Porous Graphitic Carbon in Biomedical Applications

Reversed phase chromatography is the most widely used technique in high-performance liquid chromatography (HPLC) because of its versatility. The column packing material is usually porous silica chemically bonded with a hydrocarbonaceous stationary phase such as butyl-, octyl-, or octadecylsilane. These materials, however, have limited usable pH range (~2-7.5) and they also possess undesired residual silanols due to incomplete coverage or gradual hydrolysis of the bonded phase. Improvements in bonding chemistry have led to silica-based reversed phase packings which are virtually free of residual silanols, e.g., base-deactivated reversed phase, while polymer-based reversed phase materials extended the usable pH range from 2 to ~13. The major drawbacks of polymer-based materials are their instability to high pressure and some of them may swell or shrink depending on the mobile phase used. They are, in general, also less efficient than silica-based materials for the separation of small molecules.