Efficient preconcentration of ultra-trace rhenium from geological materials via induced adsorption for accurate isotope analysis†

Abstract

Rhenium (Re) and its isotopes offer valuable information for understanding various geological processes throughout Earth's history. However, Re isotope analysis remains quite challenging owing to its ultra-trace concentration in geological materials. Previous studies have developed column chemistry and analytical methods for Re isotope analysis, but issues such as tedious pretreatment and incomplete Re recovery still exist. Herein, we present a novel procedure integrating preconcentration and fast column chemistry for Re isotope analysis. Utilizing Na₂S solution and activated carbon powder under acidified conditions, we achieved the quantitative recovery of Re from aqueous solutions via filtration while removing most matrices. Standard addition to diverse matrix solutions yielded complete Re recovery (99.6 ± 6.7%, n = 10, 2SD) and precise isotopic compositions (δ¹⁸⁷Re = −0.49 ± 0.04‰, n = 10, 2SD), as determined using multi-collector inductively coupled plasma–mass spectrometry. Our method was applied to seawater (7.1 pg g⁻¹ for Re) and solid reference materials (∼0.5–75 ng g⁻¹ for Re), which resulted in stable and high recovery with isotopic results consistent with published data. Our method exhibits efficient matrix removal with stable and essentially quantitative Re recovery, which paves the way for wide applications of Re isotopes in the earth and planetary sciences.