Dual-pipet techniques for probing ionic reactions

Novel dual-pipet electrodes prepared by pulling borosilicate theta-tubing a re described. Three types of electrochemical experiments employing such dev ices include the following: (1) generation/collection experiments in which ions are ejected from one of two micropipets ("generator") into the externa l solution and collected at the second pipet ("collector"), (2) measurement s of ohmic current-voltage curves, and (3) ion-transfer voltammetry "in the air". The first setup is used for probing ion transfers at the interface b etween two immiscible liquids and homogeneous reactions in solution involvi ng ionic species. Such experiments are reported for two model processes, i. e., simple and facilitated transfers of potassium between aqueous and organ ic phases and complexation of potassium with dibenzo-18-crown-6 in organic solution. The second arrangement is used for characterization of theta-pipe ts. The last arrangement can be useful for preparation of gas sensors. The possibility of measuring the concentration of volatile substances (e.g., am monia and nitric acid) in the gaseous phase has been demonstrated.