Current applications of capillary electrophoresis-mass spectrometry for the analysis of biologically important analytes in urine (2017 to mid-2021): A review.

Capillary electrophoresis coupled online with mass detection is a modern tool for analyzing wide ranges of compounds in complex samples, including urine. Capillary electrophoresis with mass spectrometry allows the separation and identification of various analytes spanning from small ions to high molecular weight protein complexes. Similarly to the much more common liquid chromatography-mass spectrometry techniques, the capillary electrophoresis separation reduces the complexity of the mixture of analytes entering the mass spectrometer resulting in reduced ion suppression and a more straightforward interpretation of the mass spectrometry data. This review summarizes capillary electrophoresis with mass spectrometry studies published between the years 2017 and 2021, aiming at the determination of various compounds excreted in urine. The properties of the urine, including its diagnostical and analytical features and chemical composition, are also discussed including general protocols for the urine sample preparation. The mechanism of the electrophoretic separation and the instrumentation for capillary electrophoresis with mass spectrometry coupling is also included. This review shows the potential of the capillary electrophoresis with mass spectrometry technique for the analyses of different kinds of analytes in a complex biological matrix. The discussed applications are divided into two main groups (capillary electrophoresis with mass spectrometry for the determination of drugs and drugs of abuse in urine and capillary electrophoresis with mass spectrometry for the studies of urinary metabolome).

Recent trends of capillary electrophoresis-mass spectrometry in proteomics research.

Progress in proteomics research has led to a demand for powerful analytical tools with high separation efficiency and sensitivity for confident identification and quantification of proteins, posttranslational modifications, and protein complexes expressed in cells and tissues. This demand has significantly increased interest in capillary electrophoresis-mass spectrometry (CE-MS) in the past few years. This review provides highlights of recent advances in CE-MS for proteomics research, including a short introduction to top-down mass spectrometry and native mass spectrometry (native MS), as well as a detailed overview of CE methods. Both the potential and limitations of these methods for the analysis of proteins and peptides in synthetic and biological samples and the challenges of CE methods are discussed, along with perspectives about the future direction of CE-MS. @ 2019 Wiley Periodicals, Inc. Mass Spec Rev 00:1-16, 2019.

Advances in enzyme substrate analysis with capillary electrophoresis.

Capillary electrophoresis provides a rapid, cost-effective platform for enzyme and substrate characterization. The high resolution achievable by capillary electrophoresis enables the analysis of substrates and products that are indistinguishable by spectroscopic techniques alone, while the small volume requirement enables analysis of enzymes or substrates in limited supply. Furthermore, the compatibility of capillary electrophoresis with various detectors makes it suitable for KM determinations ranging from nanomolar to millimolar concentrations. Capillary electrophoresis fundamentals are discussed with an emphasis on the separation mechanisms relevant to evaluate sets of substrate and product that are charged, neutral, and even chiral. The basic principles of Michaelis-Menten determinations are reviewed and the process of translating capillary electrophoresis electropherograms into a Michaelis-Menten curve is outlined. The conditions that must be optimized in order to couple off-line and on-line enzyme reactions with capillary electrophoresis separations, such as incubation time, buffer pH and ionic strength, and temperature, are examined to provide insight into how the techniques can be best utilized. The application of capillary electrophoresis to quantify enzyme inhibition, in the form of KI or IC50 is detailed. The concept and implementation of the immobilized enzyme reactor is described as a means to increase enzyme stability and reusability, as well as a powerful tool for screening enzyme substrates and inhibitors. Emerging techniques focused on applying capillary electrophoresis as a rapid assay to obtain structural identification or sequence information about a substrate and in-line digestions of peptides and proteins coupled to mass spectrometry analyses are highlighted.

Recent advances in the application of capillary electromigration methods for food analysis and Foodomics.

