PROPERTIES OF ELECTROLYTE-FILLED GLASS MICROELECTRODES - A MODEL ANALYSIS

A novel dynamic mathematical microelectrode model (a model of solvent and solute kinetics in electrolyte-filled microelectrodes) was deduced from experimental observations made on standard (single-barrelled, 3. 0 M KCl-filled, approximate to 10 M Omega) electrodes using (a) electr odiffusion, electro-osmosis, and continuity equations that were placed into the constraints of electrode geometry, and (b) handbook/textbook parameter values, only. The model proved to be able to faithfully rep roduce all observed electrochemical and electrical electrode propertie s, i.e. even those that constituted no part of the model's experimenta l basis. In theoretical tests, the model shows, for the standard elect rode that (a) inside the electrode, any profiles in electrical potenti al and electrolyte concentration are occurring at the most distal part (approximate to 50 mu m) of the tip region, (b) asymmetrical shifts i n electrolyte concentration just inside the electrode tip opening are the true cause of the electrode's current rectification, and (c) stron g transelectrode currents are producing water flows across the electro de orifice that may affect the volume of smaller and medium-sized cell s. In further tests, the model shows, among other things, for non-stan dard electrodes that (a) decreasing the electrode electrolyte concentr ation will give rise to marked decreases in electrolyte leakage from t he electrode, but only very minor changes in tip potential, and (b) in creasing the surface charge of the electrode glass (increases in zeta potential) and/or decreasing the electrode electrolyte concentration w ill produce increases in electro-osmotic water transport, which may be desirable for the intracellular injection of water-soluble (electro-n eutral) substances. (C) 1997 Elsevier Science B.V.