Colorimetric detection and determination of Fe(III), Co(II), Cu(II) and Sn(II) in aqueous media by acrylic polymers with pendant terpyridine motifs

Colorimetric cation responsive water soluble polymers and manageable films or membranes have been designed. The sensory materials respond with a colour change to the presence in water of Fe(III), Co(II), Cu(II), and Sn(II). The colour change is specific of each metal cation, and enables its identification (purple for iron, orange for cobalt, green for copper, and yellow for tin). The design of the materials relies on an addition monomer having a terpyridine moiety, which behaves as a dye in presence of transition metal cations due to its proven chelating capability towards these species and the colour development that always accompany the metallic complex formation. Water solutions of the sensory linear polymers allow for the UV/vis titration of Fe(III), Co(II), Cu(II), and Sn(II) with a limit of detection of 1.3 x 10(-7), 6.4 x 10(-8), 1.3 x 10(-5) and 1.4 x 10(-5) M, respectively. On the other hand, sensory kits, cut from sensory membranes, permitted the visual quantification of the cations in a dynamic range of five decades (1 x 10(-7) to 5 x 10(-3) M) for Fe(III) and Co(II) and of two decades (9 x 10(-5) to 9 x 10(-3) M) for Cu(II) and Sn(II). Titration curves can also be drawn from a picture taken to the sensory kits with a smartphone, by using the digital colour definition of the materials as analytical signal. Also, after entering into contact with hands, shapes of metallic objects (iron and cobalt containing tools) can be colour revealed by pressing the hands on paper or cotton fabrics wetted with water solutions of the linear sensory polymer. (C) 2015 Elsevier B.V. All rights reserved.