This review work presents and discusses the main applications of capillary electromigration methods in food analysis and Foodomics. Papers that were published during the period February 2013-February 2015 are included following the previous review by Garcia-Cañas et al. (Electrophoresis, 2014, 35, 147-169). Analysis by CE of a large variety of food-related molecules with different chemical properties, including amino acids, hazardous amines, peptides, proteins, phenols, polyphenols, lipids, carbohydrates, DNAs, vitamins, toxins, contaminants, pesticides, residues, food additives, as well as small organic and inorganic compounds. This work includes recent results on food quality and safety, nutritional value, storage, bioactivity, as well as applications of CE for monitoring food processing. The use, among other CE developments, of microchips, CE-MS, and chiral CE in food analysis and Foodomics is also discussed.

Recent developments and applications of capillary and microchip electrophoresis in proteomic and peptidomic analyses.

This review presents recent developments and applications of capillary and microchip electromigration methods in proteomics and peptidomics. Sample preparation methods as well as instrumental innovations in the coupling of these advanced electromigration methods with mass spectrometry detection employed in proteomic and peptidomic analyses are presented. Interesting applications of various capillary electromigration methods in bottom-up as well as top-down proteomics, including investigation of post-translational modifications of proteins are described. In addition, several examples of the use of capillary electromigration methods combined with mass spectrometry detection in clinical proteomics and peptidomics are demonstrated.

Capillary electrophoresis and herbicide analysis: present and future perspectives.

The aim of this article is to provide an overview on the potential of the CE-herbicides binomial. To this end, the methods proposed so far are discussed: their characteristics, types of samples and analytes to which the methods have been applied, sample preparation steps, if required (e.g. cleanup-preconcentration, derivatization steps), and type of detection in each case. Also, the methods are compared with counterparts based on LC, when appropriate. The role of MS detection in present and future analytical research in this field (both for identification and quantitation) are commented. The foreseeable and desirable trends in analysis of herbicides are also outlined in the light of the present trends in metabolomics as a way of knowing the pathways, the intermediate and final degradation products that can influence the crops and the food chain of humans and other animals, as a result.

Advances in chiral separations by nonaqueous capillary electrophoresis in pharmaceutical and biomedical analysis.

NACE is an alternative technique to aqueous CE in the chiral separations of partially soluble racemates. Besides, partially water-soluble or insoluble chiral selectors may be exploited in the enantiomeric resolution in NACE. The high reproducibility due to low Joule heat generation and no change in BGE concentration may make NACE a routine analytical technique. These facts attracted scientists to use NACE for the chiral resolution. The present review describes the advances in the chiral separations by NACE and its application in pharmaceutical and biomedical analysis. The emphasis has been given to discuss the selection of the chiral selectors and organic solvents, applications of NACE, comparison between NACE and aqueous CE, and chiral recognition mechanism. Besides, efforts have also been made to predict the future perspectives of NACE.

Recent advances in coupling capillary electrophoresis-based separation techniques to ESI and MALDI-MS.

Coupling CE-based separation techniques to MS creates a powerful platform for analysis of a wide range of biomolecules from complex samples because it combines the high separation efficiency of CE and the sensitivity and selectivity of MS detection. ESI and MALDI, as the most common soft ionization techniques employed for CE and MS coupling, offer distinct advantages for biomolecular characterization. This review is focused primarily on technological advances in combining CE and chip-based CE with ESI and MALDI-MS detection in the past five years. Selected applications in the analyses of metabolites, peptides, and proteins with recently developed CE-MS platforms are also highlighted.

Progress in stacking techniques based on field amplification of capillary electrophoresis.

Numerous strategies have been developed to mitigate the intrinsic low detection sensitivity that is a limitation of capillary electrophoresis. Among them, in-line stacking is an effective strategy to address the sensitivity challenge, and among the different stacking techniques, stacking based on field amplification is the most effective and simplest method of achieving high sensitivity without special complicated mechanisms or operations. This review introduces several stacking techniques based on field amplification. Field-amplified sample stacking, large-volume sample stacking, matrix field-amplified stacking injection (FASI), head-column FASI, matrix FASI combined with head-column FASI, FASI coupled with extraction and clean-up methods, electrokinetic supercharging, cation-anion selective exhaustive injection-sweeping-micellar electrokinetic chromatography, and newly developed techniques based on field amplification combined with other methods are included, and examples of straightforward methods for solving the sensitivity problem are provided. We also present a brief overview of the advantages, limitations, and future developments of these techniques.

