Determination of three phenolic acids in Cimicifugae rhizoma by capillary electrophoresis with a graphene–phenolic resin composite electrode

A novel graphene-phenolic resin composite electrode was fabricated by the in situ crosslinking of phenolic novolac resin in the presence of graphene sheets and hexamethylenetetramine for the capillary electrophoretic measurement of isoferulic acid, ferulic acid and caffeic acid in Cimicifugae rhizoma. The characterization results showed that a uniform electrically conductive composite network of graphene and phenolic resin formed in the electrode tube. The novel electrode was employed in the enhanced amperometric detection of the three phenolic acids after capillary electrophoresis separation. They could be well resolved within 10 min at a voltage of 15 kV using a 50 mM borate buffer at pH 9.2. The peak currents were linear with their concentrations over the range of 0.001 to 1 mM. The graphenebased detection electrode is characterized by high sensitivity, improved detection limits (0.18 to 0.25 mM), low detection potential (+ 0.8 V) and long-term reproducibility. The method was applied to the determination of the three phenolic acids in Cimicifugae rhizoma.