Perspective on concentration polarization effects in electrochromatographic separations

Tallarek, Ulrich; Leinweber, Felix C.; Nischang, Ivo

doi:10.1002/elps.200406167

Cited by 33 publications

(50 citation statements)

References 47 publications

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“…In the results reported by Tallarek and co-workers [32,33], a plate height decrease from 4 to 2 mm was observed at very low buffer concentration with a very slightly retained compound (k = 0.1). The authors explained this difference by a lateral mixing of the solutes due to the EOF-2.…”

Section: Comparison Of the Electrochromatographic Behavior Of The W-smentioning

confidence: 69%

“…Like the C 18 SMCs tested by Tallarek and co-workers [32,33], our underivatized W-SMC present a specific and unusual behavior in terms of EOF. The nonlinearity of the EOF velocity versus electrical field is typical of the existence of EOF-2 that allows reaching higher mobile phase velocities with high column efficiency.…”

Section: Discussionmentioning

confidence: 80%

“…When electrical double layer overlap occurs in the mesopores of the material (i.e., for small ionic strength) the macropore-mesopore interface behaves like a counterion-permselective membrane under the normal electrical field component. Furthermore, the coions are expelled from the mesopores and cannot be compensated due to counterion-permselective behavior of the mesopores [32,33]. Since the coions are expelled from the mesopores, the ionic strength is weaker in the mesopores than in the bulk solution.…”

Section: Comparison Of the Electrochromatographic Behavior Of The W-smentioning

confidence: 95%

“…Although the theoretical aspects of EOF-2 have been extensively reviewed in the literature, only few articles have brought it to the fore experimentally through CEC experiments [32,33]. To look at the influence of the SMC synthesis on the EOF-2 by tuning the skeleton size, the EOF velocities were determined at different buffer concentrations and voltages with 2 h water W-SMC-1 and W-SMC-2 by CEC experiments.…”

Section: Comparison Of the Electrochromatographic Behavior Of The W-smentioning

confidence: 99%

“…The second goal was to study the influence of the skeleton size of the SMCs (synthesized with this simplified method) in CEC in term of EOF of the second kind and efficiency. Although the existence of the EOF of the second kind (EOF-2) was demonstrated with isolated ionic particles by Dukhin [27] and then confirmed by Mishchuk and co-workers [28][29][30][31], only few recent papers have demonstrated [32,33] its existence in the case of SMCs in CEC.…”

Section: Introductionmentioning

confidence: 97%

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Electrochromatographic behavior of silica monolithic capillaries of different skeleton sizes synthesized with a simplified and shortened sol–gel procedure

et al. 2006

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Silica monolithic capillaries (SMCs) were synthesized by a sol-gel process. First, a simplification of the synthesis was proposed by replacing the calcination and the drying steps which can have tremendous effects on chromatographic and physical properties, by a single water or methanol 2 h washing step. The efficiency of such a washing step was demonstrated and the comparison of the chromatographic and electrochromatographic properties between calcined and washed SMCs has shown that such a modification did not impair retention, efficiency, and stability of the monolith. This simplified procedure was carried out to synthesize SMCs with two different skeleton sizes. These capillaries were evaluated in electrochromatography and present high efficiencies (H = 5 microm) at least equal to the best ones reported in the literature. Furthermore, the influence of the skeleton size on the EOF of the second kind (EOF-2) was investigated with unmodified SMCs used under various experimental conditions including electrical field strength and buffer concentration. The ionic strength of the mobile phase and the applied electrical field that enable this EOF-2 were related to the size of the skeleton which was tuned by the synthesis conditions.

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Section: Comparison Of the Electrochromatographic Behavior Of The W-smentioning

confidence: 69%

Section: Discussionmentioning

confidence: 80%

Section: Comparison Of the Electrochromatographic Behavior Of The W-smentioning

confidence: 95%

Section: Comparison Of the Electrochromatographic Behavior Of The W-smentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Electrochromatographic behavior of silica monolithic capillaries of different skeleton sizes synthesized with a simplified and shortened sol–gel procedure

et al. 2006

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Retention behavior of proteins in size‐exclusion electrochromatography with a low‐voltage electric field perpendicular to the liquid phase streamline

2005

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A novel preparative size-exclusion electrochromatography with an oscillatory low-voltage electric field perpendicular to the liquid phase streamline (pSEEC) was proposed with a column design of rectangular cross-section. The column of 12 cm length was packed with Sephadex G-75, and the retention behavior of bovine serum albumin (BSA) and myoglobin (Myo) was extensively investigated under various conditions. The results indicated that the partition coefficient of a charged protein increased significantly on increasing the current strength as well as the difference between its pI and pH. The partition coefficient also increased on decreasing the mobile phase conductivity. For the gel-excluded protein like BSA, the concentration polarization (CP) on the gel surface induced by the protein electromigration was the main reason for the increased retention. For a gel-permeable protein like Myo, both the CP and electrophoretic migration in the solid phase contributed to its increased retention. Further results exhibited that the polarization would be offset by diffusion, because the accumulated protein would flux back to the bulk liquid phase. Therefore, when the electrically induced mass flux was equal to the diffusion flux, the partition coefficient did not change with a further increase of the oscillatory current cycle. Finally, pSEEC was compared with SEC in the separation of protein mixtures of BSA/Myo as well as BSA/Myo/lysozyme. The results showed much better resolutions of the protein mixtures in pSEEC with the column as short as 12 cm. The potential of pSEEC for preparative protein separation was therefore demonstrated.

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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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Perspective on concentration polarization effects in electrochromatographic separations

Cited by 33 publications

References 47 publications

Electrochromatographic behavior of silica monolithic capillaries of different skeleton sizes synthesized with a simplified and shortened sol–gel procedure

Electrochromatographic behavior of silica monolithic capillaries of different skeleton sizes synthesized with a simplified and shortened sol–gel procedure

Retention behavior of proteins in size‐exclusion electrochromatography with a low‐voltage electric field perpendicular to the liquid phase streamline

Fluid dynamics in capillary and chip electrochromatography

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