CE-MS System Research Articles

Scale-Up of PTFE-Based Gas Diffusion Electrodes Using an Electrolyte-Integrated Polymer-Coated Current Collector Approach.

Nonconductive porous polymer substrates, such as PTFE, have been pivotal in the fabrication of stable and high-performing gas diffusion electrodes (GDEs) for the reduction of CO2/CO in small scale electrolyzers; however, the scale-up of polymer-based GDEs without performance penalties to technologically more relevant electrode sizes has remained elusive. This work reports on a new current collector concept that enables the scale-up of PTFE-based GDEs from 5 to 100 cm2 and beyond. The present approach builds on a multifunctional current collector concept that enables multipoint front-contacting of thin catalyst coatings, which mitigates performance losses even for high resistivity cathodes. Our improved current collector design concomitantly incorporates a flow-field functionality in a monopolar plate configuration, keeping electrolyte gaps small for increased performance. Experiments with 100 cm2 cathodes were conducted in a one-gap alkaline AEM and acid CEM system. Our design represents an important step forward in the development of larger-size CO2 electrolyzers.

High-sensitivity and high-resolution therapeutic antibody charge variant and impurity characterization by microfluidic native capillary electrophoresis-mass spectrometry

Therapeutic antibodies are a major class of pharmaceutical drugs used to treat a wide variety of diseases. They have several advantages including the high specificity and binding affinity to their molecular targets, and generally low immunotoxicity and mild adverse effects. The characterization of therapeutic antibodies is crucial to ensure drug efficacy and safety. Charge variant analysis can be used to examine the charge variant forms of therapeutic antibodies, which may reflect modifications that impact the drug quality. Native capillary electrophoresis-mass spectrometry (nCE-MS) analysis by an integrated ZipChip CE-MS system is an alternative and complementary method to cation-exchange chromatography and imaged capillary isoelectric focusing to support the characterization of charge variants. In this study, we performed nCE-MS analysis to evaluate the charge variants and impurities in therapeutic antibodies including immunoglobin G (IgG) monoclonal antibodies (mAbs), bispecific antibodies (bsAbs), and alternative formats such as therapeutic antibodies with addition or removal of antigen-binding domain. With the ZipChip CE-MS system, high-resolution charge variant separation was achieved for different types of therapeutic antibodies. Moreover, ZipChip nCE-MS analysis enabled high-sensitivity detection and identification of species with low abundance, including proteolytic cleavage and fragmentation in mAb, monospecific mAb impurities in bsAb, and O-glycosylation in alternative formats to support biopharmaceutical development and investigations.

Climate engineering management: an emerging interdisciplinary subject

Purpose Climate engineering management (CEM) as an emerging and cross-disciplinary subject gradually draws the attention to researchers. This paper aims to focus on economic and social impacts on the technologies of climate engineering themselves. However, very few research concentrates on the management of climate engineering. Furthermore, scientific knowledge and a unified system of CEM are limited. Design/methodology/approach In this paper, the concept of CEM and its characteristics are proposed and elaborated. In addition, the framework of CEM is established based on management objectives, management processes and supporting theory and technology of management. Moreover, a multi-agent synergistic theory of CEM is put forward to guide efficient management of climate engineering, which is composed of time synergy, space synergy, and factor synergy. This theory is suitable for solving all problems encountered in the management of various climate engineering rather than a specific climate engineering. Specifically, the proposed CEM system aims to mitigate the impact of climate change via refining and summarizing the interrelationship of each component. Findings Overall, the six research frontiers and hotspots in the field of CEM are explored based on the current status of research. Originality/value In terms of the objectives listed above, this paper seeks to provide a reference for formulating the standards and norms in the management of various climate engineering, as well as contribute to policy implementation and efficient management.

A novel integrated strategy for the detection and quantification of the neurotoxin β-N-methylamino-L-alanine in environmental samples.

