Simultaneous analysis of sugars and polyphenols in tobacco by CZE with amperometric detection based on a Cu₂O/MWCNT-COOH composite electrode

A composite electrode was fabricated from Cu₂O powder, carboxyl-functionalized multi-wall carbon nanotubes (MWCNT-COOH), and paraffin oil in the proportions 51:17:32 (w/w). This composite electrode was used for amperometric detection (CZE-AD) in simultaneous capillary zone electrophoretic analysis of chlorogenic acid, rutin, sucrose, glucose, mannose, and fructose in tobacco samples. Under the optimum conditions, the six analytes could be separated in 100 mmol L^-1 NaOH buffer within 30 min. Good linearity was achieved in the range 1 × 10^-7-1 × 10^-4 mol L^-1 for the two polyphenols and 5 × 10^-6-1 × 10^-3 mol L^-1 for the four sugars. The detection limits (S/N = 3) for the polyphenols and sugars were as low as 10^-8 mol L^-1 and 10^-6 mol L^-1, respectively.