Preparation of labeled iron sulfate solutions Enriched 57Fe and 58Fe-ferric oxide (Fe2O3) will be purchased from Oak ridge National Laboratory (Oak Ridge, TN, USA). The isotope compositions of iron in the 58Fe preparation (as provided by Oak ridge National Laboratories) are (mg): (weight%) 54 Fe (0.65), 56 Fe (35.6)57 Fe (3.47), and 58 Fe(60.28). The isotope compositions of iron in the 57Fe (weight%) are; 54 Fe(0.65), 56Fe(35.60), 57Fe (3.47), and 58Fe (60.28).