Electropolymerization of graphene and 5-[o-(4-bromine amyloxy) phenyl] -10,15,20-triphenylporphrin (o-BrPETPP) composite film electrode for the electrocatalytic oxidation of indirubin

The graphene and 5-[o-(4-Bromine amyloxy) phenyl]-10,15,20-triphenylporphrin (o-BrPETPP) composite (GR-o-BrPETPP) film is prepared on the glassy carbon electrode (GCE) with graphene oxide (GO) modifier through a consecutive cyclic voltammetry process, and then its electrocatalytic oxidation to indirubin is investigated. The as-prepared GR-o-BrPETPP film exhibits wrinkling paper-like structure and lower electron transfer resistance. In comparison with the o-BrPETPP/GCE and GCE, the GR-o-BrPETPP film electrode prepared for five cycles indicates an excellent electrocatalytic oxidation activity toward indirubin with about 2.2 and 13.3 times higher current response, respectively. In addition, in the 0.1 mol L−1 acetate buffer solution (pH = 4.6), the film electrode displays a linear relationship between the oxidation current and the indirubin concentration in the range from 5.0 × 10−7 mol L−1 to 2.4 × 10−5 mol L−1, and presents a detection limit of 1.0 × 10−7 mol L−1 (S/N = 3) by differential pulse voltammetry (DPV) with 220 s accumulation. Especially, this film electrode also shows a comparative sensitivity with high-performance liquid chromatography (HPLC) for the determination of the indirubin extractive of herbal medicines, showing its practical prospect in the electrochemical determination of indirubin.