Simultaneous Spectrophotometric Analysis of Fe2+ and Fe3+ Ions

Two new procedures for simultaneous spectrophotometric analysis of ferrous and ferric ions utilizing their different reactivities to a selective reagent (gallic acid) and/or reagent mixture (5-sulfosalicylic acid and 1,10-phenanthroline) were developed. The measured experimental data are treated by Artificial Neural Network. The concentration ranges used were 0.5-4.0 mg.l-1 (Fe2+) and 1.0-4.0 mg.l-1 (Fe3+) for the determination with gallic acid and 5.0-30.0 mg.l-1 (both ions) for the determination with the reagent mixture. It was demonstrated for the latter method that transition metal cations (Co2+, Ni2+, Mn2+, Cu2+, Zn2+) do not interfere and the method can be used for iron speciation analysis of Czech mineral waters. The proposed methods give precise (RSD < 2 %) and accurate results.