title: Bias current modifies the selectivity of liquid membrane ion-selective microelectrodes.
abstract: A negative bias potential of up to -80 mV applied to the back of a liquid membrane ion-selective microelectrode containing classical "K+" ion-exchanger was found to make it more selective for millimolar concentrations of K+ over micromolar concentrations of choline, tetramethylammonium, tetraethylammonium and 5-hydroxytryptamine. Conversely, positive bias potential increased severalfold the sensitivity to micromolar concentrations of these ions while decreasing the sensitivity to K+. An increase in response amplitude for millimolar changes of ion concentration was also observed in neutral carrier electrodes for Na+, K+ and Ca2+ with negative bias potential. The various ions caused the resistances of the electrodes to change; these resistance changes contributed to the changes in response amplitude, but there were additional, unexplained, factors. The phenomenon was used to test if the signal from a K+ ion-exchanger microelectrode in extracellular space in bee retina was contaminated by substances other than K+.
authors: Université de Genève, Département d'Oto-Neuro-Ophtalmologie, Switzerland.
authors: J A
authors: JA
authors: Coles
mesh_terms: D000818:Animals; D001516:Bees; D002118:Calcium / Q000378:metabolism; D004553:Electric Conductivity; D007474:Ion Exchange; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D012964:Sodium; D011188:Potassium; D002118:Calcium