吸光光度法によるppb レベルヨウ化物イオンの触媒酸化反応について

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The method for the determination of ppb level concentration of iodide ion has been developed by means of flowanalysis based on the catalytic oxidation reaction of 4,4'-bis (dimethylamino) diphenyl methane (tetrabase). A sample solution was pumped (1.6ml min-1) into a reaction solution which was a mixture of 0.4g dm-3 chloraminT(0.8ml min-1) and 0.1g dm-3 tetrabase (0.8ml min-1). The absorbance (604nm) of mixture via reaction coil (14s)was measured by flow absorption spectrometer. A linear relationship was obtained between the peak height (absorbance)and the concentration of iodide ion in the range 0〜20ppb. The detection limit (S/N=5.1) was 1.0ppb iodide ion. In this study, it was found that the relative response of I-, Br- and Cl- were 2.32×104,1.38×102 and 1.00, respectively. The oxidation potential of I2, Br2, Cl2 and ClO- are 0.54, 1.06, 1.36, 0.89V, respectively. We concluded that thoseoxidation reaction ratios were depend on the hydrophobic property of the oxidizing species because the hydrophobicoxidizing species are easy to reach the hydrophobic reduction group of tetrabase. On the other hand ClO- are hard toreach the reduction group. The cycle number of the reaction (2I-→ I2→2I-) in this method was estimated as 57.7 using the ε of oxidant oftetrabase( ε=1.21×105). The iodide ion forms the precipitants with some heavy metal ions (Ag+, Pb2+, Hg2+). It was found that the decreasedabsorbance were proportional to the concentration of the heavy metal ion when the concentration of iodide ionadded was constant.
2012-04-30

吸光光度法によるppb レベルヨウ化物イオンの触媒酸化反応について

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