Species-specific Antimony Isotope Analysis by High Performance Liquid Chromatography Coupled with Multicollector ICPMS Using Hydride Generation as an Interface

A novel method has been developed for the simultaneous online determination of the isotopic compositions of different antimony (Sb) species in a single analytical run using high-performance liquid chromatography (HPLC) coupled with multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), with hydride generation (HG) serving as the interface. Various parameters affecting the precision of Sb isotope analysis including HG conditions, transient signal processing methods and peak integration windows, were optimized. The linear regression slope method and a 100% peak integration window provided the optimal precision. Under optimized conditions, our method achieved external 2SD precisions better than 0.05‰ for both Sb(III) and Sb(V), with minimal consumption of 0.5 ng for Sb(III) and 5 ng for Sb(V). Furthermore, flow injection (FI) coupled with HG-MC-ICPMS demonstrated precise Sb isotopic analysis with sample requirements as low as 0.25 ng. The proposed methods were validated by analyzing δ¹²³Sb in synthetic solutions and reference materials. Additionally, it was applied to investigate isotopic fractionation during the reduction of Sb(V) by KI, revealing preferential reduction of the light Sb isotope(¹²¹Sb). The isotopic compositions of Sb(V) varied from -0.04- 1.18‰, fitting well with a Rayleigh fractionation model and yielding a fractionation factor (α_Sb(III)-_Sb(V)) of 0.99831. In summary, this approach enables high precision isotopic analysis of Sb(III) and Sb(V) simultaneously with reduced sample consumption, providing a powerful tool for investigating Sb isotopic fractionation in various environmental processes and advancing our understanding of the Sb biogeochemical cycle.