Fabrication of a carbon nanotube-polyurethane composite electrode by in situ polyaddition for use in amperometric detection in capillary electrophoresis

The article describes the preparation of an electrode for amperometric detection in capillary electrophoresis (CE). It consists of a copper wire that was coated with a composite consisting of carbon nanotubes and polyurethane that was fabricated by in-situ polyaddition from a mixture of polyurethane prepolymer, curing agent, and carbon nanotubes (CNTs) inside a fused silica capillary. The structure of the composite was characterized by scanning electron microscopy, X-ray diffraction, thermogravimetry and FT-IR. The results indicated that CNTs were well dispersed and embedded throughout the composite to form an interconnected conducting network. The performance and advantages of the detection electrode are demonstrated by the separation and detection of standard mixtures of the hesperidin, hesperetin, naringenin and naringin by CE. The four flavanones are well separated within 12 min in a 40 cm long capillary at a separation voltage of 12 kV using a 50 mM sodium borate buffer (pH 9.2). The CNT-based electrode offers lower detection potential (0.8 V), enhanced detection limits (0.22-0.31 mu M), lower costs of operation, high resistance to surface fouling, and improved stability. It shows long-term stability and repeatability, and relative standard deviations are < 5 % for the peak current (for n = 15). The method was applied to the determination of flavanone in the peels of citrus fruits.