Screening of organoboron compounds as potential ionophores in a miniaturized ITIES cell.

Abstract

Screening ionophores for potentiometric ion-selective electrodes is arduous as the interaction between the ion and the recognition molecule might be obscured by improper selection of the plasticizer, lipophilic salt or its concentration. Ion transfer voltammetry at the interface of two immiscible solutions (ITIES) allows for evaluating ionophores in a less complex environment. However, standard four electrode cells require up to 10 mL of organic phase for each experiment, thus, a considerable quantity of ionophores is consumed. The latter are usually expensive or synthetically demanding. In this work, we have developed a miniaturized four-electrode cell that can be easily fabricated in any laboratory from a spectrophotometric cuvette without the need for glassblower services. The cell allows evaluation of ionophore-ion interactions in volumes of organic phase as low as 200 µL. It exhibits a sym-metric diffusion profile, which facilitates the interpretation of the results compared to other low-volume setups like capillaries. It is also easier to assemble and does not need specific surface preparation (e.g. silanisation). In the initial step the electrochemical per-formance of the minaturized cell was tested using solution of tetramethylammonium chloride, and the results were compared to those obtained with a standard macroscopic setup. Next, the device was used to screen through a wide range of organoboron compounds towards their ability to recognize fluoride anions.