| Electrical field flow fractionation (ElFFF) is a separation technique, which separates particles based on electrophoretic mobility and particle size. In this work, we introduce a new approach to measure the effective electric field in ElFFF and CyElFFF techniques, a variation of ElFFF in which cyclical fields are used instead of a DC field. This method is used to determine the relation between change in carrier conductivity in a run with flowrate and their combined effect on effective field and retention in ElFFF. This technique is also used to measure the voltage drop due to double layer capacitance in CyElFFF and variation in effective field with frequency. The measured effective fields for CyElFFF and DC ElFFF technique are also compared for high molarity buffer solution as carrier. For high molarity buffer, DC ElFFF generates near-zero effective field (0.2% in 100 s) whereas CyElFFF can sustain effective field with higher voltage application.;The effective fields measured using this new technique were further used to build a comprehensive numerical modeling of CyElFFF technique. The 2-dimensional semi-empirical method developed using COMSOL multiphysics software accurately predicts the retention times and plate heights for various operating parameters.;CyElFFF was further characterized and optimized to obtain better retention and resolution to increase the overall separation efficiency. The optimization efforts involved quantifying the effects of offset voltage, frequency, flowrate, concentration of particles and sample size on retention, resolution and actual peak/void peak ratio. The optimization efforts also resulted in first particle separations using CyElFFF technique.;Finally, a diffusion-based SPLITT system was fabricated and used towards demonstration of protein separations. This technique has the potential to be used as an additional step in normal dialysis machines to separate toxins that are not effectively separated by current dialysis protocols. The toxins to be removed from the blood are "middle molecule weight toxins" such as beta2 microglobulin (B2M) and parathyroid hormone (PTH), while preserving a significant amount of Human Serum albumin (HSA). |
