Chemiluminescence determination of Iron(III) with 1, 10-phenanthroline

Abstract

Flow injection analysis with chemiluminescence detection was investigated to determine small amounts of ferric ions by means of the 1, 10-phenanthroline-hydrogen peroxidesodium hydroxide system containing cationic surfactant. The present chemiluminescence method was based on the following chemical reactions. Superoxide radical anion was produced by catalytic decomposition of hydrogen peroxide in the presence of the Fe(III)-1, 10-phenanthroline complex. The superoxide radical anion reacts with 1, 10-phenanthroline to form the 1, 2-dioxetane, which emits chemiluminescnce via a excited 3, 3'-diformyl-2, 2'dipyridyl. The limit of the determination for Fe(III) was 0.1 ppb under the optimum conditions. Furthermore, we investigated the effect and role of the micelle on the chemiluminescence by spectrophotometry. Among the examined cationic surfactants, zephiramine provided the highest enhanced chemiluminescence, with a peak intensity approximately 92 times higher than that in the absence of surfactant. The concentration ratio of Fe(III) chelate {the fraction of Fe(III) chelate adsorbed on the micelle surface} was calculated to be 16.7% by using the concentration of Fe(III) in the aqueous phase. The role of the micelle was revealed through the 3D spectra of Fe(II)-1, 10-phenanthroline complex formation, that is, the micelle enhanced the rate of chelate reaction. Furthermore, the chelate was concentrated on the micelle, and reacted with hydrogen peroxide to form the superoxide radical anion; as a result, the micelle enhanced the chemiluminescence.