Banri Ushiki
Development of a Dye Nanoparticle-coated Test Strip for speciation Analysis of minute amounts dissolved Iron(II) IonĦĦand Iron(III)
Yukiko Takahashi
Two types of dye nanoparticle coated test strips (DNTSs) for simultaneous speciation analysis of minute amounts Fe2+ and Fe(III) ions in environmental water were fabricated by loading the nanocomposites consist of bathophenanthroline disulfonate and methylthymol blue as a indicator dye respectively on a membrane filter. Both DNTSs were reacted at pH 2.3 and pH 3.3 to prevent the oxidation of Fe2+ as well as the hydrolysis of Fe(III). First, the results of DNTS for Fe2+; although Fe(III) significantly interfered to the intensity of red color of Fe2+ DNTS under fluorescent light, no interference of Fe(III) was observed under light shielding conditions. Groundwater samples indicating initial pH 7.12 and 11 Ħî were collected from a well in Nagaoka Univ. of Tech. Fe2+ concentrations of two different samples, one was treated with air bubbling for 1 minute immediately after water sampling; the other was without bubbling, were compared from the viewpoint of dissolved oxygen concentrations. A bathophenanthroline disulfonate immobilized DNTS was immersed into a sample solution (pH 2.3) for 10 seconds and then measured the intensity of red color. The DNTS succeeded in detecting the difference in Fe2+ concentration between two samples and tracking each concentration variation depends on exposing time in atmosphere. Based on the reported oxidation rate equation, estimated data were nearly same as experimental from 0 to140 min but quite different more than 140 min. Second, the results of DNTS for Fe(III); Fe2+ also reacted with the Fe(III) DNTS, the reaction rate of Fe2+ was about one sixth of that of Fe(III)
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