Figure 2.

(a) Typical PADs for assessment of antioxidant activity and whole phenolic content. (A) The zones utilized for ABTS, CUPRAC, FC and sample blank. (B) The sample zone, pretreatment zones and recognition zones on the devices. Reprinted with permission from [15]; (b) Paper-based devices for identification of antioxidant activity and whole phenolic content of the samples containing Oolong tea, black tea and red wine compared to the control. Reprinted with permission from [15]; (c). A colorimetric sensor array based on three different lanthanide ions as sensing receptors for antioxidants analysis. Reprinted with permission from [51].