Gold microspheres modified with octadecanethiol for capillary liquid chromatography

Monodispersed spherical gold particles synthesized and modified with n-octadecanethiol (C18-Au) were packed into a 100 μm I.D. capillary column and tested in capillary high-performance liquid chromatography (μHPLC). To the best of our knowledge, this represents the first report on the actual use of micron gold particles as stationary phase in a packed column μHPLC. As measured by scanning electron microscopy, the average diameter of these gold microspheres was 3.5 μm and the surface area, average pore diameter, and average pore volume were 49.4 m2/g, 4.8 nm, and 0.12 cm3/g, respectively. The retention behavior of neutral compounds on the n-octadecanethiol-modified gold microspheres was investigated by separating a mixture of small organic compounds using μHPLC. The results from the experiments show that C18-Au behaves basically as a reversed phase. The test of chemical stability of the C18-Au stationary phase under alkaline condition demonstrates that it is stable with the flushing of a mobile phase at pH 12 for at least 140 h. The C18-Au particles are also mechanically strong enough to withstand pressure up to 52 MPa. The preliminary results in this work prove the feasibility of the fabrication of C18-Au micron particles as a novel stationary phase for packed column μHPLC.