Critical parameters and optimization of a magnesium-selective liquid membrane electrode for application to human blood serum

History of the development of magnesium—selective ionophores and magnesium—selective electrodes

“…An allowable error of 1% is assumed for calculations. The calculations are based on [41], [43], and [45].…”

Development of Magnesium-Ion-Selective Microelectrodes Based on a New Neutral Carrier ETHT 5504

“…The experiments show that the effect of the lipophilic borate salt (KTpClPB) accounts primarily for the 1:1 stoichiometry of the complex between ionophore and magnesium ions, and the discrimination of calcium ions which have the same charge number but higher stoichiometry in the complex [40]. Electrodes based on membranes B showed high discrimination of Ca 2þ as described earlier [2,11,15,17,24]. The basics were discussed and correlated with experiments for the new malonic diamide ionophores [41].…”

“…Since these data are not sufficiently investigated in rats, this transformation will not be made here. Based on investigations by various authors [2,17,28], the free magnesium concentration amounts to ca. 65 to 72 % of the total magnesium concentration in human blood plasma.…”

“…Prior to the application of magnesium ion selective electrodes in clinical chemistry, there was no simple and reliable method which allowed one to determine free magnesium ions in blood. At the beginning of 1990's, the first publications on Mg 2þ -selective potentiometric measurements in human serum appeared [15,17]. It was also demonstrated that automated measurements of ionized magnesium, together with other electrolytes in blood, could be routinely performed with such analytical devices and without the necessity of any pretreatment of the specimen [17,18,[28][29][30][31].…”

“…Several carriers ETH 5282 [15], ETH 5214 [1a, 20, 22, 32], ETH 5250 [18,28], ETH 7025 [17,21,22,24,29], ETH 3832 [27,33], ETH 5506 [21,33], and the derivative of o-phenanthroline [30], have now been used in potentiometric clinical analysis. The apparent influence of calcium has to be compensated for by numerical techniques for most of the sensors specifically in the extracellular space where the Ca 2þ -exceeds the Mg 2þ -molality by a factor of ca.…”