(148c) Development of Carbon Phases On Porous Alumina for Use as Separation Media in HPLC

Carbonaceous materials are of interest as separation media due to their thermal stability and unique selectivity including the ability to separate structural isomers. Commercial carbon-clad zirconia (C/ZrO₂) has been widely used for many applications, including two-dimensional liquid chromatography (2DLC), which shows tremendous separation power for complex biological samples. However, its limited retentivity - attributed to the low surface area available with commercial porous zirconia (20 - 30 m²/g) ? limits practical application in 2DLC. We have recently addressed this problem by developing carbon phases on high surface area porous alumina (Al₂O₃, 153 m²/g, 5 μm) by chemical vapor deposition (CVD) using hexane vapor as the carbon source at elevated temperature. Carbon layers are formed throughout the pores, and the loading of carbon was varied by changing the CVD time and temperature. At all carbon loadings, C/Al₂O₃ closely matched the unique chromatographic selectivity of carbon phases. More uniform coating of carbon layers is achieved on Al₂O₃ as it requires less monolayers of carbon (5 monolayers) to fully cover the oxide in C/Al₂O₃ than does in C/ZrO₂ (11 monolayers). The resulting material is chromatographically useful as it provides good efficiency and higher retentivity than does C/ZrO₂.