Highly efficient colorimetric sensing for total antioxidant capacity of tea utilizing UiO-66(Ce) with oxidase-like activity.

The determination of total antioxidant capacity (TAC) plays a crucial role in evaluating the quality of tea. However, existing methods suffer from issues such as lengthy testing times and low sensitivity. To overcome these limitations, UiO-66(Ce) was prepared by hydrothermal synthesis and demonstrated excellent detection performance in the determination of TAC. It achieved the detection of TAC within 6 min, and showed a good linear range in the quantitative determination of three representative reducing substances, including ascorbic acid (AA), tannic acid (TA), and cysteine (Cys). The detection limits were 3.88, 1.99, and 12.59 µM, respectively. Furthermore, the sensing mechanism was systematically investigated. UiO-66(Ce) efficiently generated ·OH through the Ce(III)/Ce(IV) redox system to oxidize 3,3',5,5'-tetramethylbenzidine (TMB). Subsequently, the added antioxidants scavenged ·OH and reduced oxTMB, triggering a distinct color change and enabling rapid TAC detection. Based on the above research, we have verified the feasibility of this detection method in practical applications and successfully achieved rapid TAC determination in tea. This research provides a new method for the rapid and accurate determination of TAC, and it shows broad application potential.