毛细管离子色谱进展

从毛细管离子色谱柱制备和毛细管离子色谱仪器研制两方面评述了毛细管离子色谱目前的发展状况.毛细管离子色谱柱包括开管离子色谱柱,毛细管颗粒填充离子色谱柱以及最近几年发展起来的整体毛细管离子色谱柱.对毛细管离子色谱仪的总结包括微流量泵、小体积进样器、适合毛细管离子色谱系统的小体积抑制器、电导和光学检测器等.     

毛细管离子色谱进展

从毛细管离子色谱柱制备和毛细管离子色谱仪器研制两方面评述了毛细管离子色谱目前的发展状况。毛细管离子色谱柱包括开管离子色谱柱，毛细管颗粒填充离子色谱柱以及最近几年发展起来的整体毛细管离子色谱柱。对毛细管离子色谱仪的总结包括微流量泵、小体积进样器、适合毛细管离子色谱系统的小体积抑制器、电导和光学检测器等。     

溶胶-凝胶法制备毛细管硅胶整体柱的研究进展

毛细管硅胶整体柱作为一种新型的分离介质,在色谱领域显示出了强大的生命力。本评述介绍了溶胶-凝胶法制备毛细管硅胶整体柱的方法,重点分析了溶胶-凝胶法制备毛细管硅胶整体柱的影响因素,总结了近几年毛细管硅胶整体柱在高效液相色谱和电色谱中的应用。     

毛细管硅胶基质整体柱的制备及应用

硅胶基质整体柱具有很好的通透性，高通量，及在有机溶剂条件下稳定等优点，已应用于毛细管电色谱（CEC）和微柱高效液相色谱（μ-HPLC）。本文从分离模式的角度，对毛细管硅胶整体柱的制备方法及其应用加以系统综述。并展望了这一领域未来的发展趋势。     

整体柱在样品预处理中的应用

综述了近年来整体柱在样品预处理领域中的应用,包括整体柱样品预富集同高效液相色谱、毛细管电泳和电色谱的联用,微流控芯片中的整体柱萃取以及近年来整体柱萃取模式的改进等。引用文献65篇。     

牛血清白蛋白修饰毛细管整体柱的制备及组氨酸对映体分离

以甲基丙烯酸缩水甘油酯为单体, 乙二醇二甲基丙烯酸酯为交联剂, 环己醇和正十二醇混合溶液为致孔剂, 在最佳聚合条件下, 以偶氮二异丁腈为引发剂, 制备了毛细管整体柱基质, 并且研究了单体、交联剂及致孔剂对整体柱基质孔结构及渗透性的影响; 使用Epoxy方法在基质表面键合BSA, 制得BSA修饰的毛细管整体柱. 将此毛细管整体柱应用于毛细管电色谱中, 成功地分离出了组氨酸对映体, 分离度良好.     

一种反相毛细管液相色谱整体柱的制备方法及其色谱性能

在优化条件下成功制备了50μm、75μm、100μm和200μm等多种口径的硅胶基质毛细管液相色谱整体柱,克服了文献报道中常见的开裂、重现性差等缺点。考察了柱压降与流速的关系,以多环芳烃系列化合物评价了自制的C18硅胶基质毛细管液相色谱整体柱的色谱性能,在以甲醇-水为流动相的反相色谱条件下,5种化合物(苯、萘、联萘、芴和蒽)得到了基线分离。该柱对萘的柱效达到了67000塔板/米。     

阳离子交换毛细管整体柱的制备及其在毛细管离子色谱中的应用

以甲基丙烯酸缩水甘油酯(GMA)为功能单体,亚乙基二甲基丙烯酸酯(EDMA)为交联剂,偶氮二异丁腈(AIBN)为自由基引发剂,在三元致孔剂(正丙醇,1,4-丁二醇,水)的存在下,在320!m内径的弹性石英毛细管柱内制备得到带有环氧功能基团的聚合物整体柱基质;利用Na2SO3对其改性,制备得到磺酸基型阳离子交换毛细管整体柱。采用微流泵、毛细管检测池和紫外检测器构建了毛细管离子色谱系统,并对所制备的整体柱的流体力学参数、色谱性能参数进行评价;采用流速梯度洗脱的方式实现9种常见阳离子(Li+,Na+,NH4+,K+,Cs+,Mg2+,Ca2+,Sr2+,Ba2+)的分离分析;此色谱系统还可应用于牛奶中阳离子和三聚氰胺的分离检测。     