We describe a set of new tools for the detection and quantification of β-N-methylamino-L-alanine (BMAA) which includes a novel stable isotope-labeled BMAA standard (13C3,15N2) and a chip-based capillary electrophoresis mass spectrometry platform for separation and detection. Baseline resolution of BMAA from its potentially confounding structural isomers N-2-aminoethylglycine (AEG) and 2,4-diaminobutyric acid (2,4-DAB) is achieved using the chip-based CE-MS system in less than 1min. Detection and linearity of response are demonstrated across > 3.5 orders of dynamic range using parallel reaction monitoring (PRM). The lower limit of detection and quantification were calculated for BMAA detection at 40nM (4.8ng/mL) and 400nM (48ng/mL), respectively. Finally, the strategy was applied to detect BMAA in seafood samples purchased at a local market in Raleigh, NC where their harvest location was known. BMAA was detected in a sea scallop sample. Because the BMAA/stable isotope-labeled 13C3,15N2-BMAA (SIL-BMAA) ratio in the scallop sample was below the limit of quantification, a semiquantitative analysis of BMAA content was carried out, and BMAA content was estimated to be approximately 820ng BMAA/1g of wet scallop tissue. Identification was verified by high mass measurement accuracy of precursor (< 5ppm) and product ions (< 10ppm), comigration with SIL-BMAA spike-in standard, and conservation of ion abundance ratios for product ions between BMAA and SIL-BMAA. Interestingly, BMAA was not identified in the free protein fraction but only detected after protein hydrolysis which suggests that BMAA is tightly bound by and/or incorporated into proteins. Graphical abstract Utilization of novel 13C3,15N2-BMAA and chip-based CE-MS/MS for detection and quantification of BMAA in environmental samples.

Cause analysis and suggestion of urea consumption in denitrification system of coal-fired power plant

In the daily operation of many power plants, the urea consumption of denitration system is much more than normal. Therefore, the process of site testing and laboratory analysis are carried out. Several suggestions are given out. (1) The position of sampling hole on the exit flue of denitrification system should be redesigned. (2) The denitrification optimization and adjustment should be carried out based on the technical specifications for the operation system. (3) The flue gas CEMS system for single point sampling should be transformed into two or three point sampling mode. (4) When the coal - fired unit is shutting down, examine the ammonia injection and nozzle branch, in order to improve the operation reliability of denitration system.

Improved sensitivity by post-column chemical environment modification of CE-ESI-MS using a flow-through microvial interface.

Post-column chemical environment modification can affect detection sensitivity and signal appearance when capillary electrophoresis is coupled through electrospray ionization to mass spectrometry (CE-ESI-MS). In this study, changes in the signal intensity and peak shape of N-Acetylneuraminic acid (Neu5Ac) were examined when the modifier solution used in a flow-through microvial interface for CE-ESI-MS was prepared using an acidic or basic background electrolyte (BGE) composition. The use of a basic modifier resulted in improved detection compared to the results obtained when an acidic modifier was used in negative ion mode. Increased sensitivity and more symmetrical peak shape were obtained. Using an acidic modifier, the LOD of Neu5Ac was 47.7nM, whereas for a basic modifier, the LOD of Neu5Ac was 5.20nM. The calculated asymmetry factor at 100nM of Neu5Ac ranged from 0.71 to 1.5 when an acidic modifier was used, while the factor ranged from 1.0 to 1.1 when a basic modifier was used. Properly chosen post-column chemical modification can have a significant effect on the performance of the CE-MS system.

Capillary Zone Electrophoresis-Mass Spectrometry of Intact Proteins.

Capillary electrophoresis (CE) coupled with mass spectrometry (MS) has proven to be a powerful analytical tool for the characterization of intact proteins. It combines the high separation efficiency, short analysis time, and versatility of CE with the mass selectivity and sensitivity offered by MS detection. This chapter focuses on important practical considerations when applying CE-MS for the analysis of intact proteins. Technological aspects with respect to the use of CE-MS interfaces and application of noncovalent capillary coatings preventing protein adsorption are treated. Critical factors for successful protein analysis are discussed and four typical CE-MS systems are described demonstrating the characterization of different types of intact proteins by CE-MS. These methodologies comprise the use of sheath-liquid and sheathless CE-MS interfaces, and various types of noncovalent capillary coatings allowing efficient and reproducible protein separations. The discussion includes the analysis of lysozyme-drug conjugates and the therapeutic proteins human growth hormone, human interferon-β-1a, and human erythropoietin.

