Ephedrine sensing at the electrified liquid-liquid interface supported with micro-punched self-adhesive polyimide film

In this work, ephedrine was studied at the electrified liquid-liquid interface (LLI) supported with an array of apertures micro-punched in the self-adhesive polyimide tape. During LLI miniaturization protocol development, we have tested three arrays of needles (each containing 12, 24, or 36 pre-arranged units) used to puncture the polyimide film. Since all needles have a conical shape at the sharp site end we have created and tested the membranes with controlled penetration depth allowing for the adjustment of the pores dimensionality. The resulting membranes were characterized with ion transfer voltammetry and scanning electron microscopy. The best results were obtained for 12 micro-punched pores made with the highest studied penetration depth (equal to 1450 μm), and hence, this configuration was employed for the ephedrine sensing. As the electroanalytical method, we have employed ion transfer voltammetry (ITV). The miniaturization allowed for the ephedrine detection down to 1 μM. Ephedrine was measured alone and in the presence of caffeine.