A digital simulation study of steady-state voltammograms for the ion transfer across the liquid–liquid interface formed at the orifice of a micropipette

Digital simulation of cyclic voltammograms for the ion transfer across the micro liquid–liquid interface formed at the orifice of a glass micropipette shows that the electrochemically driven flow of ions from the inside of the micropipette to the infinitely large outer phase gives steady-state current–potential characteristics, when the shape of the tip is not cylindrical but truncated conical as usual micropipettes. Such steady-state behavior well explains experimentally observed voltammograms for ion transfer across the hydrophobic ionic liquid–water interface formed at the orifice of a micropipette with a small radius. Both the limiting current and the half-wave potential of the voltammogram vary with the angle of the inner wall of the micropipette with respect to the axis of rotational symmetry of the pipette, θ 1 , and both reach the limits predicted by the radial diffusion of the ions to the inlaid disk, that is, θ 1 = 90 ° in an asymptotic manner. The conditions for obtaining such steady-state voltammograms depend on the size of the interface and the scan rate of the applied voltage, aside from θ 1 .