Method Development and Validation for Simultaneous In Situ Fe Isotope and Multi-Element Analysis by LASS MC-ICP-MS/ICP-ToF-MS

Abstract Simultaneous acquisition of elemental and isotopic data is essential for resolving complex geochemical and biogeochemical processes but is often limited by separate analytical workflows. Here we present a laser ablation split-stream (LASS) MC-ICP-MS/ICP-ToF-MS approach for the simultaneous determination of Fe isotope ratios and multi-element concentrations from a single ablated volume. Method performance was validated using basaltic glass reference materials (BHVO-2G, BCR-2G) and in-house gelatin samples mimicking organic matrices. The obtained δ56Fe values for BHVO-2G (0.14 ± 0.27 ‰, 2s, n = 19) agree with solution-based measurements within analytical uncertainty. Elemental quantification by LASS-ICP-ToF-MS yields recoveries predominantly within 80−120%, demonstrating reliable multi-element performance under split-stream conditions. Calibration in gelatin matrices shows linear responses (R2 = 0.89−0.98) accurately reproducing validation samples for concentrations of 250 and 400 mg kg−1. The reduced linearity is attributed to variability in ablation behavior related to gelatin film heterogeneity, elemental distribution and transient signal instability during laser ablation. The δ56Fe values for the 500 mg kg−1 gelatin sample (0.12 ± 0.31 ‰, 2s, n = 19) was within the analytical uncertainty of conventional (ns)LA-MC-ICP-MS measurements (0.17 ± 0.26 ‰, 2s, n = 9). Overall, the LASS MC-ICP-MS/ICP-ToF-MS approach enables accurate simultaneous isotopic and elemental analysis across both inorganic and organic matrices, providing an effective platform for integrated isotope−element investigations in diverse fields.