An improved procedure for the electrochemical determination of serum ionized calcium

The effect of respiratory and metabolic acid‐base changes on ionized calcium concentration: in vivo and in vitro experiments in man and rat

“…Calcium-sensitive electrodes have been found to be the most direct and reliable method for the measurement of ionized calcium when applied under well defined conditions. Recently, several systems utilizing calcium sensitive electrodes have been used successfully including in uitro [5,13,16, 171 as well as in vivo measurements [14]. In the present study, pH and Ca2+ measurements were performed simultaneously to obtain optimal conditions for the evaluation of their interdependence.…”

“…Recently, several systems utilizing calcium sensitive electrodes have been used successfully including in uitro [5,13,16, 171 as well as in vivo measurements [14]. Previously, the rule of thumb or sophisticated formulae were used to predict the concentration of ionized calcium from the determined concentration of total calcium.…”

Measurement of free ion concentrations by spectrophotometry: the sample ion increment method

“…In principle, ion selective electrodes offer a nearly ideal method of measuring free ion concentrations, though only a few electrodes have gained widespread application for this purpose (27). Of these the calcium ion-selective electrode has become increasingly popular for measuring ionic calcium in serum (3,(28)(29)(30). However, direct potentiometric methods are often limited by lack of selectivity, difficulties in matching standards to samples, variations in ionic strength, and uncertainties in junction potentials.…”