Rapid Quantification of Antioxidant Capacity in Tea Using Laser-Induced Graphene Electrodes

This paper describes a new analytical method based on laser-induced graphene (LIG) electrodes for evaluating antioxidant capacity in tea by quantifying the consumption of the 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical. The LIG electrodes were produced by pyrolysis using a CO2 infrared laser source (10 electrodes were produced in 5 min). The LIG sensor was coupled to a three-dimensional (3D)-printed batch-injection analysis cell to amperometrically detect the remaining DPPH. The sensing properties included a linear range from 2 to 900 μmol L–1 (R2 > 0.99), adequate limit of detection (LOD = 0.6 μmol L–1), fast responses (∼10 s), and good precision relative standard deviation (RSD < 4.0%). The efficient concentration of tea samples necessary to reduce the initial DPPH concentration by 50% (EC50) was determined after incubation with DPPH radicals for 30 min. The results of EC50 showed good agreement with the conventional spectrophotometric results. Therefore, LIG electrodes are a powerful analytical tool for applications in teas.