Small spot and mapping analysis of gold alloys with Thermo Scientific ARL PERFORM’X Series Advanced X-Ray Fluorescence Spectrometers

Importance of Gold Alloy Analysis

Gold remains a high-value material with uses in jewelry, coins and electronics, where precise composition directly impacts cost and performance. Reliable determination of elemental distribution and homogeneity is essential to ensure quality, detect defects and prevent financial losses in both manufacturing and recycling processes.

Objectives and Study Overview

This application note demonstrates how the Thermo Scientific ARL PERFORM’X series wavelength dispersive X-ray fluorescence (WDXRF) spectrometer enables detailed small-spot measurements and high-resolution elemental mapping of gold alloys. The goal is to assess homogeneity, verify calibration accuracy, and illustrate the instrument’s ability to reveal segregation and contaminations within coin samples and bulk alloys.

Methodology and Instrumentation

The study employed the ARL PERFORM’X 4200 W XRF spectrometer with:

• 5 GN+ rhodium X-ray tube with 50 µm Be window
• Six primary beam filters, four collimators and up to nine analyzing crystals
• Two detectors and helium purge for light-element analysis
• Small-spot aperture at 0.5 mm for localized measurements
• LoadSafe cassette and Secutainer systems for liquid and powder protection

Calibration curves for Au, Ag, Cu and Zn were generated using certified reference standards on the 0.5 mm spot, applying linear regression with matrix corrections. Precision tests involved ten repeat measurements at 100 s counting time.

Main Results and Discussion

• Calibration line linearity exceeded industry requirements, with high correlation over 0–100 % concentration ranges for all four elements.
• Precision (relative standard deviation) for typical gold alloys was below 0.8 % for Au, around 1 % for Ag and Cu, and below 4 % for trace Zn.
• Small-spot analysis on two locations of a Krugerrand coin yielded Au content of 97.56 % and 97.40 %, demonstrating repeatability of better than 0.2 %.
• Elemental mapping at 0.1 mm resolution produced composite 2D overlays and separate color-coded distribution maps for Au (green), Ag (red), Cu (blue) and Zn (yellow).
• Mapping revealed a distinct band of elevated Cu and Zn and a corresponding depletion of Au that was invisible to the naked eye, illustrating the system’s capability to detect microscopic inhomogeneities.

Benefits and Practical Applications

• High-accuracy quantification supports stringent quality control and valuation of precious-metal products.
• Small-spot capability enables analysis of small features, defects or thin coatings without extensive sample preparation.
• Elemental mapping enhances process troubleshooting by visualizing segregation, inclusions and contamination patterns.
• Automated safety features and software streamline both routine and method-development workflows.

Future Trends and Potential Applications

As XRF technology advances, we anticipate:

• Integration with automated sample handling and robotics for high-throughput screening.
• Improved detector sensitivity and faster mapping to capture real-time process dynamics.
• Enhanced data analytics and machine-learning algorithms for predictive material characterization.
• Expanded application of small-spot and mapping analysis in additive manufacturing, archaeometry and microelectronics.

Conclusion

The Thermo Scientific ARL PERFORM’X WDXRF spectrometer delivers exceptional precision, accuracy and flexibility in gold alloy analysis. Its small-spot and high-resolution mapping tools reveal compositional inhomogeneities and support diverse industrial and research applications, offering a robust solution for demanding quality control and material characterization tasks.