Discrimination of apple juice and herbal liqueur brands with solid-state electrodes covered with polyaniline and thiacalixarenes

Solid-contact ion-selective electrodes based on glassy carbon electrode covered with electropolymerized polyaniline and tetrasubstituted thiacalix[4]arene ionophores with hexyl and o-pyridylamido functional groups at the lower rim have been developed and examined in the discrimination of the brands of apple juices and herbal liqueurs. For this purpose, the liquids tested were diluted and spiked with a constant amount of Fe3+ ions. The variation of the signal toward Fe3+ ions was achieved due to their involvement in the reactions with the organic ligands and the antioxidants present. As was shown, the combination of the three electrodes with various receptors makes it possible to predict the brand of apple juices and herbal liqueurs using linear discriminant analysis in 95–100% cases. The discrimination procedure makes it possible to discriminate liquids within 20 min. Besides, the electrodes developed make it possible to detect individual antioxidants (ascorbic, malic, oxalic acids, hydroquinone, and quercetin) in the range from 5.0 × 10−6 to 1.0 × 10−2 M in direct potentiometric measurements and redox titration.