A novel potentiometric sensor based on screen‐printed carbon electrode covered with electropolymerized polyaniline (PANI) and unsubstituted pillar[5]arene as ionophore has been developed and tested in potentiometric measurements of pH and metal ions. The introduction of pillar[5]arene improved the reversibility of the pH response in the range from 2.0 to 9.0 with the slope of 45 mV/pH. Among metal cations, the response to Fe3+ and Ag+ ions was referred to PANI redox conversion whereas the signal toward Cu2+ in the range from 1.0×10−6 to 1.0×10−2 M (limit of detection (LOD) 3.0×10−7 M) to specific interaction with the macrocycle.
Electronic tongue is a sensor array that aims to discriminate and analyze complex media like food and beverages on the base of chemometrics approaches for data mining and pattern recognition. In this review, the concept of electronic tongue comprising of solid-contact potentiometric sensors with polyaniline and thacalix[4]arene derivatives is described. The electrochemical reactions of polyaniline as a background of solid-contact sensors and the characteristics of thiacalixarenes and pillararenes as neutral ionophores are briefly considered. The electronic tongue systems described were successfully applied for assessment of fruit juices, green tea, beer, and alcoholic drinks They were classified in accordance with the origination, brands and styles. Variation of the sensor response resulted from the reactions between Fe(III) ions added and sample components, i.e., antioxidants and complexing agents. The use of principal component analysis and discriminant analysis is shown for multisensor signal treatment and visualization. The discrimination conditions can be optimized by variation of the ionophores, Fe(III) concentration, and sample dilution. The results obtained were compared with other electronic tongue systems reported for the same subjects.
A solid-contact potentiometric sensor has been developed on the basis of glassy carbon electrode covered with electropolymerized polyaniline and alternatively layered pillar[6]arene and Cu2+ ions films. The assembly of the surface layer was confirmed by surface plasmon resonance measurements. The number of deposited layers was selected to reach better analytical characteristics for Cu2+ determination. It was shown that better results were achieved by using five layers, the upper one consisting of the macrocycle. The addition of covering layers for polyelectrolytes (Nafion, poly(styrene sulfonate)) and Cu2+ ions did not improve sensor performance. The potentiometric sensor made it possible to determine Cu2+ ions in neutral and weakly acidic media with a linear range of the concentrations, from 3.0 μM to 10.0 mM (limit of detection 3.0 μM). The applicability of the sensor in real sample assays was confirmed by the determination of Cu2+ ions in copper vitriol, Bordeaux mixture, and polyvitamin-mineral pills of “Complivit” during an atomic emission spectroscopy analysis.
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