Determination of 5,7-dihydroxychromone and luteolin in peanut hulls by capillary electrophoresis with a multiwall carbon nanotube/poly(ethylene terephthalate) composite electrode

A novel multiwall carbon nanotube/poly(ethylene terephthalate) (MWCNT/PET) composite electrode was developed for the determination of 5,7-dihydroxychromone and luteolin in peanut hulls in combination with capillary electrophoresis (CE). The electrode was fabricated by packing a mixture of MWCNTs and melted PET in a piece of fused-silica capillary under heat. Because of the simple composition of the phenolic constituents in peanut hulls, they were used to demonstrate the performance of the fabricated electrode. The results indicated that 5,7-dihydroxychromone and luteolin were well separated within 12 min in a 40 cm long capillary at a separation voltage of 12 kV using a 50 mM borate buffer (pH 9.2). The MWCNT-based electrode exhibited significantly lower detection potentials, enhanced signal-to-noise characteristics, and higher resistance to surface fouling compared to graphite/PET composite electrode. It showed long-term stability and reproducibility with a relative standard deviation of 2.6% for the peak current (n = 15). The relation between peak current and analyte concentration was linear over about three orders of magnitude. The proposed method has been applied to determine the two bioactive constituents in real samples.