CE-MS for metabolomics: developments and applications in the period 2012-2014.

In the field of metabolomics, CE-MS is now regarded as a useful complementary analytical technique for the profiling of (highly) polar ionogenic metabolites in biological samples. Over the past few years, significant advancements have been made in CE-MS approaches for metabolic profiling studies. This paper, which is a follow-up of three previous review papers covering the years 2000-2012 [Electrophoresis 2009, 30, 276-291; Electrophoresis 2011, 32, 52-65; Electrophoresis 2013, 34, 86-98], provides an update of these developments covering the scientific literature from July 2012 to June 2014. Attention will be paid to novel interfacing techniques for coupling CE to MS and their implications for metabolomics studies. The potential of CEC-MS and MEKC-MS are also considered, and CE-MS systems for high-throughput metabolic profiling are discussed. The applicability of CE-MS for metabolomics studies is demonstrated by representative examples in the fields of biomedical, clinical, microbial, plant, environmental, and food metabolomics. An 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, general conclusions and perspectives are given.

Research on Environment Materials with NDIR NO&lt;sub&gt;2&lt;/sub&gt; Concentration Measurement by Soot Position Influence

Environment materials play important role in our daily life. It includes so many types. NO2 is one of the most important gaseous pollutants and NO2 concentration measurement system is one part of the CEMS system. There have many NO2 concentration measurement methods and NDIR is used commonly. The received angle of the measurement light is gradually decreases while the distance between soot and the receiver becomes larger; so the true infrared light intensity is smaller than the theoretical infrared light intensity and NO2 concentration is less than the actual concentration. To reduce the soot position influence, soot position influence on NO2 concentration measurement using NDIR is studied. The influence of the different soot position is analyzed. The simulation results show that the different soot position can influent the NO2 concentration accuracy. The solution method on decreasing the soot poison influence is brought out and can improve the NO2 concentration accuracy.

Capillary electrophoresis‐mass spectrometry using a flow‐through microvial interface for cationic metabolome analysis

The application of CE-MS in the field of metabolomics is underrepresented, even though it is in principle highly suited for the analysis of small charged compounds, as many metabolites are. Moreover, a robust coupling, using the sheath liquid (SL)-assisted interface was already presented more than a decade ago. A lack of concentration sensitivity is often mentioned as a reason for the underrepresentation of CE-MS in metabolomics. This is caused by postcolumn dilution of the sample with SL, which is typically delivered at a flow rate of 1-10 μL/min. In this study, we investigated the performance of the flow-through microvial (MV) assisted CE-MS interface for cationic metabolomics. With this interface, only a little liquid is added postcolumn, that is, typically 100-500 nL/min. For the evaluation, we used a metabolite mix comprising 45 important cationic metabolites and compared the sensitivity and LOD of both devices. The performance of the CE-MS system was significantly improved by using the MV-assisted interface; the sensitivity was increased more than three times and the LOD decreased more than five times. Then, we analyzed single zebrafish embryos to demonstrate the method on a volume-limited biological sample. In comparison with SL-assisted CE-MS, twice as many molecular features were found, of which several could be identified. These results demonstrate the good potential of the MV interface for enhancing the coverage of the metabolome.

Structural Characterization of Pyridylaminated Oligosaccharides Derived from Neutral Glycosphingolipids by High-Sensitivity Capillary Electrophoresis–Mass Spectrometry

