Optimization of cyclical electrical field flow fractionation

Merugu, Srinivas; Sant, Himanshu; Gale, Bruce K.

doi:10.1002/elps.201000024

Cited by 10 publications

(11 citation statements)

References 33 publications

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“…In most of CyElFFF studies 50% duty cycle voltage waveforms were used as the input voltages [4,8,[15][16][17][18]26,27]. Recently it has been shown that using higher duty cycle waveforms produces longer retention times [28].…”

Section: Simulation 3-investigation Of the Particle Retention Time Fomentioning

confidence: 99%

“…However, CyElFFF is a more complex technique relative to traditional ElFFF, and requires optimization of parameters such as amplitude, frequency, waveform shape, duty cycle and offset of the applied voltage. In addition to the electrical parameters; flow speed, carrier ionic strength and dimensions of the separation channel have significant effects on the separation resolution, and require careful selection [8].…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have examined optimal operating conditions of ElFFF systems. For instance, electric circuit modeling of an ElFFF system has been used to help determine the proper estimation of the electric field (effective field) inside the channel [8][9][10][11]. Analytical and numerical models have been created to estimate separation efficiency under different operating conditions [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

“…Analytical and numerical models have been created to estimate separation efficiency under different operating conditions [12][13][14][15]. Furthermore, several experimental studies have been done to analyze the effects of different experimental parameters on the separation performance [8,[16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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Particle Based Modeling of Electrical Field Flow Fractionation Systems

et al. 2015

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Electrical Field Flow Fractionation (ElFFF) is a sub method in the field flow fractionation (FFF) family that relies on an applied voltage on the channel walls to effect a separation. ElFFF has fallen behind some of the other FFF methods because of the optimization complexity of its experimental parameters. To enable better optimization, a particle based model of the ElFFF systems has been developed and is presented in this work that allows the optimization of the main separation parameters, such as electric field magnitude, frequency, duty cycle, offset, flow rate and channel dimensions. The developed code allows visualization of individual particles inside the separation channel, generation of realistic fractograms, and observation of the effects of the various parameters on the behavior of the particle cloud. ElFFF fractograms have been generated via simulations and compared with experiments for both normal and cyclical ElFFF. The particle visualizations have been used to verify that high duty cycle voltages are essential to achieve long retention times and high resolution separations. Furthermore, by simulating the particle motions at the channel outlet, it has been demonstrated that the top channel wall should be selected as the accumulation wall for cyclical ElFFF to reduce band broadening and achieve high efficiency separations. While the generated particle based model is a powerful OPEN ACCESS Chromatography 2015, 2 595 tool to estimate the outcomes of the ElFFF experiments and visualize particle motions, it can also be used to design systems with new geometries which may lead to the design of higher efficiency ElFFF systems. Furthermore, this model can be extended to other FFF techniques by replacing the electrical field component of the model with the fields used in the other FFF techniques.

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Section: Simulation 3-investigation Of the Particle Retention Time Fomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Particle Based Modeling of Electrical Field Flow Fractionation Systems

et al. 2015

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“…ElFFF is normally performed using a constant direct current (DC) field, which applies the electric field perpendicular to the flow in the channel, but it can also be used with an alternating current (AC) field which generates an oscillatory field. The latter method is called cyclical ElFFF (CyE1FFF). − An oscillatory field generates higher fields than in normal ElFFF, since the field is relatively high while the electrical double layer is forming and only the earliest portions of the field are used. Elution times in CyElFFF depend on generating different trajectories for the moving particles in the channel as a function the applied voltage, applied frequency, and the electrophoretic mobilities of the particles, though recent work has shown the particle size has a significant impact on elution times in many cases. − …”

mentioning

confidence: 99%

Effect of Ionic and Nonionic Carriers in Electrical Field-Flow Fractionation

2016

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A major limitation of electrical field-flow fractionation (ElFFF) is the polarization of the electrodes that occurs when using an ionic carrier liquid. As there is great interest in using ElFFF with biological materials and biological materials typically have high ionic strengths and high osmotic concentrations, we explore the effect of concentration for phosphate buffered saline (PBS), a typical ionic medium for biological samples, and for two nonionic materials common in bioparticle analysis: isopropanol (IPA) and sucrose. Their effect on retention and separations in ElFFF for increasing concentrations was observed. The results suggest that modifying the carrier solution with PBS, sucrose, and/or IPA would enable characterization and separation of biological samples in ElFFF. Specifically, changes of elution time and electrical parameters such as current, conductivity, and bulk channel resistance were observed as functions of carrier ionic and osmotic strength for the different carrier additives. PBS can be used in the micromolar range, equivalent to about 0.1% 1× PBS (150 μM). These concentrations are far from the isotonic condition of PBS (∼ 150 mM) that is normally used with biological samples. However, the nonionic additive carriers IPA and sucrose show quality retention even when added in high concentrations. The results show that IPA could be used in ratios up to 60% and that sucrose can be used in concentrations up to 0.3 M. Concentrations of 2% IPA (0.26 M) and 0.30 M sucrose are biologically isotonic conditions (275-299 mOsm/kg), and retention was readily obtained in these conditions using both DC ElFFF and cyclical ElFFF (CyE1FFF). Carriers of this type may make it possible to use ElFFF with biological samples.

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A novel method for effective field measurements in electrical field‐flow fractionation

2012

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The electric field that drives separation and retention in electrical field flow fractionation (ElFFF) and cyclical electrical field-flow fractionation (CyElFFF) is a complex function of many parameters such as carrier ionic strength and pH, voltage, channel dimensions, flowrate, and electrode material. Currently there is no accurate or in situ method to measure the field during system operation. This paper introduces a technique to measure the effective electric field during ElFFF and CyElFFF operation using transient electrical spikes. With this technique we can determine the relationship between changes in carrier conductivity and flowrate during a run and their combined effect on effective field and retention in ElFFF. This technique can also be used to measure the voltage drop due to double layer capacitance in CyElFFF and the variation in effective field with frequency of the applied field. The measured effective fields for the CyElFFF and DC ElFFF techniques are also tested with a high ionic-strength buffer solution as carrier. For a high ionic-strength buffer, DC ElFFF generates a near-zero effective field (0.2% in 100 s), whereas CyElFFF can sustain much higher effective fields (~8%) even at relatively high voltages. The ability to measure the effective field allows for experiments to provide better data and for tuning and optimization of the separation run.

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Optimization of cyclical electrical field flow fractionation

Cited by 10 publications

References 33 publications

Particle Based Modeling of Electrical Field Flow Fractionation Systems

Particle Based Modeling of Electrical Field Flow Fractionation Systems

Effect of Ionic and Nonionic Carriers in Electrical Field-Flow Fractionation

A novel method for effective field measurements in electrical field‐flow fractionation

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