[Separation performance of 1-microm silica particles as stationary phase for pressurized electrochromatography]

Bare nonporous silica particles with diameter around 1 microm were prepared. A 20 cm section of a total length of 45 cm capillary (100 microm i. d.) was packed electrokinetically and the separation performance of basic compounds was investigated in the pressurized capillary electrochromatography (pCEC) system using 1 microm nonporous bare silica spheres as stationary phase and acetonitrile-water as mobile phase. The effects of the composition of the mobile phase, the concentration of the buffer, pH value, applied voltage and so on on the separation performance were investigated. The experimental results demonstrated that the bare silica column showed a typical reversed phase separation mechanism when it was used for separation of basic compounds. The separation performance changed slightly with changing buffer concentration. Since the degree of dissociation of the basic compounds depended greatly on the pH value, the interaction between the compounds and stationary phase changed with the changing of pH value, thereby changing the resolution of the compounds. The separation performance increased with the increase of applied voltage. A column efficiency of 35 000 for o-toluidine was obtained when a voltage of 1 kV was applied.