High-sensitivity capillary electrophoresis-electrospray ionization quadrupole ion trap time-of-flight mass spectrometry (CE-ESI-QIT-TOF MS) was developed to structurally characterize four kinds of pyridylaminated (PA) oligosaccharides, i.e., lactose (Lac)-PA, globotriose (Gb3)-PA, globotetraose (Gb4)-PA, and IV(3) αGalNAc-Gb4 (Forssman antigen)-PA, derived from neutral glycosphingolipids. The CE-MS system included the head-column field-amplified sample stacking (HC-FASS) method for effective sample injection into a capillary column in CE, a sheathless interface between CE and a mass spectrometer, and MS and tandem MS (MS(2)) measurements with narrow mass range repeated high-speed switching. The total sensitivity of the developed CE-MS system was about 20,000 times higher than that of the conventional CE-MS system consisting of pressure injection, a sheath-flow interface, and a wide mass range measurement. The MS and MS(2) spectra of the four PA-oligosaccharides at a concentration of 25 amol/μL in mixtures (each 250 amol/10 μL in a tube) clearly showed protonated molecular ions ([M + H](+)) and the fragment ions responsible for the sequential elimination of saccharides. The developed CE-MS system is a powerful method for the structural characterization of glycosphingolipids extracted from very small amounts of biological materials and could be extended to the structural characterization of oligosaccharides derived from glycoproteins.

Low-Flow Sheathless Capillary Electrophoresis–Mass Spectrometry for Sensitive Glycoform Profiling of Intact Pharmaceutical Proteins

Capillary electrophoresis coupled to time-of-flight mass spectrometry (CE-TOF-MS) via a porous tip sheathless electrospray ionization (ESI) interface was studied for the characterization of pharmaceutical glycoproteins. To achieve optimal glycoform separation, background electrolytes of low pH were used in conjunction with a capillary with a neutral coating exhibiting near-zero electroosmotic flow. Crucial interfacing parameters, like ESI voltage and ESI tip-to-end plate distance, were optimized for very low flow rates (∼5 nL/min) in order to attain maximum sensitivity and stable performance. Under optimal conditions, the sheathless CE-MS interface provided significantly increased ionization efficiencies for intact proteins and decreased ionization suppression leading to detection limits in the picomolar-range. Analysis of a sample of recombinant human interferon-β allowed the assignment of at least 18 glycoforms, plus a variety of deamidation, succinimide, and oxidation products, representing a considerable improvement over sheath-liquid CE-MS. The sheathless CE-MS system also proved highly suitable for the glycoprofiling of recombinant human erythropoietin, revealing 74 glycoforms in a 60-min run. In addition, oxidation and acetylation products were detected, overall resulting in assignment of more than 250 different isoforms. Semiquantitative glycoprofiles could be derived for both pharmaceutical proteins, with estimated glycoform concentrations analyzed ranging from 0.35 to 950 nM. These profiles may be very useful for quality control of biopharmaceuticals and their biosimilars.

Capillary electrophoresis‐mass spectrometry methods for tryptic peptide mapping of therapeutic antibodies

Tryptic peptide mapping is routinely used in the biotech industry to confirm primary sequence, cell line stability, and to analyze posttranslational modifications. Peptide analysis is generally done by reverse phase liquid chromatography with UV or mass spectrometric detection. This method provides excellent resolution and sequence coverage. However, traditional methods are slow, and generally cannot detect small, hydrophilic peptides due to coelution with the column void volume. In this work, complementary CE-MS peptide analysis methods have been developed. The analyses are performed on a traditional CE-MS instrument with a sheath interface, and also on a novel sheathless interface that promises improved resolution and limit of detection. The methods were performed on a tryptic digest of a therapeutic monoclonal antibody for which LC-MS detects 97% sequence coverage. The 3% not covered consists of 11 peptides containing three amino acids or fewer, including two in the critical complementarity binding domain. Without further processing, the same tryptic digest was analyzed by CE-MS. Separation and detection of the 11 small peptides was achieved on CE-MS systems with both interfaces. The sheathless system produced better peak capacity and gave mass spectra with significantly less noise, while the sheath system proved to have better repeatability.

Development of a novel switchable CE-MS interface with predictive trajectories for high-throughput proteomics studies

