CE-MS with electrokinetic supercharging and application to determination of neurotransmitters

Advancements in Multiple-Step On-Line Preconcentration Techniques for Enhanced Sensitivity in Capillary Electrophoresis

Multiple-step on-line preconcentration, a combination of at least two stacking techniques has been developed to increase the sensitivity in capillary electrophoresis (CE) for analytes in various samples. It is usually conducted sequentially, or in some cases, synergistically, where different stacking modes occur simultaneously. Multiple-step techniques allow simultaneous preconcentration and separation of various kinds of analytes in different complex samples in a single CE run. This review aims to provide recent advances in multiple-step on-line preconcentration techniques in CE. We critically review technical papers published for the last 7 years up until July 2024, subsequently organized according to the combination of the main stacking techniques, that is, field amplification, large volume sample stacking, transient isotachophoresis, micelle to solvent or micelle to cyclodextrin stacking, and others. The procedures, fundamental mechanism, analytical figures of merits achieved, and their feasibility for complicated sample matrices are reviewed.

Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications-Updated and completely revised edition

This review is in support of the development of selective, precise, fast, and validated capillary electrophoresis (CE) methods. It follows up a similar article from 1998, Wätzig H, Degenhardt M, Kunkel A. "Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications," pointing out which fundamentals are still valid and at the same time showing the enormous achievements in the last 25 years. The structures of both reviews are widely similar, in order to facilitate their simultaneous use. Focusing on pharmaceutical and biological applications, the successful use of CE is now demonstrated by more than 600 carefully selected references. Many of those are recent reviews; therefore, a significant overview about the field is provided. There are extra sections about sample pretreatment related to CE and microchip CE, and a completely revised section about method development for protein analytes and biomolecules in general. The general strategies for method development are summed up with regard to selectivity, efficiency, precision, analysis time, limit of detection, sample pretreatment requirements, and validation.

Recent advances (2019-2021) of capillary electrophoresis-mass spectrometry for multilevel proteomics

Multilevel proteomics aims to delineate proteins at the peptide (bottom-up proteomics), proteoform (top-down proteomics), and protein complex (native proteomics) levels. Capillary electrophoresis-mass spectrometry (CE-MS) can achieve highly efficient separation and highly sensitive detection of complex mixtures of peptides, proteoforms, and even protein complexes because of its substantial technical progress. CE-MS has become a valuable alternative to the routinely used liquid chromatography-mass spectrometry for multilevel proteomics. This review summarizes the most recent (2019-2021) advances of CE-MS for multilevel proteomics regarding technological progress and biological applications. We also provide brief perspectives on CE-MS for multilevel proteomics at the end, highlighting some future directions and potential challenges.

Capillary Electrophoresis-Mass Spectrometry for the Direct Analysis of Metabolites in Highly Saline Samples Using In-Capillary Preconcentration

Capillary electrophoresis-mass spectrometry (CE-MS) is gaining interest for metabolomics studies because of its high separation efficiency, selectivity, and versatility. The ability to inject nanoliters from only a few microliters of sample in the injection vial makes this approach very suited for volume-limited applications. However, the low injection volumes could compromise the detection sensitivity of CE-MS, thereby potentially limiting its scope in metabolomics. To overcome this issue, online sample preconcentration methods have been developed to increase sample-loading volumes without hampering the intrinsic high separation efficiency of CE. In this protocol, online preconcentration with sample stacking based on pH junction was assessed for the direct profiling of endogenous metabolites in rat brain microdialysates. Sample stacking was realized by a pre-injection of ammonium hydroxide, followed by a large sample injection (i.e., about 17% of the total capillary volume). It is shown that this relatively simple and fast preconcentration procedure is fully compatible with the high-salt concentration in microdialysates and significantly improves the detection sensitivity of the CE-MS method.

A Hypothesis From Metabolomics Analysis of Diabetic Retinopathy: Arginine-Creatine Metabolic Pathway May Be a New Treatment Strategy for Diabetic Retinopathy

Diabetic retinopathy is one of the serious complications of diabetes, which the leading causes of blindness worldwide, and its irreversibility renders the existing treatment methods unsatisfactory. Early detection and timely intervention can effectively reduce the damage caused by diabetic retinopathy. Metabolomics is a branch of systems biology and a powerful tool for studying pathophysiological processes, which can help identify the characteristic metabolic changes marking the progression of diabetic retinopathy, discover potential biomarkers to inform clinical diagnosis and treatment. This review provides an update on the known metabolomics biomarkers of diabetic retinopathy. Through comprehensive analysis of biomarkers, we found that the arginine biosynthesis is closely related to diabetic retinopathy. Meanwhile, creatine, a metabolite with arginine as a precursor, has attracted our attention due to its important correlation with diabetic retinopathy. We discuss the possibility of the arginine-creatine metabolic pathway as a therapeutic strategy for diabetic retinopathy.

Recent (2018-2020) development in capillary electrophoresis

Development of new capillary electrophoresis (CE) methodology and instrumentation, as well as application of CE to solve new problems, remains an active research area because of the attractive features of CE compared to other separation techniques. In this review, we focus on the representative works about sample preconcentration, separation media or capillary coating development, detector construction, and multidimensional separation in CE, which are judiciously selected from the papers published in 2018-2020.

Recent developments in capillary and microchip electroseparations of peptides (2019-mid 2021)

The review provides a comprehensive overview of developments and applications of high performance capillary and microchip electroseparation methods (zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography) for analysis, microscale isolation, and physicochemical characterization of peptides from 2019 up to approximately the middle of 2021. Advances in the investigation of electromigration properties of peptides and in the methodology of their analysis, such as sample preparation, sorption suppression, EOF control, and detection, are presented. New developments in the individual CE and CEC methods are demonstrated and several types of their applications are shown. They include qualitative and quantitative analysis, determination in complex biomatrices, monitoring of chemical and enzymatic reactions and physicochemical changes, amino acid, sequence, and chiral analyses, and peptide mapping of proteins. In addition, micropreparative separations and determination of significant physicochemical parameters of peptides by CE and CEC methods are described.

CE-MS for metabolomics: Developments and applications in the period 2018-2020

Capillary electrophoresis-mass spectrometry (CE-MS) is now a mature analytical technique in metabolomics, notably for the efficient profiling of polar and charged metabolites. Over the past few years, (further) progress has been made in the design of improved interfacing techniques for coupling CE to MS; also, in the development of CE-MS approaches for profiling metabolites in volume-restricted samples, and in strategies that further enhance the metabolic coverage. In this article, which is a follow-up of a previous review article covering the years 2016-2018 (Electrophoresis 2019, 40, 165-179), the main (technological) developments in CE-MS methods and strategies for metabolomics are discussed covering the literature from July 2018 to June 2020. Representative examples highlight the utility of CE-MS in the fields of biomedical, clinical, microbial, plant and food metabolomics. A complete overview of recent CE-MS-based metabolomics studies is given in a table, which provides information on sample type and pretreatment, capillary coatings, and MS detection mode. Finally, some general conclusions and perspectives are given.