Monitoring the on-line concentration and separation of gold nanoparticles using the reversed electrode polarity stacking mode and micellar electrokinetic chromatography.

In this study, I separated gold nanoparticles (Au NPs) using the reversed electrode polarity stacking mode (REPSM) of a capillary electrophoresis system for on-line enhancement prior to performing micellar electrokinetic chromatography (MEKC). In the first part of this paper, I discuss the effects of several new and important parameters, the nature of the added salt, the pH of the sample matrix, and the size of the injection buffer plug that appears after introducing the samples, on the systems' on-line concentration and separation performance for a variety of sample compositions. In the second part of this paper, I describe my use of the optimized conditions to monitor the migration of the Au NPs during the concentration and separation processes. The results of these studies suggest that combining REPSM with MEKC is a very good strategy for the on-line concentration and separation of Au NPs at trace concentrations.