Abstract The capillary electrophoresis (CE)-mass spectrometry (MS) interface is anticipated to have pivotal roles to play in biomarker discovery, elucidation and validation, and in diagnostics, as well as in drug discovery. We are developing a CE-MS system as the natural extension of our Label-Free Intrinsic Imaging (LFiI™) platform, allowing a large increase in analytical power. One of the most powerful analytical tools in bio-analytical science applications is the mass spectrometer, allowing identification and extraordinary resolving power. However, this instrument too has shortcomings – it really needs a separation system ahead of it. Traditionally liquid chromatogaphy (LC) or 2D-gel separation have been coupled to MS with relative robustness. However LC techniques are not ideally suited to the analysis of biomolecules, with the use of denaturing solvents, expensive columns etc. while flat gel systems have serious shortcomings in sensitivity, reproducibility, dynamic range, quantification and throughput. These are largely overcome with capillary approaches, such as the Label Free Intrinsic Imaging system, the Peregrine, developed by deltaDOT Ltd of London. The CE-MS interface being developed by deltaDOT QSTP (Qatar Science and Technology Park) will be based on our real-time pattern recognition known as ‘predictive trajectories’ (‘PT’) and biomolecular switching on the LFiI platform, to allow specific protein bands, selected ‘on the fly’, to be separated and quantified, before they undergo trypsin digestion, injection and full MS analysis in a Waters high-definition mass spectrometer (‘Synapt’). Such an interface considerably reduces the system noise by giving a switch opportunity to analyse selected bands of interest from the bulk of background buffer and highly concentrated proteins of low interest. Another significant advantage of such an approach would arise from a more coherent signal where peptide fragments of the same protein would elute together, as opposed to traditional liquid chromatography where any peptide fragments could come from any proteins from the sample, requiring heavy and slow analyses processing. Based on work in our QSTP labs, we present preliminary data of analyses undertaken with partners in Qatar University on a range of proteomic targets and other analytes. We show how the unique combination of LFiI + PT + HDMS Q-Tof can provide a significant enhancement in analytical power.

Capillary electrophoresis–mass spectrometry of intact basic proteins using Polybrene–dextran sulfate–Polybrene-coated capillaries: System optimization and performance

A capillary electrophoresis–mass spectrometry (CE–MS) method using sheath liquid electrospray ionization interfacing was studied and optimized for the analysis of intact basic proteins. To prevent protein adsorption, capillaries with a noncovalent positively charged coating were utilized. Capillaries were coated by subsequent rinsing with solutions of Polybrene, dextran sulfate and Polybrene. The coating proved to be fully compatible with MS detection, causing no background signals and ionization suppression. The composition of the sheath liquid and BGE was optimized using the model proteins α-chymotrypsinogen A, ribonuclease A, lysozyme and cytochrome c. A sheath liquid of isopropanol–water–acetic acid (75:25:0.1, v/v/v) at 2 μL min −1 resulted in optimal signal intensities for most proteins, but caused dissociation of the heme group of cytochrome c. Optimum protein responses were obtained with a BGE of 50 mM acetic acid (pH 3.0), which allowed a baseline separation of the test protein mixture. Several minor impurities present in the mixture could be detected and provisionally identified using accurate mass and a protein modification database. The selectivity of the CE–MS system was investigated by the analysis of acetylated lysozyme. Eight highly related species, identified as non-acetylated lysozyme and lysozyme acetylated in various degrees, could be distinguished. The CE–MS system showed good reproducibility yielding interday (three weeks period) RSDs for migration time and peak area within 2% and 10%, respectively. With the CE–MS system, determination coefficients ( R 2) for protein concentration and peak area were higher than 0.996, whereas detection limits were between 11 and 19 nM.

Relevance and use of capillary coatings in capillary electrophoresis–mass spectrometry

Over the last two decades, coupled capillary electrophoresis (CE)-mass spectrometry (MS) has developed into a generally accepted technique with a wide applicability. A growing number of CE-MS applications make use of capillaries where the internal wall is modified with surface coating agents. In CE-MS, capillary coatings are used to prevent analyte adsorption and to provide appropriate conditions for CE-MS interfacing. This paper gives an overview of the various capillary coating strategies used in CE-MS. The main attention is devoted to the way coatings can contribute to a proper CE-MS operation. The foremost capillary coating methods are discussed with emphasis on their compatibility with MS detection. The role of capillary coatings in the control of the electroosmotic flow and the consequences for CE-MS coupling are treated. Subsequently, an overview of reported applications of CE-MS employing different coating principles is presented. Selected examples are given to illustrate the usefulness of the coatings and the overall applicability of the CE-MS systems. It is concluded that capillary coatings can enhance the performance and stability of CE-MS systems, yielding a highly valuable and reproducible analytical tool.

