A METHOD FOR THE MEASUREMENT OF IONIZED MAGNESIUM

The role of ionized magnesium (Mg++) in biological processes only rece ntly has received experimental attention and is not yet clearly define d. Several efforts to develop ion-selective electrodes (ISEs) sensitiv e to magnesium have been reported, and significant progress has been a chieved with the use of ionophore-based selective electrodes involving malondiamide subunits. We evaluated a magnesium ISE based on one of t hese carriers in the AVL 988-4 Na/Mg/Ca/pH analyzer (AVL Scientific, R oswell, Ga). We studied the performance of this analyzer in terms of p recision, linearity, and relative accuracy. Precision of the electrode was excellent, with a linear response over the pathologically signifi cant range. Accuracy of Mg++ measurement is difficult to assess becaus e of the lack of a reference method and primary standards. The ISE wil l provide the much-needed technology for evaluating the use of Mg++ in patient care management.