Current pulse based reference electrodes without liquid junctions

Reference electrodes with hydrophobic ion-doped polymeric membranes offer a promising alternative to reference electrodes with conventional salt bridges. This letter introduces the current pulse operation of liquid junction free reference electrodes. A brief current pulse is applied to a cation exchanger membrane, releasing a well-controlled amount of cations from the membrane into the sample and, thereby, determining the boundary potential of the sample/reference membrane interface. Measurements with ion-selective electrodes (ISEs) are performed relative to these reference electrodes immediately after the current pulse and exhibit the same Nernstian responses as typical for potentiometry, which is demonstrated with Cl^- ISE measurements. The use of current pulse based reference electrodes avoids the sample sensitivity and clogging of conventional salt bridges and the often poorly controlled loss of bridge electrolyte into samples. Current mode measurements in serum over 2 days showed a much higher stability of the reference potential than conventional potentiometric measurements with the same ion-doped polymeric membranes.