Abstract: EDTA was used as an enhancer for Fe²⁺ catalyzed light emission from luminol oxidation by dissolved oxygen. As a result, the limit of detection for ferrous ion with flow injection analysis was improved by a factor of 160 by addition of EDTA to the luminol solution. Fe²⁺ and Fe³⁺ were determined simultaneously with a novel copper-coated zinc reductor minicolumn installed in one of the shunt after sample splitting in the manifold. The reductor minicolumn can be used for 3000 determinations at least. The dynamic range of determination was 1×10^-9 ~ 1×10^-5 mol·L^-1, with the limit of detection of 2.7×10^-10 and 3.5×10^-10 mol·L^-1, for Fe²⁺ and Fe³⁺, respectively. The precision for determination of 2×10^-7 mol·L^-1 of Fe²⁺ and Fe³⁺ was 2.3% and 4.0% (n = 8), respectively, at a sampling rate of 60 h^-1. Cr³⁺ and Co²⁺ interfere. Fe²⁺ and Fe³⁺ in mixture were determined with satisfactory results. Samples of Fe²⁺ and Fe³⁺ were determined simultaneously and the results in good agreement with the standard spectrophotometric method. Indications were shown that EDTA functions as an enhancer, Fe²⁺ as a catalyst, and oxygen is the oxidant of the chemiluminescent reaction, and the mechanism of the reaction was discussed.

Key words: Flow injection analysis, Ethylenediamine tetraacetic acid, Ferrous ion, Ferric ion, Luminol, Chemiluminescent assay