Why does the pre-cell mass filter of the Neoma MS/MS MC-ICP-MS revolutionize collision/reaction cell technology?

Significance of the Topic

Collision/reaction cell (CRC) technology coupled with a pre-cell mass filter addresses challenging isobaric interferences in multicollector ICP-MS, especially for complex matrices such as laser ablation samples. By preselecting a narrow mass window, the Neoma MS/MS MC-ICP-MS significantly enhances control over reaction chemistry, leading to more reliable and interference-free isotope ratio measurements.

Objectives and Study Overview

This study introduces the Neoma MS/MS MC-ICP-MS, featuring a double Wien filter ahead of the hexapole CRC. Key objectives include demonstrating how pre-cell mass filtering improves reaction predictability, reduces unwanted molecular interferences, and expands the range of practical isotope applications, from solution analyses to in-situ laser ablation.

Methodology and Instrumentation Used

The instrument integrates three main stages:

• Filter: A double Wien filter with an adjustable slit disperses ions by m/z, allowing only a defined mass window (e.g., m/z 29 for silicon) to enter the CRC.
• React: A hexapole collision/reaction cell introduces gases such as O₂, SF₆, H₂, or He to shift or neutralize interferences.
• Separate: A magnetic sector and multicollector array measure isotope ratios under low- or high-resolution conditions.

This configuration maintains high ion transmission and predictable mass bias following the exponential fractionation law.

Main Results and Discussion

• Si in HNO₃: Pre-filtering around m/z 29 suppressed 28Si interferences, doubling Si sensitivity compared to unfiltered CRC.
• Titanium isotopes: Clean TiO⁺ spectra (m/z 62–66) achieved by pre-filtering and O₂ reaction gas, eliminating Ca, V, Cr, and Fe interferences.
• Rb-Sr in situ dating: A narrow 103–107 amu window removed matrix peaks (e.g., 103Rh, 107Ag), isolating SrF reaction products for interference-free 87Sr/87Rb ratios.
• Potassium isotopes: Using H₂/He to neutralize ArH, low-resolution K isotope analysis on 25 ppb samples achieved 0.03‰ external reproducibility, outperforming traditional high-resolution methods.
• Sensitivity and Abundance Sensitivity: Pre-filtering reduces space‐charge effects and unwanted scattering, yielding sensitivity equal or superior to prior MC-ICP-MS models and thermal ionization standards.

Benefits and Practical Applications

• Predictable CRC reactions for robust interference removal
• Improved precision in isotope ratio measurements across Fe, Sr, Nd, Hf, Pb, U, and others
• Extension to challenging in-situ and laser ablation–MC-ICP-MS applications
• Capability to measure traditionally high-resolution systems (e.g., K isotopes) at low resolution
• Enhanced sensitivity enables analysis of smaller sample sizes

Future Trends and Applications

Ongoing developments will likely focus on integrating MS/MS pre-filtering with advanced reaction gases and laser sources to expand in situ geochronology, environmental tracer studies, and nano-scale analyses. Further miniaturization and automation may enable real-time monitoring in industrial and field settings.

Conclusion

The Neoma MS/MS MC-ICP-MS with its double Wien pre-cell mass filter represents a transformative advance in CRC-MC-ICP-MS technology. By simplifying CRC chemistry and eliminating major interferences, it achieves higher sensitivity, superior abundance sensitivity, and broader application scope without sacrificing mass bias control.

References

1. Moynier F, Hu Y, Wang K, Zhao Y, Gérard Y, Deng Z, et al. Potassium isotopic composition of various samples using a dual-path collision cell-capable multiple-collector inductively coupled plasma mass spectrometer, Nu instruments Sapphire. Chemical Geology. 2021;571:120144.
2. Ku Y, Jacobsen SB. Potassium isotope anomalies in meteorites inherited from the protosolar molecular cloud. Science Advances. 2020;6(41).
3. Schwieters J, Jung G. Double Wien Filter. EP 3769334B1. 2022.
4. Schwieters J, Elliott TR, Coath CD. Multi detector mass spectrometer and spectrometry method filter. US 10867780B2. 2020.
5. Bevan D, Coath CD, Lewis J, Schwieters J, Lloyd N, Craig G, et al. In situ Rb–Sr dating by collision cell, multicollection inductively-coupled plasma mass-spectrometry with pre-cell mass-filter, (CC-MC-ICPMS/MS). Journal of Analytical Atomic Spectrometry. 2021;36(5).
6. Bevan D, Coath C, Lewis J, Schwieters J, Lloyd N, Craig G, et al. Detrital K-Feldspar Geochronology by Collision Cell MC-ICPMS/MS. Goldschmidt Abstracts. 2020.
7. Pfeifer M, Lewis J, Coath C, Schwieters J, Elliott T. In situ Titanium Isotope Measurements in Meteorites Using the Collision Cell MC-ICPMS, Proteus. Goldschmidt Abstracts. 2019.
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9. Télouk P, Albalat E, Tacail T, Arnaud-Godet F, Balter V. Steady analyses of potassium stable isotopes using a Thermo Scientific Neoma MC-ICP-MS. Journal of Analytical Atomic Spectrometry. 2022;6.