Kinetic Spectrophotometric Determination of Iron(II) Based on Its Inhibitory Effect on the Oxidation of Methylthymol Blue by Bromate

Abstract

A simple and sensitive kinetic-spectrophotometric method
has been described for the determination of trace amounts of
iron(II). The proposed method is based on the inhibitory
effect of iron(II) on the oxidation of methylthymol blue by
bromate in the sulfuric acid media and at 35ºC, which was
monitored at 440 nm. The variables affecting the rate of the
reaction were investigated and the optimum conditions were
established. Iron(II) can be measured in the range of 1.0-200.0
ng/mL with a detection limit of 0.6 ng/mL. The relative
standard deviations for ten replicate analysis of 50 and 160
ng/mL of Fe(II) were obtained 1.2% and 2.0 %, respectively.
The method was found to be relatively selective in the
presence of foreign ions. The developed method was
successfully applied to the determination of iron(II) in pharmaceutical
products and real water samples.