TIMS: Long Term Reproducibility of Nd Isotopic Data Acquired on TRITON Plus

Importance of the Topic

Neodymium isotopic measurements at the parts-per-million level are essential in fields such as geochronology, geochemistry, cosmochemistry and environmental science. High precision and long-term reproducibility under varied sample loads enable accurate age dating, tracing elemental sources and studying planetary processes.

Objectives and Study Overview

This application note evaluates the one-year precision and reproducibility of Nd isotope ratios acquired on a Thermo Scientific TRITON Plus TIMS using static mode measurements with a virtual amplifier setup. The performance was assessed on Nd metal standard loads from 500 ng down to 100 ng over 73 analytical runs spanning one year.

Methodology

Samples of Merck Nd standard (170335) were loaded onto double zone-refined rhenium filaments with phosphoric acid as an activator. Measurements were performed in static multi-collection mode using 1011 Ω amplifiers. A virtual amplifier scheme rotated amplifier–cup connections in cycles to average out gain calibration biases. Acquisition parameters included 320–480 ratio measurements per run, baseline acquisition prior to each block, and exponential mass bias correction normalized to the 146Nd/144Nd ratio.

Used Instrumentation

• Thermo Scientific TRITON Plus Thermal Ionization Mass Spectrometer
• 1011 Ω Faraday amplifiers
• Virtual amplifier switching hardware
• Zone-refined rhenium double filament assemblies

Main Results and Discussion

Long-term external reproducibility (2RSD) of 143Nd/144Nd ratios was 2–5 ppm/amu for 500 ng loads (n=57) and 2–6 ppm/amu for 100 ng loads (n=16) over one year. Analyses with higher 142Nd ion beam intensities (9–10 V) achieved 1 h run times, whereas lower intensities (5 V) required 1.5 h. Results demonstrate that rotating the amplifier–cup associations effectively mitigates amplifier gain drift, yielding reproducible isotope ratios comparable to literature benchmarks.

Benefits and Practical Applications

The optimized static mode with virtual amplifier provides:

• Faster analysis times (1 h) while maintaining high precision
• Reliable long-term stability for routine Nd isotopic measurements
• Sensitivity down to 100 ng sample loads

This approach supports high-throughput workflows in geochemical laboratories and enhances data quality for chronological and tracer studies.

Future Trends and Possibilities

Future developments may include further miniaturization to push sample load limits below 100 ng, integration of advanced amplifier technologies to improve signal stability, and automation of filament handling for increased throughput. Expanding virtual amplifier concepts to other isotopic systems could broaden high-precision applications.

Conclusion

The TRITON Plus TIMS static mode using a virtual amplifier configuration delivers robust long-term reproducibility of Nd isotopes at 2–6 ppm/amu over one year. This method enables faster turnaround and supports routine high-precision geochemical analyses.

References

1. Caro et al. (2003) Nature, 423, 428–432.
2. Boyet and Carlson (2005) Science, 309, 576–581.
3. Delmonte et al. (2008) Geophysical Research Letters, 35, L07703.
4. Harvey and Baxter (2009) Chemical Geology, 258, 251–257.
5. Thermo Fisher Scientific (2014) Application Note 30015.