High-precision Fe isotopic analysis of whole blood for biomedical purposes without prior isolation of the target element

Abstract

Recently, it has been documented that Fe isotopic analysis of whole blood and serum by means of multi-collector ICP-mass spectrometry (MC-ICP-MS) provides promising results in a biomedical context and, thus, there is a demand for simple, fast and reliable methodologies, providing a high sample throughput. In this work, the possibility of Fe isotopic analysis by MC-ICP-MS directly in acid-digested whole blood and, thus, without prior Fe isolation was evaluated. The influence of the main mineral matrix elements and the effect of potentially remaining organic compounds were first systematically evaluated using synthetic solutions. The Fe isotopic composition was biased low in the presence of matrix elements such as Na and K, while it was biased high for glucose concentrations ≥ 1% (w/v). Nevertheless, after dilution of the whole blood sample digest to 0.75–1.5 mg L⁻¹ of Fe, followed by adequate correction for instrumental mass discrimination using a combination of internal (with admixed Ni) and external correction, MC-ICP-MS isotope ratio measurements provided accurate and precise results. For actual samples, the Fe isotopic data thus obtained agree well with those obtained using the reference procedure, based on prior chromatographic isolation of Fe from acid-digested blood.