Improvement of the Eakins and Brown method for measuring 59Fe and 55Fe in blood and other iron-containing materials by liquid scintillation counting and sample preparation using microwave digestion and ion-exchange column purification of iron

The simultaneous measurement of 59 Fe and 55 Fe in whole blood by liquid scintillation counting by the Eakins and Brown (EB) method is extensively used in iron absorption studies. The EB method requires many steps which increase the chances of error and decrease its sensitivity. We describe two modifications to the above method consisting of microwave digestion and column purification of iron. This “New Method” (NM) is simpler and more precise, and sensitive than the EB method. Counting efficiencies with the NM are similar for 59 Fe (75%) as with the EB method but are better for 55 Fe (29% for NM vs 22%), and cross counting from 59 Fe into the 55 Fe window is lower with the NM (3.7–4.5%) than with the EB method (10–12%). For the NM, recoveries of radioactive blood samples, in relation to processed standards ranged from 100 to 103% for 59 Fe and 101 to 113% for 55 Fe. For the EB method, recoveries ranged from 94 to 99% for 59 Fe and from 88 to 93% for 55 Fe. Even with very low counts, average intrarun CV with the NM was lower than 5.4% for either isotope, while it was as high as 10.0% for 55 Fe with the EB method.