Determination of Iron(II) in Pharmaceuticals Based on Its Catalytic Effect on the Bromate–Crystal violet Reaction by Spectrophotometric Detection

Abstract

A simple, selective, and sensitive kinetic spectrophotometric method with no need for removing
iron(III) interference is proposed for determination of iron(II) in pharmaceutical and water samples.
This method is based upon the catalytic effect of iron(II) on the sodium bromate–crystal violet system
in acidic media. Decolourization of crystal violet was used to monitor the reaction
spectrophotometrically at 630 nm. The variables affecting the reaction rate were investigated. Under
the optimum conditions, iron(II) can be determined in the range of 0.10 – 3.0 μg mL-1 with a 3σ
detection limit of 0.025 μg mL-1. The relative standard deviations for ten replicate determinations of
0.50, 1.0, and 1.5µg mL-1 were 1.94%, 0.43%, and 0.28%, respectively. The influence of various
foreign species was studied and it was found that without addition of a masking agent, Fe(III) did not
interfere with the Fe(II) determination up to 50-fold concentration of this ion. This method could be
used successfully for determination of the iron(II) content of spiked water and pharmaceutical
samples.