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Title: Determination of ferrous and total iron in refractory spinels

Accurate and precise determination of the redox state of iron (Fe) in spinels presents a significant challenge due to their refractory nature. The resultant extreme conditions needed to obtain complete dissolution generally oxidize some of the Fe(II) initially present and thus prevent the use of colorimetric methods for Fe(II) measurements. To overcome this challenge we developed a hybrid oxidimetric/colorimetric approach, using Ag(I) as the oxidimetric reagent for determination of Fe(II) and 1,10-phenanthroline as the colorimetric reagent for determination of total Fe. This approach, which allows determination of Fe(II) and total Fe on the same sample, was tested on a series of four geochemical reference materials and then applied to the analysis of Fe(Ni) spinel crystals isolated from simulated high-level-waste (HLW) glass and of several reagent magnetites. Results for the reference materials were in excellent agreement with published values, with the exception of USGS BIR-1, for which higher Fe(II) values and lower total Fe values were obtained. The Fe(Ni) spinels showed Fe(II) values at the detection limit (ca. 0.05 wt% Fe) and total Fe values slightly higher than obtained by total elemental analysis. For the magnetite samples, total Fe values were in agreement with reference results, but a wide range inmore » Fe(II) values was obtained indicating various degrees of conversion to maghemite.« less
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0003-2670; 830403000
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Analytica Chimica Acta; Journal Volume: 910
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
Country of Publication:
United States
ferrous iron; spinel; 1,10-phenanthroline; nickel; hydrofluoric acid; silver; potentiometry; ferrous ethylenediammonium sulfate; ferrous ammonium sulfate, potassium bromide