z-Potential analyses using micro-electrical field flow fractionation with fluorescent nanoparticles

Increasingly growing application of nanoparticles in biotechnology requires fast and accessible tools for their manipulation and for characterization of their colloidal properties. In this work we determine the z-potentials for polystyrene nanoparticles using micro-electrical field flow fractionation (k-EFFF) which is an efficient method for sorting particles by size. The data obtained by k-EFFF were compared to z-potentials determined by standard capillary electrophoresis. For proof of concept, we used polystyrene nanoparticles of two different sizes, impregnated with two different fluorescent dyes. Fluorescent emission spectra were used to evaluate the particle separation in both systems. Using the theory of electrophoresis, we estimated the z-potentials as a function of size, dielectric permittivity, viscosity and electrophoretic mobility. The results obtained by the k-EFFF technique were confirmed by the conventional capillary electrophoresis measurements. These results demonstrate the applicability of the k-EFFF method not only for particle size separation but also as a simple and inexpensive tool for measurements of nanoparticle z-potentials.