Preparation and Characterization of Gold Nanoparticle-Modified Silica Monolith for Capillary Electrochromatography

A novel silica monolithic stationary phase functionalized with octadecanethiol gold nanoparticles (GNPs) was prepared for capillary electrochromatography (CEC). The bare silica monolith was prepared by a sol-gel process and then modified chemically with 3-mercaptopropyltrimethoxysilane, followed by immobilization of GNPs and modification by octadecanethiol. The relationship between plot of plate height and the linear velocity on octadecanethiol GNPs-modified silica monolith (Silica-GNPs-C18) was investigated, and a minimum plate height of about 7.8 μm for toluene was obtained. The electroosmotic flow characteristics of the Silica-GNPs-C18 and bare silica monolith (Silica) were studied by varying the percentage of organic modifier in buffer and buffer pH. To evaluate the column performance, hydrophobic alkylbenzenes as model compounds were tested on the prepared Silica, thiol-modified silica monolith (Silica-SH), and Silica-GNPs-C18. The electrochromatographic retention behavior of alkylbenzenes on Silica-GNPs-C18 column was also investigated. The experiment results showed that Silica-GNPs-C18 column exhibits typical reversed-phase electrochromatographic behavior toward neutral solutes. Reversed-phase CEC separations of four selected polar phenols were also demonstrated on Silica-GNPs-C18 column using mobile phase containing 15% methanol.