Analysis of Silicon Isotope Ratios Using the NexION 5000 ICP-MS

Introduction

Silicon (Si), the second most abundant element in the earth’s crust, has three stable isotopes: ²⁸Si, ²⁹Si, and ³⁰Si, with natural abundances of approximately 92.23%, 4.67%, and 3.1%, respectively. Since these ratios can slightly vary based on the source, Si isotope analysis can be leveraged to investigate various Si processing mechanisms, such as rock aging and weathering, silica deposition in plants, and silicon cycling in oceans via diatom skeletons. Because variations in isotope ratios are often very small, the measurement techniques used to determine isotope ratios must be highly sensitive, selective, and stable.

Although multi-collector mass spectrometers have traditionally been used for isotope ratio analysis due to their high sensitivity and resolution, also allowing simultaneous measurement of all masses of interest, they are expensive to own and operate due to the specialized nature of the instrument. Instead, a modern sequential spectrometer, exemplified by the NexION^® 5000 multi-quadrupole ICP-MS, offers a high duty cycle, remarkable sensitivity, and advanced technologies for mitigating spectral interferences. It serves not only quantitative analysis but also isotope ratio determination.

This work demonstrates the suitability of the NexION 5000 ICP-MS for Si isotope ratio analysis based on the system’s exceptional accuracy and stability as well as easy-to-use Syngistix^™ for ICP-MS software.