Chiral selectors in CE: recent developments and applications.

This review article provides an overview of the recent advances in enantioanalysis by use of electrophoretic techniques. Due to the big number of publications in the subject mentioned above, this article is focused on chiral method developments and applications published from 2008 until 2011, and it demonstrates chiral selectors used in CE. Numerous chiral selectors have been used over the years, and these include the cyclic and the linear oligo- and polysaccharides, the branched polysaccharides, the polymeric and monomeric surfactants, the macrocyclic and other antibiotics, and the crown ethers. Different dual-selector systems are also presented in this article, and the results are compared with those obtained by use of a single chiral selector. Finally, several pharmaceutical and biomedical applications based on chiral recognition are summarized.

CE-MS for the analysis of intact proteins 2010-2012.

Since its introduction in 1987, CE-MS has become an increasingly important technique for the analysis of biomolecules. Since our previous update on CE-MS methods within the field of intact protein analysis (Electrophoresis 2011, 32, 66-82), a variety of interesting methodological improvements and applications have been reported in literature. Therefore, this article presents an overview of the development and application of CE-MS for intact protein analysis as published between June 2010 and June 2012. The article is divided in sections that treat CE coupled to MS through ESI, MALDI, and ICP ionization, respectively. In the section about CE-ESI-MS, technological developments with respect to CE-MS interfacing, prevention of protein adsorption, and chip-based CE-MS are treated in more detail. Novel interfacing strategies and the development of improved capillary coating strategies appeared to be the major developments. Furthermore, in all sections, the applicability of CE-MS for intact protein analysis is demonstrated by representative examples, including important developments in the fields of biopharmaceutical characterization and the analysis of proteins in biological samples. Finally, some general conclusions and future perspectives are given.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2010-2012).

CE has been alive for over two decades now, yet its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with updates published in 2009 and 2011 and covers material published through to June 2012. It includes developments in the field of stacking, covering all methods from field amplified sample stacking and large volume sample stacking, through to isotachophoresis, dynamic pH junction and sweeping. Attention is also given to online or inline extraction methods that have been used for electrophoresis.

CE-MS for metabolomics: developments and applications in the period 2010-2012.

CE-MS has emerged as a powerful technique for the profiling of (highly) polar and charged metabolites in biological samples. This review provides an update of the most recent developments in CE-MS for metabolomics covering the scientific literature from July 2010 to June 2012. The present paper is an update of two previous review papers covering the years 2000-2010 (Electrophoresis 2009, 30, 276-291; Electrophoresis 2011, 32, 52-65). Emerging technological developments used in CE-MS for metabolomics are discussed, such as the use of novel interfacing techniques for coupling CE to MS. Representative examples illustrate the applicability of CE-MS in the fields of biomedical, clinical, microbial, plant, environmental and food metabolomics. Concerning targeted and non-targeted approaches, a comprehensive overview of recent CE-MS-based metabolomics studies is given in a table. Information on sample type and pretreatment, capillary coatings and MS detection mode is provided. Finally, general conclusions and perspectives are provided.

Contemporary sample stacking in analytical electrophoresis.

Sample stacking is a term denoting a multifarious class of methods and their names that are used daily in CE for online concentration of diluted samples to enhance separation efficiency and sensitivity of analyses. The essence of these methods is that analytes present at low concentrations in a large injected sample zone are concentrated into a short and sharp zone (stack) in the separation capillary. Then the stacked analytes are separated and detected. Regardless of the diversity of the stacking electromigration methods, one can distinguish four main principles that form the bases of nearly all of them: (i) Kohlrausch adjustment of concentrations, (ii) pH step, (iii) micellar methods, and (iv) transient ITP. This contribution is a continuation of our previous reviews on the topic and brings an overview of papers published during 2010-2012 and relevant to the mentioned principles (except the last one which is covered by another review in this issue).

