1997 Volume 67 Issue 2 Pages 43-48
It is generally accepted that ionized magnesium (Mg^<2+>) is the physiologically active form of magnesium in the blood, however, it has been difficult to measure Mg^<2+>. Recently, a novel ion selective electrode (ISE) for Mg was developed by NOVA biomedical. As the NOVA8 (NOVA biomedical, U.S.A.) was utilized to examine Mg^<2+> measurement using NOVA8 was investigated, in preliminary studies. We assessed the reproducibility of three levels of Mg^<2+> measurements, the linearity of standard diluted solution, whether the carry-over occurs, the stability of Mg electrode by means of within-run and day-to-day measuring on three levels (0.35, 0.50, and 1.60 mmol/l Mg^<2+>), the effects of cations on Mg electrode, and the recovery ration of Mg^<2+>. The reproducibility of Mg^<2+> was well correlated (coefficient of variation[CV]: 0.0〜1.71%). Measurements of Mg^<2+> by ISE was well correlated with the standard aqueous solutions containing MgCl_2 from 0.2 to 3.0 mmol/l (r=0.99, y=0.88x+0.07). Carry-over did not occur. Using three levels of aqueous control, the within-run CV was <2.9%, the day-to-day CV was <1.2%, By adding 5.0 mmol/l Ca^<2+>, the apparent increase in the Mg^<2+> activity (0.21 mmol/l) as shown. But the concentration of Ca^<2+> was clinically insignificant. When Mg^<2+> was added to plasma samples, 97〜98% of recovery ratio was observed. These results suggest that the NOVA8 is a useful equipment to measure Mg^<2+>.