毛细管电色谱柱制备技术的进展

介绍了毛细管电色谱开管柱、填充柱和整体柱的各种制备技术及其优势与不足,特别是对于近期发展的毛细管电色谱整体柱的制备方法及其应用进行了系统综述。引用文献100篇。     

混合模式毛细管聚合物整体柱的制备及应用

混合模式毛细管整体色谱柱由于保留机理多样,具有很好的应用前景。本文以[2-（甲基丙烯酰基氧基）乙基]二甲基-（3-磺酸丙基）氢氧化铵（SPE）为单体,乙二醇二甲基丙烯酸酯（EDMA）为交联剂,偶氮二异丁腈（AIBN）为引发剂,正丙醇/1,4-丁二醇/水三元体系为致孔剂,制备了聚合物基质SPE-co-EDMA毛细管液相色谱整体柱。通过系统优化致孔剂和反应物种类和配比、引发剂的用量、反应时间和反应温度等因素,提高了整体柱的柱效、机械强度、渗透性和重复性。结果表明该毛细管整体柱在10 MPa内具有良好的机械强度,渗透性为2.17×10^-14 m²,而且批次内和批次间峰面积的重现性（RSD）分别为1.0%和4.6%。以极性和非极性的多种化合物评价了该毛细管整体柱的色谱性能,结果表明该柱在高有机相中具有亲水相互作用机理,在低有机相中具有反相作用机理,显示出混合模式分离特性。     

Characterization of some physical and chromatographic properties of monolithic poly(styrene-co-divinylbenzene) columns

Monolithic capillary columns were prepared by copolymerization of styrene and divinylbenzene inside a 200 microm i.d. fused silica capillary using a mixture of tetrahydrofuran and decanol as porogen. Important chromatographic features of the synthesized columns were characterized and critically compared to the properties of columns packed with micropellicular, octadecylated poly(styrene-co-divinylbenzene) (PS-DVB-C18) particles. The permeability of a 60 mm long monolithic column was slightly higher than that of an equally dimensioned column packed with PS-DVB-C18 beads and was invariant up to at least 250 bar column inlet pressure, indicating the high-pressure stability of the monolithic columns. Interestingly, monolithic columns showed a 3.6 times better separation efficiency for oligonucleotides than granular columns. To study differences of the molecular diffusion processes between granular and monolithic columns, Van Deemter plots were measured. Due to the favorable pore structure of monolithic columns all kind of diffusional band broadening was reduced two to five times. Using inverse size-exclusion chromatography a total porosity of 70% was determined, which consisted of internodule porosity (20%) and internal porosity (50%). The observed fast mass transfer and the resulting high separation efficiency suggested that the surface of the monolithic stationary phase is rather rough and does not feature real pores accessible to macromolecular analytes such as polypeptides or oligonucleotides. The maximum analytical loading capacity of monolithic columns for oligonucleotides was found to be in the region of 500 fmol, which compared well to the loading capacity of the granular columns. Batch-to-batch reproducibility proved to be better with granular stationary phases compared to monolithic stationary phase, in which each column bed is the result of a unique column preparation process.     

Effect of the carrier gas pressure on the dynamic and separation characteristics of divinylbenzene-based monolithic capillary columns for gas chromatography

The efficiency and dynamic characteristics of divinylbenzene-based monolithic capillary columns for gas chromatography were analyzed using a test mixture composed of five light hydrocarbons. The chromatographic properties of these columns were evaluated within the framework of two varieties of the van Deemter equation, the classical one and that proposed by Giddings (with consideration given to the pressure drop across the column). An analysis of the van Deemter curves demonstrated that the main contribution to peak smearing comes from the diffusion processes in the mobile phase. The contribution from the resistance to mass transfer between the mobile and stationary phases is less important. Negative values obtained for A in the van Deemter equation and for C _s in the Giddings model, parameters that characterize the stationary phase structure and mass transfer kinetics in the stationary phase, have no physical meaning, a result calling for further studies of this type of monolithic capillary columns since the classical theory supposed these parameters to be strictly positive. Under optimal conditions, the HETP of the monolithic columns was found to be 3 to 4 times smaller than that typical of open capillary columns of the same diameter.     

Recent developments of monolithic and open‐tubular capillary electrochromatography (2017–2019)

Capillary electrochromatography, which combined the high selectivity of high‐performance liquid chromatography and the high separation efficiency of capillary electrophoresis, is an attractive separation tool. In this review, the developments on monolithic and open tubular capillary electrochromatography during 2017 to August 2019 are summarized. Considering the development of novel stationary phases is the most active research field in capillary electrochromatography, monolithic capillary electrochromatography is classified according to the polymer‐based and hybrid monolithic columns, while open‐tubular capillary electrochromatography is categorized by cyclodextrin, silica, polymer, nanomaterials, microporous materials, and biomaterials‐based open tubular columns.     

