共查询到20条相似文献,搜索用时 93 毫秒
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Capillary electrochromatography (CEC) is a liquid phase analytical separation technique that is generally carried out with packed capillary columns by electroosmotically driven mobile phase at high electric field strength. The analytes are separated by virtue of the differences in their distribution between the mobile and stationary phases and, if charged in their electrophoretic mobilities as well. It is thus considered a hybrid of liquid chromatography and capillary electrophoresis and is expected to combine the high peak efficiency of capillary zone electrophoresis (CZE) with the versatility and loading capacity of HPLC. This review explores the potential use of on-line mass spectrometric detection for CEC. It discusses key design issues that focus on the physical and electrical arrangement of the CEC column with respect to the electrospray orifice inlet. The salient features of the sheathless, sheath flow and liquid junction interfaces that are frequently employed while coupling a CEC column to an electrospray ionization mass spectrometry system are also highlighted. Possible configurations of the CEC column outlet that would obviate the need for pressurizing the capillary column are also presented. While coupling CEC with MS both the nature of the interface and the configuration of the column outlet will determine the optimal arrangement. The review also discusses bandspreading that occurs when a connecting tube is employed to transfer mobile phase from the column outlet to the atmospheric region of the electrospray source with a concomitant loss in sensitivity. Selected examples that highlight the potential of this technique for a wide range of applications are also presented. 相似文献
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A review is presented on the current state of the art and future trends in the development of sol-gel stationary phases for capillary electrochromatography (CEC). The design and synthesis of stationary phases with prescribed chromatographic and surface charge properties represent challenging tasks in contemporary CEC research. Further developments in CEC as a high-efficiency liquid-phase separation technique will greatly depend on new breakthroughs in the area of stationary phase development. The requirements imposed on CEC stationary phase performance are significantly more demanding compared with those for HPLC. The design of CEC stationary phase must take into consideration the structural characteristics that will provide not only the selective solute/stationary phase interactions leading to chromatographic separations but also the surface charge properties that determine the magnitude and direction of the electroosmotic flow responsible for the mobile phase movement through the CEC column. Therefore, the stationary phase technology in CEC presents a more complex problem than in conventional chromatographic techniques. Different approaches to stationary phase development have been reported in contemporary CEC literature. The sol-gel approach represents a promising direction in this important research. It is applicable to the preparation of CEC stationary phases in different formats: surface coatings, micro/submicro particles, and monolithic beds. Besides, in the sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. One remarkable advantage of the sol-gel approach is the mild thermal conditions under which the stationary phase synthesis can be carried out (typically at room temperature). It also provides an effective pathway to integrating the advantageous properties of organic and inorganic material systems, and thereby enhancing and fine-tuning chromatographic selectivity of the created hybrid organic-inorganic stationary phases. This review focuses on recent developments in the design, synthesis, characterization, properties, and applications of sol-gel stationary phases in CEC. 相似文献
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依据分子印迹技术(MIT)制备的分子印迹聚合物(MIP)颗粒对模板分子及其结构类似物具有特异性识别和选择性吸附作用,同时具有较大的比表面积和快速的传质动力学特性,因而被广泛用作液相色谱固定相和固相萃取材料。将MIP颗粒作为固定相应用于毛细管电色谱(CEC),结合了CEC的快速、高效和MIP的高亲和性、高选择性的特点,成为分析科学领域最具有发展前景的分离技术之一。MIP颗粒在CEC领域有几种不同的应用形式: 作为填充材料填充到毛细管柱中;作为嵌入材料嵌入到毛细管柱内部不同基质的骨架中;作为准固定相添加到CEC运行缓冲溶液中。本文综述了近几年MIP颗粒在CEC领域应用的发展,对该领域今后的发展前景进行了展望。 相似文献
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Summary Capillary electrochromatography (CEC) is classed as a hybrid technique between CE and HPLC and it combines the advantages
of both these techniques. However, in some cases the disadvantages are also brought to light and some of these are difficult
to resolve. For example the analysis of basic compounds using CEC. The problems of tailing peaks during HPLC analysis of basic
compounds was resolved by end capping the residual silanol groups, but in CEC these are the groups that generate the electroosmotic
flow. The analysis of basic compounds is crucial within the pharmaceutical industry where a high percentage of the drug actives
are basic. Specially designed Continuous Beds stationary phases (CB) can mean that each application can have a specific stationary
phase. In order to overcome the problem associated with the analysis of basic compounds using electrochromatography, we have
designed a CB stationary phase with a positive charge, which could be operated using negative voltage. The resulting chromatography
showed almost gaussian peaks for bases like nortriptyline which tail significantly using stationary phase typically used in
