A sensor array made up of nanostructured Langmuir-Blodgett (LB) films is used as an electronic tongue capable of identifying sucrose, quinine, NaCl, and HCl at the parts-per-billion (ppb) level, being in some cases 3 orders of magnitude below the human threshold. The sensing units comprise LB films from conducting polymers and a ruthenium complex transferred onto gold interdigitated electrodes. Impedance spectroscopy is used as the principle of detection, and the importance of using nanostructured films is confirmed by comparing results from LB films with those obtained from cast films.