This study reports a reinvestigation of background electrolyte selection strategy for performance improvement in CE‐LIF of peptides and proteins. This strategy is based on the employment of high ...concentrations of organic species in BGE possessing high buffer capacity and low specific conductivity in order to ensure excellent stacking preconcentration and separation resolution of fluorescently tagged peptides and proteins. Unlike universal UV detection, the use of such BGEs at high concentrations does not lead to degradation of LIF detection signals at the working excitation and emission wavelengths. At the same buffer ionic strength, pH and electric field, an “inorganic‐species‐free” BGE (or ISF BGE) for CE‐LIF of fluorescently labeled beta amyloid peptide Aβ 1–42 (a model analyte) offered a signal intensity and peak efficiency at least three‐times higher than those obtained with a conventional BGE normally used for CE‐LIF, while producing an electric current twice lower. Good peak performance (in terms of height and shape) was maintained when using ISF BGEs even with samples prepared in high‐conductivity phosphate buffer saline matrix. The advantageous features of such BGEs used at high concentrations over conventional ones in terms of high separation resolution, improved signal intensities, tuning of EOF magnitudes and minimization of protein adsorption on an uncoated fused silica capillary are demonstrated using Alexa‐488‐labelled trypsin inhibitor. Such BGE selection approach was applied for investigation of separation performance for CE‐LIF of ovalbumin labelled with different fluorophores.
It is reported herein a new approach to study the orientation and density of mouse antibody 27 grafting on magnetic beads, serving for immunoassays and biosensors with fluorescent 28 detection of ...biomolecules. This approach is based on selective enzymatic digestion of target 29 grafted antibodies at a specific site below the hinge position to provide F(ab’)2 and Fc 30 fragments, followed by separation and determination of these fragments with size exclusion 31 chromatography (SEC) coupled with fluorescence detection (FLD). The developed method was 32 applied for evaluation of immunoglobulin (IgG2a) grafting capacity on three different 33 biofunctionalized magnetic beads (i.e., Tosyl-activated, carboxylic, protein G). Tosyl-activated 34 and protein G beads at different optimal grafting IgG: bead ratios (i.e.,110 μg: 1000 μg and 240 35 μg: 1000 μg, respectively) exhibited superior grafting capacity than carboxylic counterparts. 36 Under the optimized conditions, more than 70 % of antibodies were grafted on tosyl-activated 37 and protein G beads in the right orientation. This approach was then demonstrated with different 38 commercially available antibodies specific to amyloid-beta peptide 1-42 (Aβ1-42) for magneto-39 immunoassays and fluorescent detection of this peptide that is an established biomarker for 40 molecular diagnosis of Alzheimer’s disease.
This work reports on the development of the first capillary electrophoresis methodology for the elucidation of extracellular vesicles’ (EVs) electrokinetic distributions. The approach is based on ...capillary electrophoresis coupled with laser-induced fluorescent (LIF) detection for the identification and quantification of EVs after their isolation. Sensitive detection of these nanometric entities was possible thanks to an ‘inorganic-species-free’ background electrolyte. This electrolyte was made up of weakly charged molecules at very high concentrations to stabilize EVs, and an intra-membrane labelling approach was used to prevent EV morphology modification. The limit of detection for EVs achieved using the developed CE-LIF method reached 8 × 109 EV/mL, whereas the calibration curve was acquired from 1.22 × 1010 to 1.20 × 1011 EV/mL. The CE-LIF approach was applied to provide the electrokinetic distributions of various EVs of animal and human origins, and visualize different EV subpopulations from our recently developed high-yield EV isolation method.
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•A new CE-LIF tool for characterization and quantification of EVs was developed.•The new BGE was applied for excellent performance of CE-LIF of EVs.•Intra-membrane labelling was optimized without incurring EV morphology modification.•Separation and detection of EVs from different animal and human origins were implemented.
We construct a numerical scheme for a model of two-phase flows. The keystone is the treatment of nonconservative terms using stationary contact discontinuities. The nonconservative terms are absorbed ...into left-hand and right-hand states of the local stationary contact discontinuity at each grid node. The numerical scheme is built by taking into accounts the states on both sides of local contact discontinuities as supplemented facts of a standard numerical approximation for the conservative part of the system. The scheme is shown to possess interesting properties: it preserves the positivity of the volume fractions in both phases and the positivity of the gas density, it is well-balanced and satisfying the numerical minimum entropy principle in the gas phase.
