Recent advances in CE and CEC of pollutants

Recent advances in CE and CEC separation, detection and sample preparation/preconcentration methodologies, for the determination of a variety of compounds having current or potential environmental relevance, have been overviewed. The reviewed literature has illustrated the wide range of CE applications available, indicating a continuing interest in CE and CEC in the environmental field. New developments in chip-based CE systems are also discussed.     

Recent progress in polar stationary phases for CEC

This review summarizes most of the recent developments in the preparation and application of polar stationary phases for CEC covering the literature published since the year 2004. These polar stationary phases have been adopted for separation of analytes by the modes of packing column CEC, open-tubular CEC (o-CEC) and monolithic column CEC. Currently, development of o-CEC using biomolecules, such as protein and DNA, as the immobilized ligands is highlighted partly due to the simplicity of preparation. Furthermore, monolithic columns have been extended quickly, particularly inorganic materials-based monoliths, such as silica, zirconia, hafnium, etc., as an alternative to packed columns have been developed quickly.     

Recent accomplishments in the field of enantiomer separation by CEC

The present review intends to summarize recent developments in the field of enantioselective separations and analysis by CEC. It covers studies published in English language in common peer-reviewed journals within the period between 2003 and 2006. Both, methods making use of chiral mobile phase additives as well as chiral stationary phases for electrochromatographic enantiomer separations, are reviewed. Achievements that have been made on the various column technologies, such as open-tubular, particle-packed, inorganic, organic and particle-fixed (hybrid-type) monolithic as well as molecularly imprinted polymer phases, are discussed.     

Recent advances in the analysis of antibiotics by CE and CEC

This article reviews the most recent developments concerning the determination of antibiotics by CE and CEC. The most employed CE separation modes were CZE and MEKC although microemulsion electrokinetic capillary chromatoghraphy was also employed. For the first time, CE was coupled to MS that was applied as a specific and confirmatory detection technique for the analysis of antibiotics. The analytical characteristics of the developed methodologies as well as the different applications reported in the literature on this subject from June 2005 until May 2007 are included in this article. To give the most relevant information on this topic, the experimental conditions employed to achieve the analysis of antibiotics by CE and CEC are provided together with the main applications performed in the pharmaceutical, agrochemical, biological, food, and environmental fields, emphacizing sample preparation requirements needed in each case.     

Recent developments in CE and CEC of peptides (2009-2011)

The review brings a comprehensive survey of the recent developments of high-performance electroseparation methods in capillary and microchip formats: zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography and electrochromatography. Applications of these techniques to analysis, isolation, purification and physicochemical and biochemical characterization of peptides are described. Advances in the investigation of electromigration properties of peptides, and in the methodology of their analysis, such as sample preparation, adsorption suppression, EOF control and detection, are presented. New developments, in particular, CE and CEC modes are reported and several types of their applications to peptide analysis are described: conventional qualitative and quantitative analysis, determination in complex (bio)matrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid, sequence and chiral analysis, and peptide mapping of proteins. Some micropreparative peptide separations are shown and capabilities of CE and CEC techniques to provide relevant physicochemical characteristics of peptides are demonstrated.     

Recent applications in nanoliquid chromatography

Since its first introduction by Karlsson and Novotny in 1988 nano-LC has emerged as a complementary and/or competitive separation method to conventional HPLC, offering several advantages such as higher efficiency, ability to work with minute sample sizes and lower consumption of mobile phases, and better compatibility with MS, etc. Although its use was not so extended initially, in the last years new and interesting applications have appeared which deserve to be carefully considered. The aim of this review is therefore to provide an updated and critical survey of different nano-LC applications in analytical chemistry.     

Recent applications in capillary electrochromatography

The most recent and important applications in capillary electrochromatography (CEC) are summarized, covering literature published since May 2001. A selection of new developments in stationary phases for CEC is highlighted, and enantiomeric separations and chiral stationary phases are discussed. Also, CEC applications of biological molecules, pharmaceuticals, and applications in the field of industrial and environmental analysis are summarized. For this review three modes of CEC were taken into account, i.e., packed-column CEC, CEC using monolith technology, and open-tubular CEC.     

Recent applications in capillary electrochromatography

In this review research papers on the application of CEC are summarized that have been published between May 2003 and May 2005. First, a short overview is given of trends and developments in CEC that may increase the applicability of the separation technique. Next, application-oriented research using CEC is described in biochemical studies, including proteomics and genomics, in the analysis of food and natural products, and in pharmaceutical, industrial, and environmental analysis.     

UV-polymerized butyl methacrylate monoliths with embedded carboxylic single-walled carbon nanotubes for CEC applications

The preparation of polymeric monoliths with embedded carboxy-modified single-walled carbon nanotubes (c-SWNTs) and their use for capillary electrochromatography (CEC) is described. Carbon nanotube composites were obtained by preparing a polymerization mixture in the presence of increasing c-SWNT concentrations, followed by UV initiation. The novel stationary phases were studied by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Using short UV-polymerization times, the optimized porogenic solvent (a binary mixture of 1,4-butanediol and 2-propanol) gave rise to polymeric beds with homogenously dispersed embedded c-SWNTs. The CEC features of these monoliths were evaluated using polycyclic aromatic hydrocarbons (PAHs), non-steroidal anti-inflammatory drugs (NSAIDs) and chiral compounds. The monolith prepared in the presence of c-SWNTs showed enhanced resolution of the text mixtures, including a remarkable capability to separate enantiomers. Graphical Abstract

UV-polymerized polymeric monoliths with embedded c-SWNTs for CEC applications     

Recent applications of capillary electrochromatography

A review is presented of the most important recent applications of capillary electrochromatography (CEC) for the analysis of acidic, basic, and neutral compounds, of biomolecules, environmental substances, natural products, pharmaceuticals, and chiral compounds. Packed-column CEC (packed-CEC), open-tubular (OT-CEC), as well as pressure-assisted CEC (pseudo-CEC) are hereby considered. Papers published between July 1999 and April 2001 were taken into account. Applications before July 1999 have been reviewed in Electrophoresis 1999, 20, 3027-3065.     

