Electrokinetic preconcentration of magnetite core - carboxylic shell nanoparticles by capillary electrophoresis

Online electrokinetic preconcentration of magnetite core/carboxylic shell nanoparticles (MNPs) was studied by capillary electrophoresis using reversed and suppressed electroosmotic flow (EOF). 50mM sodium borate pH 9.5 was used as a background electrolyte. CTAB additive was used to reverse EOF and commercial polyvinylalcohol (PVA)-coated capillaries were used for EOF suppressed studies. Analyses in PVA-coated capillaries were more reproducible and therefore, the setup was further optimized in terms of water plug injection time, sample injection time, and voltage. Within the optimal conditions, the MNPs dispersed in water are electrokinetically loaded into BGE consisting of 50mM sodium borate pH 9.5 using -10kV for 120s. In comparison with the hydrodynamic injection of 5s by 50mbar, the electrokinetic injection allows 860-fold preconcentration of MNPs.