Rhenium and osmium analysis in soil and rock samples: a review of ultra-trace detection methods

Abstract

Accurately quantifying rhenium (Re) and osmium (Os) at ultra-trace concentrations in geological matrices, such as soils and rocks, is essential for progress in Earth sciences. The isotopic compositions of these elements serve as critical geochronometers and geochemical tracers, providing valuable insights into mantle evolution, crustal recycling, and ore deposit formation. However, their extremely low natural abundances, often ranging from picograms per gram (pg g⁻¹) to nanograms per gram (ng g⁻¹), present significant analytical challenges that require methods with exceptionally low detection limits.This review presents a detailed comparative analysis of leading analytical approaches for Re and Os determination in geological samples, emphasizing their lower limit of detection (LLD) performance. Mass spectrometry-based techniques, particularly Negative Thermal Ionization Mass Spectrometry (N-TIMS) and Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS), are identified as the most effective methods for achieving ultra-low detection limits. N-TIMS has historically demonstrated superior performance in reaching the lowest absolute LLDs for osmium, frequently attaining picogram-level sensitivity due to its high ionization efficiency and advanced detector technologies. For rhenium, MC-ICP-MS, especially when integrated with advanced chromatographic separation protocols, achieves LLDs in the sub-pg g⁻¹ range. Attaining this level of sensitivity depends not only on instrumental capabilities but also on comprehensive analytical strategies, including meticulous sample preparation, stringent control of procedural blanks, and sophisticated measures for reducing spectral and matrix interferences.To ensure methodological reliability and precision, this review also examines the use of certified reference materials in geological sample analysis. Ongoing advancements in these analytical methodologies remain vital for furthering geochemical research and enhancing our understanding of Earth's intricate history.