Stable suspensions enable accurate TXRF determination of dispersed Rb and Sr in ore samples

The rapid and accurate determination of rubidium (Rb) and strontium (Sr) in ore samples is crucial for the exploration and development of critical metal resources. Total reflection X-ray fluorescence (TXRF) spectrometry offers a promising alternative to inductively coupled plasma mass spectrometry (ICP-MS) due to its minimal sample consumption and rapid analysis. However, direct analysis of powder samples is hampered by inhomogeneous residue formation, known as the "coffee-ring effect," and severe spectral interference, particularly between Rb Kβ and U Lα lines. Herein, we developed a novel TXRF method based on stable suspensions to address these challenges. By integrating hydrodynamic simulation and experimental validation, ethylene glycol (EG) was selected as the optimal dispersion medium, effectively suppressing particle sedimentation and eliminating the coffee-ring effect. Furthermore, a novel quantification approach combining Compton scattering as an internal standard with spectral deconvolution was established, which successfully corrected for matrix effects and resolved the Rb/U spectral overlap. Analysis of three real ore samples demonstrated strong agreement with ICP-MS results (relative error of Sr: 2.18 %-4.58 %; optimized error of Rb ≤ 5.10 %), confirming the method's reliability and practicality for high-throughput and near-in-situ analysis. This work provides a robust technical approach for rapid quantification of strategic critical elements and promotes the application of TXRF in efficient mineral resource utilization.