A novel approach to size separation of gold nanoparticles by capillary electrophoresis–evaporative light scattering detection

Abstract

A simple and rapid methodology to separate and characterize gold nanoparticles (AuNPs) in aqueous medium by capillary electrophoresis-evaporative light scattering detection (CE-ELSD) is presented.First, a controlled synthesis procedure to obtain water-soluble AuNPs, by varying the trisodium citrate concentration was described. These free AuNPs were separated by capillary zone electrophoresis (CZE) based on the differences in the charge-to-mass ratio of the AuNPscitrate in a mixed buffer of ammonium acetate (20 mM), containing tris(hydroxymethyl)-aminomethane (Tris, 20 mM) and 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS; 10 mM) at pH 8.5.Under optimal working conditions, three small different-sized AuNPs were successfully separated whose average sizes were 3.5, 6.5 and 10.5 nm. The average diameter was lower than 1.2 nm for all of them (calculated by high-resolution transmission electron microscopy, TEM). Thus, this CE-based method was able to separate AuNPs that differ by only 3 nm in diameter. It can be a valuable methodology for the rapid and cost-effective characterization of other nanomaterials in the future in aqueous solutions.

DLS and zeta potential – What they are and what they are not?

“…This is a limitation of DLS especially for polydisperse samples. To increase resolution prior size-separation of particles can be done [87]. Latest DLS instruments can be coupled with analytical instruments which enable DLS to determine size of every fraction precisely.…”

Use of capillary electrophoresis for characterisation of vinyl‐terminated Au nanoprisms and nanooctahedra

“…The capillary was reconditioned prior to each sample injection by rinsing with water for 2 min, 0.1 M NaOH for 5 min, water for 5 min and background electrolyte for 5 min, all these steps with a high‐flush pressure of 2 bar. Aqueous buffer solution used for the separation of AuNPs was a mixture of 10 mM Tris with 20 mM SDS at pH 8.5, following the indications of a previous research . AuNPs were introduced into the capillary by positive pressure at 50 mbar for 10 s (approximately 8 nL according to the Poiseuille equation) in a ‘sandwich’ injection with the introduction of buffer at 50 mbar for 10 s before and after the injection of the sample.…”

Improved separation and size characterization of gold nanoparticles through a novel capillary zone electrophoresis method using poly(sodium4‐styrenesulfonate) as stabiliser and a stepwise field strength gradient

“…Completely and highly resolved peak were showed by the authors only for AuNP of larger difference in size (5.3, 40.1, and 59.9 nm . Recently a novel approach to size separation of AuNP by CE coupled to evaporative light scattering detection was reported able to separate particles differing by only 3 nm in diameter . Indeed the electropherogram acquired under the best resolution conditions showed a marked overlapping between the peak corresponding to 6.5 and 10.5 nm sizes.…”

“…Otherwise alternative detection modes have been adopted . CE coupled to ICP‐MS or to evaporative light scattering detection revealed as a high resolution analytical tool. However, the coupling of CE to such detection systems needs the development of a proper interface and the adjustment of various experimental parameters, thus raising the cost and the complexity of the whole instrumentation.…”