Low-blank chemistry for Zn stable isotope ratio determination using extraction chromatographic resin and double spike-multiple collector-ICP-MS

Abstract

A new low-blank Zn separation method employing an extraction chromatographic resin using Aliquat 336 (commercially available as TEVA resin) has been developed for Zn isotope composition determination by double spike-multiple collector-ICP-MS. The silicate sample solution containing 0.1 μg Zn in 0.5 mol L⁻¹ HBr containing 0.15% ascorbic acid (AA) is passed through a 1 mL column with 0.33 mL TEVA resin. While Zn is absorbed, major elements are eluted with 0.5 mol L⁻¹ HBr with AA. Afterwards, Zn was recovered with 2 mol L⁻¹ HNO₃. Recovery yield using silicate samples was 96.7 ± 6.8% (n = 10) and total blank was 0.05 ng (n = 6). The blank level is from 1/300 to 1/20 of previous studies, meaning 0.1 μg of Zn is sufficient for analysis. The ⁶⁷Zn–⁷⁰Zn double spike method was used in MC-ICP-MS. δ⁶⁶Zn of three USGS standard silicate reference materials (BHVO-1, AGV-1 and PCC-1) and seven GSJ silicate reference materials (JB-1, -2, -3, JA-1, -2, -3 and JP-1) were determined. Reproducibility of δ⁶⁶Zn of the total silicates was 0.19‰ (2SD). δ⁶⁶Zn of three carbonaceous chondrites (Orgueil, Murchison and Allende) were also determined and compared with those of references.