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An innovative smart label for naked-eye protein food freshness evaluation, based on polymeric sensing films, is presented. The proposed device consists of six miniaturized sensors, obtained by cova...

The deprotonation of quinolic resin P-127 and iminodiacetic resin Amberlite IRC-718 has been studied. The process of salt transfer into the resin phase is considered to be an important contributor to the deprotonation process. Estimation of the salt transfer was based on the principle of equal activity of the salt in both phases at equilibrium. Two assumptions were made: sorbed alkali metal ions are not associated with functional groups, while all hydrogen ions are associated with functional groups. The associated hydrogen ions and functional groups do not contribute to the internal ionic strength value. Two thermodynamic models, describing the deprotonation of ion-exchange resin, were used and compared: the Gibbs−Donnan-based model of Bukata and Marinsky and the model proposed by Erik Hogfeldt. Thermodynamic characteristics of the resins' deprotonation are obtained using two different thermodynamic approaches. Hogfeldt's three-parameter model provides a better agreement with experimental data. The fitt...

A method for determining the total concentration of a metal ion originally present in a solution (c tot ) and the ratio of total to free metal ion (Z M ) is proposed. It consists of putting different aliquots of the sample (V) in contact with the resin (w) in batch, by keeping the acidity constant, and determining the concentration of the sorbed metal ion c. Then 1/c is plotted against V/w, and c tot and Z M are calculated from the straight line obtained. The chemical model that allows evaluation of the ratio of total to free metal ion is illustrated and discussed. Some synthetic systems are examined to demonstrate the validity of the procedure.

The sorption of metal ions on chelating resins is believed to take place through complexation by the active groups. Thus the selectivity of the resin for different metals is expected to be comparable to the complexing properties of a monomer having a structure similar to that of the active groups. This correlation can be done in a quantitative way on the basis of the Gibbs-Donnan model, which allows prediction of the extraction coefficients of metal ions on a chelating resin from the complexation constants, and other quantities, such as the concentration of the counterion in solution. In the case of chelating resins containing iminodiacetic groups, the selectivity toward some divalent metal ions is much worse than expected from the complexation by iminodiacetate in aqueous solution