Analytical Sciences

Capillary Electrochromatography on Monolithic Silica Columns

Hiroshi KOBAYASHI,* Chris SMITH,** Ken HOSOYA,* Tohru IKEGAMI,* and Nobuo TANAKA* 

*Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto 606-8585, Japan
**Centers for Disease Control, 4770 Buford Highway, Atlanta, GA 30341-3724, U.S.A.

Monolithic silica columns prepared from tetramethoxysilane in a fused-silica capillary was octadecylsilylated, and evaluated by capillary electrochromatography. A plate height of 3 - 4 um was obtained in an 80% acetonitrile-20% aqueous buffer (pH 8) under optimized conditions. An ODS phase having a high surface coverage, prepared by using octadecyldimethylchlorosilane, resulted in slow separation and a low column efficiency due to a slow electroosmotic flow. The results show that faster separation is achieved (i) with an ODS phase with a low surface coverage, (ii) with an ODS phase prepared by using octadecyltrichlorosilane, or (iii) by pressure-assisted CEC utilizing the high permeability of monolithic silica columns.

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