Abstract
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 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.
Highlights
Separation and characterization of nanoparticles can be effectively achieved by the family of separation techniques called field flow fractionation (FFF) [1]
The UV fractograms obtained from the normal Electrical Field Flow Fractionation (ElFFF) experiments and simulations (Figure 5a,b, respectively), demonstrate that increased input voltage yields increased retention time of the particles, and this trend is successfully predicted by the simulations
cyclical electrical field flow fractionation (CyElFFF) experiments and simulations (Figure 6) demonstrate that peak positions are in close agreement among measured and simulated fractograms
Summary
Separation and characterization of nanoparticles can be effectively achieved by the family of separation techniques called field flow fractionation (FFF) [1]. In this method, a separation field is applied perpendicular to the parabolic flow inside a parallel plate channel. Electrical field flow fractionation (ElFFF) is one of the members of the FFF family, in which an electric field is applied across the separation channel [2]. In this technique, particles are separated based on their size and electrophoretic mobility. Given that ElFFF does not include a membrane, ions remain inside the channel during the ElFFF separation
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