CEC. 相似文献
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Capillary electrochromatography (CEC) is an emerging technique that combines features of both micro-capillary high-performance liquid chromatography (microHPLC) and capillary electrophoresis (CE). This separation technique possesses high speed and the efficiency of an electro-driven system, while the selectivity and sample loadability compare to those of a packed capillary LC column. Since the separation mechanism is based on that of HPLC, the concept of isoeluotropic strength and selectivity of solvents as well as the on-column focusing techniques for sample introduction used in LC can be applied in CEC. This article examines some of these features of CEC in the context of our own experiences with the technique. More specifically, emphasis is placed on applications of CEC to the analysis of DNA adducts of polyaromatic hydrocarbons by coupling CEC to mass spectrometry. It is shown that, with proper selection of mixed organic modifiers in the mobile phase, i.e. ternary and quaternary mobile phases, complex DNA adduct mixtures derived from in vitro reactions can be separated isocratically with improved selectivity and much greater speed than by HPLC. Additionally, the speed of the analysis is further enhanced by employing a step gradient. Furthermore, CEC may be easily coupled to mass spectrometry such that the characterization of each isolated component from the mixtures is performed on-line with the separation. By using on-column focusing, the sample loadability onto a CEC column is improved. 相似文献
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Qing Liu Lin Wang Zhuoheng Zhou Qiuquan Wang Lijuan Yan Bo Zhang 《Electrophoresis》2014,35(6):836-839
CEC is a high performance electrodriving liquid phase separation technique. It does not need complex and sophisticated high pressure instrumentation for nanoflow driving. This is attractive for parallel multicolumn analysis. To this end, high throughput methods for column preparation are needed to support the use of multiple columns. In this study, we directly used CEC mobile phase solution as the packing solvent, and realized rapid preparation of capillary columns based on a single particle fritting technology. The method presented high preparation throughput compared with other reported methods based on various fritting technologies. The single particle fritting approach promoted column preparation throughput to 1 column/h, including all the fritting, packing and conditioning steps. The rapidly prepared columns showed consistently high efficiency of up to 150 000 plates per meter, and usefulness in reversed phase CEC of neutral, charged and biomolecules. With standard peptides as the sample, excellent long term reproducibility (better than 0.8%RSD, ten days, for retention times) was observed. 相似文献
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This work presents the application of membrane technology for the fabrication of stationary phase for CEC columns using the technique based on phase inversion of polymer solution. A blend of polyimide P84 and sulphonated poly(ether ether ketone was processed via immersion precipitation dry‐wet spinning into small‐bore porous fiber. The morphology, zeta potential, and performance of the porous structure in the CEC separation were investigated. Noncharged molecules (as markers of the electroosmotic flow) and small organic compounds were injected into the column, driven under the application of voltage, and detected on the electropherogram. The proof of concept of applying porous membrane structure as stationary phase for CEC was shown and possible optimization to improve efficiency and selectivity was suggested. 相似文献
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毛细管电色谱具有高分离效率、多种保留机制和高选择性的优点。近年来,利用毛细管电色谱进行对映异构体的手性拆分受到了广泛关注。相对于传统的填充柱和开管柱,整体柱在手性拆分方面具有显著优势。与手性硅基整体柱相似,手性有机聚合物整体柱由于具有大孔,可产生较高的流速而压降较小。该文综述了近十年手性有机聚合物整体柱制备方法的研究进展,将手性有机聚合物整体柱的制备方法分为"原位聚合法"和"手性修饰法"两种,虽然前者制备简单并广泛应用于早期研究,但聚合混合液成分的微小改变即可引起最终聚合物的形态变化,并且大部分带丙烯基的手性选择剂较难从市场购买。因此,手性修饰法因作为手性选择剂基质的整体柱制备且优化只需进行一次的优势而受到普遍关注。亲核取代、杂环开环和点击化学是常用的修饰手段。该文总结了这两种制备方法的应用,同时对未来的研究方向提出参考性意见。 相似文献
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Benzodiazepines, namely flunitrazepam and its three major metabolites, were successfully separated by microemulsion electrokinetic chromatography. Separation was achieved using an untreated fused-silica capillary (48 cm (effective length 40 cm) x 50 num) at 25 kV; detection was performed by UV at 220 nm. The microemulsion system consisted of 70 mM octane, 800 mM 1-butanol, 80 mM sodium dodecyl sulfate (SDS) and 10 mM borate buffer, pH 9. Very high efficiencies (up to 400 000 plates) and resolution better than 3 were achieved. Since this technique is not compatible with mass spectrometry (MS) detection, a capillary electrochromatographic (CEC) method was developed to separate flunitrazepam and its metabolites. The effects of mobile phase composition and pH as well as voltage and temperature were systematically investigated. The optimized CEC method allowed the baseline separation of the investigated compounds. For the on-line coupling of CEC with electrospray ionization-mass spectrometry, the column was connected to a void fused-silica capillary using a Teflon connection. This configuration was found efficient and suitable for hyphenation of commercial CEC and MS instrumentation using commercially available CEC columns. 相似文献