The miniaturization of potentiometric sensors is developing only slowly. ISFET technology has not yet brought great breakthroughs in this respect. Potentiometric microelectrode arrays are developed however for DNA analysis. As potentiometry moves into new and unexpected applications such as biomolecules, multiply charged molecules, DNA, marker proteins, viruses and bacteria, dissolution testing..., the need for miniaturized sensors and arrays will grow. Possibly, planar screen printed electrodes can be applied. Use of the electrodes in hydrodynamic conditions may be needed. The use of FIA and HPLC for rapid screening of electrode compositions is explained. This provides new insights into these chemically dynamic sensor systems, and into the interaction of organic ionic molecules with surfaces.