Dynamics of Capillary Electrochromatography: Experimental Study of Flow and Transport in Particulate Beds

Chen, Guofang; Pačes, Martin; Marek, M.; Zhang, Yukui; Seidel‐Morgenstern, A.; Tallarek, Ulrich

doi:10.1002/ceat.200401939

Cited by 14 publications

(12 citation statements)

References 115 publications

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“…A 500 lm id glass-lined metal tubing was used as the slurry reservoir. SSI two-way and three-way valves (ERC, Riemerling, Germany) were placed between the pneumatic pump and slurry reservoir for pressure release and slurry injection, respectively [33]. An in-line MicroFilter with a PEEK polymer frit (Upchurch Scientific, Oak Harbor, WA) was connected to the capillary outlet before the packing process started.…”

Section: Preparation Of Packed Capillariesmentioning

confidence: 99%

Packing density of slurry‐packed capillaries at low aspect ratios

Ehlert

Rösler

Tallarek³

2008

J of Separation Science

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The average interparticle voidage or porosity (epsilon(inter)) in cylindrical capillaries is studied in dependence on the column diameter (d(c)) to particle diameter (d(p)) ratio for 5 < d(c)/d(p) < 50. Using optimized slurry and packing solvents, high pressure and ultrasonication, 5 mum-sized porous C18-silica particles were slurry-packed into fused-silica capillaries having ids from 30 to 250 mum. Packing densities are assessed by a polystyrene standard which is size-excluded from the intraparticle pore space of the packings. For d(c)/d(p) > 35 densely packed beds are realized (epsilon(inter) = 0.36-0.37), while for decreasing aspect ratios an exponential increase in epsilon(inter )is observed reaching epsilon(inter ) approximately 0.47 at d(c)/d(p) = 5. This behaviour is ascribed to a combination of the geometrical wall effect operating in the direct vicinity of the column wall, caused by the inability of the particles to form a dense packing against the hard surface of the column wall, and particle characteristics like the size distribution, shape and surface roughness. Results are compared with the literature data to address also the importance of absolute particle size in studying structure-transport relations in packed beds in dependence on the aspect ratio d(c)/d(p).

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Section: Preparation Of Packed Capillariesmentioning

confidence: 99%

Packing density of slurry‐packed capillaries at low aspect ratios

Ehlert

Rösler

Tallarek³

2008

J of Separation Science

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“…To summarize, the dependence of m av in packed beds is a consequence of basically three contributions [109,110]: (i) normal or conventional EDL behavior at the particles' external surface, leading to a decrease of mobility with increasing ionic strength, (ii) generation of intraparticle volumetric EOF (increasing with increasing ionic strength), and (iii) the porosity of a particle. The last contribution results from the fact that conducting electrolyte in the particle introduces a normal component to the electrical field at its outer surface.…”

Section: Electroosmotic Perfusive Flow In Packed Beds Of Porous Partimentioning

confidence: 99%

“…An important parameter for analyzing intraparticleforced convection with EOF in packed beds of porous particles is the intraparticle EDL overlap represented by r intra /l D [20,42,[109][110][111], where r intra denotes the mean pore radius. The results of detailed experimental studies of the electroosmotic mobility (m av ) in packed beds of particles with different intraparticle porosities and pore sizes are shown in Fig.…”