Efficient and highly reproducible capillary electrophoresis–mass spectrometry of peptides using Polybrene‐poly(vinyl sulfonate)‐coated capillaries

The potential of capillaries noncovalently coated with a bilayer of oppositely charged polymers for the analysis of peptides by CE-MS was investigated. Bilayer coatings were produced by subsequently rinsing fused-silica capillaries with a solution of Polybrene (PB) and poly(vinyl sulfonate) (PVS). The PB-PVS coating showed to be fully compatible with MS detection causing no ionization suppression or background signals. The bilayer coating provided a considerable EOF at low pH, thereby facilitating the fast separation of peptides using a BGE of formic acid (pH 2.5). Under optimized CE-MS conditions, for enkephalin peptides high separation efficiencies were obtained with plate numbers in the range of 300,000-500,000. It is demonstrated that both the cancellation of the hydrodynamic capillary flow induced by the nebulizer gas and a sufficiently high-data acquisition rate are crucial for achieving these efficiencies. The overall performance of the CE-MS system using PB-PVS-coated capillaries was evaluated by the analysis of a tryptic digest of cytochrome c. The system provided an efficient separation of the peptide mixture, which could be effectively monitored by MS/MS detection allowing identification of at least 13 peptides within a time interval of 1.5 min. In addition, the PB-PVS coating proved to be very consistent yielding stable CE-MS patterns with highly favorable migration time reproducibilities (RSDs < 1% over a 3-day period).

Detection of nitroaromatic and cyclic nitramine compounds by cyclodextrin assisted capillary electrophoresis quadrupole ion trap mass spectrometry

An Agilent 3DCE capillary electrophoresis system using sulfobutylether-β-cyclodextrin (SB-β-CD)–ammonium acetate separation buffer pH 6.9 was coupled to a Bruker Esquire 3000+ quadrupole ion trap mass detector via a commercially available electrospray ionization interface with acetonitrile sheath flow. The CE–MS system was applied in negative ionization mode for the resolution and detection of nitroaromatic and polar cyclic or caged nitramine energetic materials including TNT [2,4,6-trinitrotoluene, formula mass (FW) 227.13], TNB (1,3,5-trinitrobenzene, FW 213.12), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine, FW 222.26) HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, FW 296.16), and CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, FW 438.19). The CE–MS system conformed to the high-performance liquid chromatography with ultraviolet absorbance detection (HPLC–UV) and HPLC–MS reference methods for the identification of energetic contaminants and their degradation products in soil and marine sediment samples.

Expression of P-glycoprotein, multidrug-resistance proteins 1 and 2 in CEM, CEMVBL, CEME1000, MDCKIIMRP1 and MDCKIIMRP2 cell lines

Expression of P-glycoprotein, multidrug-resistance proteins 1 and 2 in CEM, CEMVBL, CEME1000, MDCKIIMRP1 and MDCKIIMRP2 cell lines

On-column sample enrichment for capillary electrophoresis sheathless electrospray ionization mass spectrometry: evaluation for peptide analysis and protein identification.

Although several designs have been advanced for coupling sample enrichment devices to a sheathless electrospray ionization-mass spectrometry (MS) interface on a capillary electrophoresis (CE) column, most of these approaches suffer from difficulties in fabrication, and the CE separation efficiency is degraded as a result of the presence of coupling sleeves. We have developed a design that offers significant improvements in terms of ease of fabrication, durability, and maintenance of the integrity of the CE-separated analyte zones. Capillaries with different inside and outside diameters were evaluated to optimize the performance of the CE-MS system, resulting in a mass limit of detection of 500 amol for tandem MS analysis of a standard peptide using a 20-microm-i.d. capillary. The improved design incorporates an efficient method to preconcentrate a sample directly within the CE capillary followed by its electrophoretic separation and detection using a true zero dead-volume sheathless CE-MS interface. Testing of this novel CE-MS system showed its ability to characterize proteomic samples such as protein digests, in-gel-digested proteins, and hydrophobic peptides as well as to quantitate ICAT-labeled peptides.