Analytical Sciences

Flow-Injection SpectrophotometricDetermination of Nanogram Levels of Iron(III) withN,N-Dimethylformamide

Adem ASAN, Muberra ANDAC, and IbrahimISILDAK 

Ondokuz Mayis University, Faculty ofScience, Department of Chemistry, 55139 Kurupelit-Samsun,Turkey

A simple and fast flow-injectionspectrophotometric method has been described for the determination ofiron(III). The method is based on the measurement of absorbance intensityof the complex that is formed between iron(III) andN,N-dimethylformamide (DMF) at 310 nm. The carrier streamwas just a mixture of water and DMF at ratio 5% (v/v). The method ishighly selective; most of the 30 metal ions and anions tested did noteffect on the determination of iron(III) even when present up to 1000-foldexcess over iron(III). The calibration graph for iron(III) obtained underoptimized conditions were linear in the range 5 - 90 ng ml^-1with a detection limit of 0.1 ng ml^-1 for a 20 µl injectionvolume. The reproducibility was satisfactory, with a relative standarddeviation of 2.4% (n = 5) in the range of 5 - 90 ng ml^-1of iron(III). The sampling rate was over 60 h^-1. The developedmethod was succesfully applied to the determination of total iron in riverwater, seawater, hot spring water and iron alloy samples. The accuracy ofthe method was evaluated using the standard addition method and checked bythe certified reference metal alloy samples.

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