High precision copper and zinc isotopes with Neoma MS/MS MC-ICP-MS

Significance of the Topic

The isotopic composition of copper and zinc serves as a sensitive tracer in a wide range of scientific disciplines. In geosciences, these isotopes reveal processes such as planetary formation, core–mantle differentiation, mineralization, weathering, and biogeochemical cycling. In environmental science, copper and zinc isotope ratios trace anthropogenic contamination pathways across soil, water, and atmosphere. In biomedical research, isotopic analysis of these essential metals supports metallomics studies, disease diagnostics, and metabolic investigations.

Objectives and Overview of the Study

This study demonstrates the capabilities of the Thermo Scientific Neoma MS/MS MC-ICP-MS instrument to measure high-precision copper and zinc isotope ratios. Three experimental configurations were evaluated, varying solution concentration, plasma conditions (wet vs. dry), and mass resolution to assess sensitivity, mass bias behavior, and reproducibility at concentrations from 100 ppb to 1 ppm.

Methodology and Instrumentation

The experiments employed standard-sample bracketing with self-referencing of isotope ratios, automatic interference correction via Qtegra ISDS software, and mass bias correction using the exponential law based on the 66Zn/64Zn ratio. Three analytical runs used different nebulizer and desolvator systems, plasma conditions, and resolution settings to compare performance across configurations.

Instrumentation Used

Neoma MS/MS MC-ICP-MS with pre-cell mass filter in full ion transmission mode, SIS spray chamber for wet plasma, ESI Apex Omega desolvating nebulizer for dry plasma, microFAST MC™ syringe injection system, Ni "X" skimmer and Jet sampler cones, and Qtegra Intelligent Scientific Data Solution software.

Main Results and Discussion

The Neoma MS/MS MC-ICP-MS achieved copper sensitivities up to 208 V/ppm and zinc sensitivities up to 197 V/ppm, exceeding by factors of two to ten the performance of other MC-ICP-MS instruments. Mass bias followed the exponential law with high linearity (R2 > 0.99). External reproducibility at 100 ppb was around 0.21–0.29‰ (2SD) for δ65Cu and 0.06–0.10‰ for δ67Zn and δ68Zn. At 1 ppm, reproducibility improved to 0.0115‰ (δ65Cu) and 0.018–0.023‰ (δ67Zn and δ68Zn), demonstrating ppm-level precision.

Benefits and Practical Applications of the Method

The enhanced sensitivity and precision permit robust isotope measurements at low sample concentrations, reducing sample and reagent consumption. This capability supports diverse applications including cosmochemistry, metallogenic exploration, environmental monitoring of metal pollution, and medical metallomics for disease biomarker discovery.

Future Trends and Potential Applications

Advances in collision/reaction cell techniques and higher resolution MS/MS configurations may further lower detection limits and improve interference removal. Integration with automated sample preparation and double-spike methodologies can expand isotopic studies in complex matrices and biological systems. Broader adoption in environmental forensics and clinical diagnostics is anticipated.

Conclusion

The Thermo Scientific Neoma MS/MS MC-ICP-MS in full transmission mode delivers unparalleled sensitivity and precision for copper and zinc isotope analysis. Predictable, exponential mass bias behavior and low-ppm reproducibility across diverse plasma conditions affirm its suitability for cutting-edge geochemical, environmental, and biomedical research.

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