The calcium selective electrode—a possible tool in dental research

Abstract

Ion selective potentiometry is widely used for analytical purposes in biologic research. The Ca selective electrode offers an inexpensive and easily handled means for studying ionized calcium. It does not affect the process studied, and may, for example, combined with an automatic recorder, give running information on dynamic systems.

The calcium electrode responds in accordance with the Nernst equation and has a theoretical range of 1–10⁻⁶ M Ca²⁺. The electrode is influenced by changes in temperature, in pH and also in concentration of buffer solution. The Ca sensitive membrane is adversely affected by acetic acid but tolerates lactate/lactic acid buffers. Best linearity in calibration curves for Ca²⁺ in lactate buffers is found in concentrations from 10⁻⁴ M to 10⁻² M Ca.

In a 5% Na lactate/lactic acid buffer, pH 5, with 0.5 M KNO₃ as an ionic strength adjuster, a straight calibration curve, Nernstian slope factor 27 mV/decade, is found from 10⁻⁴ to 1 M Ca.