Electrokinetic Effects on the Transport of Charged Analytes in Biporous Media with Discrete Ion-Permselective Regions

Leinweber, Felix C.; Pfafferodt, Matthias; Seidel‐Morgenstern, A.; Tallarek, Ulrich

doi:10.1021/ac050609o

Cited by 29 publications

(37 citation statements)

References 52 publications

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“…Indeed, charge-selectivity is a rather ubiquitous phenomenon. In this respect, the EDL thickness dimensions, but remains comparable to the mesopore sizes (with d pore L 10 nm) [86]. Due to the macropore dimensions, the interparticle or interskeleton macropore space (consequently, a packed bed or the monolith as a whole) is charge-nonselective.…”

Section: Introductionmentioning

confidence: 91%

Ionic conductance of nanopores in microscale analysis systems: Where microfluidics meets nanofluidics

Höltzel

Tallarek²

2007

J of Separation Science

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143

153

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In this tutorial review we illustrate the origin and dependence on various system parameters of the ionic conductance that exists in discrete nanochannels as well as in nanoporous separation and preconcentration units contained as hybrid configurations, membranes, packed beds, or monoliths in microscale liquid phase analysis systems. A particular complexity arises as external electrical fields are superimposed on internal chemical and electrical potential gradients for tailoring molecular transport. It is demonstrated that the variety of geometries in which the microfluidic/nanofluidic interfaces are realized share common, fundamental features of coupled mass and charge transport, but that phenomena behind the key steps in a particular application can be significantly tuned, depending on the morphology of a material. Thus, the understanding of morphology-related transport in internal and external electrical potential gradients is critical to the performance of a device. This addresses a variety of geometries (slits, channels, filters, membranes, random or regular networks of pores, etc.) and applications, e. g., the gating, sensing, preconcentration, and separation in multifunctional miniaturized devices. Inherently coupled mass and charge transport through ion-permselective (charge-selective) microfluidic/nanofluidic interfaces is analyzed with a stepwise-added complexity and discussed with respect to the morphology of the charge-selective spatial domains. Within this scenario, the electrostatics and electrokinetics in microfluidic and nanofluidic channels, as well as the electrohydrodynamics evolving at microfluidic/nanofluidic interfaces, where microfluidics meets nanofluidics, define the platform of central phenomena.

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Section: Introductionmentioning

confidence: 91%

Ionic conductance of nanopores in microscale analysis systems: Where microfluidics meets nanofluidics

Höltzel

Tallarek²

2007

J of Separation Science

Self Cite

143

153

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“…Transport of charged species in the CP zones is diffusion limited. In multiparticle systems like packed beds, CP zones develop around each spatially discrete particle [43][44][45][46][47]65]. CP has been intensively investigated in membrane science over the past decades.…”

Section: Electrical-field-dependent Retentionmentioning

confidence: 99%

“…Compared with the unpacked capillaries used in CZE, coupled mass and charge transport in packed capillaries are much more complex due to concentration polarization (CP), which is induced locally around any stationary phase particle of the bed by the applied electrical field [43][44][45][46][47]. CP originates in electrical double layer (EDL) overlap inside the charged pores of porous particles that are characterized by mesopore (and even micropore) sizes.…”

Section: Introductionmentioning

confidence: 99%

“…It involves the formation of background ion concentration gradients at charge-selective interfaces upon the passage of an electrical current normal to these interfaces [50]. CP for a cation-selective stationary phase particle is characterized by a depleted CP zone along its anodic hemisphere, where counterions enter the particle in the direction of the applied field, and an enriched CP zone along its cathodic hemisphere, where counterions leave the particle [43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

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Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Nischang¹,

Höltzel²,

Tallarek³

2010

Electrophoresis

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We analyze the systematic and substantial electrical field-dependence of electrochromatographic retention for four counterionic peptides ([Met5]enkephalin, oxytocin, [Arg8]vasopressin, and luteinizing hormone releasing hormone (LHRH) ) on a strong cation-exchange (SCX) stationary phase. Our experiments show that retention behavior in the studied system depends on the charge-selectivity of the stationary phase particles, the applied voltage, and the peptides' net charge. Retention factors of twice positively charged peptides ([Arg8]vasopressin and LHRH at pH 2.7) decrease with increasing applied voltage, whereas lower charged peptides (oxytocin and [Met5]enkephalin at pH 2.7, [Arg8]vasopressin and LHRH at pH 7.0) show a concomitant increase in their retention factors. The observed behavior is explained on the basis of electrical fieldinduced concentration polarization (CP) that develops around the SCX particles of the packing. The intraparticle concentration of charged species (buffer ions, peptides) increases with increasing applied voltage due to diffusive backflux from the enriched CP zone associated with each SCX particle. For twice charged and on the SCX phase strongly retained peptides the local increase in mobile phase ionic strength reduces the electrostatic interactions with the stationary phase, which explains the decrease of retention factors with increasing applied voltage and CP intensity. Lower charged and weaker retained peptides experience a much stronger relative intraparticle enrichment than the twice-charged peptides, which results in a net increase of retention factors with increasing applied voltage. The CP-related contribution to electrochromatographic retention of peptides on the SCX stationary phase is modulated by the applied voltage, the mobile phase ionic strength, and the peptides' net charge and could be used for selectivity tuning in difficult separations.

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“…The mass transfer rate from inter-particle to intraparticle could be influenced by the CP and documented by Tallarek and coworkers [20][21][22][23]. The EF induces depleted and enriched zones of charged molecules around one single particle when electric double layer (EDL) overlap occurs.…”

Section: Control Equation In Single Beadmentioning

confidence: 99%

Protein adsorption‐dependent electro‐kinetic pore flow: Modeling of ion‐exchange electrochromatography with an oscillatory transverse electric field

et al. 2010

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Electro-kinetic acceleration of protein mass transfer was studied by dynamic chromatographic experiments and computer simulations on IEC with an oscillatory transverse electric field (EF) perpendicular to the mobile-phase flow (pIEEC). The breakthrough behavior of BSA was investigated at different electric current densities. A two-dimensional mathematical model has been established to describe the electro-kinetic convection-diffusion behavior of protein adsorption in a single adsorbent particle. The equation was coupled with the axial dispersion model to simulate the dynamic adsorption process in the pIEEC. The model parameters were determined by independent experiments or calculations. It was found that protein adsorption led to an exponential decrease of intraparticle electro-kinetic flow with increasing protein adsorption. Taking this effect into consideration, the model calculations could well describe dynamic breakthrough curves. Moreover, protein distribution in adsorbents was observed to present excursion along the periodical oscillatory EF direction. At the beginning of pIEEC, intraparticle convection caused by the EF contributed more to the enhancement of dynamic binding capacity. Finally, it was confirmed that both the EOF and electrophoresis contributed to the acceleration of mass transfer.

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Electrokinetic Effects on the Transport of Charged Analytes in Biporous Media with Discrete Ion-Permselective Regions

Cited by 29 publications

References 52 publications

Ionic conductance of nanopores in microscale analysis systems: Where microfluidics meets nanofluidics

Ionic conductance of nanopores in microscale analysis systems: Where microfluidics meets nanofluidics

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Protein adsorption‐dependent electro‐kinetic pore flow: Modeling of ion‐exchange electrochromatography with an oscillatory transverse electric field

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