We have developed a new method for the rapid and inexpensive determination of the total polyphenol index (TPI) in wines by simply immersing our sensory film in red or white wines and visually checking the colour change (qualitative analysis) or by analysing a photo taken of the film with a smartphone (quantitative analysis). This sensory material is straightforward and inexpensively prepared; it requires no monomer synthesis, is based on 100% commercially available monomers, and contains benzenediazonium salt motifs, which in the presence of phenols and/or polyphenol-based structures produce coloured diazo compounds. These sensory motifs are chemically anchored to the polymeric structure, and, accordingly, no migration of organic substances from the material occurs in the sensing process. Our method needs neither reagents nor sample pretreatment and has been contrasted with the standard TPI determination, i.e., measuring the absorbance of diluted wine at 280 nm, obtaining reliable data for white and red wines.