Section: Electroosmotic Perfusive Flow In Packed Beds Of Porous Partimentioning

confidence: 99%

Fluid dynamics in capillary and chip electrochromatography

Nischang

Tallarek

2007

Electrophoresis

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This review is concerned with the phenomenological fluid dynamics in capillary and chip electrochromatography (EC) using high-surface-area random porous media as stationary phases. Specifically, the pore space morphology of packed beds and monoliths is analyzed with respect to the nonuniformity of local and macroscopic EOF, as well as the achievable separation efficiency. It is first pointed out that the pore-level velocity profile of EOF through packed beds and monoliths is generally nonuniform. This contrasts with the plug-like EOF profile in a single homogeneous channel and is caused by a nonuniform distribution of the local electrical field strength in porous media due to the continuously converging and diverging pores. Wall effects of geometrical and electrokinetic nature form another origin for EOF nonuniformities in packed beds which are caused by packing hard particles against a hard wall with different zeta potential. The influence of the resulting, systematic porosity fluctuations close to the confining wall over a distance of a few particle diameters becomes aggravated at low column-to-particle diameter ratio. Due to the hierarchical structure of the pore space in packed beds and silica-based monoliths which are characterized by discrete intraparticle (intraskeleton) mesoporous and interparticle (interskeleton) macroporous spatial domains, charge-selective transport prevails within the porous particles and the monolith skeleton under most general conditions. It forms the basis for electrical field-induced concentration polarization (CP). Simultaneously, a finite and -- depending on morphology -- often significant perfusive EOF is realized in these hierarchically structured materials. The data collected in this review show that the existence of CP and its relative intensity compared to perfusive EOF form fundamental ingredients which tune the fluid dynamics in EC employing monoliths and packed beds as stationary phases. This addresses the (electro)hydrodynamics, associated hydrodynamic dispersion, as well as the migration and retention of charged analytes.

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“…In contrast to the dynamic models referred to above, this approach is based upon the modeling of the trajectories of each individual molecule, requires extremely powerful computers in order to compute the motion of a statistically significant number of molecules and is not further considered in this review. Other theoretical work absent from this review includes (i) a stochastic model describing the consequences of wall adsorption in CE [84], (ii) the temperature-dependent interconversion models of dynamic electrophoresis [85][86][87][88], (iii) the simulation model for electroinjection analysis and electrophoretically mediated microanalysis [89], (iv) the affinity electrophoresis models of Andreev et al [90] and Fang and Chen [91][92][93][94], which describe affinity interactions in CE under simplified electromigration conditions, (v) the models of Cann and coworkers describing interacting systems in ZE [95], MBE [96] and IEF [97][98][99], (vi) the models predicting analyte separation in CEC [100][101][102][103][104], (vii) all multi-dimensional models that describe electrokinetically driven mass transport and separations in microfabricated chip devices, such as those of Ermakov et al [105], Bianchi et al [106], Chatterjee [107], Sounart and Baygents [108], Datta and Ghosal [109] and Hirokawa et al [110], (viii) the model of electrokinetic sample injection for capillary CZE with consideration of the electrode configuration [111], (ix) the models that predict sample zone formation, distortion and solute separation in continuous flow electrophoresis [112,113] and recycling electrophoresis [114][115][116], (x) the models describing off-gel electrophores...…”

Section: Introductionmentioning

confidence: 99%

Dynamic computer simulations of electrophoresis: A versatile research and teaching tool

et al. 2010

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Software is available, which simulates all basic electrophoretic systems, including moving boundary electrophoresis, zone electrophoresis, ITP, IEF and EKC, and their combinations under almost exactly the same conditions used in the laboratory. These dynamic models are based upon equations derived from the transport concepts such as electromigration, diffusion, electroosmosis and imposed hydrodynamic buffer flow that are applied to user-specified initial distributions of analytes and electrolytes. They are able to predict the evolution of electrolyte systems together with associated properties such as pH and conductivity profiles and are as such the most versatile tool to explore the fundamentals of electrokinetic separations and analyses. In addition to revealing the detailed mechanisms of fundamental phenomena that occur in electrophoretic separations, dynamic simulations are useful for educational purposes. This review includes a list of current high-resolution simulators, information on how a simulation is performed, simulation examples for zone electrophoresis, ITP, IEF and EKC and a comprehensive discussion of the applications and achievements.

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Dynamics of Capillary Electrochromatography: Experimental Study of Flow and Transport in Particulate Beds

Cited by 14 publications

References 115 publications

Packing density of slurry‐packed capillaries at low aspect ratios

Packing density of slurry‐packed capillaries at low aspect ratios

Fluid dynamics in capillary and chip electrochromatography

Dynamic computer simulations of electrophoresis: A versatile research and teaching tool

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