Recent applications of mechanochemistry in enantioselective synthesis

In recent years, sustainable organocatalysis has become a relevant target in asymmetric organic synthesis. Among the most successful strategies to achieve “greener” organocatalyzed processes are (1) the elimination of solvent from reaction media, and (2) the use of alternative activation energies such as solvent-free mechanochemistry in high speed ball mills. In recent years we have stepped up efforts in the pursuit of organocatalysts and biocatalysts that allow reactions to take place in the absence of solvent and under mechanochemical activation. In this article we present the application of small dipeptides as chiral organocatalysts under solvent-free and high-speed ball milling conditions, with focus on the asymmetric aldol addition reaction. Finally, we report on recent results using supported enzymes for the resolution of racemic β-amino acids and amines, under mechanochemical conditions.     

Recent advances and applications in QDs-based sensors

As a unique nanomaterial, quantum dots (QDs) are not only applied in fluorescent labeling and biological imaging, but are also utilized in novel sensing systems. Because QDs have attractive optoelectronic characteristics, QD-based sensors present high sensitivity in detecting specific analytes in the chemical and biochemical fields. In this review, we describe the basic principles and different conjugation strategies in QD-based sensors. An overview of recent advances and various models of QD-sensing systems is also provided. Furthermore, perspectives for sensors based on QDs are discussed.     

Recent applications of capillary isoelectric focusing

After the advent of capillary isoelectric focusing (CIEF) in the 80's several approaches have been developed in order to use the technique in routine analyses. The recent years showed an extensive increase in the applications of this technique employing its exceptionally high-resolution power. Methodological improvements, as well as hyphenation with other electrophoretic and chromatographic separation procedures, proved the versatility of CIEF in studies of clinically important proteins, recombinant product, cell lysates and other complex mixtures. The combination of CIEF with mass spectrometry detection is one of the major challenges for studying proteomics. This review collected the recent applications of CIEF including innovations in the experimental setup, remedies for the presence of salts in samples, calibration of the pH gradient, carrier ampholyte-free isoelectric focusing, the progress in micropreparation, two-dimensional separations, etc.     

毛细管微乳电动色谱应用的研究进展

近年来毛细管微乳电动色谱(MEEKC)研究的范围不断扩大,其分离分析的化合物类型也不断增多。该文综述了2002年以来MEEKC应用的研究进展,指出了目前MEEKC研究中存在的一些问题,对今后的研究发展方向进行了展望。     

Recent applications of microemulsion electrokinetic chromatography

Compared to MEKC, the presence of a water-immiscible oil phase in the microemulsion droplets of microemulsion EKC (MEEKC) gives rise to some special properties, such as enhanced solubilization capacity and enlarged migration window, which could allow for the improved separation of various hydrophobic and hydrophilic compounds, with reduced sample pretreatment steps, unique selectivities and/or higher efficiencies. Typically, stable and optically clear oil-in-water microemulsions containing a surfactant (SDS), oil (octane or heptane), and cosurfactant (1-butanol) in phosphate buffer are employed as separation media in conventional MEEKC. However, in recent years, the applicability of reverse MEEKC (water-in-oil microemulsions) has also been demonstrated, such as for the enhanced separation of highly hydrophobic substances. Also, during the past few years, the development and application of MEEKC for the separation of chiral molecules has been expanded, based on the use of enantioselective microemulsions that contained a chiral surfactant or chiral alcohol. On the other hand, the application of MEEKC for the characterization of the lipophilicity of chemical substances remains an active and important area of research, such as the use of multiplex MEEKC for the high-throughput determination of partition coefficients (log P values) of pharmaceutical compounds. In this review, recent applications of MEEKC (covering the period from 2003 to 2005) are reported. Emphases are placed on the discussion of MEEKC in the separation of chiral molecules and highly hydrophobic substances, as well as in the determination of partition coefficients, followed by a survey of recent applications of MEEKC in the analysis of pharmaceuticals, cosmetics and health-care products, biological and environmental compounds, plant materials, and foods.     

Recent applications of bifunctional trityl groups

Triphenylmethyl derivatives represent an important class of dyestuffs as well as a useful family of protecting groups widely used in organic synthesis to transiently block various functional moieties. These applications are well documented and have been a subject of a number of reviews. Here we focus instead on some novel applications of a trityl which make good use of its ability to easily form a stabilised cation in combination with additional peripheral functionalities. Topics covered include applications in bioconjugation, cross-linking, mass-spectrometry, fluorescence and optics.     

Recent applications of microemulsion electrokinetic chromatography

Microemulsions are used in a similar way as micellar solutions are used for separations in capillary electrophoresis. Within the last approximately six years, a number of papers have appeared in the literature in which the separation characteristics of microemulsion electrokinetic chromatography (MEEKC) have been investigated. The total number of papers dealing with MEEKC is now close to 100. One of the major fields of application for MEEKC has been the characterization of the lipophilicity of chemical substances but the technique has also been applied for the analysis of substances within the fields of natural products, pharmaceuticals, vitamins, peptides, proteins, and nucleic acid bases as well as nucleosides. An overview of the applications is given together with the microemulsions used for each application.