With an increasing consumption and production of healthy dietary products rich in antioxidants, a simple and cost effective test is required for the measurement of the antioxidant capacity of these products. In this research, a paper based colorimetric method for sensitive detection of antioxidants in beverage was developed. The colorimetric detection was based on the reaction of the antioxidant with a chromogenic reagent consisted of silver ions and silver nanoparticles (AgNPs) or silver nanoplates (AgNPls) which acted as seeding nucleation. Silver ions was reduced by antioxidant compounds to silver(0) deposited on AgNPs or AgNPls, resulting in larger clusters of AgNPs or AgNPls. The colorimetric response on the paper changed from white to brown depending on the concentration of antioxidant involved. Ascorbic acid was selected as the representative of antioxidant species and the method showed a linear response in the concentration range from 0 to 1 mM ascorbic acid (R2 0.990). Common beverage ingredients like reducing sugars did not interfere with the paper based. The method was applied to determine the amount of antioxidant in tea samples and the results could be presented in term of ascorbic acid equivalents (AAE). This assay is particularly appealing for remote sensing applications, where specialized equipment is not available.
