Iron Isotope Ratios of <scp>IAEA B5</scp> Basalt and Whole‐Rock Reference Materials ( <scp>JB</scp> ‐2, <scp>BHVO</scp> ‐2, <scp>AGV</scp> ‐1, <scp>BE</scp> ‐N and <scp>RGM</scp> ‐1) Determined by Multi‐Collector Inductively Coupled Plasma‐Mass Spect

Iron isotopes are increasingly applied in Earth science fields, including cosmochemistry, geochemistry and environmental sciences. Refining non‐traditional stable isotope systematics requires well‐characterised isotopic reference materials to ensure accuracy and precision. Consequently, the direct comparison of data obtained from different laboratories is a key prerequisite for establishing reliable isotopic systematics. Here, we describe a new Fe isotope measurement method using multi‐collector‐ICP‐MS. The Fe isotope ratios of widely used geological reference materials (JB‐2, BHVO‐2, BE‐N, AGV‐1 and RGM‐1) were measured and new Fe isotope values for IAEA‐B5 (basalt from Mount Etna, Italy) are recommended. Anion exchange chromatography was used to separate Fe from the rest of the matrix. Mass bias was corrected using a standard‐sample‐standard bracketing method combined with Ni‐doping. Iron isotope ratios of JB‐2, BHVO‐2, BE‐N, AGV‐1 and RGM‐1 show strong agreement with published values and fall within reported analytical uncertainties. Based on these results, we validate and propose δ 56 Fe = 0.103 ± 0.064 (2 s ) and δ 57 Fe = 0.141 ± 0.068 (2 s ) as recommended values for IAEA‐B5. We further advocate the IAEA‐B5 as a robust and complementary reference material for analytical validation and quality control in Fe isotope studies, providing both a supplement to and an alternative for established iron isotope reference materials.