•A novel electrokinetic preconcentration technique based on multiple isotachophoresis with repetitive hydrodynamic injection.•Stacking of a sample plug representing up to 300% of the total capillary ...length was successfully demonstrated.•Quantification of Aβ 1-40 amyloid peptide down to 50nM with UV detection was made possible with 6 M-ITP cycles.
A novel electrokinetic preconcentration technique based on multiple isotachophoresis (M-ITP) realised in a micro-bored capillary to improve sensitivity for capillary electrophoresis with hydrodynamic injection was developed. The M-ITP operation relies on pressure-assisted pushing of a preconcentrated sample plug after the first ITP process back to the injection end of the capillary, followed by a large volume hydrodynamic injection prior to application of the second ITP step. This operational cycle was repeated as many times as desired with very good repeatability of the peak areas and peak heights at each ITP round (RSD less than 8%). Using imidazole and benzoate as models for cationic and anionic analytes, important insights into the mechanism of this electrokinetic preconcentration process with and without the presence of the electro-osmotic flow (EOF) at acidic and basic conditions were provided. Stacking of the benzoate ion, selected as one model analyte, in the presence of EOF and from a sample plug representing up to 300% of the total capillary length was successfully demonstrated. M-ITP was then demonstrated through the enrichment of the Aβ 1-40 amyloid peptide, considered as one of the biomarkers for biochemical diagnosis of Alzheimer’s disease. Quantification of Aβ 1-40 down to 50nM with UV detection was made possible with 6 M-ITP cycles.
It is reported in this study a new approach for modulation and even suppression of the electroosmotic flow (EOF) to achieve better electrokinetic preconcentration in capillary electrophoresis. This ...is based on the augmentation of the buffer’s concentrations to very high levels (more than a thousand of mM) without recourse to any dynamic/permanent coating nor viscous gel. The use of large weakly charged molecules as background electrolyte’s constituents allows working at extreme concentration ranges without penalty of high electric currents and Joule heating. By this way, the electroosmotic mobility could be modulated over a wide range (2–60 × 10−5 cm2 V−1 s−1 under alkaline conditions), and suppressed to levels equivalent to those obtained with several neutral coatings. The highest buffer concentrations, and the lowest EOF magnitudes, accordingly, were achieved with diethanolamine/3-(Cyclohexylamino)-1-propanesulfonic acid (ionic strength (IS) of 250 mM, pH 9.5), Tris(hydroxymethyl)aminomethane (Tris)/2-(Cyclohexylamino)ethanesulfonic acid (CHES) (IS of 280 mM, pH 8.7) and triethanolamine/2-(Cyclohexylamino)ethanesulfonic acid (IS of 250 mM, pH 8.5). For demonstration, this new approach was applied for sensitive determination of core-shell magnetic nanoparticles (CSMNPs) having high potential for healthcare applications such as imaging agents for diagnostics and controllable cargos for nanomedicine. Different profiles were achieved for purpose-made and commercial magnetic nanoparticles using CE coupled with light-emitting-diode induced fluorescence (LEDIF) detection. The best performance for EOF-assisted preconcentration and CE-LEDIF of CSMNPs was achieved with these nanoparticles prepared in TRIS/CHES (IS 10 mM, pH 8.4) for preconcentration, and separation under BGE of TRIS/CHES (IS 100 mM, pH 8.4). Compared to the conventional capillary electrophoresis (CE-UV) method for characterization of magnetic nanoparticles, our proposed approach with fluorescent detection and EOF-assisted preconcentration offers almost 350-fold sensitivity improvement. Furthermore, our scheme can be used for monitoring the interaction between CSMNPs and target pharmaceutical molecules, serving for drug delivery development. A preliminary study with two antibiotics using this approach revealed that kanamycin interacts better with the target nanoparticles than amikacin.
