Analysis of silica nanoparticles by capillary electrophoresis coupled to an evaporative light scattering detector

A simple and rapid methodology has been developed to identify and separate silica nanoparticles (SiO₂NPs) of different sizes in aqueous solution by capillary zone electrophoresis coupled to an evaporative light scattering detector (CE-ELSD). SiO₂NPs were separated using 3 mM ammonium acetate buffer, containing 1% methanol at pH 6.9. SiO₂NPs of 20, 50 and 100 nm were successfully separated under the optimum experimental conditions. CE coupled to ELSD has been proven to be an effective separation technique to determine particles with such small sizes, although the peaks are very close to each other, and it is a promising technique that may allow the separation of other types of nanoparticles. Confirmation by TEM and quantification of the SiO₂ content was also carried out by inductively coupled plasma-mass spectrometry (ICP-MS). The new method was applied to the analysis of real samples, in order to assess its ability to avoid matrix effects in the determination of SiO₂NPs in these kinds of samples.