A high-efficiency capillary electrophoresis-based method for characterizing the sizes of Au nanoparticles

In this paper, we present a highly efficient capillary electrophoresis (CE)-based method for characterizing the sizes of Au nanoparticles (NPs). We used the reversed electrode polarity stacking mode (REPSM) of CE for on-line enhancement of the detection and separation of Au NPs. Under the on-line enhancement separation conditions [buffer: SDS (70 mM) and 3-cyclohexylamino-1-propanesulfonic acid (10 mM) at pH 10.0; applied voltage: 20 kV; using the REPSM for sample concentration], the detection sensitivity toward the Au NPs improved by up to 260-fold. A linear relationship (R2 = 0.994) existed between the electrophoretic mobilities and the sizes of the Au NPs within the range of diameters from 5.3 to 59.9 nm; the relative standard deviations of the electrophoretic mobilities for these NPs were below 0.6%. When using these conditions to analyze Au NPs produced through seed-assisted synthesis, a good correlation existed between the sizes obtained using CE and those provided by transmission electron microscopy. Furthermore, the analyses performed using CE were rapid (<4 min) and required very low sample volumes (several nanoliters), yet they proceeded with high sensitivity. These findings confirm that CE is an efficient tool for characterizing the sizes of NPs.