A multi-point calibration method for electron probe microanalysis (EPMA) of indium in sphalerite (ZnS)

Area of Science:

• Geochemistry
• Analytical Chemistry
• Materials Science

Background:

• Electron probe microanalysis (EPMA) is crucial for elemental quantification in minerals.
• Accurate trace element analysis in sphalerite (ZnS) is vital for understanding geological processes.
• Existing calibration methods can limit precision and detection limits for specific elements.

Purpose of the Study:

• To develop and validate a multi-point calibration approach for trace indium analysis in sphalerite using EPMA.
• To assess the performance of the new method regarding precision, detection limits, and potential interferences.
• To compare the multi-point calibration method with traditional single-point calibration techniques.

Main Methods:

• Utilized indium and cadmium-doped ZnS crystals for calibration standards across a concentration range (0-1500 µg/g).
• Performed EPMA measurements using two distinct analytical conditions (25 kV/100 nA and 7 kV/200 nA).
• Evaluated key performance metrics including beam stability, lower limits of detection and quantification, reproducibility, and precision.

Main Results:

• The multi-point calibration approach yielded a 2-3 times improvement in analytical precision compared to single-point calibration.
• Achieved lower detection limits for indium down to approximately 20 µg/g.
• Addressed potential issues such as spectral line overlap (Cd) and chemical shifts from non-matrix matched standards.

Conclusions:

• The multi-point calibration strategy offers superior accuracy and sensitivity for trace indium determination in sphalerite via EPMA.
• This method enhances the reliability of quantitative analysis for geological and materials science research.
• The developed technique provides a robust framework for trace element analysis in complex matrices.