Germanium stable isotope measurements by double-spike MC-ICPMS

Area of Science:

• Geochemistry
• Cosmochemistry
• Analytical Chemistry

Background:

• Precise measurement of mass-dependent germanium (Ge) isotope compositions is crucial for geochemical and cosmochemical studies.
• Existing analytical methods require refinement for improved accuracy and efficiency.

Purpose of the Study:

• To present robust analytical procedures for measuring mass-dependent Ge isotope compositions.
• To validate these procedures using different mass spectrometers and sample introduction systems.
• To assess the utility of Ge isotopes in geochemical and cosmochemical investigations.

Main Methods:

• Utilized a ⁷⁰Ge-⁷³Ge double spike technique with multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS).
• Employed two mass spectrometers (ThermoScientific Neptune Plus and Neoma) and two sample introduction systems: a hydride generator (HGX-200) and a desolvator (Aridus II).
• Validated the procedures using standard solutions, geological materials (basalts), and iron meteorites.

Main Results:

• Achieved high precision with external reproducibility of ±0.09‰ for δ ^74/70Ge.
• Demonstrated efficient separation of Ge from sample matrices, yielding accurate concentration and isotope data.
• Observed excellent agreement between data generated using the hydride generator and the Aridus II desolvator.
• Identified δ ^74/70Ge variations up to ~2‰ across samples.

Conclusions:

• The developed analytical procedures are accurate and precise for Ge isotope measurements.
• The Aridus II desolvator offers an easier and effective alternative for sample introduction in Ge isotope analysis.
• Mass-dependent Ge isotope variations provide valuable insights into geochemical and cosmochemical processes.