Tip Potential and Resistance of Micro-Electrodes Filled with KCI Solution by Boiling and Nonboiling Methods

Micro-electrodes were filled with 3-M KCI by two different methods. One group of electrodes was filled by boiling in KCI solution (boiled electrodes), and the other group was filled by capillarity, using glass fibers inside the electrode (glass fiber electrodes). The tip potential and the resistance of these electrodes were measured under various conditions. There was no significant correlation between the tip potential and the resistance in both groups of electrode. The boiled electrodes had larger tip potential (-12.7 mV) than the glass fiber electrodes (-0.2 mV) in sea water. The tip potential of boiled electrodes was decreased by increasing ionic concentrations and lowering the pH of external medium, by addition of divalent cation (Ca and Mg), and by lowering the temperature. The tip potential of glass fiber electrode was less affected by these changes. When electrodes containing glass fiber were filled with KCI solution by boiling, their tip potential was not much different from that in the boiled electrode without glass fiber. Furthermore, electrodes, filled with 3-M KCI without glass fiber and without boiling by using alcohol method, had a small tip potential (-2A mV). The tip potential of electrodes seems to be increased by boiling. Similar values of resting potential were obtained by both boiled and glass fiber electrodes. This is probably due to the fact that the tip potential in KCI solution was nearly the same as that in sea water which contained 465-mM NaCl, 10.8-mM CaC12, and 48.3-mM MgC12.