The recent efforts focused on improving the design of the ITIES setup, including reducing the surface area of the interface from the cm 2 to µm 2 range. Macroscopic cells included an hourglass design, in which the volume of the phases was still considerable, but the interface area could be reduced. Smaller volumes were achieved by enclosing one of the phases in a pulled glass micropipette . However, such a design results in an asymmetric diffusion profile, with radial diffusion for ions transferring from the outside to the inside of the pipette and planar diffusion of the species travelling in the opposite direction. As the mass transport is controlled by the radial diffusion of the reactants and products outside the pipette, the aqueous phase should be located inside the pipette to study ion-ionophore interaction. Although, thanks to low currents, it is possible to use a two-electrode system, the considerable resistance of the electrolyte in the micropipette tip (10-20 MΩ) precludes fast scan rates . If the organic phase is enclosed in such a pipette, its inner surface must be made hydrophobic, e.g. through silanization, to prevent interface movement during the potential sweep. The interface's position in such capillaries can change up to 70 µm for potential changes between -100 and +600 mV. Another approach was to separate the phases using a thin inert membrane with an array of microholes, for example, fabricated using laser photoablation in a polyester film subsequently attached at the end of a 2 mm diameter tube . To prevent wetting the membrane surface by a single solvent, one side of the membrane must be hydrophilic while the other is hydrophobic. If adequately prepared this approach allows symmetric radial diffusion from both interface sides. However, fabrication requires the use of a high-power laser. The glue used to attach the membrane to the test tube should be resistant to the organic solvent to prevent mechanical failure and leakage of its ionic constituents that could contaminate the phase. Miniaturization and reduction of the volume of organic phase can be achieved also by gelling of the phase but similar problems encounter as for potentiometric sensing.