Abstract
The authors have constructed a micro-glass pH electrodes of the size about 60 to 80 micra in diameter and 4 to 9mm long and the electrode characteristics and applicabilities to the intracellular pH measurements were studied.
1. Paired with a KCl-filled micropipette leading to a reference electrode, the micro-glass pH electrode was confirmed to give an electromotive force per pH unit which closely satisfied the theoretical requirement of Nernst equation.
2. Tested for a standard buffer of known pH, this micro-glass pH electrode gave pH readings as reproducible as did a large glass pH electrode; thus the standard deviation of mean of ten consecutive measurements was 0.005 pH for both electrodes.
3. This micro-glass pH electrode was applied to the intracellular pH measurement of the sap of a single cell of Nitella flexilis, a fresh water alga. Stable intracellular pH recordings were obtained with minute fluctuations less than 2 mV (0.04 pH) for the period of at least 30 minutes, during which a normal plasma streaming continued around the electrode and up to the very edge of the cut end. The mean pH of the sap was 5.6 at 20°C for a lot obtained from pond in November, in a good agreement with a previous measurement by IRWIN (1923, 1930). From two consecutive measurements in one and the same cell, it was concluded that a single pH measurement in Nitella gave a pH reading which was reproducible with errors of less than 0.1 pH.
