Determination of Mg++ concentration by 31P nuclear magnetic resonance of ATP

Determination curves were obtained for the measurement of Mg++ concentration based on chemical shift (δαβ) and the coupling constant (Jαβ) of FT-nuclear-magnetic resonance (FT-NMR). The chemical shift of 31P in ATP was dependent on the Mg++ concentration and showed a nearly straight line for Mg++ determination in the range of 0 ∼ 5.0 mM concentration. The coupling constant of 31P was dependent on Mg++ concentrations in the range of 1.0 ∼ 5.0 mM, but did not show any dependency at concentrations under 0.5 mM. When Mg++ and Ca++ coexisted the determination curve founded on the chemical shift could not be used for Mg++ determination unless the concentration of one of the ions or amount of total ions in the solution was known. In addition, the coupling constant was not useful for the preparation of the determination curve because of its irregular value. (author)