title: A surface fit approach with a disposable optical tongue for alkaline ion analysis.
abstract: A disposable optical tongue for the alkaline ions Na(I) and K(I) is described. The two-sensor layout prepared on a transparent support consists of non-specific polymeric membranes working by ionophore-chromoionophore chemistry. The non-specific behavior of the membranes was controlled by means of the crown ether-type ionophore present. The imaging of the tongue, after reaction for 3 min with the unknown solution, by means of a conventional flatbed scanner working by transmission mode, makes it possible to calculate the H (hue) value of the hue, saturation, value (HSV) color space used as a robust and precise analytical parameter. The modelling of the response of the two-sensor tongue as a sigmoidal surface is used to characterize the behavior of the tongue and as a basis to infer the concentration values. To compute the concentration of two analytes from the two hue values obtained using the optical tongue, a surface fit approach was used. The tongue works over a wide dynamic range (1.0×10(-4)-0.1 M both in Na(I) and K(I)). The sensing membranes show good intramembrane (1.4% RSD) and intermembrane precision (0.71% RSD) and lifetime (around 45 days in darkness). The procedure was used to analyze Na(I) and K(I) in different types of natural waters (tap and mineral), validating the results against a reference procedure.
authors.affiliation: ECsens, Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Granada, Spain.
authors.forename: M M
authors.initials: MM
authors.lastname: Erenas
authors.forename: O
authors.initials: O
authors.lastname: Piñeiro
authors.forename: M C
authors.initials: MC
authors.lastname: Pegalajar
authors.forename: M P
authors.initials: MP
authors.lastname: Cuellar
authors.forename: I
authors.initials: I
authors.lastname: de Orbe-Payá
authors.forename: L F
authors.initials: LF
authors.lastname: Capitán-Vallvey