The Influence of Sample Acidification on the Speciation of Iron(II) and Iron(III)

Abstract

The influence of sample acidification on the speciation of iron in aqueous solutions has been investigated. When hydrochloric acid is used, iron(II) is transformed into several moieties, believed to be chloro-complexes, whose chromatographic properties are quite different from those of the parent iron(II) species. This process is favored by high (>0.5 M) HCl concentrations.

The determination of iron in acidified samples can be complicated by this transformation, especially if the chromatographic process used cannot separate all the iron species formed. This study points to the necessity to carefully characterize and specify the prevailing sample conditions when iron speciation is done. The strong influence exerted by acidification would suggest that the data obtained be classified as 'conditional', specifying the acid concentration at which measurements were done.

Key Words:

• Element speciation
• ion chromatography
• element selective detector
• element transformation