水圏試料中微量溶存鉄（II）の比色定量における至適pH条件に関する再検討

概要

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The pH conditions for the colorimetric determination of Fe(II) in oxic natural water samples were reexamined for analyses using PDTS (ferrozine) or bathophenanthroline disulfonic acid salt for the fixation of Fe(II) onboard a boat without an electricity supply. Bathophenanthroline disulfonic acid salt enhanced the reduction of Fe(III) to Fe(II), and produced an overestimation of the Fe(II) concentration in the water of a natural lake. PDTS enhanced the reduction of Fe(III) at pH 4.0, but showed almost no reduction of Fe(III) at pH 6.8. Oxidation of Fe(II) was observed at pH 9.0. PDTS at pH 6.8 showed no variation in Fe redox speciation in water within 30 h. As analyzed in the field onboard a boat, the Fe(II) concentration of a Japanese lake was measured by using the latter conditions with a solid-phase Fe(II)-ferrozine complex. Under irradiation with sunlight, the formation of Fe(II) on the lake surface was observed during the daytime. In contrast, the Fe(II) concentration in another lake that received no sunlight did not show a significant change within 6 h of sampling. This finding suggests that a portion of Fe(II) is stabilized by complexation with ligands present in the water. This estimate is supported by the difference between the Fe(II) concentration of identical river water samples measured using this method (26 nmol L−1) and chemiluminescence (0.8 nmol L−1).
社団法人　日本分析化学会の論文