During 24-26.02.2019 the Suprachem 2019 conference took place at University of Würzburg (Germany). The UT Analytical chemistry chair was represented by two posters: Optimization of the reaction pathway for the synthesis of substituted 1,3-bis(carbazolyl)urea anion receptors by Alo Rüütel and Mihkel Ilisson and From receptor-anion binding ladder to ion-selective electrode by Kerli Martin, Sandip A. Kadam, Ulriika Mattinen, Johan Bobacka and Ivo Leito.
The presentation from Alo and Mihkel focused on optimization of the synthesis route of anion receptors (ionophores) based on the 1,3-bis(carbazolyl)urea building block, augmented with additional amide functionalities (see the poster). The developed synthesis route is very valuable for the synthesis of a wide variety of analogous receptors (ionophores) that have previously been demonstrated to bind carboxylates with high affinity (see K. Martin et al, Eur. J. Org. chem. 2017, 5231-5237).
Kerli Martin et al present the first practical application of such receptors: a solid-contact acetate-selective electrodes. For acetate anion the electrodes show linearity over the activity range of 10-4.50 – 10-1.10 with a sub-Nernstian slope of -51.3 mV per decade and a detection limit of 10-5.00. The anion-selectivity pattern of these electrodes deviates markedly from the pattern found in DMSO solution and from the Hofmeister pattern. The selectivity coefficients of SCN–, I–, NO3– and Br– decrease by 3-5 orders of magnitude when adding the studied ionophore to the membrane. The selectivity coefficients of hydrophilic anions such as Cl–, F–, HPO42–, and SO42– are significantly lower than in case of the ionophore-free control membrane. All in all, it is clear that a lot of work is still needed for improving the selectivity of the electrode.
This work has been accepted for publication: K. Martin et al Electroanalysis 2019 (the link will work soon).
The combined contributions from our group stood out from the majority (the conference altogether had 27 oral and 111 poster presentations) by a clear line of development from fundamental research (receptor design) to highly practical application (ion-selective electrode).
(Photos: above left: Mihkel Ilisson explaining his work to Dr Diane Smith from Wiley; right: Poster by Kerli Martin et al)