title: Determination of ferrous and ferric iron in aqueous biological solutions.
abstract: A solvent extraction method was employed to determine ferrous and ferric iron in aqueous samples. Fe(3+) is selectively extracted into the organic phase (n-heptane) using HDEHP (bis(2-ethylhexyl) hydrogen phosphate) and is then stripped using a strong acid. After separation, both oxidation states and the total iron content were determined directly by ICP-MS analysis. This extraction method was refined to allow determination of both iron oxidation states in the presence of strong complexing ligands, such as citrate, NTA and EDTA. The accuracy of the method was verified by crosschecking using a refinement of the ferrozine assay. Presented results demonstrate the ability of the extraction method to work in a microbiological system in the presence of strong chelating agents following the bioreduction of Fe(3+) by the Shewanella alga BrY. Based on the results we report, a robust approach was defined to separately analyze Fe(3+) and Fe(2+) under a wide range of potential scenarios in subsurface environments where radionuclide/metal contamination may coexist with strongly complexing organic contaminants.
authors.affiliation: Earth and Environmental Sciences Division, Los Alamos National Laboratory, 1400 University Drive, Carlsbad, NM 88220, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Pepper
authors.forename: M
authors.initials: M
authors.lastname: Borkowski
authors.forename: M K
authors.initials: MK
authors.lastname: Richmann
authors.forename: D T
authors.initials: DT
authors.lastname: Reed
mesh_terms: D002614:Chelating Agents / Q000737:chemistry; D005591:Chemical Fractionation; D019343:Citric Acid / Q000737:chemistry; D004492:Edetic Acid / Q000737:chemistry; D007501:Iron / Q000032:analysis* / Q000378:metabolism; D008024:Ligands; D013058:Mass Spectrometry; D009571:Nitrilotriacetic Acid / Q000737:chemistry; D010084:Oxidation-Reduction; D020592:Shewanella / Q000378:metabolism*; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D008024:Ligands; D012996:Solutions; D012997:Solvents; D014874:Water Pollutants, Chemical; D019343:Citric Acid; D004492:Edetic Acid; D007501:Iron; D009571:Nitrilotriacetic Acid