Determination of Aqueous FeIII/III Electron Self-Exchange Rates Using Enriched Stable Isotope Labels, Ion Chromatography, and Inductively Coupled Plasma Mass Spectrometry

Gary E. Kozerski, Michael A. Florentino, Michael E. Ketterer

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5 Scopus citations


A strategy is described for rapid on-line measurement of electron self-exchange rates between aqueous FeIII and FeII in aqueous solution using stable 57Fe-labeled reactants, cation chromatography, and inductively coupled plasma mass spectrometry. The self-exchange is monitored by mixing the reactants and performing timewise separations of FeII and FeIII ions. Separations are completed in 30-60 s using a weak phosphonic/carboxylic acid cation exchange guard column and 0.1-0.5 M aqueous HClO4 eluent. The resulting time series of 56Fe and 57Fe chromatograms display systematic changes in isotopic abundances from which the self-exchange rate constant, k11, is obtained. Two different schemes are used for mixing and sampling the reaction mixture; using a peristaltically pumped flow reactor, reaction half-lives on the order of 30 s can be monitored. A series of k11 results are obtained under a variety of temperature (2.0, 21.6, and 25.0 °C) and ionic strength conditions (0.10, 0.50, and 0.55 M aqueous HClO4) which are congruent with three previously published radiolabeling studies for this reaction.

Original languageEnglish (US)
Pages (from-to)783-788
Number of pages6
JournalAnalytical Chemistry
Issue number4
StatePublished - Dec 1 1997


ASJC Scopus subject areas

  • Analytical Chemistry

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