Rapid in situ laser digestion for high-precision barium isotope analysis of barite using double spike MC-ICP-MS

Abstract

Accurate isotope analysis of chemically resistant minerals such as barite remains a significant challenge due to their poor solubility and the labor-intensive nature of conventional sample preparation techniques. Here, we present a novel, rapid in situ laser digestion method for high-precision, high-spatial-resolution barium (Ba) isotope analysis of barite, using a ¹³⁵Ba–¹³⁷Ba double spike and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). This rapid in situ laser digestion technique enables the instantaneous thermal decomposition of barite within a water microdroplet, followed by direct isotope analysis of the resulting solution after addition of the ¹³⁵Ba–¹³⁷Ba double spike, eliminating the need for extensive sample pretreatment and chemical purification. Analysis of four natural barite samples using this method yielded δ^137/134Ba values in excellent agreement with reference values, with long-term external precision better than ±0.05‰ (2SD). The proposed method significantly advances Ba isotope analysis, enabling rapid, high-precision measurements of insoluble minerals with minimal sample handling and high spatial resolution.