Electrokinetics represents an extremely versatile family of techniques that can be used to manipulate particles and fluid in microfluidic devices. This dissertation focused on taking techniques commonly used on a macroscale and developing microscale equivalents utilizing electrokinetics to effectively manipulate and separate microparticles. This analysis focuses on chromatography and separation trains as macroscale techniques translated to microfluidic insulator-based electrokinetic devices. The geometries of insulating post arrays embedded in microchannels were optimized using a combination of mathematical simulations and experimentally derived correction factors. Two particle separations were experimentally demonstrated: a separation based on differences in particle size and a separation based on differences in particle charge. The introduction of nonlinear electrophoresis into the electrokinetics paradigm prompted the creation of an empirical electrokinetic equilibrium condition, an experimentally derived, geometry independent value unique to different particles. This term takes into account particle-particle interactions and the presence of an electric field gradient to help simulate the impact of nonlinear electrophoresis on particle motion and provide an estimate trapping voltages for particles using similar suspending media. Finally, a cascade device design was presented as a type of separation train, built to filter larger contaminants from complex particle suspensions. Sample purification for a scheme involving manual device transferring of sample versus the cascade device, which required no manual transfer, demonstrated a notably lower sample loss in the cascade device. Bacteriophages were effectively enriched using the cascade scheme, demonstrating the potential use of this technique for purifying valuable biological samples