Contactless conductivity detection for analytical techniques: developments from 2010 to 2012.

The developments in the field of capacitively coupled contactless conductivity detection in the approximate period from July 2010 to June 2012 are traced. Few reports concerning fundamental studies or new detector designs have appeared. On the other hand, applications in standard CZE are flourishing and contactless conductivity measurements are increasingly being employed as part of novel or more sophisticated experimental systems. Work on the lab-on-chip devices integrating contactless conductivity detection is continuing. A range of reports on the use of the simple yet powerful detection technique of contactless conductivity measurements in chromatographic separation as well as for analytical methods not including a separation step have also appeared.

Recent advances in the combination of capillary electrophoresis with mass spectrometry: from element to single-cell analysis.

This overview deals with the latest development of electrophoresis in capillaries and microfluidic devices coupled to MS detection. A wide selection of relevant articles covers the literature published from January 2010 till June 2012 as a continuation of the review article on the same topic by Pantuckova et al. [Electrophoresis 2011, 32, 43-51]. Special attention is paid to the new improvements in instrumentation and methodology of three interfacing methods, ESI, matrix-assisted desorption/ionization, and ICP. Representative examples illustrate applications in the proteomics, glycomics, metabolomics, biomarker research, forensics, pharmacology, food analysis and single-cell analysis. The combinations of MS with capillary versions of electrochromatography, ITP, IEF, and micellar electrokinetic chromatography are not included.

Recent advances in the application of CE to forensic sciences, an update over years 2009-2011.

The present article reviews and comments the applications of capillary electrophoresis in the different areas of forensic sciences covering the time from the second half of 2009 until the first part of 2011, being the latest update of previous reviews covering the years from 2001 to 2009. Numerous articles reporting applications of capillary electrophoresis to analytical problems of potential interest for the forensic researchers and scientists can be found in the most qualified journals of analytical chemistry, analytical biochemistry, pharmacology, toxicology, laboratory medicine, human genetics, etc. However, the present review has been focused on discussing only the most relevant examples of analytical applications of capillary electrophoretic and electrokinetic techniques published in the following fields: (i) illicit and abused drugs, (ii) ions and small molecules of forensic interest, (iii) proteins and peptides of forensic interest, (iv) dyes and inks, (v) forensic DNA. The present review collects and comments on 60 references.

Recent advances in the analysis of antibiotics by CE and CEC.

This article reviews the recent developments achieved in the analysis of antibiotics by CE and CEC. CZE has mainly been employed although other separation modes have also been used. Different detection systems coupled to CE have been reported for antibiotic determination. Enhancement on sensitivity through the use of diverse offline, inline, and online preconcentration approaches is also described. Special attention has been paid to sample treatment steps and to the applications developed in different research areas such as the pharmaceutical, biological, food, and environmental. This manuscript covers the period of time from the previous review published in June 2009 until May 2011.

Capillary electrophoresis of natural products: highlights of the last five years (2006-2010).

An extensive search of the published research and review articles indicated a growing number of works that employed electroseparation techniques. Capillary zone electrophoresis (CZE) and electrokinetic chromatography (EKC), in particular, were found to be popular for the analyses of natural products. This review outlines the important developments in this field over the years, especially during the 2006-2010 period. An overview of the natural product applications such as pharmaceuticals/herbal products, fingerprinting and quality control, food and food contaminants, and toxicological compounds of interest to forensics were presented. Important areas of detection strategies, microchips, sample preconcentration, and chiral separations were also discussed. Hence, quick information was provided on the researches already undertaken and the possibilities of unexplored areas. In addition, fundamental concepts for the understanding of CZE and EKC and their suitability for natural products analyses were briefly discussed.

Recent progress in analytical capillary isotachophoresis.

Capillary ITP is currently used as one of the most important tools for preseparation and preconcentration of trace analytes in complex or diluted samples. This contribution is a continuation of a series of regularly published reviews on the topic and covers the last 2 years. It brings a survey of related literature organized into following sections: theory and methodology, instrumentation and techniques, and applications.