Open-tubular capillary electrochromatography using carboxylatopillar[5]arene as stationary phase.

Pillar[n]arenes have achieved much interest in material chemistry and supramolecular chemistry due to unusual pillar shape structure and high selectivity toward guest. However, pillar[n]arenes have not yet been applied in capillary electrochromatography. This work at first time reports that carboxylatopillar[5]arene is used as a stationary phase in open-tubular capillary electrochromatography. Carboxylatopillar[5]arene not only possess the advantages of pillar[n]arenes but also provide free carboxy groups for immobilizing on the inner wall of capillary column via covalent bonding. The characterization of SEM and FT-IR indicated that carboxylatopillar[5]arene was successfully grafted on the inner wall of capillary. The baseline separation of model analytes including neutral, basic, and acidic compounds, nonsteroidal anti-inflammatory drugs and dansyl-amino acids have been achieved thanks to the electron-rich cavity of carboxylatopillar[5]arene and hydrophobic interactions between the analytes and stationary phase. The intraday, interday, and column-to-column precisions (RSDs) of retention time and peak area for the neutral analytes were all less than 3.34 and 9.65%, respectively. This work indicates that pillar[n]arenes have great potential in capillary electrochromatography as novel stationary phase.