Ion-selective Potentiometry Research Articles

Determination of sodium by ion-selective potentiometry

Determination of sodium by ion-selective potentiometry

Determination of chloride, sodium and potassium in salted foodstuffs using ion-selective electrodes and the dry sample addition method.

The “dry sample addition” method of ion-selective potentiometry is described. This incremental or spiking method requires the addition of a known mass of solid sample directly to a standard solution containing the ion to be measured. Dissolution of the sample produces a change in electrode potential which is related to the sample composition. Dry sample addition has been applied to the analysis of foodstuffs containing up to 2.8% of salt. The chloride, sodium and potassium concentrations are determined by Philips solid-state and plastic ion-selective electrodes. Comparison of this method with titrimetry and atomic-absorption spectrometry gave satisfactory results. The advantages gained in cost, speed of analysis and reliability using ion-selective measurement are discussed.

The calcium selective electrode--a possible tool in dental research.

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.