TIMS (Thermal Ionization Mass Spectrometry)

TRITON Plus (Thermo Fisher Scientific)

TIMS is a mass spectrometry that precisely measures the isotopic composition of an element that is placed in a high-vacuum ion source. The element of interest loaded on a metal filament is ionized by heating the filament at a high temperature. The ion beam is introduced into the magnetic sector mass analyzer to separate the ions based on their mass. The ion beam current is measured either by Faraday cups or secondary electron multipliers (SEM).

In TIMS analysis, it is necessary to separate and extract only the target element with high purity from the sample prior to measurement, which makes the analysis by TIMS complicated. Also, it is not easy to measure elements with large ionization potential such as Hf and Th. For these reasons, isotope measurement using ICP-MS is getting more common in recent geochemistry. However, TIMS has a kinetic energy distribution of about 0.5 eV, which is extremely small compared to ionization by plasma (more than 100 eV). Therefore, recent TIMS instruments with improved ion optics and detectors are capable of determining the isotopic ratios with an external precision of several ppm. In our laboratory, we utilize TIMS for analyzing isotope compositions of Sr, Mo, Te, Nd, Sm, Er, Yb, Os, Pb, Th, and U in terrestrial and extraterrestrial materials.