Porous Monoliths: Stationary Phases of Choice for High Performance Liquid Chromatography in Various Formats

 Modern porous monoliths have been conceived as a new class of stationary phases for high performance liquid chromatography (HPLC) in classical columns in the early 1990s and later extended to the capillary format. These monolithic materials are prepared using simple processes carried out in an external mold (inorganic monoliths) or within the confines of the column (organic monoliths and all capillary columns). These methods afford macroporous materials with large through-pores that enable applications in a rapid flow-through mode. Since all the mobile phase must flow through the monolith, the convection considerably accelerates mass transport within the monolithic separation medium and improves the separations. As a result, the monolithic columns perform well even at very high flow rates. The applications of monolithic capillary columns are demonstrated on numerous separations in the HPLC mode.     

Monolithic stationary phases for fast ion chromatography and capillary electrochromatography of inorganic ions

The focus of this review is on current developments in monolithic stationary phases for the fast analysis of inorganic ions and other small molecules in ion chromatography (IC) and capillary electrochromatography (CEC), concentrating in particular on the properties of organic (polymer) monolithic materials in comparison to inorganic (silica-based) monoliths. The applicability of these materials for fast IC is discussed in the context of recent publications, including the range of synthesis and modification procedures described. While commercial monolithic silica columns already show promising results on current IC instrumentation, polymer-based monolithic stationary phases are currently predominantly used in the capillary format on modified micro-IC systems. However, they are beginning to find application in IC particularly under high pH conditions, with the potential to replace their particle-packed counterparts.     

Capillary columns with in situ formed porous monolithic packing for micro high-performance liquid chromatography and capillary electrochromatography.

Capillary columns with monolithic stationary phase were prepared from silanized fused-silica capillaries of 75 microns I.D. by in situ copolymerization of divinylbenzene either with styrene or vinylbenzyl chloride in the presence of a suitable porogen. The porous monolithic support in this study was used either directly or upon functionalization of the surface to obtain a stationary phase that was appropriate for the separation of peptides by capillary electrochromatography (CEC). The main advantages of monolithic columns are as follows. They do not need retaining frits, they do not have charged particles that can get dislodged in high electric field, and they have relatively high permeability and stability. Whereas such columns are designed especially for CEC, they find application in micro high-performance liquid chromatography (mu-HPLC) as well. Five different porogens were employed to prepare the monolithic columns that were examined for permeability and porosity. The flexibility of fused-silica capillaries was not adversely affected by the monolithic packing and the longevity of the columns was satisfactory. This may also be due to the polymerization technique, which resulted in a fluid-impervious outer layer of the monolith that precluded contact between the fused-silica surface and the liquid mobile phase. For the most promising columns, the conductivity ratios and the parameters of the simplified van Deemter equation, both in mu-HPLC and CEC, were evaluated. It was found that the efficiency of the monolithic columns in CEC was significantly higher than in mu-HPLC in the same way as observed with capillary columns having conventional particulate packing. This is attributed to the relaxation of band-broadening with electroosmotic flow (EOF) with respect to that with viscous flow. It follows then that the requirement of high packing uniformity to obtain high efficiency may also be relaxed in CEC. Angiotensin-type peptides were separated by CEC with columns packed with a monolithic stationary phase having fixed n-octyl chains and quaternary ammonium groups at the surface. Plate heights of about 8 microns were routinely obtained. The mechanism of the separation is based on the interplay between EOF, chromatographic retention and electrophoretic migration of the positively charged peptides. The results of the complex migration process, with highly nonlinear dependence of the migration times on the organic modifier and the salt concentration, cannot be interpreted within the framework of classical chromatography or electrophoresis.     