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•EOF suppression and modulation in silica capillaries without recourse to coating or gel is reported.•A new principle of EOF-assisted electrokinetic preconcentration for CE-LIF is proposed.•The first method for CE-LIF of core-shell magnetic nanoparticles (CSMNPs) was developed.•Detection and interaction study of CSMNPs could be realized with a 350-fold sensitivity improvement.
•New design of CE-C4D purpose-made system.•CE-C4D methods for analyses of β-lactam-based antibiotics.•Affordable tool for quality control and detection of counterfeiting of antibiotic formulations.
A ...simple and inexpensive approach for determination of various antimicrobial drugs using a purpose-made compact capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C4D) is reported. The objective of the work is to propose an affordable and easily-implemented tool for quality control and detection of counterfeiting of antibiotic formulations in resource constrained developing countries. The design of the purpose-made CE-C4D system was improved according to the feedback from over 10 years of use of our previous instrument. CE-C4D methods were for the first time developed to analyze β-lactam-based antibiotics commonly used in Vietnam, including single- β-lactam antibiotics (i.e. Cephalexin, Cefotaxime Sodium, Cefixime and Sulbactam) as well as β-lactams co-formulated with Sulbactam (i.e. Amoxicillin, Ampicillin, Cefoperazone and Sulbactam). Single β-lactam antibiotics were analyzed using a background electrolyte (BGE) composed of Tris/Ace (10 mM, pH 7.8) whereas β-lactam – Sulbactam combinations were simultaneously separated using a BGE containing Tris/Ace (10 mM, pH 7.5). The best achieved detection limits were 2.0 mg/L and 1.0 mg/L for these two groups, respectively. Good agreement between results obtained from CE-C4D and standard confirmation methods (LCMS) was achieved, with a coefficient of determination, r2, of 0.9991. The applicability of the developed CE-C4D method was demonstrated for quality control of 24 β-lactam-based antimicrobial drugs available in Vietnam.
We consider the Riemann problem for the system of shallow water equations with horizontal temperature gradients (the Ripa system). The model under investigation has the form of a nonconservative ...system, and it is hyperbolic, but is not strictly hyperbolic. We construct all solutions of the Riemann problem. It turns out that there may be up to three distinct solutions. A resonant phenomenon which causes the colliding shock waves is observed, where multiple waves associated with different characteristic fields propagate with the same shock speed.
In this study, for the first time we report on a comprehensive overview of different strategies to hyphenate droplet-based sample handling and preparation with electrophoretic separation in different ...formats (i.e. microchip and capillary electrophoresis). Droplet-interfaced electrophoresis is an emerging technique in which micro/nanometric droplets are used as a bridge and carrier of target analytes between sample treatment and electrokinetic separation steps, thus being expected to overcome the challenges of working dimension mismatch and low degree of module integration. This review covers all works on this topic from 2006 (the year of the first communication) up to 2020, with focus being given to three principal interfacing strategies, including droplets in immiscible phases, digital microfluidics with electrowetting-on-dielectric principle and inkjet droplet generation. Different instrumental developments for such purpose, the viewpoints on pros and cons of these designs as well as application demonstrations of droplet-interfaced electrokinetic strategies are discussed.
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•Strategies for droplet-interfacing in microscale electrophoresis are reviewed.•Technological aspects and application demonstrations of droplet-CE/MCE are discussed.•Viewpoints on their positive features and limitations are given.•Perspectives on the development of droplet-interfaced CE/MCE are provided.
•Simple and inexpensive method for determination of rare earth elements with portable CE-C4D.•A new arrangement for the portable CE-C4D instrument is reported.•The method was applied for ...determination of rare earth elements in ore and anti-corrosion coating samples.•Good agreement between results from CE-C4D and the confirmation method (ICP-MS) was achieved.
The employment of an in-house-made capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C4D) as a simple and inexpensive solution for simultaneous determination of many rare earth elements (REEs) in ore samples from Vietnam, as well as in anti-corrosion coating samples is reported. 14 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were determined using an electrolyte composed of 20mM arginine and 10mM α-hydroxyisobutyric acid adjusted to pH 4.2 with acetic acid. The best detection limit achieved was 0.24mg/L using the developed CE-C4D method. Good agreement between results from CE-C4D and the confirmation method (ICP-MS) was achieved, with a coefficient of determination (r2) for the two pairs of data of 0.998.
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