Natural polyphenols found in health supplements and drinks
have
antioxidant and anti-inflammatory properties. In particular, to determine
the beneficial qualities of antioxidant drinks and beverages, consumers
demand precise quantification of the total amount of polyphenols as
on-site detection. Herein, we developed a new concept of portable
beads suitable for the field detection available: colorimetric quantification
of polyphenols equipped with color converting software applications
in a smartphone or tablet PC. The yellowish beads contain ferric ions
to react with polyphenol to produce blackish metal-phenolic complexes.
It is simple to perform the detection procedure: dipping the beads
in the analytical sample and outtaking a photoconverting
into RGB color values and quantification of the existed polyphenol.
The overall process was completed within 5 min. Compared with the
Folin–Ciocalteu assay, which is a representative optical sensor
kit for total phenolic content, the bead-based sensor showed a better
limit of detection of 0.0415 mM for tannic acid and comparable sensing
capability for a polyphenol-containing plant extract and brewed tea.
The beads conserved the shape and sensitivity after months of storage
or under environmental interference such as a change in the temperature.