Micellar and Microemulsion Electrokinetic Chromatography
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Micellar electrokinetic chromatography
Microemulsion
Surface charge
Zeta potential
Charge density
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Contemporary findings in the field of insulator-based electrokinetics have demonstrated that in systems under the influence of direct current (DC) fields, dielectrophoresis (DEP) is not the main electrokinetic mechanism responsible for particle manipulation but rather the sum of electroosmosis, linear and nonlinear electrophoresis. Recent microfluidic studies have brought forth a methodology capable of experimentally estimating the nonlinear electrophoretic mobility of colloidal particles. This methodology, however, is limited to particles that fit two conditions: (i) the particle charge has the same sign as the channel wall charge and (ii) the magnitude of the particle ζ-potential is lower than that of the channel wall. The present work aims to expand upon this methodology by including particles whose ζ-potential has a magnitude larger than that of the wall, referred to as "type 2" particles, as well as to report findings on particles that appear to still be under the influence of the linear electrophoretic regime even at extremely high electric fields (∼6000 V/cm), referred to as "type 3" particles. Our findings suggest that both particle size and charge are key parameters in the determination of nonlinear electrophoretic properties. Type 2 microparticles were all found to be small (diameter ∼ 1 μm) and highly charged, with ζ-potentials above -60 mV; in contrast, type 3 microparticles were all large with ζ-potentials between -40 and -50 mV. However, it was also hypothesized that other nonconsidered parameters could be influencing the results, especially at higher electric fields (>3000 V/cm). The present work also aims to identify the current limitations in the experimental determination of μEP,NL and propose a framework for future work to address the current gaps in the evolving topic of nonlinear electrophoresis of colloidal particles.
Dielectrophoresis
Particle (ecology)
Surface charge
Zeta potential
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Electrophoretic light scattering
Surface charge
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Micellar electrokinetic chromatography
Microemulsion
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Electrophoresis in an alternating electric field is the basis for electroacoustical measurements. These measurements provide new means of investigating the electrokinetic properties of colloidal systems. In order to relate electroacoustical signals to the charge and the size of colloidal particles, an expression is required for the dynamic electrophoretic mobility of colloidal particles in a continuous fluid. In this paper, an exact analytical solution to the problem is given for an arbitrary ratio between the particle radius and the electric double-layer thickness, in the case where the electrokinetic potential of the uniformly charged particle is small and unaffected by the alternating field.
Particle (ecology)
Electrophoretic light scattering
Alternating current
Electric charge
Colloidal particle
Electrohydrodynamics
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Microemulsion
Micellar electrokinetic chromatography
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1. The conditions are described which are necessary for the comparison of certain types of electrokinetic potentials. An experimental comparison is made of (a) electrophoresis of quartz particles covered with egg albumin; and (b) similar experiments by Briggs on streaming potentials. A slight, consistent, difference is found between the electrophoretic potential and the streaming potential. This difference is probably due to the difference in the protein preparations used rather than to real difference in the electrophoretic and streaming potentials. 2. Data are given which facilitate the measurements and enhance the precision of the estimation of electrical mobilities of microscopic particles.
Streaming current
Potential difference
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Zeta potential
Coalescence (physics)
Streaming current
Electrophoretic light scattering
Alternating current
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Abstract The elution order of the hop α‐ and β‐acids has been studied under different modes of electrokinetic separation. A model is advanced to explain the shorter migration times of the more hydrophobic β‐acids compared to the α‐acids in micellar electrokinetic chromatography (MEKC). For quality control of the bitter principles in hops, the ruggedness of electrokinetic separation could be improved by replacing MEKC by microemulsion electrokinetic chromatography (MEEKC).
Micellar electrokinetic chromatography
Microemulsion
Gradient elution
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The electrokinetic potentials and surface charge densities of the silica surface are interpreted from both electrophoretic mobility and electro-osmosis measurements. Comparison of the data shows smaller magnitudes for both the potentials and surface charge interpreted from the electrophoretic mobility over the range of KCl concentration studied (10–5–0.1 mol dm–3). The interpreted surface charge densities increase indicating that effective adsorption of the negative chloride ions to the negative surface occurs. The silica surface is therefore postulated to be non-classical in nature. It is suggested that the retardation effect and therefore the electrophoretic potentials are underestimated in the electrophoresis problem.
Surface charge
Charge density
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