Potentiometric Carboxylate Sensors Based on Carbazole-Derived Acyclic and Macrocyclic Ionophores

Abstract

Solid-contact ion-selective electrodes with carbazole-derived ionophores were prepared. They were characterized as acetate sensors, but can be used to determine a number of carboxylates. The potentiometric response characteristics (slope, detection limit, selectivity, and pH sensitivity) of sensors prepared with different membrane compositions (ionophore, ionophore concentration, anion exchanger concentration, and plasticizer) were evaluated. The results show that for the macrocyclic ionophores, a larger cavity provided better selectivity. The sensors exhibited modest selectivity for acetate but good selectivity for benzoate. The carbazole-derived ionophores effectively decreased the interference from lipophilic anions, such as bromide, nitrate, iodide, and thiocyanate. The selectivity, detection limit, and linear range were improved by choosing a suitable plasticizer and by reducing the ionophore and anion exchanger concentrations. The influence of the electrode body’s material upon the composition of the plasticized poly(vinyl chloride) membrane, and thus also upon the sensor characteristics, was also studied. The choice of materials for the electrode body significantly affected the characteristics of the sensors.

One Hundred Carboxylate Receptors

“…The second strategy relies on dissolving the receptor into the ISE membrane cocktail, thus embedding the ionophore into the electrode body. 6,7 Here, no specific functional group is necessary for immobilization. However, this introduces the possibility for the ionophore that it may leak into the analyte solution from the ISE membrane.…”

Macrocyclic versus open-chain carbazole receptors for carboxylate binding

“…As can be concluded from the p K a values (in DMSO) of pyrrole (23.0), indole (20.9) and carbazole (19.9), 32 the acidity of the pyrrole ring can be increased not only by attaching electron-withdrawing groups but also by conjugation with the benzene ring. 33 The groups of Jurczak, 34 Sessler, 35 and Gale 36,37 and our group 38–40 have used the carbazole ring as an effective component of anion receptors. The carbazole ring is used not only because of its higher acidity but also for its rigidity.…”

“…It has been demonstrated that carbazole's rigid skeleton enables the introduction of various functionalities, which makes it an ideal moiety for the design of anion receptors. 34–40…”

Perchlorate Solid-Contact Ion-Selective Electrode Based on Dodecabenzylbambus[6]uril

“…Solid-contact materials based on conducting polymers (e.g., PEDOT-see Figure 1b, poly(aniline), poly(pyrrol), etc.) are conveniently made by electrodeposition-polymerization of the monomer on an electrode, such as glassy carbon (GC) [78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. It has also been shown that some conducting polymers, polymerized in the presence of different anions, can behave as ISMs for cations or anions [79,85,86].…”