Carbon nanotube/poly(ethylene‐co‐vinyl acetate) composite electrode for capillary electrophoretic determination of esculin and esculetin in Cortex Fraxini

In this report, a novel carbon nanotube/poly(ethylene‐co‐vinyl acetate) (CNT/EVA) composite electrode was developed for the amperometric detection in CE. The composite electrode was fabricated by packing a mixture of CNTs and melted EVA in a piece of fused‐silica capillary under heat. It was coupled with CE for the separation and detection of esculin and esculetin in Cortex Fraxini, a traditional Chinese medicine, to demonstrate its feasibility and performance. Esculin and esculetin have been well separated within 9 min in a 40 cm long capillary at a separation voltage of 12 kV using a 50 mM borate buffer (pH 9.2). The new CNT‐based CE detector offered significantly lower detection potentials, yielded enhanced S / N characteristics, and exhibited high resistance to surface fouling and enhanced stability. It showed long‐term stability and reproducibility with relative standard deviations of less than 5% for the peak current ( n =15) and should also find a wide range of applications in other microfluidic analysis systems.