Determination of the total antioxidant capacity of the Chinese tea based on a novel "peroxidase/zirconium phosphonate"composite electrochemical sensor.

In this work, a novel zirconium phosphonate (ZrPRR) was prepared by decorating both the aminoethoxy- group (R) and the carboxypropyl- group (R) on the zirconium phosphate layers in order to manipulate further the immobilization of the peroxidase (POD), and an antioxidant biosensor with higher sensitivity was constructed by dropping the POD/ZrPRR composite onto the glassy carbon electrode surface. The activity of the POD/ZrPRR composite was detected by Uv-vis spectra. The direct electrochemical behavior, the electrocatalytic response to dissolved oxygen and hydrogen peroxide, as well as the ability to detect total antioxidant capacity in tea sample were investigated by the methods of cyclic voltammetry. The results indicated that the immobilization of POD in ZrPRR nanosheets matrix enhanced the enzymatic activity, and achieved the fast and direct electron transfer between POD and glassy carbon electrode. Moreover, the POD/ZrPRR composite modified electrode show the electrocatalytic response to hydrogen peroxide in the linear range of 8.8×10 to 8.8×10 mol L, with the detection limit of 3.3×10 mol L. Attributing to the sensitive response to dissolved oxygen, the total antioxidant capacity can be detected directly in the real tea water by this POD/ZrPRR composite modified electrode.