Optimising the accuracy of energy dispersive x-ray fluorescent (EDXRF) method for gold alloy purity measurements

The demand for gold-based transaction products is increasing, driven by the need for faster and more efficient analytical solutions. Conventional methods for determining gold alloy purity, such as fire assay, are destructive, time-consuming, and require complex laboratory-based analysis. The Energy-Dispersive X-Ray Fluorescent (EDXRF) offers a modern, non-destructive alternative to traditional fire assay methods, requiring minimal sample preparation while delivering rapid results. This research examines the role of matrix-specific corrections in enhancing the accuracy of EDXRF analysis for gold alloys. A hybrid approach combining empirical calibration with standardless Fundamental Parameter (FP) methods was employed to enhance the quantification of gold (Au), silver (Ag), and copper (Cu) across a purity range of 75.00 wt.% to 99.99 wt.%. Key challenges addressed include matrix effects (interelement interference), spectral overlaps, and irregular sample geometry, which contribute to measurement inaccuracies. The methodology involved optimizing instrument parameters, refining calibration conditions, standardizing sample preparation, and applying matrix-effect correction factors. To validate the robustness of the optimized EDXRF method, results were compared with fire assay analyses using Certified Reference Materials (CRMs) and commercial gold alloy samples. The study successfully improved EDXRF precision and accuracy through targeted matrix corrections, achieving a near-perfect regression coefficient (r² ≈ 0.9999) for gold calibration curves across all tested metals. Measurement errors were minimized to <0.1% relative error, while relative standard deviations (%rsd) were reduced to <0.11% for pure Au, 0.16% for binary Au-Ag/Au-Cu alloys, and <0.20% for ternary Au-Ag-Cu alloys. A Student’s t-test confirmed the null hypothesis, demonstrating statistical equivalence between EDXRF and fire assay mean values. Overall, this study has successfully established a robust and optimised EDXRF analytical framework for accurate gold alloy purity measurement, offering a reliable non-destructive alternative to conventional destructive analytical techniques.