Electronic tongue for qualitative analysis of aqueous solutions of salts using thick-film technology and metal electrodes

An electronic tongue for the qualitative analysis of aqueous solutions of salts has been developed. The following set of electrodes was used: RuO2, Ag, and Cu in thick-film technology and Au, Pb, Zn and Ni as small bars of the corresponding metal. The response of the designed "electronic tongue" was tested on a family of samples containing pure salt and complex mixtures. The electrodes were used as potentiometric un-specific sensors and the e.m.f. of each electrode in contact with a certain aqueous solution was used as input signal for a PCA analysis. The study showed that the set of electrodes were capable to discriminate between aqueous solutions of salts basically by their different content in anions and cations (the anions SO42-, Cl-, PO4H2-, CO3H-, NO3- and cations Na+ and K+ were studied). In order to better analyze the basis for the discrimination power shown by the electronic tongue, a quantitative analysis was also envisaged. A fair estimation of the concentrations of the different ions in the solutions studied appeared to be possible using this electronic tongue design.