A new strategy for improving the precision and accuracy of isotope ratio analysis by quadrupole ICP-MS with the optimization of ion beam trajectory

Abstract

Non-traditional stable isotopes are widely utilized in geoscience and other fields. However, it remains challenging to analyze many samples quickly with high accuracy and precision. In this study, new optimization strategies are proposed to improve the precision and accuracy of isotope ratio analysis using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). The instrument voltage parameters of cell entrance/exit voltage (CEV), cell rod offset (CRO), and quadrupole rod offset (QRO) were optimized to control the ion trajectory and reduce mass discrimination. The detector's signal acquisition parameters were also optimized to improve the precision of isotope ratio analysis. After optimization, the mass deviations in B, Sr, and Pb isotope measurements were significantly reduced to −0.25%, −0.13%, and −0.34%, respectively. The proposed isotope analysis method was applied to geological standard reference materials, including AGV-2, BCR-2, BHVO-2, GSR-7, GSD-21, GSD-23, and GSS-14. The measured values of B, Sr, and Pb isotopes were in agreement with the reported values. The precision values (2SD) for B, Sr, and Pb were better than 1.20‰, 0.34‰, and 0.00308, respectively. This approach enables direct analysis of various geological matrices without chemical separation and purification, making it possible to rapidly process large sample batches. It provides a more economical and simpler alternative, favoring the development of isotope-related applications in more fields.