Yoshikazu Iizuka

A Study on the Determination of Ionized Calcium with an Ion-Selective Electrode

The properties of a calcium ion electrode (Orion Research Incorporated) were evaluated and the possibility of its application to medical and dental areas was studied. The electrode potential was affected by various factors; for example, the potential was increased by such monovalent cations as potassium or sodium, and by divalent cations such as magnesium. On the other hand, the potential was decreased by such anions as fluorine, phosphor and others. The decrease of the Nernst factor and the loss of linearity at a low concentration of calcium in the presense of those salts seems to be a characteristic trend of this electrode. Moreover, there were various other factors affecting the electrode potential: pH, ionic strengh, temperature of sample solution and others. In addition, variation from the normal potential is observed occasionally during repeated or continual use of the electrode.Therefore, in calcium determination of biological samples containing many various salts andions, the adjustment of pH and ionic strength is an essential procedure, and also the other affecting factors must be taken into consideration.It is possible to determine roughly the calcium content of the teeth if these affecting factors are taken into account. However, this electrode seems to be of limited usefulness because of the difficulty in adjusting these various factors.