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

•Importance of EOF modulation with electrokinetic injection of NPs is given.•Electrokinetic injection of carboxylic NPs is possible in PVA-coated capillary.•Amount of injected NPs increases linearly with injection time up to 240 s.•NPs need to be dispersed in water to achieve high preconcentration factors.•Under optimal conditions 860-fold preconcentration are achieved.

Online electrokinetic preconcentration of magnetite core/carboxylic shell nanoparticles (MNPs) was studied by capillary electrophoresis using reversed and suppressed electroosmotic flow (EOF). 50 mM 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 50 mM sodium borate pH 9.5 using −10 kV for 120 s. In comparison with the hydrodynamic injection of 5 s by 50 mbar, the electrokinetic injection allows 860-fold preconcentration of MNPs.