The ABTS-microzone plate and scanometry as a simple and fast colorimetric assay for determining the total antioxidant capacity of plant extract

Abstract

The 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS)-microzone plate as an antioxidant sensor was developed by immobilizing the ABTS reagent onto the screen-printed paper. The individual circular microzone, served as a sensing zone has a blue color that will decolorize within antioxidant addition in the concentration-dependent favor. The scanometric detection system that uses a flatbed scanner and color analysis program like ImageJ was applied to the antioxidant sensor, while its analytical performance was optimized by using quercetin. The use of the pre-generated ABTS radical for constructing the paper-based sensor, as well as the application of the scanometric method, is the novelty of this study. The result showed that the sensor showed a linear signal (r = 0.9997) within quercetin addition (0.1–1.0 mM) at 8 min with the detection limit (LOD) of quercetin at 0.03 mM and presented good precision (RSD < 3%) and accuracy (98–101% recovery) in total antioxidant capacity (TAC) determination. TAC of various plant extracts was successfully determined (as mM quercetin equivalent) by using the antioxidant sensor, while the result was parallel with that determined by the spectrophotometric method, suggesting the feasibility of the proposed method as an alternate method for TAC determination.