Homogeneous Edge-Plane Carbon as Stationary Phase for Reversed-Phase Liquid Chromatography

Carbon stationary phases have been widely used in HPLC due to their unique selectivity and high stability. Amorphous carbon as a stationary phase has at least two sites of interaction with analytes: basal-plane and edge-plane carbon sites. The polarity and adsorptivity of the two sites are different. In this work, the edge-plane carbon stationary phase is prepared by surface-directed liquid crystal assembly. Specific precursor polymers form discotic liquid crystal phases during the pyrolysis process. By using silica as the substrate to align the discotic liquid crystal, edge-plane carbon surfaces were formed. Similar efficiencies as observed for Hypercarb were observed in chromatograms. The column efficiency was studied as a function of linear flow rate. A minimum reduced plate height of 6 was observed in these studies. To evaluate the performance of the homogeneous edge-plane carbon stationary phase, linear solvation energy relationships were used to compare these ordered carbon surfaces to commercially available carbon stationary phases, including Hypercarb. Reversed-phase separations of nucleosides, nucleotides, and amino acids and derivatives were demonstrated using the ordered carbon surfaces, respectively. The column batch-to-batch reproducibility was also evaluated. The retention times for the analytes were reproducible within 1-6% depending on the analyte.