Silica-based monoliths for rapid peptide screening by capillary liquid chromatography hyphenated with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Capillary liquid chromatography based on particulate and monolithic stationary phases was used to screen complex peptide libraries by fast gradient elution coupled on-line to electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS). A slightly modified commercial electrospray interface consisting of a fused-silica transfer capillary and low dead volume stainless steel union at which the electrospray voltage was grounded enabled the effluent of all the capillary columns to be directly sprayed into the mass spectrometer. Stable electrospray conditions were generated over a wide range of mobile phase compositions, alleviating the need for a tapered end of the spray capillary, pneumatic assistance or preheated nebulizer gas. Since the identification of complex samples containing numerous isobaric substances is facilitated by chromatographic separation prior to mass spectrometry, stationary phase materials have been employed which offer a fast, efficient elution and, due to the complexity of samples, a high loading capacity. Silica-based monolithic capillary columns combine these three characteristics in a unique manner due to a tailored adjustment of both macro- and mesopore sizes in the highly porous silica structure. As we demonstrate by a comparative study of the silica-based monolithic and packed capillaries for LC/MS analysis of complex peptide libraries, silica monoliths show superior performance over packed beds of small-diameter particles with respect to analysis time and separation efficiency. Libraries with more than 1000 different peptides could be screened in less than 20 min.     

A study of the efficiency of monolithic silica gel capillary columns for gas chromatography

The efficiency and dynamic characteristics of seven silica-gel-based monolithic capillary columns were analyzed by separating on them a mixture of five light hydrocarbons. For helium carrier gas flowing at an optimum velocity, the height equivalent to a theoretical plate was found to be 0.15–0.20 mm, values comparable to those typical of packed capillary columns. An analysis of the Van Deemter curves for the columns under study demonstrated that the main contribution to the smearing of the chromatographic zone comes from the diffusional processes in the mobile phase while the mass transfer between the mobile and stationary phases plays only a minor role. At the same time, the parameter A in the Van Deemter equation, which characterizes the degree of column packing uniformity, was found to be negative. This result contradicts the classical theory of chromatography and calls for further studies of monolithic capillary columns.     

Preparation and characterisation of anion-exchange latex-coated silica monoliths for capillary electrochromatography

Silica monoliths coated with functionalised latex particles have been prepared for use in monolithic ion-exchange capillary electrochromatography (IE-CEC) for the separation of inorganic anions. The ion-exchange monoliths were prepared using 70 nm quaternary ammonium, anion-exchange latex particles, which were bound electrostatically to a monolithic silica skeleton synthesised in a fused silica capillary. The resulting stationary phases were characterised in terms of their chromatographic performance and capacity. The capacity of a 50 microm diameter 25 cm latex-coated silica monolith was found to be 0.342 nanoequivalents and 80,000 theoretical plates per column were typically achieved for weakly retained anions, with lower efficiency being observed for analytes exhibiting strong ion-exchange interaction with the stationary phase. The electroosmotic flow (EOF) was reversed after the latex-coating was applied (-25.96 m2 V(-1) s(-1), relative standard deviation (RSD) 2.8%) and resulted in anions being separated in the co-EOF mode. Ion-exchange interactions between the analytes and the stationary phase were manipulated by varying the ion-exchange selectivity coefficient and the concentration of a competing ion (phosphate or perchlorate) present in the electrolyte. Large concentrations of competing ion (greater than 1M phosphate or 200 mM perchlorate) were required to completely suppress ion-exchange interactions, which highlighted the significant retention effects that could be achieved using monolithic columns compared to open tubular columns, without the problems associated with particle-packed columns. The latex-coated silica monoliths were easily produced in bulk quantities and performed reproducibly in acidic electrolytes. The high permeability and beneficial phase ratio makes these columns ideal for micro-LC and preconcentration applications.     

Study of a monolithic silica capillary column coated with poly(octadecyl methacrylate) for the reversed-phase liquid chromatographic separation of some polar and non-polar compounds

The performance of a monolithic silica capillary column coated with poly(octadecyl methacrylate) (ODM column) for the reversed-phase liquid chromatographic separation of some polar and non-polar compounds was studied, and the results were compared to those obtained by using a monolithic silica capillary column modified with octadecylsilyl-(N,N-diethylamino)silane (ODS column). Benzene and naphthalene derivatives, polycyclic aromatic hydrocarbons (PAHs), steroids, alkyl phthalates, and tocopherol homologues were used as test samples. In general, compounds with aromatic character, rigid and planar structures, and lower length-to-breadth ratios (more compacted structures) seem to have more preference for the polymer coated stationary phase (ODM). Compounds with acidic character have also a higher retention on ODM columns because of the presence of ester groups in the stationary phase. The polymer coated column allowed the separation of some PAHs, alkyl phthalates, steroids, and of beta- and gamma-tocopherol isomers which cannot be separated under the same conditions on ODS columns, while keeping similar column efficiency. These results allowed to suggest ODM columns as a good alternative to conventional ODS columns for reversed-phase liquid chromatography.