Measurement of the enriched stable isotope 58Fe in iron related disorders- comparison of INAA and MC-ICP-MS

As a safer alternative for the use of radioactive tracers, the enriched stable ⁵⁸Fe isotope has been introduced in studies of iron metabolism. In this study this isotope is measured with instrumental neutron activation analysis (INAA) in blood samples of patients with iron related disorders and controls after oral ingestion of a ⁵⁸Fe containing pharmaceutical. Results were compared with those derived from MC-ICP-MS, applied on the same samples, and analytical and practical aspects of the two techniques were compared. Both techniques showed an increased absorption and incorporation in red blood cells of the ⁵⁸Fe isotope in iron deficient patients in contrast to the controls. In all individuals results of INAA measurements were in good agreement with those of MC-ICP-MS (|zeta| < 2). Uncertainties in INAA are substantially higher than those achievable by MC-ICP-MS but the INAA technique offers a high specificity and selectivity for iron close to 100%. In contrast to INAA, sample preparation before measurement is very critical in MC-ICP-MS and interferences with ⁵⁸Ni and ⁵⁴Cr may hamper the measurement of ⁵⁸Fe and ⁵⁴Fe respectively. Since it takes at least five days after irradiation to reduce the activity of interfering radionuclides (mainly ²⁴Na), INAA is a more time consuming procedure; the need of a nuclear reactor facility makes it also less accessible than MC-ICP-MS. Costs are comparable. Both INAA and MC-ICP-MS are able to adequately measure changes in iron isotope composition in blood when an enriched stable iron isotope is applied in clinical research. Although MC-ICP-MS is more sensitive, is faster and has easier access, in INAA preparative steps before measurement are simpler and there are hardly demands on the kind and size of the samples. This may be relevant working with biomaterials in a clinical setting.

Large-sample neutron activation analysis in mass balance and nutritional studies

Low concentrations of elements in food can be measured with various techniques, mostly in small samples (mg). These techniques provide only reliable data when the element is distributed homogeneously in the material to be analysed either naturally or after a homogenisation procedure. When this is not the case or homogenisation fails, a technique should be applied that is able to measure in samples up to grams and even kilograms and regardless of the distribution of the element. An adaptation of neutron activation analysis (NAA), called large-sample NAA, has been developed and proven accurate and may be an attractive alternative in food research and mass balance studies. Like standard NAA, large-sample NAA can be used to measure both toxic and trace elements relevant for nutrition.