Redox speciation of iron in waters by resin-based column chromatography

Abstract

Speciation of iron in waters is very important in aiming at the elucidation of biogeochemical cycling of iron and its role in the environment. However, the low concentration of iron in waters, the reversibility of Fe(II) and Fe(III) species and the complexation of the oxidation states of both forms of iron by organic matter demand rigorous sampling and sample-handling procedures. Also required are fast, versatile analytical methods that facilitate preconcentration and/or separation of the species prior to detection at extremely low levels with reasonably high precision and selectivity without altering the integrity of the species in the samples being analyzed. We discuss how most of these requirements can be successfully fulfilled by resin-based mini-columns and micro-columns. We also emphasize the problems associated with iron redox state reversibility during sample pretreatment before analysis using the reported protocols.