NMR分光法による水評価

概要

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The line width (half width) of 17O magnetic resonance and spin-lattice relaxation time, T1, of 17O and 2H nuclei were measured for pure water at 298 K by NMR spectroscopy. The values of T1 for 17O and 2H nuclei in the water were constant in the pH range of 1 to 13, whereas the broadening of 17O-half width occurred in the pH range of 5 to 9. The rotational correlation times of 17O and 2H nuclei calculated from the T1 values agreed well with those so far reported. Therefore, the rotational movement of the water molecule is independent of pH. The broadening of half widths depends on the exchange rates of proton in water and the coupling between 17O and 1H. These exchange rate constants and coupling constant were estimated from the broadening data. The values of T1 for 22 kinds of commercial natural water contained to about 1.5-650ppm (mg·dm-3) as CaCO3 hardness agreed well with T1 for the pure water, while the half widths fitted on the curve of half width-pH obtained from the pure water. From these results, the half widths for pure water and ordinary natural water can not use as the factor for a size of water clusters suggested by Matsushita.