication approach and used for chiral amino acid and drug analyses for the first time.The{(HQA)(ZnCl_(2))(2.5H_(2)O)}n nanocrystal and the corresponding chiral stationary phase were systematically characterised using a series of analytical techniques including scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy,circular dichroism,X-ray photoelectron spectroscopy,thermogravimetric analysis,and Brunauer-Emmett-Teller surface area measurements.In opentubular capillary electrochromatography(CEC),the novel chiral column exhibited strong and broad enantioselectivity toward a variety of chiral analytes,including 19 racemic dansyl amino acids and several model chiral drugs(both acidic and basic).The chiral CEC conditions were optimised,and the enantioseparation mechanisms are discussed.This study not only introduces a new high-efficiency member of the MOF-type CSP family but also demonstrates the potential of improving the enantioselectivities of traditional chiral recognition reagents by fully using the inherent characteristics of porous organic frameworks.

原位分子印迹毛细管电色谱柱的制备及其对非对映异构体的分离

采用原位聚合的方法直接在毛细管柱中合成出辛可宁印迹聚合物。该聚合物与毛细管内壁共价结合连为一体形成整体式毛细管柱,扫描电镜显示其具有大的流通孔结构。采用压力辅助毛细管电色谱模式拆分了非对映异构体抗疟药物辛可宁和辛可尼丁,柱效远高于其在高效液相色谱分离中的柱效。考察了电压、外压、温度、流动相表观pH值和乙腈含量对分离结果的影响。通过对上述条件的优化,可以在2min内完成辛可宁和辛可尼丁的快速分离。

毛细管电色谱和加压毛细管电色谱的进展与应用

毛细管电色谱(CEC)以内含色谱固定相的毛细管为分离柱,以电渗流为驱动力,既可以分离带电物质也可以分离中性物质。它结合了毛细管电泳和高效液相色谱两者的优点,兼具高柱效、高分辨率、高选择性和高峰容量的特点,同时具有色谱和电泳的双重分离机理。然而,"纯粹"的电色谱在实际应用中有着天然的弱点,即:在电流通过毛细管柱中的流动相时容易产生气泡(焦耳热作用),从而使电流中断和电渗流停止,毛细管柱必须被重新用流动相润湿后方能再次使用。加压毛细管电色谱(pCEC)将液相色谱中的压力流引入CEC系统中,不仅解决了气泡、干柱等问题,而且实现了定量阀进样和二元梯度洗脱。CEC和pCEC作为微分离领域的两种前沿技术,满足了当前复杂样品分析和分析仪器微型化的需求,近年来获得了广泛的关注。本文综述了这两种技术近来的发展,包括仪器、色谱固定相的发展,总结了其在生命科学、药物分析、食品安全以及环保样品分析等方面的应用进展,评述了各方法的特点,并展望了CEC和pCEC今后的发展和应用前景。