Wall-jet ion sensor based on ion transfer processes at a polarized room-temperature ionic liquid membrane

Abstract

Room-temperature ionic liquid (RTIL) membrane is used to construct a wall-jet ion sensor based on the ion transfer processes at a polarized interface between RTIL and an aqueous electrolyte solution. The stream of the aqueous phase with an injected sample plug containing an electroactive ion is led against the RTIL membrane through a silver tube, which is covered with an AgCl layer, and which serves simultaneously as one of two reference electrodes in a four-electrode cell. The effects of the applied potential, the ion concentration, the volume flow rate of the mobile aqueous phase, and the injected sample volume on the chronoamperometric response of the sensor to the test samples containing tetraethylammonium cation (TEA+) as a model ion are demonstrated. The applicability of the available theory of the wall-jet electrode against which a vertical stream is flowing that is much smaller in diameter than the electrode is confirmed for this sensor. Analytical characteristics for the flow injection analysis of the studied model ion are estimated including excellent repeatability characterized by the relative standard deviation (1.64%) of the average current at the ion concentration (0.5 μmol dm−3), a low limit of detection (22.5 nmol dm−3), and the wide linear dynamic range exceeding three orders of magnitude (1 × 10−7–2 × 10−4 mol dm−3).