Solid sensory polymer substrates for the quantification of iron in blood, wine and water by a scalable RGB technique†
Iron in blood serum, wine and water has been visually detected and quantified quickly by processing photographs of an iron colorimetric sensory polymer substrate. The photographs may be taken with a conventional digital camera or Smartphone. The sensory materials were designed following a straightforward strategy. A proven iron organic chelator was easily transformed into an acrylic monomer and further copolymerized with hydrophilic co-monomers to render a membrane comprised of a hydrophilic, gel-like, polymer network. The film-like membrane generated was cut into small-diameter sensory discs. Thus, upon immersion of the sensory disks in blood serum, wine, and water, a colour development was rapidly observed which could be easily correlated with the iron concentration of the samples. RGB digital parameters obtained from photographs of the sensors were processed statistically using principal component analysis (PCA) and used to elaborate titration curves and quantify iron concentrations. The response time of the sensory films was short, 15 min, and the concentrations measured in water ranged from 56 ppb to 56 ppm. This broad range covers the U.S. Environmental Protection Agency (EPA) and European Union (EU) drinking water standards for iron in drinking water (<300 and 200 ppm, respectively), the typical iron content in wines (1 to 10 ppm) and the normal range of iron in the blood serum in men (0.8–1.8 ppm). This methodology for detecting and quantifying chemical species avoids the time-consuming sample preparation, expensive laboratory techniques, and specialized personnel needed to carry out conventional analytical methods.