In conclusion, the miniature electrochemical cell allows lower reagent consumption during measurements. At the same time, it is possible to observe ion transfer mechanisms as in a standard electrochemical cell. In addition, the miniature cell did not require a long waiting time for the liquid/liquid interface to be established, which was necessary for the standard cell. For this reason, the measurement time could be significantly reduced. The interaction of organoboron compounds with fluoride anions detected by various electrochemical and optical techniques has been widely described in the literature. At the same time, it is impossible to study the direct transfer of fluoride ions across the liquid/liquid interface due to its high hydrophilicity. The energy for such transfer is higher than that it is required to transfer the supporting electrolyte (here LiCl). This is also supported by the experiments performed in a three-phase junction setup, in which the redox probe is expelled from the organic phase more easily than the opposite transfer of fluoride ions can occur . Modifying the organic phase with an ionophore, which lower the transfer energy of fluoride, could solve this problem. In this section, 19 organoboron compounds from different classes including aromatic boronic acids (1-8), oxaboroles (9-14), cyclic dibenzoborinines (15-17) and triarylboranes (18-19) were used. Most of these compounds were obtained in small amounts; thus, the miniature cell developed in this project was crucial for screening organoboron compounds as potential ionophores of fluoride anion. The compounds were selected on the basis of their high fluoride affinity and stability under measurement conditions. Boronic acids and their derivatives show weak to moderate Lewis acidic properties. In general, multiboronic acids show higher Lewis acidity with respect to their monoboronic analogues, thus we have decided to test ortho-, meta-and paraphenylenediboronic acids as well as 1,3,5-benzenetriboronic acid (7). The synergistic effect of two adjacent boronic groups (5, 6, 8) further increases boron atom Lewis acidity which would be beneficial for the fluoride binding . This property can also be enhanced by the functionalization of aromatic ring with electron withdrawing fluoro substituents (3, 6). Another method to enhance the fluoride binding is to incorporate the boron atom into a cyclic structure. For instance, benzoxaborole (9) exhibits higher Lewis acidity with respect to phenylboronic acid which is manifested by lower pKa value of the former compound (7.3 vs. 8.8) . Lewis acidity can further be enhanced in silicon congeners of benzoxaboroles, namely benzosiloxaboroles (10-13) . Within the latter group, we have tested the compound bearing the pendant boronic group (11) and derivatives containing two oxaborole rings (12-13). Finally, the systematic replacement of hydroxyl group with aromatic substituent elevates Lewis acidity of the boron centre. Thus, we have decided to include in this study dibenzo fused boracycles such as dibenzoborinines (15-17) as well as triarylboranes (18-19). The selection of these particular systems was additionally rationalized by their high stability under ambient conditions when compared to typical diarylborinic acids (Ar2BOH) or triarylboranes (Ar3B).