High-Precision Measurements of ⁴⁴Ca/⁴⁰Ca Using Multiple-Collector Inductively Coupled Plasma Mass Spectrometry...

Area of Science:

• Geochemistry
• Isotope Geochemistry
• Analytical Chemistry

Background:

• Accurate determination of calcium (Ca) isotopic composition is crucial for understanding geological processes.
• Traditional methods face challenges with matrix element interferences and analytical precision.
• Existing techniques often require complex column chemistry or collision cell equipment.

Purpose of the Study:

• To develop a novel, high-precision method for measuring Ca isotopic composition in geological samples.
• To eliminate matrix element interferences using a simplified chromatographic separation.
• To enhance the accuracy and applicability of Ca isotope analysis in Earth science.

Main Methods:

• Column chromatography utilizing N,N,N',N'-tetraoctyl-1,5-diglycolamide (TODGA) resin for Ca purification.
• Multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) without collision cell equipment.
• Cold plasma technique to minimize Argon (Ar+) interference during Ca isotope measurements.

Main Results:

• Successful elimination of matrix elements, including Sr, with improved tolerance compared to previous methods.
• Direct measurement of 44Ca/40Ca achieved with suppressed Ar+ background (<300 mV).
• Measured isotopic values (δ44/40Ca, δ44/42Ca, ε40Ca) for reference materials align with established data.
• Demonstrated long-term precision better than 0.10‰ (2 standard deviations) for δ values.

Conclusions:

• The developed method offers a robust and precise approach for Ca isotope analysis in geological samples.
• Simplified column chemistry and effective matrix element removal lower analytical complexity.
• This advancement is expected to expand the Ca isotope dataset and its utilization in Earth science research.