A Rapid Method for Preparing Hematite Reference Material for In-situ Determination of Iron Isotope Ratios

The advent of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has opened new avenues for investigating iron isotope cycling across various temporal and spatial scales in biological and geological processes. However, accurate and precise measurements of iron isotopes in hematite have been hindered by the lack of matrix- matched reference materials. In this study, we developed hematite reference materials (RMs) by combining nanopowder pelletization and solid-phase sintering techniques. Nano-Fe2O3 powder was compressed into pellets and subsequently sintered at 1000 degrees C for 120 min. This method produced stable targets with sufficient mechanical strength suitable for in-situ analysis. The prepared hematite exhibited excellent cohesion, smooth surfaces, and dense structures, making it highly suitable for laser ablation analysis. We demonstrated the homogeneity of iron isotopic composition through repeated measurements using LA-MC-ICP-MS. The delta 56 Fe IRMM014 values for the initial powder, sintered pellets, and unsintered pellets were 0.45 +/- 0.04%o (2SD, N=20), 0.44 +/- 0.04%o (2SD, N=21), and 0.45 +/- 0.02%o (2SD, n=3), respectively, indicating high consistency. The integration of pressed powder pellet techniques with high-temperature sintering provides a rapid and convenient method for developing matrix-matched RMs. This approach shows potential for creating diverse matrix-matched reference materials for various analytical applications.